JP5617989B2 - Image decoding apparatus, image decoding method, and image decoding program, and receiving apparatus, receiving method, and receiving program - Google Patents

Description

  The present invention relates to an image decoding technique, and more particularly to an intra-screen decoding technique.

As a typical moving image compression encoding method, MPEG-4 AVC / H. There are H.264 standards. MPEG-4 AVC / H. In H.264, encoding is performed in units of macro blocks obtained by dividing a picture into a plurality of rectangular blocks. The size of the macroblock is defined as 16 × 16 pixels in the luminance signal regardless of the image size. The macro block includes a color difference signal, but the size of the color difference signal included in the macro block differs depending on the color difference format of the image to be encoded. 8
When the pixel and color difference format is 4: 2: 2, the color difference signal is 8 × 16 pixels, and when the color difference format is 4: 4: 4, the color difference signal is 16 × 16 pixels.

The color difference format represents the ratio of the number of sampled pixels of three signals of one luminance information and two color difference information as X: Y: Z. MPEG-4 AVC / H. The color difference format of an image to be encoded and decoded in H.264 is 4: 2: 0, 4: 2: 2, 4: 4: 4, and monochrome.

FIG. 3 is a diagram for explaining each color difference format of an image. X indicates the position of the pixel of the luminance signal on the screen plane of the image, and ◯ indicates the position of the pixel of the color difference signal.
In 4: 2: 0 shown in FIG. 3A, the color difference signal is 2 in both the horizontal and vertical directions with respect to the luminance signal.
A color difference format sampled at a density of one part. In 4: 2: 0, the color difference signal may be sampled at the position shown in FIG.
4: 2: 2 shown in FIG. 3B is a color difference format in which the color difference signal is sampled with a density of 1/2 in the horizontal direction and the same density in the vertical direction with respect to the luminance signal.
4: 4: 4 shown in FIG. 3C is a color difference format in which both the luminance signal and the color difference signal are sampled at the same density.
Monochrome shown in FIG. 3D is a color difference format having only a luminance signal without a color difference signal.

Note that the luminance signal and the color difference signal are encoded and decoded as a set in order to share encoding information such as motion compensation. In 4: 4: 4, one luminance signal and two color difference signals are independently used. 3
There is also a mechanism for encoding and decoding as one monochrome.

AVC / H. In the H.264 system, a method of predicting from already encoded / decoded blocks in an encoding / decoding target picture is used. This method is called intra prediction. In addition, motion compensation that predicts motion from a reference picture using a picture that has already been encoded / decoded as a reference picture is used. A technique for predicting motion by this motion compensation is called inter prediction.

First, AVC / H. A unit for switching the intra prediction mode in the intra prediction in the H.264 intra coding will be described. 4A to 4C are diagrams for explaining a unit for switching the intra prediction mode. AVC / H. In the H.264 intra coding, “4 × 4 intra prediction”, “16 ×
Three types of “16 intra prediction” and “8 × 8 intra prediction” are prepared.

In “4 × 4 intra prediction”, a luminance signal of a macro block (luminance signal 16 × 16 pixel block, color difference signal 8 × 8 pixel block) is divided into 16 × 4 × 4 pixel blocks, and divided 4 × 4 pixel units. Then, a mode is selected from nine types of 4 × 4 intra prediction modes, and intra prediction is sequentially performed (FIG. 4A).
In “16 × 16 pixel intra prediction”, a mode is selected from four types of 16 × 16 intra prediction modes in units of 16 × 16 pixel blocks of the luminance signal, and intra prediction is performed (FIG. 4B).
In “8 × 8 pixel intra prediction”, the luminance signal of a macro block is divided into four 8 × 8 pixel blocks, and a mode is selected from nine types of 8 × 8 intra prediction modes in units of divided 8 × 8 pixels. Then, intra prediction is sequentially performed (FIG. 4C).

In addition, for color difference signal intra prediction, when the color difference format is 4: 2: 0 or 4: 2: 2, a mode is selected from four types of color difference signal intra prediction modes in units of macroblocks, and intra prediction is performed. Is done.

When 16 × 16 pixel intra prediction is selected, the luminance signal intra prediction mode is encoded as one mode of the syntax element mb_type indicating the type of the macroblock,
The intra prediction mode of the color difference signal is encoded separately.
When 4 × 4 intra prediction is selected, the intra prediction modes of the 16 luminance signals are encoded successively, and then the intra prediction mode of the color difference signal is encoded.
When the 8 × 8 intra prediction is selected, the intra prediction modes of the four luminance signals are sequentially encoded, and then the intra prediction mode of the color difference signal is encoded.

Next, AVC / H. A unit for inter prediction in H.264 inter coding will be described. FIGS. 5A to 5H are diagrams for explaining a macroblock partition and a sub-macroblock partition. To simplify the explanation here,
Only the pixel block of the luminance signal is drawn. In the MPEG series, the macroblock is defined by a square area. Generally, AVC / H. In the MPEG series including the H.264 system, 1
A block defined by 6 × 16 pixels (16 horizontal pixels and 16 vertical pixels) is called a macroblock. Furthermore, AVC / H. In the H.264 system, a block defined by 8 × 8 pixels is called a sub macroblock. The macroblock partition refers to each small block obtained by further dividing the macroblock for motion compensation prediction. The sub-macroblock partition refers to each small block obtained by further dividing the sub-macroblock for motion compensation prediction.

FIG. 5A is a diagram showing that a macroblock is composed of one macroblock partition composed of a luminance signal of 16 × 16 pixels and two corresponding color difference signals. Here, this configuration is referred to as a 16 × 16 mode macroblock type.
In FIG. 5B, the macro block is composed of two macro block partitions each composed of a luminance signal of 16 × 8 pixels (horizontal 16 pixels, vertical 8 pixels) and two corresponding color difference signals. FIG. The two macroblock partitions are arranged vertically. Here, this configuration is called a 16 × 8 mode macroblock type.
In FIG. 5 (c), the macroblock is composed of two macroblock partitions composed of a luminance signal of 8 × 16 pixels (horizontal 8 pixels, vertical 16 pixels) and two corresponding color difference signals. FIG. The two macroblock partitions are arranged side by side. Here, this configuration is referred to as an 8 × 16 mode macroblock type.
FIG. 5D is a diagram showing that a macroblock is composed of four macroblock partitions each composed of a luminance signal of 8 × 8 pixels and two corresponding color difference signals. These four macroblock partitions are arranged vertically and horizontally. This configuration is referred to as an 8 × 8 mode macroblock type.
FIG. 5E is a diagram showing that a sub macroblock is composed of one submacroblock partition composed of a luminance signal of 8 × 8 pixels and two corresponding color difference signals. Here, this configuration is referred to as an 8 × 8 mode sub-macroblock type.
In FIG. 5F, the sub-macroblock is composed of two sub-macroblock partitions composed of a luminance signal of 8 × 4 pixels (horizontal 8 pixels, vertical 4 pixels) and two corresponding color difference signals. FIG. These two sub-macroblock partitions are arranged vertically. This configuration is referred to as an 8 × 4 mode sub-macroblock type.
In FIG. 5G, the sub-macroblock is composed of two macroblock partitions each composed of a luminance signal of 4 × 8 pixels (horizontal 4 pixels, vertical 8 pixels) and two corresponding color difference signals. FIG. The two macroblock partitions are arranged side by side. Here, this configuration is called a 4 × 8 mode sub-macroblock type.
FIG. 5 (h) is a diagram showing that a sub macroblock is composed of four submacroblock partitions each composed of a luminance signal of 4 × 4 pixels and two corresponding color difference signals. These four sub-macroblock partitions are arranged two by two vertically and horizontally. Here, this configuration is called a 4 × 4 mode sub-macroblock type.

AVC / H. In the H.264 encoding method, a mechanism that can be selected and used from the above motion compensation block sizes is adopted. First, as the motion compensation block size for each macroblock, one of 16 × 16, 16 × 8, 8 × 16, and 8 × 8 mode macroblock types can be selected. When the macro block type of 8 × 8 mode is selected, the motion compensation block size in units of sub macro blocks is 8 × 8.
, 8 × 4, 4 × 8, and 4 × 4 mode sub-macroblock types can be selected.

ISO / IEC 14496-10 Information technology-Coding of audio-visual objects-Part 10: Advanced Video Coding

When encoding information about the intra prediction mode of the image signal, information about the intra prediction mode of the luminance signal and information about the intra prediction mode of the color difference signal are encoded and arranged in the encoded bit string. If the arrangement is not adapted to the color difference format, the processing efficiency may deteriorate.

The present invention has been made in view of such circumstances, and an object thereof is to provide an image decoding technique capable of efficiently decoding an image signal by intra prediction of a luminance signal and a color difference signal corresponding to the color difference format. is there.

An image decoding apparatus that decodes information related to an intra prediction mode and performs intra prediction decoding of an image signal including a luminance signal and a color difference signal in units of blocks, and derives an intra luminance prediction mode value means for deriving a value of the intra luminance prediction mode When the color difference format is 4: 2: 2, the color difference format is determined based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal derived by the intra luminance prediction mode deriving unit. The value of the intra color difference prediction mode is derived from the conversion table indicating the value of the 4: 2: 2 intra color difference prediction mode. When the color difference format is not 4: 2: 2, the color difference signal is predicted without using the conversion table. Intra color difference prediction mode based on the value of intra luminance prediction mode of the prediction block at the same position as the block And the intra prediction mode deriving means for deriving the plurality of intra luminance prediction modes in which the reference destinations are arranged in the vertical direction in the conversion table. There is provided an image decoding device characterized in that at least values representing a plurality of intra color difference prediction modes in a prediction direction closest to each of the directions are indicated.
An image decoding method for decoding information relating to an intra prediction mode and performing intra prediction decoding on an image signal including a luminance signal and a color difference signal in units of blocks, and an intra luminance prediction mode derivation step for deriving a value of the intra luminance prediction mode When the color difference format is 4: 2: 2, the color difference format is calculated based on the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal, which is derived in the intra luminance prediction mode deriving step. Derives the value of the intra color difference prediction mode from the conversion table indicating the value of the 4: 2: 2 intra color difference prediction mode, and if the color difference format is not 4: 2: 2, the color difference signal is not used without using the conversion table. Intra color difference prediction based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block. An intra color difference prediction mode derivation step for deriving a mode value, and the conversion table scales the prediction directions of a plurality of intra luminance prediction modes whose reference destinations are arranged in the vertical direction by a factor of two in the vertical direction. There is provided an image decoding method characterized in that at least a value indicating a plurality of intra color difference prediction modes in a prediction direction closest to each of a plurality of directions derived from the above is indicated.
An image decoding program for causing a computer to decode information related to an intra prediction mode and performing intra prediction decoding of an image signal including a luminance signal and a color difference signal in units of blocks, and for calculating an intra luminance prediction mode value. When the mode derivation step and the color difference format are 4: 2: 2, based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal, which is derived in the intra luminance prediction mode derivation step. If the color difference format is not 4: 2: 2, the value of the intra color difference prediction mode is derived from the conversion table indicating the value of the intra color difference prediction mode of 4: 2: 2, and the conversion table is not used. Intra-brightness prediction mode of the prediction block at the same position as the prediction block of the color difference signal The intra color difference prediction mode deriving step for deriving the value of the intra color difference prediction mode based on the image, and the conversion table includes the prediction directions of the plurality of intra luminance prediction modes whose reference destinations are arranged in the vertical direction. There is provided an image decoding program characterized in that at least values representing a plurality of intra color difference prediction modes in a prediction direction closest to each of a plurality of directions derived by scaling twice in the vertical direction are shown.
A receiving device that decodes information related to an intra prediction mode from an encoded stream and performs intra prediction decoding on an image signal including a luminance signal and a color difference signal in units of blocks, and includes encoded data obtained by encoding a moving image. A receiving unit for receiving, a packet processing unit for packet-processing the encoded data to generate the encoded stream, an intra luminance prediction mode deriving unit for deriving a value of an intra luminance prediction mode from the encoded stream, and color difference When the format is 4: 2: 2, the color difference format is 4: 2 based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal derived by the intra luminance prediction mode deriving unit. : Deriving the value of the intra color difference prediction mode from the conversion table indicating the value of the intra color difference prediction mode of 2, If the difference format is not 4: 2: 2, the intra color difference prediction mode value is derived based on the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal without using the conversion table. Each of a plurality of directions derived by scaling the prediction directions of a plurality of intra luminance prediction modes whose reference destinations are arranged in the vertical direction to double the vertical direction in the conversion table. There is provided a receiving apparatus characterized in that at least a value representing a plurality of intra color difference prediction modes in a prediction direction closest to is shown.
A receiving method for decoding intra-prediction mode information from an encoded stream and intra-predicting an image signal including a luminance signal and a color difference signal in units of blocks, wherein encoded data obtained by encoding a moving image is encoded A receiving step for receiving, a packet processing step for packetizing the encoded data to generate the encoded stream, an intra luminance prediction mode deriving step for deriving a value of an intra luminance prediction mode from the encoded stream, and a color difference When the format is 4: 2: 2, the color difference format is 4: based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal derived in the intra luminance prediction mode deriving step. 2: Intra color difference prediction from the conversion table indicating the value of the intra color difference prediction mode of 2: 2. When the mode value is derived and the color difference format is not 4: 2: 2, the intra color difference prediction is performed based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal without using the conversion table. An intra color difference prediction mode derivation step for deriving a mode value, and the conversion table scales the prediction directions of a plurality of intra luminance prediction modes whose reference destinations are arranged in the vertical direction by a factor of two in the vertical direction. There is provided a receiving method characterized in that at least values representing a plurality of intra color difference prediction modes in a prediction direction closest to each of a plurality of directions derived from the above are indicated.
A reception program for causing a computer to decode information related to an intra prediction mode from an encoded stream and performing intra prediction decoding of an image signal including a luminance signal and a chrominance signal in units of blocks, in which a moving image is encoded A receiving step for receiving data; a packet processing step for packetizing the encoded data to generate the encoded stream; and an intra luminance prediction mode deriving step for deriving a value of an intra luminance prediction mode from the encoded stream; When the color difference format is 4: 2: 2, the color difference format is determined based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal derived in the intra luminance prediction mode deriving step. 4: 2: 2 conversion color indicating the value of the intra color difference prediction mode. If the color difference format is not 4: 2: 2, the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal is used without using the conversion table. An intra color difference prediction mode deriving step for deriving a value of the intra color difference prediction mode based on the computer; There is provided a reception program characterized in that at least a value representing a plurality of intra color difference prediction modes in a prediction direction closest to each of a plurality of directions derived by scaling twice in the direction is indicated.

It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

According to the present invention, an image signal can be efficiently decoded by intra prediction of a luminance signal and a color difference signal corresponding to a color difference format.

It is a block diagram which shows the structure of the image coding apparatus of embodiment. It is a block diagram which shows the structure of the image decoding apparatus of embodiment. It is a figure explaining the color difference format of an image. AVC / H. It is a figure explaining the unit which switches the intra prediction mode of H.264 system. AVC / H. It is a figure explaining the unit which performs inter prediction of H.264 system. It is a figure explaining the tree block prescribed | regulated by a present Example, and an encoding block. It is a figure explaining the division mode prescribed | regulated by a present Example. It is a figure explaining the value and prediction direction of the intra prediction mode prescribed | regulated by a present Example. It is a figure of an example for demonstrating the position of the block prescribed | regulated by a present Example. It is a figure explaining an example of the definition of a syntax at the time of encoding color difference format information with the sequence parameter set used as the header which encodes the information regarding the encoding of the whole sequence prescribed | regulated by a present Example. It is a figure explaining the division | segmentation method of the color difference signal of the encoding block in the NxN division | segmentation in the case of the intra prediction prescribed | regulated in a present Example. It is a block diagram which shows the structure of the 2nd encoding bit stream production | generation part of the image coding apparatus of embodiment. It is a block diagram which shows the structure of the 2nd encoding bit stream decoding part of the image decoding apparatus of embodiment. It is a conversion table which calculates the value of an intra color difference prediction mode from the value of the syntax element used by the decoding side prescribed | regulated by a present Example, and the value of the intra brightness prediction mode of the prediction block of the same position as the prediction block of a color difference signal. This is a conversion table for calculating the value of the intra color difference prediction mode from the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal when the color difference format specified in this embodiment is 4: 2: 2. . The intra color difference prediction mode value used on the encoding side defined in this embodiment and the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal, that is, the prediction block of the luminance signal belonging to the same prediction unit, are set to the intra. It is a conversion table which calculates the value of the syntax element regarding color difference prediction mode. It is a figure which shows the entropy encoding or decoding order of the syntax element regarding the intra brightness | luminance prediction mode by embodiment, and an intra color difference prediction mode. It is an example of the syntax rule for encoding and decoding of the encoding information of the encoding block unit prescribed | regulated by a present Example. It is an example of the syntax rule for encoding and decoding of the encoding information of the prediction unit prescribed | regulated by a present Example. It is a flowchart explaining the process sequence of the encoding process of the encoding block performed by the 2nd encoding bit stream production | generation part of embodiment, and a prediction block unit. It is a flowchart explaining the common encoding process sequence used by step S1003 of FIG. 20, step S1007, step S1010, and step S1013 of embodiment. It is a flowchart explaining the common encoding process procedure used by step S1005 of FIG. 20, step S1009, step S1012, and step S1015 of embodiment. It is a flowchart explaining the process sequence of the decoding process of the encoding block performed by the 2nd encoding bit stream decoding part of embodiment and a prediction block unit. It is a flowchart explaining the common decoding process procedure used by step S2003 of FIG. 23 of embodiment, step S2007, step S2010, and step S2013. It is a flowchart explaining the common decoding process procedure used also by step S2005 of FIG. 23, step S2009, step S2012, and step S2015 of embodiment. It is a flowchart explaining the calculation processing procedure of the value of the intra color difference prediction mode used by step S2202 of FIG. 25 of embodiment. It is a figure explaining the correspondence of the prediction direction of the brightness | luminance signal in case a color difference format is 4: 2: 2, and the intra prediction of a color difference signal. It is a figure explaining the correspondence of the prediction direction of the luminance signal in case a color difference format is 4: 2: 0, and the intra prediction of a color difference signal.

In the present embodiment, with regard to video coding, in particular, in units of blocks obtained by dividing a picture into rectangles having an arbitrary size and shape, coding has already been coded and decoded, and decoding has been decoded (hereinafter decoded). The amount of code is reduced by using intra prediction in which prediction is performed from the pixel values of the surrounding blocks and inter prediction by motion compensation from already decoded pictures.

  First, techniques used in this embodiment and technical terms are defined.

(Color difference format)
The color difference format of an image to be encoded and decoded in the description of the embodiment is AVC /
H. It is assumed that monochrome, which is also a target of the H.264 system, 4: 2: 0, 4: 2: 2, 4: 4: 4, and a luminance signal and a color difference signal are encoded and decoded as a set. However, regarding the description regarding the color difference signal, the description in the case of monochrome is omitted. In the present embodiment, the method of independently encoding the luminance signal and the color difference signal at 4: 4: 4 is assumed to be monochrome.

(About tree blocks and coding blocks)
In the embodiment, as shown in FIG. 6, the inside of the screen is equally divided into square units of any same size. This unit is defined as a tree block, and is used as a basic unit of address management for specifying an encoding / decoding target block (an encoding target block in encoding and a decoding target block in decoding) in an image. Except for monochrome, the tree block is composed of one luminance signal and two color difference signals. The size of the tree block can be freely set to a power of 2 in accordance with the picture size and the texture in the screen. In order to optimize the encoding process according to the texture in the screen, the tree block hierarchically divides the luminance signal and chrominance signal in the tree block as necessary into four parts (two parts vertically and horizontally), The block can be made smaller in block size. Each block is defined as a coding block, and is a basic unit of processing when performing coding and decoding. Except for monochrome, the coding block is also composed of one luminance signal and two color difference signals. The maximum size of the coding block is the same as the size of the tree block. An encoded block having the minimum size of the encoded block is called a minimum encoded block, and can be freely set to a power of 2.

In FIG. 6, the encoding block A is a single encoding block without dividing the tree block. The encoding block B is an encoding block formed by dividing a tree block into four. The coding block C is a coding block obtained by further dividing the block obtained by dividing the tree block into four. The coding block D is divided into 4 tree blocks.
It is an encoded block that is obtained by further dividing the block obtained by dividing into four hierarchically twice.
It is a coding block of the minimum size.

In the description of the embodiment, the color difference format is 4: 2: 0, the size of the tree block is set to 64 × 64 pixels for the luminance signal, and 32 × 32 pixels for the color difference signal, and the minimum coding block size is set. The luminance signal is set to 8 × 8 pixels, and the color difference signal is set to 4 × 4 pixels.
In FIG. 6, the size of the coding block A is 64 × 64 pixels for the luminance signal and 32 × 3 for the color difference signal.
The size of the encoding block B is 32 × 32 pixels for luminance signals and 16 for color difference signals.
The size of the coding block C is 16 × 16 pixels for the luminance signal and 8 × 8 pixels for the color difference signal, and the size of the coding block D is 8 × 8 pixels for the luminance signal and 4 × for the color difference signal.
4 pixels. When the color difference format is 4: 4: 4, the size of the luminance signal and the color difference signal of each coding block is equal. When the color difference format is 4: 2: 2, the size of the coding block A is 32 × 64 pixels for the color difference signal, the size of the coding block B is 16 × 32 pixels for the color difference signal, and the size of the coding block C is The color difference signal is 8 × 16 pixels, and the size of the coding block D, which is the smallest coding block, is 4 × 8 pixels.

(About prediction mode)
In the coding block unit, switching is performed between intra prediction in which prediction is performed from surrounding image signals that have been encoded / decoded and inter prediction in which prediction is performed from image signals of images that have been encoded / decoded.
A mode for identifying the intra prediction and the inter prediction is defined as a prediction mode (PredMode). The prediction mode (PredMode) is either intra prediction (MODE_INTRA) or inter prediction (MODE_I
NTER) as a value and can be selected and encoded.

(About split mode, prediction block, prediction unit)
When intra prediction and inter prediction are performed by dividing the screen into blocks, prediction is performed by dividing an encoded block as necessary in order to reduce the unit for switching the method of intra prediction and inter prediction. A mode for identifying the division method of the luminance signal and the color difference signal of the coding block is defined as a division mode (PartMode). Furthermore, this divided block is defined as a prediction block. As shown in FIG. 7, four types of partition modes (PartMode) are defined according to the method of dividing the luminance signal of the coding block. The division mode (PartMode) of the coded block luminance signal (FIG. 7A) regarded as one prediction block without being divided is 2N ×.
2N division (PART_2Nx2N), the luminance signal of the coding block is divided into two in the horizontal direction, and the division mode (PartMode) of the two prediction blocks (FIG. 7B) is set to 2N × N division (PART_2Nx
N) The luminance signal of the coding block is divided in the vertical direction, and the division mode (PartMode) of the coding block having two prediction blocks (FIG. 7C) is N × 2N division (PART_Nx2N)
Then, the division mode (PartMode) of the luminance signal of the encoded block that is divided into four prediction blocks by horizontal and vertical equal division (FIG. 7D) is defined as N × N division (PART_NxN). Except for N × N division (PART_NxN) of intra prediction (MODE_INTRA), the color difference signal is also divided for each division mode (PartMode) in the same manner as the vertical / horizontal division ratio of the luminance signal. The vertical / horizontal division ratio of the color difference signal of the N × N division (PART_NxN) coding block of intra prediction (MODE_INTRA) varies depending on the type of the color difference format, which will be described later.

In order to specify each prediction block within the coding block, a number starting from 0 is assigned to the prediction block existing inside the coding block in the coding order. This number is defined as a split index PartIdx. A number described in each prediction block of the encoded block in FIG. 7 represents a partition index PartIdx of the prediction block. FIG.
In the 2N × N division (PART_2NxN) shown in FIG. N shown in FIG.
In the × 2N division (PART_Nx2N), the division index PartIdx of the left prediction block is set to 0, and the division index PartIdx of the right prediction block is set to 1. N × N division (P
ART_NxN) sets the partition index PartIdx of the upper left prediction block to 0, the partition index PartIdx of the upper right prediction block to 1, and the partition index Par of the lower left prediction block
tIdx is set to 2, and the division index PartIdx of the lower right prediction block is set to 3.

In addition, since the prediction block of the luminance signal and the color difference signal at the same position has high correlation in both intra prediction and inter prediction, the encoding information of the prediction block of the luminance signal and the color difference signal is stored in one prediction unit in the embodiment. Are encoded and decoded. Also, the division index PartIdx is assigned to the prediction unit, and the same value is assigned to the division index PartIdx in the prediction block of the luminance signal and the color difference signal at the same position.

When the prediction mode (PredMode) is intra prediction (MODE_INTRA), the division mode (Part 1) is used except for the coding block D (the luminance signal is 8 × 8 pixels) which is the smallest coding block.
Mode) defines 2N × 2N partition (PART_2Nx2N), and only the coding block D, which is the smallest coding block, has a partition mode (PartMode) of 2N × 2N partition (PART_2Nx2N) and N × N partition (
PART_NxN) is defined.

When the prediction mode (PredMode) is inter prediction (MODE_INTER), the partition mode (PartMode) is 2N × 2N partition (PART_2Nx2N) except for the coding block D which is the smallest coding block.
) 2N × N partition (PART_2NxN) and N × 2N partition (PART_Nx2N) are defined, and only the coding block D, which is the smallest coding block, has a partition mode (PartMode) of 2N × 2N partition (PA).
RT_2Nx2N), 2N x N split (PART_2NxN), and N x 2N split (PART_Nx2N) plus N x
N division (PART_NxN) is defined. In addition to the smallest encoded block, N × N division (PART_N
The reason for not defining xN) is that, except for the smallest encoded block, the encoded block can be divided into four to represent a small encoded block.

(Intra prediction and intra prediction mode)
In the intra prediction, the pixel value of the processing target block is predicted from the pixel values of the decoded blocks in the same screen. In the encoding apparatus and decoding apparatus of the present embodiment, 34 intra prediction modes are selected and intra prediction is performed. FIG. 8 is an explanatory diagram of the value of the intra prediction mode and the prediction direction defined in this embodiment. The direction indicated by the solid arrow indicates the prediction direction of intra prediction, that is, the direction referred to by intra prediction, and intra prediction of the pixel at the start point of the arrow is performed with reference to the decoded pixel in the direction indicated by the arrow of the adjacent block. . The number indicates the value of the intra prediction mode. The intra prediction mode (intraPredMode) includes vertical prediction (intra prediction mode intraPredMode = 0) that predicts in the vertical direction from the above decoded block, and horizontal prediction (intra prediction mode intraPredMode) that predicts in the horizontal direction from the left decoded block. =
1) average prediction (by calculating the average value from surrounding decoded blocks)
Intra prediction mode (intraPredMode = 2), in addition to average prediction (intraPredMode = 3) that predicts at an angle of 45 degrees from surrounding decoded blocks, it also predicts diagonally at various angles from surrounding decoded blocks 30 angle prediction (intra prediction mode intraPredMod
e = 4 ... 33) is defined.

The intra prediction mode is prepared for each of the luminance signal and the color difference signal, and the intra prediction mode for the luminance signal is defined as the intra luminance prediction mode, and the intra prediction mode for the color difference signal is defined as the intra color difference prediction mode. In the encoding and decoding of the intra luminance prediction mode, when it is determined that the encoding side can predict from the intra luminance prediction mode of the surrounding block using the correlation with the intra luminance prediction mode of the surrounding block. If it is determined that it is better to set a different value for the intra luminance prediction mode than the information for identifying the block to be referenced and predict from the intra luminance prediction mode of the neighboring blocks, the intra luminance prediction mode is further set. A mechanism for encoding or decoding the value of is used. By predicting the intra luminance prediction mode of the block to be encoded / decoded from the intra luminance prediction modes of the neighboring blocks, the amount of code to be transmitted can be reduced. On the other hand, in the coding and decoding of the intra chrominance prediction mode, the intra luminance prediction mode is used on the encoding side by utilizing the correlation with the intra luminance prediction mode of the prediction block of the luminance signal at the same position as the prediction block of the chrominance signal. From the value of the intra luminance prediction mode to predict the value of the intra color difference prediction mode,
When it is determined that it is better to set a unique value for the intra color difference prediction mode than for prediction from the intra luminance prediction mode, a mechanism for encoding or decoding the value of the intra color difference prediction mode is used. By predicting the intra color difference prediction mode from the intra luminance prediction mode, the amount of code to be transmitted can be reduced.

(Conversion block)
As in the prior art, in this embodiment, the code amount is reduced by using orthogonal transform such as DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), etc. that transforms a discrete signal into the frequency domain and its inverse transform. . Conversion or inverse conversion is performed in units of transform blocks obtained by hierarchically dividing an encoded block into four. In the embodiment, 32 × 32 pixels, 16 × 16 pixels, 8 × 8 pixels, 4 ×
Define 4 conversion sizes of 4 pixels, 32 × 32 conversion, 16 × 16 conversion, 8 × 8 conversion,
It is assumed that 4 × 4 conversion and respective inverse conversion are performed.

(Position of tree block, coding block, prediction block, transform block)
The position of each block including the tree block, the encoding block, the prediction block, and the transform block described in the present embodiment is the origin (0, 0) of the pixel position of the upper left luminance signal on the luminance signal screen. And the pixel position of the upper left luminance signal included in each block area is represented by two-dimensional coordinates (x, y). The direction of the coordinate axis is a right direction in the horizontal direction and a downward direction in the vertical direction, respectively, and the unit is one pixel unit of the luminance signal. Of course, the luminance signal and the color difference signal have the same image size (number of pixels) and the color difference format is 4: 4: 4. Of course, the luminance signal and the color difference signal have a different color size format of 4: 4.
Even in the case of 2: 0, 4: 2: 2, the position of each block of the color difference signal is represented by the coordinates of the pixel of the luminance signal included in the block area, and the unit is one pixel of the luminance signal. In this way, not only can the position of each block of the color difference signal be specified, but also the relationship between the positions of the luminance signal block and the color difference signal block can be clarified only by comparing the coordinate values. FIG. 9 is a diagram showing an example for explaining the positions of blocks defined in this embodiment when the color difference format is 4: 2: 0. 9 indicates the position of the pixel of the luminance signal on the screen plane of the image, and ◯ indicates the position of the pixel of the color difference signal. 9 is a luminance signal block E of 8 × 8 pixels and at the same time a block F of color difference signals of 4 × 4 pixels. ▲ is the position of the pixel of the luminance signal at the top left of the block E of the luminance signal of 8 × 8 pixels indicated by the dotted line. Therefore, ▲ is the position of the luminance signal block E of 8 × 8 pixels indicated by the dotted line, and the coordinates of the luminance signal of the pixel indicated by ▲ are the coordinates of the block E of the luminance signal of 8 × 8 pixels indicated by the dotted line. Become. Similarly, ▲ is also the pixel position of the upper left luminance signal pixel included in the area of the block F of the color difference signal of 4 × 4 pixels indicated by the dotted line. Therefore, ▲ also becomes the position of the block F of the color difference signal of 4 × 4 pixels indicated by the dotted line, and the coordinates of the luminance signal of the pixel indicated by ▲ are 4 × 4 indicated by the dotted line.
It becomes the coordinates of the block F of the color difference signal of the pixel. In the embodiment, when the coordinates of the defined luminance signal block and the x component and y component of the coordinate of the color difference signal are the same regardless of the type of the color difference format, the shape and size of the block. Only define these blocks in the same position.

FIG. 1 is a block diagram showing a configuration of a moving picture encoding apparatus according to an embodiment. The moving image encoding apparatus according to the embodiment includes a color difference format setting unit 101, an image memory 102, an intra prediction unit 103, an inter prediction unit 104, an encoding method determination unit 105, a residual signal generation unit 106, an orthogonal transform / quantization. Unit 107, inverse quantization / inverse orthogonal transform unit 108, decoded image signal superimposing unit 109,
A decoded image memory 111, a first encoded bit string generation unit 112, a second encoded bit string generation unit 113, a third encoded bit string generation unit 114, and an encoded bit string multiplexing unit 115 are provided.

The color difference format setting unit 101 sets the color difference format of the image signal to be encoded. The color difference format may be determined by determining the color difference format from the encoded image signal supplied to the color difference format setting unit 101, or may be set from the outside. Only the luminance signal is supplied to the first encoded bit string generation unit 112 as the information of the color difference format set to 4: 2: 0, 4: 2: 2, or 4: 4: 4, and the second code Bit string generator 1
13, the encoding process based on the color difference format is performed. Although not shown, the image memory 102, the intra prediction unit 103, the inter prediction unit 104, the encoding method determination unit 105, the residual signal generation unit 106, the orthogonal transform / quantization unit 107, and the inverse quantization in FIG.・
The inverse orthogonal transform unit 108, the decoded image signal superimposing unit 109, and the third encoded bit string generating unit 114 also perform encoding processing based on the set color difference format, and the encoded information storage memory 110 and the decoded image memory 111 are processed. Then, management is performed based on the set color difference format.

The image memory 102 temporarily stores image signals to be encoded supplied in time order. The image signals to be encoded stored in the image memory 102 are rearranged in the encoding order, divided into a plurality of encoding block units in a plurality of combinations according to the setting, and further divided into prediction block units. And supplied to the intra prediction unit 103 and the inter prediction unit 104.

The intra prediction unit 103 performs each division mode (Pa
a plurality of intra luminance prediction modes and intra color difference prediction modes for each of the luminance signal and color difference signal of the prediction block to be encoded from the decoded image signal stored in the decoded image memory 111 in units of prediction blocks corresponding to rtMode) Each intra prediction is performed according to, and an intra prediction signal is obtained. The intra color difference prediction mode is a value predicted from the intra luminance prediction mode according to the color difference format, or 0 (horizontal direction), 1 (vertical direction), 2 (average value), which are representative intra prediction modes, Select only 3 (45 degrees oblique).
A method for predicting the intra color difference prediction mode from the intra luminance prediction mode will be described later.

A prediction residual signal is obtained by subtracting an intra prediction signal in units of prediction blocks for each pixel from a signal to be encoded supplied in units of prediction blocks. An evaluation value for evaluating the amount of code and the amount of distortion is calculated using the prediction residual signal, and the most suitable mode from the viewpoint of the amount of code and the amount of distortion among a plurality of intra prediction modes for each prediction block. And the intra prediction information corresponding to the selected intra prediction mode, the intra prediction signal, and the evaluation value of the intra prediction are supplied to the encoding method determining unit 105 as the intra prediction candidates of the prediction block. In addition,
A prediction processing unit for performing intra prediction will be described later.

The inter prediction unit 104 performs each division mode (Pa
rtMode), that is, in units of prediction blocks, from the decoded image signals stored in the decoded image memory 111, a plurality of inter prediction modes (L0 prediction, L1 prediction, bi-prediction), and reference images, respectively. Inter prediction is performed to obtain an inter prediction signal. At that time, a motion vector search is performed, and inter prediction is performed according to the searched motion vector. In the case of bi-prediction, inter-prediction of bi-prediction is performed by averaging or weighting and adding two inter-prediction signals for each pixel. A prediction residual signal is obtained by subtracting the inter prediction signal in units of prediction blocks for each pixel from the signal to be encoded supplied in units of prediction blocks. An evaluation value for evaluating the amount of code and the amount of distortion is calculated using the prediction residual signal, and the most suitable mode from the viewpoint of the amount of code and the amount of distortion among a plurality of inter prediction modes for each prediction block. And the inter prediction information corresponding to the selected inter prediction mode, the inter prediction signal, and the evaluation value of the inter prediction are supplied to the encoding method determination unit 105 as inter prediction candidates for the prediction block.

The encoding method determination unit 105 selects an optimal code based on the intra prediction evaluation value corresponding to the intra prediction information selected for each prediction block and the inter prediction evaluation value corresponding to the inter prediction information. Divided block method, prediction mode (
PredMode) and division mode (PartMode) are determined, and encoded information including intra prediction information or inter prediction information according to the determination is supplied to the second encoded bit string generation unit 113, and the encoded information storage memory 110 And the prediction signal subjected to intra prediction or inter prediction according to the determination is supplied to the residual signal generating unit 106 and the decoded image signal superimposing unit 109.

The residual signal generation unit 106 generates a residual signal by subtracting the prediction signal subjected to intra prediction or inter prediction from the image signal to be encoded for each pixel, and supplies the residual signal to the orthogonal transform / quantization unit 107.

The orthogonal transform / quantization unit 107 performs orthogonal transform and quantization for transforming the supplied residual signal into a frequency domain such as DCT or DST according to a quantization parameter, and performing orthogonal transform / quantization. A signal is generated and supplied to the third encoded bit string generation unit 114 and the inverse quantization / inverse orthogonal transform unit 108.

The first encoded bit string generation unit 112 calculates the value of the syntax element related to the encoding information of the sequence, the picture, and the slice unit according to the semantic rule that defines the meaning of the syntax element and the derivation method, Entropy coding is performed on the value of the syntax element in accordance with syntax rules, such as variable length coding and arithmetic coding, to generate the first coded bit string, and the coded first coded bit string is coded. Bit string multiplexing unit 1
15 is supplied. The value of the syntax element relating to the color difference format is also calculated by the first encoded bit string generation unit 112. A syntax element relating to the color difference format is calculated from the color difference format information supplied from the color difference format setting unit 101. FIG. 10 shows an example of syntax definition when the color difference format information is encoded with a sequence parameter set which is a header for encoding information relating to the encoding of the entire sequence defined in the present embodiment. The syntax element chroma_format_idc indicates the type of color difference format. The meaning of the syntax element chroma_format_idc is 0 for monochrome, 1 for 4: 2: 0, and 2 for 4.
: 2: 2, 3 represents 4: 4: 4. Also, the syntax element separate_colour_plane_flag
Means whether the luminance and color difference signals are encoded separately, separate_colour_pl
When the value of ane_flag is 0, it indicates that the two color difference signals are associated with the luminance signal and encoded. When the value of the syntax element chroma_format_idc is 1, it represents that the luminance signal and the two color difference signals are encoded separately. Only when the value of the syntax element chroma_format_idc is 3, that is, when the color difference format is 4: 4: 4, the value of chroma_format_idc can be set to 0 or 1, and in other color difference formats, the syntax element separate_c is always set.
Encoding is performed assuming that the value of olour_plane_flag is 0.

The second encoded bit string generation unit 113 is determined by the encoding method determination unit 105 for each prediction block, in addition to the encoding information for each encoding block, according to semantic rules that define the meaning of the syntax element and the derivation method. A value of a syntax element related to the encoded information is calculated. Specifically, in addition to coding information in units of coding blocks such as a coding block division method, prediction mode (PredMode), and division mode (PartMode), values of syntax elements related to coding information in units of prediction blocks Is calculated. When the prediction mode (PredMode) is intra prediction, the value of the syntax element regarding the intra prediction mode including the intra luminance prediction mode and the intra color difference prediction mode is calculated. When the prediction mode (PredMode) is inter prediction, the inter prediction mode Then, a value of a syntax element related to inter prediction information such as information specifying a reference image and a motion vector is calculated. The value of each calculated syntax element is subjected to entropy coding by variable length coding, arithmetic coding, etc. in accordance with syntax rules to generate a second coded bit string, and the coded second coding The bit string is supplied to the encoded bit string multiplexing unit 115. Details of the syntax element calculation related to the intra luminance prediction mode and the intra color difference prediction mode performed by the second encoded bit string generation unit 113 and the details of the entropy encoding process will be described later.

The third encoded bit sequence generation unit 114 performs entropy encoding by variable length encoding, arithmetic encoding, etc. according to a prescribed syntax rule for the orthogonal transform and quantized residual signal,
A third encoded bit string is generated, and the third encoded bit string is converted into an encoded bit string multiplexing unit 11.
5 is supplied.

The encoded bit string multiplexing unit 115 generates a bit stream by multiplexing the first encoded bit string, the second encoded bit string, and the third encoded bit string in accordance with a prescribed syntax rule. Output a bitstream.

The inverse quantization / inverse orthogonal transform unit 108 performs inverse quantization and inverse orthogonal transform on the orthogonal transform / quantized residual signal supplied from the orthogonal transform / quantization unit 107 to calculate a residual signal, and decodes it. This is supplied to the image signal superimposing unit 109. The decoded image signal superimposing unit 109 includes a prediction signal that has been intra-predicted or inter-predicted according to the determination by the encoding method determining unit 105, and a residual that has been inversely quantized and inversely orthogonal transformed by the inverse quantization / inverse orthogonal transform unit 108. The decoded image is generated by superimposing the signal and stored in the decoded image memory 111. Note that the decoded image may be stored in the decoded image memory 111 after filtering processing that reduces block distortion or the like due to encoding.

FIG. 2 is a block diagram showing a configuration of a moving picture decoding apparatus according to an embodiment corresponding to the moving picture encoding apparatus of FIG. The moving picture decoding apparatus according to the embodiment includes an encoded bit string separation unit 201, a first
Coded bit string decoding section 202, second coded bit string decoding section 203, third coded bit string decoding section 204, color difference format management section 205, intra prediction section 206, inter prediction section 207, inverse quantization / inverse orthogonal A conversion unit 208, a decoded image signal superimposing unit 209, an encoded information storage memory 210, a decoded image memory 211, and switches 212 and 213 are provided.

The bit stream supplied to the encoded bit string separation unit 201 is separated according to a rule of a prescribed syntax, and the first encoded bit string indicating the encoded information in sequence, picture, and slice units is the first encoded bit string decoding The second encoded bit sequence that is supplied to the unit 202 and includes encoding information in units of encoded blocks is supplied to the second encoded bit sequence decoding unit 203, and includes a residual signal that is subjected to orthogonal transform and quantization. Are supplied to the third encoded bit string decoding unit 204.

The first encoded bit string decoding unit 202 entropy-decodes the supplied first encoded bit string in accordance with the syntax rule, and each value of the syntax element regarding the encoded information in units of sequences, pictures, and slices. Get. In accordance with the semantic rules that define the meaning of the syntax element and the derivation method, the sequence, the picture, and the value of the syntax element regarding the encoded information in units of slices, the sequence, the picture,
Also, encoding information for each slice is calculated. The first encoded bit string decoding unit 202 is an encoded bit string decoding unit corresponding to the first encoded bit string generation unit 112 on the encoding side, and the sequence encoded by the first encoded bit string generation unit 112, It has a function of returning to each encoded information from an encoded bit string including encoded information in units of pictures and slices. The color difference format information encoded by the first encoded bit string generation unit 112 is a syntax element related to the color difference format information obtained by entropy decoding the second encoded bit string by the first encoded bit string decoding unit 202. Calculate from the value. According to the syntax rules and semantic rules shown in FIG. 10, the type of the color difference format is specified from the value of the syntax element chroma_format_idc, and the value of the syntax element chroma_format_idc is 0 for monochrome, 1 for 4: 2: 0, and 2 for 4 : 2: 2, 3 becomes 4: 4: 4. Furthermore, when the value of the syntax element chroma_format_idc is 3, the syntax element separate_colour_plane_fla
g is decoded to determine whether the luminance signal and the color difference signal are encoded separately. The calculated color difference format information is supplied to the color difference format management unit 205.

The color difference format management unit 205 manages the supplied color difference format information. The supplied chrominance format information is supplied to the second encoded bit string decoding unit 203, and the encoding block and prediction block encoding information calculation processing based on the chrominance format information is performed. Although not explicitly shown in the figure, the third encoded bit string decoding unit 204, the intra prediction unit 206, the inter prediction unit 207, the inverse quantization / inverse orthogonal transform unit 208, and the decoded image signal superimposing unit 209 in FIG. Decoding processing based on the color difference format information is performed, and the encoding information storage memory 210 and the decoded image memory 211 are managed based on the color difference format information.

The second encoded bit string decoding unit 203 entropy-decodes the supplied first encoded bit string in accordance with the syntax rule, and each of the syntax elements related to the encoded information of the encoded block and the prediction block unit. Get the value. In accordance with the semantic rules that define the meaning of the syntax element and the derivation method, the code of the encoding block unit and the prediction block unit is calculated from the value of the syntax element related to the supplied encoding block unit and the encoding information of the prediction block unit. Calculation information is calculated. The second encoded bit string decoding unit 203 is an encoded information calculation unit corresponding to the second encoded bit string generation unit 113 on the encoding side, and is encoded by the second encoded bit string generation unit 113. It has the function to return to each encoding information from the 2nd encoding bit sequence containing the encoding information of a block and a prediction block unit. Specifically, from each syntax element obtained by decoding the second encoded bit string according to a prescribed syntax rule, a coding block division method, a prediction mode (PredMode),
In addition to the division mode (PartMode), when the prediction mode (PredMode) is intra prediction, an intra prediction mode including an intra luminance prediction mode and an intra color difference prediction mode is obtained. On the other hand, when the prediction mode (PredMode) is inter prediction, inter prediction information such as the inter prediction mode, information for specifying a reference image, and a motion vector is obtained. When the prediction mode (PredMode) is intra prediction, the intra prediction mode 206 including the intra luminance prediction mode and the intra color difference prediction mode is supplied to the intra prediction unit 206 through the switch 212, and the prediction mode (Pr
When edMode) is inter prediction, the inter prediction information such as the inter prediction mode, the information for identifying the reference image, and the motion vector is supplied to the inter prediction unit 207 through the switch 212. In addition, the entropy decoding process performed in the second encoded bit string decoding unit 203, and the intra luminance prediction mode, and the intra luminance difference prediction mode value calculation process from the syntax elements related to the intra luminance difference prediction mode, are calculated. Details of the processing will be described later.

The third encoded bit string decoding unit 204 calculates a residual signal that has been orthogonally transformed and quantized by decoding the supplied encoded bit string, and inverse-quantized and quantized the residual signal that has been orthogonally transformed and quantized. This is supplied to the inverse orthogonal transform unit 208.

The intra prediction unit 206 generates a predicted image signal by intra prediction from the decoded peripheral blocks stored in the decoded image memory 211 according to the supplied intra luminance prediction mode and the intra prediction mode including the intra color difference prediction mode. Then, the predicted image signal is supplied to the decoded image signal superimposing unit 209 via the switch 213. The unit for performing intra prediction will be described later.

The inter prediction unit 207 uses motion compensation from the decoded reference picture stored in the decoded image memory 211 using the inter prediction mode supplied, information specifying the reference picture, and inter prediction information such as a motion vector. A predicted image signal is generated by inter prediction, and the predicted image signal is supplied to the decoded image signal superimposing unit 209 via the switch 213. In the case of bi-prediction, the two motion-compensated prediction image signals of L0 prediction and L1 prediction are adaptively multiplied and weighted to generate a final prediction image signal.

The inverse quantization / inverse orthogonal transform unit 208 performs inverse orthogonal transform and inverse quantization on the orthogonal transform / quantized residual signal decoded by the third coded bit string decoding unit 204 to perform inverse orthogonal transform. Obtain a dequantized residual signal.

The decoded image signal superimposing unit 209 includes a prediction image signal predicted by the intra prediction unit 206 or the inter prediction unit 207, and a residual signal that has been inversely orthogonally transformed / inversely quantized by the inverse quantization / inverse orthogonal transformation unit 208. Are decoded, the decoded image signal is decoded, and the decoded image memory 211 is decoded.
To store. When stored in the decoded image memory 211, the decoded image may be stored in the decoded image memory 211 after filtering processing that reduces block distortion or the like due to encoding is performed on the decoded image. The decoded image signals stored in the decoded image memory 211 are output in the output order.

Next, a prediction processing unit for intra prediction, which is one of the points of the embodiment, will be described in detail.

First, the minimum unit of orthogonal transformation in the present embodiment will be described. In image coding, low-frequency component image quality degradation is conspicuous, but high-frequency component image quality degradation is less noticeable. Reduce the amount. However, since it is difficult to sufficiently divide the 2 × 2 conversion into frequency components, the code amount reduction effect is low. Also, if each of the intra prediction, transform, and quantization processing units is made too small, the number of corresponding processing units increases, and the processing becomes complicated. Therefore, in this embodiment, the minimum unit of orthogonal transformation is 4 × 4 pixels.

Next, the minimum unit of intra prediction in the present embodiment, that is, the minimum size of the prediction block in the case of intra prediction will be described. In the intra prediction, since the pixel value of the processing target block is predicted from the pixel values of the surrounding decoded blocks in the same screen, it is necessary to complete the decoding process before encoding and decoding the subsequent block. Specifically, using the intra-predicted prediction signal, a residual signal is calculated, and the residual signal is subjected to orthogonal transformation, quantization, and inverse quantization,
By performing inverse transformation and superimposing with the prediction signal, the decoding process is completed, and the subsequent block becomes in a state where intra prediction is possible. Therefore, intra prediction needs to be performed in units that are equal to or larger than the size of the smallest transform block. This is because if intra prediction is performed in units smaller than the minimum transform block size, then orthogonal transform cannot be performed and decoding processing cannot be performed. Therefore, in this embodiment, the minimum unit of intra prediction, that is, the minimum size of the prediction block at the time of intra prediction is also set to 4 × 4 pixels similarly to the minimum unit of orthogonal transform.

Next, the minimum size of the encoded block in the present embodiment will be described. In the minimum coding block, the prediction mode (PredMode) defines intra prediction (MODE_INTRA), and the inter prediction and partition mode (PartMode) define N × N division. N × N division is a division mode (PartMode) in which the luminance signal of an encoded block is divided into four prediction blocks by horizontal and vertical equal division.
However, in this embodiment, since the minimum unit of intra prediction is 4 × 4 pixels, the minimum size of the encoded block is 8 × 8 pixels in the luminance signal.

Next, a method of dividing the color difference signal of the encoded block by N × N division at the time of intra prediction will be described. FIG. 11 is a diagram for explaining a method of dividing a color difference signal of an encoded block by N × N division at the time of intra prediction.

When the color difference format is 4: 2: 0, the minimum size of the coding block is 8 × for the luminance signal.
If the number of pixels is 8, the minimum size of the encoded block is 4 × 4 pixels in the color difference signal, and no further division is possible. Therefore, in this embodiment, the color difference format is 4
In the case of 2: 0, when the prediction mode is intra prediction and the partition mode (PartMode) is N × N partition, as shown in FIG. Intra-prediction is performed in units of 4 × 4 pixels as four prediction blocks by division, but the luminance signal is predicted as one prediction block without dividing the encoded block in the chrominance signal as shown in FIG. 11B. Similar to the block size, intra prediction is performed in units of 4 × 4 pixels. Note that the division index PartIdx of the prediction block of the color difference signal is set to 0.

When the color difference format is 4: 2: 2, if the minimum size of the encoded block is 8 × 8 pixels in the luminance signal, the minimum size of the encoded block is 4 × 8 pixels in the color difference signal. Although it can be divided equally, it cannot be divided vertically. Therefore, in the present embodiment, when the color difference format is 4: 2: 2, when the prediction mode is intra prediction and the division mode (PartMode) is N × N division, as shown in FIG. In the luminance signal, the encoded block is divided into 4 prediction blocks by dividing horizontally and vertically into four prediction blocks.
Intra prediction is performed in units of four pixels. As shown in FIG. 11C, in the color difference signal, the encoded block is equally divided only horizontally and is not divided vertically. Intra prediction is performed in units of four pixels. Note that the division index PartIdx of the prediction block of the color difference signal is set to 0 and 2 in the encoding order (from top to bottom). The reason why the division index PartIdx of the lower block is set to 2 is that the prediction block below the color difference signal is at the same position as the prediction block of the luminance signal division index PartIdx.

The prediction block of the chrominance signal and the prediction block of the luminance signal are in the same position. The reference position of the prediction block of the chrominance signal and the prediction block of the luminance signal is the coordinate position of the pixel at the upper left corner of the prediction block. Say the same.

When the color difference format is 4: 4: 4, if the minimum size of the encoded block is 8 × 8 pixels in the luminance signal, the minimum size of the encoded block is 8 × 8 pixels in the color difference signal. Similarly to the above, four prediction blocks can be obtained by horizontal and vertical equal division. Therefore, in the present embodiment, when the color difference format is 4: 4: 4, when the prediction mode is intra prediction and the division mode (PartMode) is N × N division, as shown in FIG. In the luminance signal, intra-prediction is performed in units of 4 × 4 pixels as four prediction blocks by equally dividing the encoded block horizontally and vertically, and the encoded block is also horizontally converted from the color difference signal as shown in FIG. 4 × as 4 prediction blocks by vertical equal division
Intra prediction is performed in units of four pixels. Similar to the luminance signal, the partition index PartIdx of the prediction block of the color difference signal is also in the encoding order (upper left, upper right, lower left, lower right), 0, 1
2 and 3.

In the embodiment, regardless of the type of the chrominance format, when the values of the division index PartIdx of the prediction block of the luminance signal and the division index PartIdx of the prediction block of the chrominance signal are the same, the position of the prediction block of the luminance signal is indicated. Since the coordinates (the coordinates of the pixel at the top left of the prediction block) and the coordinates indicating the position of the prediction block of the color difference signal (the coordinates of the pixel at the top left of the prediction block) are also the same, they are assumed to be at the same position. .

Next, when the chrominance format is 4: 2: 0, the encoded block is divided into four luminance signals and chrominance signals by N × N division of inter prediction, and the luminance signal is 4 × 4 pixels, and the chrominance signal is 2 × 2. Consider the case of a pixel prediction block. In inter prediction, inter prediction by motion compensation is performed using common encoding information for both the luminance signal and the color difference signal. However, in the motion compensation of the color difference signal with the color difference format of 4: 2: 0, the luminance signal uses a value obtained by scaling the magnitude of the value of the reference motion vector by half in both the horizontal and vertical components. Unlike intra prediction, inter prediction does not use decoded signals of neighboring blocks in the same image, and therefore it is possible to use an inter prediction processing unit smaller than the orthogonal transform processing unit. Therefore, orthogonal transformation can be performed in a unit larger than that of the prediction block. Therefore, even if the encoding block is divided into four and the inter prediction is performed in units of 2 × 2 pixels even with the color difference signal, the unit is not necessarily in units of 2 × 2 pixels. There is no need to perform orthogonal transformation, and after performing inter prediction of the four prediction blocks,
By combining the four prediction blocks, a residual signal in units of 4 × 4 pixels can be calculated, and orthogonal transformation can be performed in units of 4 × 4 pixels.

Therefore, in the N × N division of the inter prediction, it is assumed that the luminance signal and the color difference signal are equally divided both horizontally and vertically regardless of the type of the color difference format to form four prediction blocks.

Next, points relating to the intra prediction mode, which is a feature of the embodiment, regarding the encoding processing of the encoded block and the encoded information in units of prediction blocks performed by the second encoded bit string generation unit 113 in FIG. The explanation is centered. FIG. 12 is a block diagram showing the configuration of the second encoded bit string generation unit 113 of FIG.

As shown in FIG. 12, the second encoded bit string generation unit 113 in FIG. 1 includes a syntax element calculation unit 121 related to encoding information in units of encoded blocks, a syntax element calculation unit 122 related to an intra luminance prediction mode, an intra It comprises a syntax element calculation unit 123 related to the color difference prediction mode, a syntax element calculation unit 124 related to inter prediction information, an intra prediction mode encoding control unit 125, and an entropy encoding unit 126. In each unit constituting the second encoded bit string generation unit 113, processing corresponding to the color difference format information supplied from the color difference format setting unit 101 is performed, and a prediction mode and a division mode (PartMode) in units of encoded blocks are performed. Etc., processing corresponding to the encoded information is performed.

The syntax element calculation unit 121 related to the coding information for each coding block calculates the value of the syntax element related to the coding information for each coding block, and sends the calculated value of each syntax element to the entropy coding unit 126. Supply. Intra prediction of coded block (
MODE_INTRA) or prediction mode (PredMode) to determine inter prediction (MODE_INTER),
And the value of the syntax element regarding the partition mode (PartMode) for determining the shape of the prediction block is calculated by the syntax element calculation unit 121 of the encoding information in units of the encoding block.

The syntax element calculation unit 122 related to the intra luminance prediction mode sets the value of the syntax element related to the intra luminance prediction mode of the prediction block of the luminance signal when the prediction mode (PredMode) of the encoded block is intra prediction (MODE_INTRA). The calculated value of each syntax element is supplied to the entropy encoding unit 126. The syntax element related to the intra luminance prediction mode is a flag indicating whether or not prediction can be performed from the intra luminance prediction mode of the surrounding blocks. Syntax element prev_intra_luma_pred_flag [x0] [y0
], A syntax element mpm_idx [x0] that is an index that points to the prediction block of the prediction source
[y0] and a syntax element rem_in indicating an intra luminance prediction mode in units of prediction blocks
tra_luma_pred_mode [x0] [y0]. Note that x0, and y0 are coordinates indicating the position of the prediction block. In calculating the value of the syntax element related to the intra luminance prediction mode,
This is a flag indicating that the value is used when prediction is possible from the intra-brightness prediction mode of the surrounding block using the correlation with the intra-brightness prediction mode of the surrounding block stored in the encoded information storage memory 110. Syntax element prev_intra_luma_pred_flag [x0
] [y0] is set to 1 (true), and a value specifying the reference destination is set in the syntax element mpm_idx [x0] [y0], which is an index indicating the prediction block of the prediction source. , Prev_intra_luma_pred_flag [x0] [y0] is set to 0 (false), and a value specifying the intra luminance prediction mode is set to the syntax element rem_intra_luma_pred_mode [x0] [y0] indicating the intra luminance prediction mode to be encoded.

In addition, when the number of intra luminance prediction modes of the prediction block in the coding block differs depending on the division block, and the division mode (PartMode) is 2N × 2N division, the intra luminance of one set of prediction blocks for each coding block. The value of the syntax element regarding the prediction mode is calculated. When the division mode is N × N division, the value of the syntax element regarding the intra luminance prediction mode of four sets of prediction blocks is calculated for each coding block.

The syntax element calculation unit 123 related to the intra color difference prediction mode, when the prediction mode (PredMode) of the coding block is intra prediction (MODE_INTRA), the syntax element related to the intra color difference prediction mode of the prediction block of the color difference signal intra_chroma_pred_mode [x0] [
The value of y0] is calculated, and the value of the calculated syntax element intra_chroma_pred_mode [x0] [y0] is supplied to the entropy encoding unit 126. In calculating the value of the syntax element related to the intra chrominance prediction mode, the correlation between the prediction block of the luminance signal at the same position as the prediction block of the chrominance signal and the intra luminance prediction mode of the prediction block of the chrominance signal is used. When prediction is possible from the intra luminance prediction mode of the prediction block of the luminance signal at the same position as the prediction block, the value of the intra color difference prediction mode is predicted from the value of the intra luminance prediction mode, and the intra color difference prediction mode cannot be predicted from the intra luminance prediction mode In such a case, 0 (horizontal direction), 1 (horizontal direction), 2 (
The code amount is reduced by using a mechanism for setting any one of (average value) and 3 (45 degrees oblique).

Here, a method for predicting the value of the intra color difference prediction mode from the value of the intra luminance prediction mode and the value of the syntax element related to the intra color difference prediction mode on the decoding side will be described.
FIG. 14 shows a syntax element intra_ch related to the intra color difference prediction mode defined in this embodiment.
It is a conversion table that calculates the value of the intra color difference prediction mode from the value of roma_pred_mode [x0] [y0] and the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal, and using this conversion table, On the decoding side, the value of the intra color difference prediction mode is calculated.
When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0, the value of the intra color difference prediction mode is predicted from the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal according to the color difference format. Is done.

The color difference format is 4: 2: 0 or 4: 4: 4 and the syntax element intra_chroma_pre
When the value of d_mode [x0] [y0] is 0, the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal becomes the value of the intra color difference prediction mode as it is.

The color difference format is 4: 2: 2 and the syntax element intra_chroma_pred_mode [x0] [y0
] Is 0, the intra color difference prediction mode value is calculated according to the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal, using the conversion table shown in FIG. FIG. 15 is a diagram for predicting the value of the intra color difference prediction mode from the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal when the color difference format specified in this embodiment is 4: 2: 2. It is a conversion table.

When the color difference format is 4: 2: 2, when the value of the intra color difference prediction mode is predicted from the value of the intra luminance prediction mode, the value is left as it is as 4: 2: 0 or 4: 4: 4. First, the reason for calculating using the conversion table of FIG. 15 will be described. The color difference format is 4
: 2: 2 shows that the color difference signal is half of the luminance signal in the horizontal direction as shown in FIG.
Is a color difference format sampled at the same density in the vertical direction. Therefore, when intra prediction of a color difference signal is performed in a prediction direction scaled by a factor of two in the horizontal direction with respect to each prediction direction of the intra luminance prediction mode, or a prediction direction in the vicinity thereof, a color difference signal prediction block Is equivalent to or close to equivalent to the intra prediction of the luminance signal of the prediction block at the same position.

This will be described in more detail with reference to FIG. In FIG. 27, the color difference format is 4: 2.
: Is a figure explaining the correspondence of the prediction direction of the intra prediction of the luminance signal in the case of 2, and a color difference signal. In FIG. 27, x indicates the pixel position of the luminance signal, and ◯ indicates the pixel position of the color difference signal. In 4: 2: 2, the color difference signal is sampled (sampled) in half in the horizontal direction with respect to the luminance signal. FIG. 27A shows the sampled pixel positions of the 4: 2: 2 luminance signal and the color difference signal. The code P1 is a pixel that is intra-predicted, and the code P2 is a pixel that is referred to during intra-prediction (actually, since it is filtered, the adjacent pixel is also referred to). Reference numeral 2701
The arrow from the pixel P1 to the pixel P2 shown in FIG. 4 indicates the intra prediction direction of the pixel P1 of the luminance signal.

FIG. 27B shows an array of pixels of the color difference signal sampled by 1/2 in the horizontal direction. Here, in the case of performing the intra prediction of the color difference signal, if the half scaling is not performed in the horizontal direction, the intra prediction direction of the pixel P1 of the color difference signal becomes the arrow direction indicated by reference numeral 2702, and the color difference signal In this pixel arrangement, the pixel P3 is erroneously referred to. However, the correct reference destination is the pixel P2. Therefore, the intra prediction direction of the luminance signal is scaled by a factor of 1/2 in the horizontal direction to obtain the intra prediction direction of the color difference signal, thereby calculating the correct intra prediction direction in the arrangement of the color difference signals as indicated by reference numeral 2703. Then, the pixel adjacent to the upper side which is the correct reference destination in the intra prediction direction is acquired.

In FIGS. 27A and 27B, the case where the pixel adjacent to the upper side of the prediction block is referred to has been described, but the same applies to the case where the pixel adjacent to the left side is referred to. In the case of the pixel adjacent to the left side, the intra prediction direction of the luminance signal is scaled twice in the vertical direction (this is equivalent in terms of obtaining the vector direction by scaling by 1/2 in the vertical direction). Thus, the correct intra prediction direction in the chrominance signal array is calculated, and pixels adjacent to the left, which are the correct reference destinations, are included ahead of the intra prediction direction (including some pixels adjacent to the upper side). .

  Therefore, in the conversion table of FIG. 15, as indicated by the dotted arrows in FIG. 8, the values of the intra luminance prediction modes in which the reference destinations are arranged in the horizontal direction (on the horizontal axis) are 3, 18, 10, 19, 4 , 20, 11, 21, 0, 22, 12, 23, 5, 24, 13, 25, 6, the prediction closest to the prediction direction calculated by scaling them by a factor of 2 in the horizontal direction Select the value of the intra color difference prediction mode for the direction, and set the value of the intra color difference prediction mode to 19, 4, 20, 20, 11, 11, 21, 0, 0, 0, 22, 12, 12, 23, 23, respectively. 5, 24. Scaling the prediction direction of intra prediction by a factor of two in the horizontal direction is equivalent to scaling by a factor of two in the vertical direction. Therefore, when intra prediction of a color difference signal is performed in a prediction direction scaled twice in the vertical direction with respect to each prediction direction of the intra luminance prediction mode or a prediction direction in the vicinity thereof, the same position as the prediction block of the color difference signal It is equivalent to or close to the intra prediction of the luminance signal of the prediction block. Therefore, in the conversion table of FIG. 15, as shown in FIG. When 1, 30, 16, 31, 8, 32, 17, 33, 9 is selected, the value of the intra color difference prediction mode in the prediction direction closest to the prediction direction calculated by scaling twice in the vertical direction is selected. The intra-color difference prediction mode values are 10, 18, 3, 26, 27, 28, 15, 1, 16, 31, 32, 33, 9, 9, 9, 9.

On the other hand, when the color difference format is 4: 2: 0 or 4: 4: 4, when predicting the value of the intra color difference prediction mode from the value of the intra luminance prediction mode, the intra prediction direction of the luminance signal and the intra of the color difference signal are calculated. Since the prediction directions match, it is not necessary to convert the value of the intra luminance prediction mode to the value of the intra color difference prediction mode. This will be described with reference to FIG. FIG.
8 is a diagram for explaining a correspondence relationship between the prediction direction of the luminance signal and the intra prediction of the color difference signal when the color difference format is 4: 2: 0. In FIG. 28A, the color difference format is 4: 2: 0.
In this case, the arrangement of the luminance signal and the color difference signal is shown, and the color difference signal is sampled (sampled) in both horizontal and vertical directions with respect to the luminance signal. Pixel P1 indicated by reference numeral 2704
The arrow from to the pixel P2 indicates the intra prediction direction of the pixel P1 of the luminance signal. In this case, in the color difference signal arrangement shown in FIG. 28B, the intra prediction direction of the luminance signal remains as it is.
As indicated by reference numeral 2705, it is the intra prediction direction of the color difference signal, and it is possible to correctly refer to the reference pixel P2 of the pixel P1 of the color difference signal.

When the intra prediction unit 103 also predicts the value of the intra color difference prediction mode in consideration of the above points, the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal according to the color difference format. To predict the value of the intra color difference prediction mode. That is, when the color difference format is 4: 2: 0 or 4: 4: 4 and the value of the intra color difference prediction mode is predicted, the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal is used as it is. The color difference prediction mode value is used. Color difference format is 4: 2:
15, when the intra color difference prediction mode value is predicted, the intra color difference prediction mode value is set according to the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal, using the conversion table shown in FIG. calculate.

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 1 to 4, the value of the syntax element intra_chroma_pred_mode [x0] [y0] and the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal In combination, the value of the intra color difference prediction mode is calculated.

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 1, the value of the intra color difference prediction mode is 0 or 1 depending on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal. Takes a value.

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 2, the value of the intra color difference prediction mode is 1 or 2 depending on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal. Takes a value.

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 3, the value of the intra color difference prediction mode is 2 or 3, depending on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal. Takes a value.

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 4, the value of the intra color difference prediction mode takes a value of 3.

FIG. 16 shows the syntax element intra_chroma_pred_mode for the intra color difference prediction mode from the value of the intra color difference prediction mode and the prediction block at the same position as the prediction block of the color difference signal, that is, the value of the intra luminance prediction mode of the prediction block of the luminance signal belonging to the same prediction unit. [x0
] [y0] is a conversion table for calculating the value, and the conversion table in FIG. 16 corresponds to the conversion table in FIG. Using the conversion table shown in FIG. 16, the encoding side calculates the value of the syntax element intra_chroma_pred_mode [x0] [y0].

When the value of the intra color difference prediction mode is 0, the syntax element intra_chroma_pred_mo is used according to the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal.
The value of de [x0] [y0] is 0 or 1.

When the value of the intra color difference prediction mode is 1, the syntax element intra_chroma_pred_mo is used according to the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal.
The value of de [x0] [y0] is 0, 1 or 2.

When the value of the intra color difference prediction mode is 2, the syntax element intra_chroma_pred_mo is used according to the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal.
The value of de [x0] [y0] is 0, 2 or 3.

When the value of the intra color difference prediction mode is 3, the syntax element intra_chroma_pred_mo is used according to the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal.
The value of de [x0] [y0] is 0, 3 or 4.

When the value of the intra color difference prediction mode is from 4 to 33, this indicates that the intra color difference prediction mode is predicted from the value of the intra luminance prediction mode of the prediction block at the same position, and the syntax element intra_chroma_pred_mode [x0] [y0] The value is 0. However, when the color difference format is 4: 2: 2 and the value of the intra color difference prediction mode is predicted, the intra prediction unit 10
3, the intra color difference prediction mode value is calculated according to the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal using the conversion table shown in FIG. Values of 4, 5, 9, 10, 11, 12, 15, 16,
Only one of the values 18, 19, 20, 21, 22, 23, 24, 26, 27, 28, 31, 32, and 33 can be taken.

When specifying the prediction block of the luminance signal at the same position as the prediction block of the color difference signal, it may be specified by referring to the division index PartIdx that specifies each prediction block, You may specify by referring the coordinate which shows a position.

In addition, since the number of intra color difference prediction modes of the prediction block in the coding block differs depending on the type of the color difference format supplied from the color difference format setting unit 101, when the color difference format is 4: 2: 0, the coding block The value of the syntax element regarding the intra color difference prediction mode of one prediction block is calculated every time.

Note that the number of intra color difference prediction modes of the prediction block in the coding block differs depending on the combination of the division mode and the color difference format. The value of the syntax element regarding the intra color difference prediction mode of one prediction block is calculated. When the division mode is N × N division and the color difference format is 4: 2: 0, the value of the syntax element related to the intra luminance prediction mode of one prediction block is calculated for each coding block. When the division mode is N × N division and the color difference format is 4: 2: 2, the value of the syntax element related to the intra luminance prediction mode of two prediction blocks is calculated for each coding block. When the division mode is N × N division and the color difference format is 4: 4: 4, the value of the syntax element regarding the intra luminance prediction mode of four prediction blocks is calculated for each coding block.

The inter-prediction information syntax element calculation unit 124 uses the prediction mode (
When PredMode) is inter prediction (MODE_INTER), a value of a syntax element related to inter prediction information in units of prediction blocks is calculated, and the calculated value of each syntax element is supplied to the entropy encoding unit 126. The inter prediction information in units of prediction blocks includes information such as an inter prediction mode (L0 prediction, L1 prediction, bi-prediction), an index for specifying a plurality of reference images, and a motion vector.

The entropy encoding unit 126
A value of a syntax element related to encoding information in units of encoding blocks supplied from the syntax element calculation unit 121 related to encoding information in units of encoding blocks;
A value of a syntax element related to the intra luminance prediction mode of the prediction block of the luminance signal supplied from the syntax element calculation unit 122 related to the intra luminance prediction mode;
Prediction block unit supplied from the syntax element calculation unit 124 of the inter prediction information and the value of the syntax element related to the intra color difference prediction mode of the prediction block of the color difference signal supplied from the syntax element calculation unit 123 related to the intra color difference prediction mode The value of the syntax element related to the inter prediction information is entropy-encoded according to a predetermined syntax rule. At this time, the intra prediction mode encoding control unit 125 controls the order of the entropy encoding of the intra luminance prediction mode and the intra color difference prediction mode according to the division mode and the color difference format, and the entropy encoding unit 126 performs the intra prediction mode. Entropy encoding processing of the intra luminance prediction mode and the intra color difference prediction mode is performed in the order instructed by the encoding control unit 125.

The order of entropy encoding in the intra luminance prediction mode and the intra color difference prediction mode in the N × N division in the entropy encoding unit 126 controlled by the intra prediction mode encoding control unit 125 will be described. FIG. 17 is a diagram illustrating entropy encoding or decoding order of syntax elements related to the intra luminance prediction mode and the intra color difference prediction mode according to the embodiment. FIGS. 17 (a), 17 (b), and 17 (c) show entropy encoding and decoding orders when the color difference format is 4: 2: 0, 4: 2: 2, and 4: 4: 4, respectively. . L0, L1, L2, and L3 have luminance signal division indexes PartIdx of 0,
This indicates that the syntax element is related to the intra luminance prediction modes 1, 2, and 3, and C0
, C1, C2, and C3 indicate that the division index PartIdx of the chrominance signal is a syntax element related to the intra chrominance prediction mode of the prediction blocks of 0, 1, 2, and 3, respectively.

When the color difference format is 4: 2: 0, C0 is encoded immediately after L0 is encoded, and then L1, L2, and L3 are encoded. (C1, C2, and C3 do not exist and are not encoded.)

When the color difference format is 4: 2: 2, L0 is encoded, C0 is encoded immediately after L0, subsequently L1 and L2 are encoded, C2 is encoded immediately after L2, and then L3 is encoded. (C1 and C3 do not exist and are not encoded.)

When the color difference format is 4: 4: 4, L0 is encoded, C0 is encoded immediately after L0, and subsequently encoded in the order of L1, C1, L2, C2, L3, and C3.

That is, the inter luminance prediction mode and the intra color difference prediction mode belonging to the same prediction unit are continuously encoded.

  When entropy encoding is performed in the encoding order shown in FIG. 17, there are the following advantages.

The first advantage is that the processing is simple when the value of the intra color difference prediction mode is calculated from the value of the syntax element related to the intra color difference prediction mode obtained by entropy decoding of the encoded bit string on the decoding side. Can be raised.

In the encoding order shown in FIG. 17, the intra color difference is always referred to by referring to the value of the intra prediction mode calculated from the syntax element regarding the intra luminance prediction mode encoded immediately before regardless of the prediction mode, the division mode, and the color difference format. The prediction mode is calculated, and the process can be simplified.

As a second advantage, when the prediction mode is intra prediction and the division mode is N × N division,
It is possible to increase the delay time of a series of processes related to the intra prediction of the color difference signal prediction block on the decoding side.

In the coding order shown in FIG. 17, the prediction block of the color difference signal at the same position as the prediction block of the luminance signal belonging to the same prediction unit immediately after entropy encoding the syntax element L0 related to the intra luminance prediction mode of the prediction block of the luminance signal. By encoding the syntax element C0 related to the intra color difference prediction mode of the current image by entropy coding, the decoding side is the same as the prediction block of the luminance signal immediately after entropy decoding the syntax element L0 related to the intra luminance prediction mode of the prediction block of the luminance signal. Since the syntax element C0 related to the intra color difference prediction mode of the prediction block of the position color difference signal can be entropy-decoded and the calculation of the intra color difference prediction mode can be started early, the subsequent intra prediction process of the color difference signal is also accelerated. To start Can be, when processing intra prediction of the prediction blocks of the intra prediction and the color difference signal of the prediction block of the luminance signal in parallel, can be shortened delay time of each process regarding color difference signals. Note that the color difference format is 4: 2: 2 or 4: 4:
In the case of 4, the partition index PartIdx that refers to the decoded signal of the prediction block of the chrominance signal whose division index PartIdx is 0 by early starting the intra prediction process of the prediction block of the chrominance signal whose division index PartIdx is 0 corresponding to C0. Can start intra prediction processing of prediction blocks other than 0 earlier. Note that the syntax element L0 related to the intra luminance prediction mode is encoded on the decoding side by encoding the syntax element C0 related to the intra color difference prediction mode before the syntax element L1 related to the intra luminance prediction mode.
Although the start of the entropy decoding process of 1, L2, and L3 is delayed, in order to start the intra prediction process of the prediction block corresponding to L1, a series of decoding processes related to the prediction block corresponding to L0 referred to in the intra prediction Since it is necessary to complete (intra prediction, inverse quantization, inverse orthogonal transform), there is almost no demerit of delaying entropy decoding of L1, L2, and L3.

Next, with respect to the decoding process of the encoded information in units of the encoded block and the prediction block performed in the second encoded bit string decoding unit 203 in FIG. Explained. FIG. 13 shows the second encoded bit string decoding unit 2 in FIG.
3 is a block diagram showing the configuration of 03. FIG.

As illustrated in FIG. 13, the second coded bit string decoding unit 203 in FIG. 2 includes an intra prediction mode decoding control unit 221, an entropy decoding unit 222, a coding information calculation unit 223 for each coding block, an intra luminance prediction mode. Calculation unit 224, intra color difference prediction mode calculation unit 225
The inter prediction information calculation unit 226 is configured. Second encoded bit string decoding unit 20
3, processing corresponding to the color difference format information supplied from the color difference format management unit 205 is performed, and processing corresponding to encoding information such as a prediction mode and a division mode for each encoding block is performed. Is called.

The entropy decoding unit 222 is a coding block supplied from the coding bit string separation unit,
And entropy decoding of a coded bit string including coding information in units of prediction blocks in accordance with a predetermined syntax rule, values of syntax elements relating to coding information in units of coding blocks, and intra luminance prediction modes of prediction blocks of luminance signals The value of the syntax element for the
The value of the syntax element regarding the intra color difference prediction mode of the prediction block of the color difference signal and the value of the syntax element regarding the inter prediction information in units of prediction blocks are obtained. At that time, the intra prediction mode decoding control unit 221 controls the order of the entropy decoding of the intra luminance prediction mode and the intra color difference prediction mode according to the division mode and the color difference format, and the entropy decoding unit 222 controls the intra prediction mode decoding control unit. The entropy decoding process of the intra luminance prediction mode and the intra color difference prediction mode is performed in the order instructed in 221. The intra prediction mode decoding control unit 221 is a control unit corresponding to the intra prediction mode coding control unit 125 on the coding side, and is set by the intra prediction mode coding control unit 125 according to the division mode and the color difference format. The decoding order of the intra prediction mode that is the same as the encoding order of is set, and the decoding order of the intra prediction mode of the entropy decoding unit 222 is controlled.
The entropy decoding unit 222 is a decoding unit corresponding to the encoding-side entropy encoding unit 126, and performs entropy decoding processing according to the same rules as the syntax rules used in the entropy encoding unit 126. That is, the intra prediction mode decoding process is performed in the same order as the encoding order shown in FIG. That is, the inter luminance prediction mode and the intra color difference prediction mode belonging to the same prediction unit are successively decoded.

The value of the syntax element relating to the coding information in units of coding blocks obtained by decoding is supplied to the coding information calculation unit 223 in units of coding blocks, and the syntax elements relating to the intra luminance prediction mode of the prediction block of the luminance signal The value is an intra luminance prediction mode calculation unit 224.
The value of the syntax element related to the intra color difference prediction mode calculation unit 225 of the prediction block of the color difference signal is supplied to the intra color difference prediction mode calculation unit 225, and the value of the syntax element related to the inter prediction information for each prediction block is calculated as the inter prediction information. To the unit 226.

The coding information calculation unit 223 for each coding block calculates coding information for each coding block from the value of the syntax element related to the supplied coding information for each coding block,
This is supplied to the intra prediction unit 206 or the inter prediction unit 207 via the switch 212.

The coding information calculation unit 223 for each coding block is a coding information calculation unit corresponding to the syntax element calculation unit 121 related to coding information for each coding block on the coding side, and calculates according to the same semantic rule. Intra prediction of coded block (MODE_INTRA)
Alternatively, a value related to the prediction mode (PredMode) for determining the inter prediction (MODE_INTER) and the partition mode (PartMode) for determining the shape of the prediction block are calculated by the encoding information calculation unit 223 for each encoding block.

The intra luminance prediction mode calculation unit 224 is a coding information calculation unit 22 for each coding block.
The prediction mode (PredMode) of the coding block calculated in step 3 is intra prediction (MODE_INTRA)
In this case, the intra luminance prediction mode of the prediction block of the luminance signal is calculated from the value of the syntax element related to the intra luminance prediction mode of the prediction block of the supplied luminance signal, and is supplied to the intra color difference prediction mode calculation unit 225. This is supplied to the intra prediction unit 206 via the switch 212. The intra luminance prediction mode calculation unit 224 is an encoding information calculation unit corresponding to the syntax element calculation unit 122 related to the intra luminance prediction mode on the encoding side,
Calculate according to the same semantic rules. The syntax element related to the intra luminance prediction mode is a syntax element prev_intra_luma_pred_flag [x0] [y0], which is a flag indicating whether prediction can be performed from the intra luminance prediction mode of surrounding blocks, and a syntax that is an index indicating the prediction block of the prediction source Element mpm_idx [x0] [y0] and a syntax element rem_intra_luma_pred_mode indicating an intra luminance prediction mode in units of prediction blocks
[x0] [y0]. In the calculation of the intra luminance prediction mode, using the correlation with the intra luminance prediction mode of the surrounding blocks stored in the encoded information storage memory 210,
The syntax element prev_intra_luma_pred_flag [x0] [y0], which is a flag indicating that the value is used when prediction is possible from the intra-brightness prediction mode of the surrounding block, is 1 (true), and indicates the prediction block of the prediction source The syntax element mpm_ that is the index
The intra luminance prediction mode of the surrounding prediction block indicated by idx [x0] [y0] is set as the intra luminance prediction mode of the prediction mode. Syntax element prev_intra_luma_pred
When _flag [x0] [y0] is 0 (false), the syntax element re indicating the decoded intra luminance prediction mode is used instead of predicting the intra luminance prediction mode from the surrounding prediction blocks.
The intra luminance prediction mode is calculated from the value of m_intra_luma_pred_mode [x0] [y0].

In addition, when the number of intra luminance prediction modes of the prediction block in the coding block differs according to the division mode, and the division mode is 2N × 2N division, the intra luminance prediction mode of one set of prediction blocks for each coding block. When the division mode is N × N division, the value of the intra luminance prediction mode of four sets of prediction blocks is calculated for each coding block.

The intra color difference prediction mode calculation unit 225 is a coding information calculation unit 22 for each coding block.
The prediction mode (PredMode) of the coding block calculated in step 3 is intra prediction (MODE_INTRA)
In this case, the intra color difference from the value of the syntax element intra_chroma_pred_mode [x0] [y0] and the intra luminance prediction mode value supplied from the intra luminance prediction mode calculation unit regarding the intra color difference prediction mode of the prediction block of the supplied color difference signal The prediction mode value is calculated and supplied to the intra prediction unit 206 via the switch 212. The intra color difference prediction mode calculation unit 225 is an encoding information calculation unit corresponding to the syntax element calculation unit 123 related to the intra color difference prediction mode on the encoding side, and calculates according to the same semantic rule. In the calculation of the value of the intra color difference prediction mode, the correlation between the prediction block of the luminance signal at the same position as the prediction block of the color difference signal and the intra luminance prediction mode of the prediction block is used. When it is determined that the prediction can be made from the intra luminance prediction mode of the prediction block of the luminance signal at the same position as the prediction block of the current image, the value of the intra color difference prediction mode is predicted from the value of the intra luminance prediction mode, and the prediction is performed from the intra luminance prediction mode. If it is determined that it is better to set a unique value for the intra color difference prediction mode than 0 (horizontal direction), 1 (horizontal direction), 2 ( The code amount is reduced by using a mechanism for setting any one of (average value) and 3 (45 degrees oblique).

FIG. 14 is a conversion table for calculating the value of the intra color difference prediction mode from the value of the syntax element intra_chroma_pred_mode [x0] [y0] and the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal. The intra color difference prediction mode value is calculated using the conversion table. The intra luminance prediction mode refers to the intra luminance prediction mode calculated from the value of the syntax element related to the intra luminance prediction mode decoded immediately before in the decoding order. By performing encoding and decoding in the encoding or decoding order of FIG. 17, it is easy to specify the intra luminance prediction mode to be referred to. Also, as described on the encoding side, when the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0, the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal according to the color difference format The value of the intra color difference prediction mode is predicted from the value of. If the color difference format is 4: 2: 0 or 4: 4: 4 and the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0,
The value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal becomes the value of the intra color difference prediction mode as it is. When the color difference format is 4: 2: 2 and the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0, the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal is converted according to the conversion table shown in FIG. From this value, the value of the intra color difference prediction mode is calculated. FIG. 15 is a diagram for predicting the value of the intra color difference prediction mode from the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal when the color difference format specified in this embodiment is 4: 2: 2. It is a conversion table.

When the prediction mode (PredMode) of the coding block is inter prediction (MODE_INTER), the inter prediction information calculation unit 226 calculates inter prediction information from the value of the syntax element related to the inter prediction information in units of prediction blocks, and calculates The value of the inter prediction information is supplied to the inter prediction unit 207 via the switch 212. The inter prediction information calculation unit 226 is a coding information calculation unit corresponding to the syntax element calculation unit 124 of the inter prediction information on the coding side, and calculates according to the same semantic rule. The calculated inter prediction information for each prediction block includes information such as an inter prediction mode (L0 prediction, L1 prediction, bi-prediction), an index for specifying a plurality of reference images, and a motion vector.

Next, syntax rules used in the present embodiment will be described focusing on points related to the intra prediction mode that is a feature of the embodiment. FIG. 18 is an example of a syntax rule for encoding and decoding encoding information in units of encoding blocks used in the entropy encoding unit 126 on the encoding side and the entropy decoding unit 222 on the decoding side. It is an example of the syntax rule for encoding and decoding of the encoding information of the prediction unit used in the entropy encoding unit 126 on the encoding side and the entropy decoding unit 222 on the decoding side.
In FIG. 18, x0 and y0 are coordinates indicating the position of the encoded block. 18 is an encoding block unit, and when the partition mode (PartMode) is 2N × 2N partition (PART_2Nx2N), according to the syntax rule shown in FIG. 19, the entropy encoding of the encoding information of one set of prediction units, or It shows that entropy decoding is performed. Furthermore, when the partition mode (PartMode) is N × N partition (PART_NxN), it indicates that entropy encoding or entropy decoding of the encoded information of four sets of prediction units is performed according to the syntax rule shown in FIG. ing.

FIG. 19 shows a syntax rule for encoding the encoding information of the prediction unit. X0 in FIG.
, And y0 are coordinates indicating the position of the prediction unit and the prediction block in the luminance signal. FIG.
9 indicates a prediction block unit, and when the prediction mode (PredMode) is intra prediction (MODE_INTRA), entropy coding or entropy decoding of syntax elements related to a set of prediction block unit intra luminance prediction modes is performed. ing. Prediction mode (PredMo
de) is intra prediction (MODE_INTRA), prev_intra_luma_pred_flag [x0] [y0
] Entropy coding or entropy decoding of the syntax element prev_intra
When _luma_pred_flag [x0] [y0] is 1 (true), the syntax element mpm_idx [x0] [y0]
Entropy coding or entropy decoding of the syntax element prev_intra_
If luma_pred_flag [x0] [y0] is 0 (false), the syntax element rem_intra_luma_pred_
Entropy encoding or entropy decoding of mode [x0] [y0] is performed.

Furthermore, it shows that entropy encoding or entropy decoding of the syntax element intra_chroma_pred_mode [x0] [y0] regarding the intra color difference prediction mode is performed according to the color difference format and the division index PartIdx. ChromaArrayType is a variable indicating a color difference format, and 0 is monochrome (originally includes 4: 4: 4 and includes a mode in which a luminance signal and a color difference signal are independently encoded, but in this case, it is regarded as monochrome). 1 is 4: 2.
: 0, 2 represents 4: 2: 2, 3 represents 4: 4: 4.

The color difference format is 4: 2: 0, 4: 2: 2, or 4: 4: 4 (ChromaArrayType
The division index PartIdx is 0, or the color difference format is 4: 2: 2 (Chr
omaArrayType is 2), split index PartIdx is 2, or color difference format is 4: 4
: Indicates that entropy coding or entropy decoding of the syntax element intra_chroma_pred_mode [x0] [y0] related to the intra color difference prediction mode in units of prediction blocks is performed when any of 4 (ChromaArrayType is 3) is satisfied Yes. That is, when the color difference format is 4: 2: 0, only when the division index PartIdx is 0, the entropy of the syntax element related to the inter color difference prediction mode whose division index PartIdx is 0 immediately after the syntax element related to the inter luminance prediction mode. When the coding or entropy decoding is performed and the color difference format is 4: 2: 2, the interleave of the same split index PartIdx is immediately after the syntax element related to the inter luminance prediction mode only when the split index PartIdx is 0 or 2. Entropy coding or entropy decoding of syntax elements related to the color difference prediction mode is performed, and when the color difference format is 4: 4: 4, the division index PartIdx is 0, 1, 2, 3 Syntax element It shows the same entropy coding syntax elements related to inter chrominance prediction mode division index PartIdx, or be carried out entropy decoding immediately. In the case of 2N × 2N partition (PART_2Nx2N), this corresponds to the case where the partition index PartIdx is 0, and the syntax element related to the inter color difference prediction mode whose partition index PartIdx is 0 immediately after the syntax element related to the inter luminance prediction mode. Entropy encoding or entropy decoding is performed.

Next, the processing procedure of the encoding process of the encoded block and the encoded information performed in the second encoded bit string generation unit 113 in FIG. 1 is changed to the intra prediction mode that is the feature of the embodiment. The explanation will focus on the points involved. FIG. 20 is a flowchart for explaining a processing procedure of coding processing in units of prediction blocks and prediction blocks performed by the second encoded bit string generation unit 113 in FIG.

First, on the encoding side, a syntax element calculation unit 121 for encoding information in units of encoding blocks calculates values of syntax elements related to encoding information including a prediction mode and a division mode of the encoding block, and entropy encoding is performed. Entropy coding is performed by the unit 126 (S
1001). Subsequently, the prediction mode (PredMode) of the coded block is set to intra prediction (MODE_I
If it is not (NTRA) (NO in S1002), the process proceeds to step S1016, where the syntax element calculation unit 124 for inter prediction information calculates the value of the syntax element for inter prediction for each prediction block according to the division mode, and performs entropy coding. Entropy encoding is performed by the unit 126 (S1016), and this encoding process is terminated. Prediction mode of coding block (
If PredMode) is intra prediction (MODE_INTRA) (YES in S1002), step S1
It progresses to the encoding process of intra prediction mode after 003.

Subsequently, when the prediction mode of the coding block is intra prediction, the syntax element calculation unit 122 and the entropy coding unit 126 regarding the intra luminance prediction mode perform intra luminance prediction of a prediction block whose luminance signal division index PartIdx is 0 A mode encoding process is performed (S1003).

Here, the encoding process procedure of the intra luminance prediction mode of the prediction block of the luminance signal performed by the syntax element calculation unit 122 and the entropy encoding unit 126 regarding the intra luminance prediction mode will be described with reference to the flowchart of FIG. FIG. 21 is a flowchart illustrating the coding process procedure of the intra luminance prediction mode of the prediction block of the luminance signal performed by the syntax element calculation unit 122 and the entropy coding unit 126 regarding the intra luminance prediction mode. First, the syntax element calculation unit 12 related to the intra luminance prediction mode.
2, the value of each syntax element relating to the intra luminance prediction mode of the prediction block of the luminance signal is calculated (S1101). At this time, the value of the intra luminance prediction mode is compared with the intra luminance prediction mode of the surrounding blocks, and when there is a prediction block having the same value, the value of the syntax element prev_intra_luma_pred_flag [x0] [y0] is 1 (true) If the value specifying the reference destination is set in the syntax element mpm_idx [x0] [y0] that is an index that points to the prediction block of the prediction source, and there is no prediction block with the same value, the syntax element The value of prev_intra_luma_pred_flag [x0] [y0] is set to 0 (false), and the value specifying the intra luminance prediction mode is set to the syntax element rem_intra_luma_pred_mode [x0] [y0] indicating the intra luminance prediction mode. Subsequently, the entropy encoding unit 126 performs entropy encoding on the value of each syntax element related to the intra luminance prediction mode of the prediction block of the luminance signal (S1102), and the present encoding process ends. In addition, the encoding process procedure of FIG.
This is a common encoding process procedure used in step S1007, step S1010, and step S1013 in addition to step S1003 in FIG.

Again, referring back to FIG. 20, the color difference format is 4: 2: 0, 4: 2: 2 or 4: 4.
: 4 (YES in S1004), the syntax element calculation unit 123 related to the intra color difference prediction mode and the entropy coding unit 126 use the color index difference index PartIdx.
The encoding process of the intra color difference prediction mode of the prediction block with 0 is performed (S1005). If the color difference format is not 4: 2: 0, 4: 2: 2, or 4: 4: 4, that is, if the color difference format is monochrome (NO in S1004), there is no prediction block for the color difference signal, so the step Skipping S1005, the process proceeds to the next step S1006.

Here, the encoding process procedure of the intra color difference prediction mode of the prediction block of the color difference signal performed by the syntax element calculation unit 123 and the entropy encoding unit 126 regarding the intra color difference prediction mode will be described with reference to the flowchart of FIG. FIG. 22 is a flowchart illustrating the coding process procedure of the intra color difference prediction mode of the prediction block of the color difference signal performed by the syntax element calculation unit 123 and the entropy coding unit 126 regarding the intra color difference prediction mode. First, the syntax element calculation unit 12 related to the intra color difference prediction mode.
3, the value of each syntax element relating to the intra color difference prediction mode of the prediction block of the color difference signal is calculated (S1201). At this time, the syntax element intra_chroma_pred_mo regarding the intra color difference prediction mode is calculated using the conversion table shown in FIG. 16 from the value of the intra color difference prediction mode and the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal.
Calculate the value of de [x0] [y0]. Subsequently, the entropy encoding unit 126 performs entropy encoding on the value of each syntax element related to the intra color difference prediction mode of the prediction block of the color difference signal (S1202), and the present encoding process ends. Note that the encoding processing procedure of FIG.
This is a common encoding process procedure used in step S1009, step S1012, and step S1015 in addition to step S1005 of 0.

Returning to FIG. 20 again, when the coding block division mode is not N × N division, that is, when the division mode is 2N × 2N (NO in S1006), the division index PartIdx
Since there is only a prediction block of 0 and there is no intra prediction mode to be encoded any more, the present encoding process is terminated.

On the other hand, when the division mode of the encoded block is N × N division (YES in S1006), the process proceeds to the intra prediction mode encoding process for a prediction block whose division index PartIdx is greater than zero. First, in the encoding process procedure of FIG. 21, the encoding process of the intra luminance prediction mode of the prediction block whose luminance signal division index PartIdx is 1 is performed (S1007). Subsequently, when the color difference format is 4: 4: 4 (YES in S1008), the encoding process of FIG. 22 performs the encoding process in the intra color difference prediction mode of the prediction block having the color difference signal division index PartIdx of 1 ( S1009). When the color difference format is not 4: 4: 4, that is, when the color difference format is 4: 2: 0, 4: 2: 2, or monochrome (NO in S1008).
Since there is no prediction block having the color difference signal division index PartIdx of 1, the process skips step S1009 and proceeds to the next step S1010.

Subsequently, in the encoding process procedure of FIG. 21, the encoding process of the intra luminance prediction mode of the prediction block whose luminance signal division index PartIdx is 2 is performed (S1010). Subsequently, when the color difference format is 4: 2: 2 or 4: 4: 4 (YES in S1011), the intra color difference prediction mode of the prediction block having the color difference signal division index PartIdx of 2 in the encoding processing procedure of FIG. Encoding processing is performed (S1012). The color difference format is 4: 2: 2 or 4
: If not 4: 4, that is, if the color difference format is 4: 2: 0 or monochrome (
(NO in S1011), since there is no prediction block having a color difference signal division index PartIdx of 2, skip step S1012 and proceed to the next step S1013.
Subsequently, the encoding process procedure of FIG. 21 performs the encoding process of the intra luminance prediction mode of the prediction block whose luminance signal division index PartIdx is 3 (S1013). Subsequently, when the color difference format is 4: 4: 4 (YES in S1014), the encoding process of FIG. 22 performs the encoding process of the intra color difference prediction mode of the prediction block having the color difference signal division index PartIdx of 3 ( S1015). When the color difference format is other than 4: 4: 4, that is, when the color difference format is 4: 2: 0, 4: 2: 2 or monochrome (NO in S1014),
Since there is no prediction block having the color difference signal division index PartIdx of 3, step S
Step 1015 is skipped and the encoding process is terminated.

According to this encoding process, the intra luminance prediction mode and the intra color difference prediction mode belonging to the same prediction unit are sequentially encoded in the order shown in FIG. 17, and the decoding is performed immediately before the calculation of the intra color difference prediction mode on the decoding side. Since the calculation process is performed by referring to the calculated intra luminance prediction mode, decoding of the intra color difference mode is performed at an optimal timing while improving the coding efficiency of the intra color difference mode by referring to the intra luminance prediction mode. Processing can be performed.

Next, the processing procedure of decoding processing of encoded information in units of prediction blocks and prediction blocks performed in the second encoded bit string decoding unit 203 in FIG. 2 relates to the intra prediction mode that is a feature of the embodiment. The explanation will focus on the points. FIG. 23 is a flowchart for explaining a processing procedure of decoding processing in units of encoded blocks and prediction blocks performed by the second encoded bit string decoding unit 203 in FIG. 2.

First, on the decoding side, the entropy decoding unit 222 entropy-decodes the encoded bit string to obtain the value of the syntax element related to the encoded information including the prediction mode and the division mode of the encoded block (S2001). The encoding information value including the prediction mode and the division mode of the encoded block is calculated from the value of each syntax element decoded by the encoding information calculation unit 223. Subsequently, when the prediction mode (PredMode) of the encoded block is not intra prediction (MODE_INTRA) (NO in S2002), the process proceeds to step S2016, where entropy decoding is performed by the entropy decoding unit 222, and inter prediction is performed for each prediction block according to the division mode. A value of a syntax element related to information is obtained, and the inter prediction information calculation unit 226 calculates the value of inter information for each prediction block according to the division mode (S2016), and the decoding process ends. When the prediction mode (PredMode) of the encoded block is intra prediction (MODE_INTRA) (YES in S2002), the process proceeds to decoding processing in intra prediction mode in step S2003 and subsequent steps.

Subsequently, when the prediction mode of the encoded block is intra prediction, the entropy decoding unit 2
22 and the luminance index division index PartIdx in the intra luminance prediction mode calculation unit 224
The decoding process of the intra-brightness prediction mode of the prediction block with 0 is performed (S2003).

Here, the decoding process procedure of the intra luminance prediction mode of the prediction block of the luminance signal performed by the entropy decoding unit 222 and the intra luminance prediction mode calculation unit 224 will be described with reference to the flowchart of FIG. FIG. 24 is a flowchart illustrating the decoding process procedure of the intra luminance prediction mode of the prediction block of the luminance signal performed by the entropy decoding unit 222 and the intra luminance prediction mode calculation unit 224. First, the entropy decoding unit 222 performs entropy decoding on the encoded bit string, and obtains the value of each syntax element related to the intra luminance prediction mode of the prediction block of the luminance signal (S2101). Subsequently, the intra luminance prediction mode calculation unit 224 of the intra luminance prediction mode calculates the value of the intra luminance prediction mode of the prediction block of the luminance signal from the value of each syntax element decoded in step S2101 (S2102). ). In this case, the syntax element prev_intra_luma_pred_flag [x0] [y0
] Is 1 (true), the intra luminance prediction mode of the surrounding prediction block indicated by the syntax element mpm_idx [x0] [y0], which is an index indicating the prediction block of the prediction source, is predicted. The mode is the intra luminance prediction mode. Syntax element prev_i
When the value of ntra_luma_pred_flag [x0] [y0] is 0 (false), the intra luminance prediction mode is calculated from the value of the syntax element rem_intra_luma_pred_mode [x0] [y0] indicating the intra luminance prediction mode, and this decoding process is terminated. To do. Note that the decoding processing procedure in FIG. 24 includes steps S2007, S2010, and S201 in addition to step S2003 in FIG.
3 is a common decryption processing procedure used in FIG.

Returning to FIG. 23 again, the color difference format is 4: 2: 0, 4: 2: 2 or 4: 4.
: 4 (YES in S2004), the entropy decoding unit 222 and the intra chrominance prediction mode calculation unit 225 perform the decoding process of the intra chrominance prediction mode of the prediction block whose division index PartIdx of the chrominance signal is 0 (S2005). Note that the color difference format is 4: 2:
If it is not 0, 4: 2: 2, or 4: 4: 4, that is, if the color difference format is monochrome (NO in S2004), there is no color difference signal prediction block, so step S20.
05 is skipped and the process proceeds to the next step S2006.

Here, the decoding process procedure of the intra color difference prediction mode of the prediction block of the color difference signal performed by the entropy decoding unit 222 and the intra color difference prediction mode calculation unit 225 will be described with reference to the flowchart of FIG. FIG. 25 is a flowchart illustrating the decoding process procedure of the intra color difference prediction mode of the prediction block of the color difference signal performed by the entropy decoding unit 222 and the intra color difference prediction mode calculation unit 225. First, the entropy decoding unit 222 performs entropy decoding on the encoded bit string to obtain the value of the syntax element intra_chroma_pred_mode [x0] [y0] regarding the intra color difference prediction mode of the prediction block of the color difference signal (S2201).
Subsequently, the intra color difference prediction mode calculation unit 225 calculates the value of the intra color difference prediction mode of the prediction block of the color difference signal (S2202). Here, the intra color difference prediction mode calculation unit 2
The calculation process procedure of the intra color difference prediction mode of the prediction block of the color difference signal performed in 25 will be described using the flowchart of FIG. FIG. 26 is a flowchart showing the calculation processing procedure of the intra color difference prediction mode performed in step S2202 of FIG. First, the syntax element intra_chroma_p for the intra color difference prediction mode of the prediction block of the color difference signal
It is determined whether the value of red_mode [x0] [y0] is 0 (S2301). If the value is 0 (S230)
1 YES), the process proceeds to step S2302. Color difference format is 4: 2: 0 or 4: 4
: 4 (YES in S2302), the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal is used as it is as the value of the intra color difference prediction mode (step S2303), and this calculation process is terminated. On the other hand, the color difference format is 4: 2: 0 or 4
: 4: 4, that is, 4: 2: 2 (NO in S2302), the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal is calculated based on the conversion table shown in FIG. The value of the color difference prediction mode is calculated (step S2304), and this calculation process ends. On the other hand, if the value of intra_chroma_pred_mode [x0] [y0] is non-zero, (S
2301), using the conversion table of FIG. 14, the value of the intra luminance prediction mode is converted to the value of the intra color difference prediction mode (step S2305), and this calculation process is terminated. At this time, the value of the syntax element intra_chroma_pred_mode [x0] [y0] related to the intra color difference prediction mode decoded in step S2201 and the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal, that is, the latest step The value of the syntax element is calculated using the conversion table shown in FIG. 14 from the value of the intra luminance prediction mode calculated in step 1, and the decoding process is terminated. Note that the decryption processing procedure in FIG. 25 is the same as step S20 in FIG.
In addition to 05, this is a common decoding processing procedure used in step S2009, step S2012, and step S2015.

Returning to FIG. 23 again, when the division mode of the encoded block is not N × N division, that is, when the division mode is 2N × 2N (NO in S2006), the division index PartIdx
Since there is only a prediction block with 0, there is no intra prediction mode to decode any more,
The decryption process ends.

On the other hand, when the division mode of the encoded block is N × N division (YES in S2006), the process proceeds to the decoding process in the intra prediction mode of the prediction block in which the division index PartIdx is greater than zero. First, the decoding process procedure of FIG. 24 performs the decoding process of the intra luminance prediction mode of the prediction block whose luminance signal division index PartIdx is 1 (S2007). Subsequently, when the color difference format is 4: 4: 4 (YES in S2008), the decoding process of the intra color difference prediction mode of the prediction block having the division index PartIdx of 1 is performed according to the processing procedure of FIG. 25 (S
2009). When the color difference format is not 4: 4: 4, that is, when the color difference format is 4: 2: 0, 4: 2: 2 or monochrome (NO in S2008), the prediction block whose color difference signal division index PartIdx is 1 is Since it does not exist, step S2009 is skipped and the process proceeds to next step S2010.

Subsequently, the decoding process of the intra luminance prediction mode of the prediction block having the luminance signal division index PartIdx of 2 is performed in the processing procedure of FIG. 24 (S2010). Subsequently, when the chrominance format is 4: 2: 2 or 4: 4: 4 (YES in S2011), the decoding process of the intra chrominance prediction mode of the prediction block having the chrominance signal division index PartIdx of 2 in the processing procedure of FIG. (S2012). If the color difference format is neither 4: 2: 2 or 4: 4: 4, that is, if the color difference format is 4: 2: 0 or monochrome (NO in S2011)
) Since there is no prediction block having a color difference signal division index PartIdx of 2, the process skips step S2012 and proceeds to the next step S2013.

Subsequently, the decoding process of the intra luminance prediction mode of the prediction block having the luminance signal division index PartIdx of 3 is performed in the processing procedure of FIG. 24 (S2013). Subsequently, when the color difference format is 4: 4: 4 (YES in S2014), the decoding process of the intra color difference prediction mode of the prediction block in which the color difference signal division index PartIdx is 3 is performed by the processing procedure of FIG. 25 (S20).
15). When the color difference format is other than 4: 4: 4, that is, when the color difference format is 4: 2: 0, 4: 2: 2 or monochrome (NO in S2014), a prediction block whose division index PartIdx of the color difference signal is 3 Since step S2015 does not exist, step S2015 is skipped and the decoding process is terminated.

According to the present decoding process, the intra luminance prediction mode and the intra color difference prediction mode belonging to the same prediction unit are sequentially decoded in the order shown in FIG. 17, and are decoded and calculated immediately before the calculation of the intra color difference prediction mode. Since the calculation process is performed by referring to the intra luminance prediction mode, the decoding process of the intra color difference mode can be performed at an optimal timing while improving the coding efficiency of the intra color difference mode by referring to the intra luminance prediction mode. it can.

The moving image encoded stream output from the moving image encoding apparatus of the embodiment described above has a specific data format so that it can be decoded according to the encoding method used in the embodiment. Therefore, the moving picture decoding apparatus corresponding to the moving picture encoding apparatus can decode the encoded stream of this specific data format.

When a wired or wireless network is used to exchange an encoded stream between a moving image encoding device and a moving image decoding device, the encoded stream is converted into a data format suitable for the transmission form of the communication path. It may be transmitted. In that case, a video transmission apparatus that converts the encoded stream output from the video encoding apparatus into encoded data in a data format suitable for the transmission form of the communication channel and transmits the encoded data to the network, and receives the encoded data from the network Then, a moving image receiving apparatus that restores the encoded stream and supplies the encoded stream to the moving image decoding apparatus is provided.

The moving image transmitting apparatus is a memory that buffers the encoded stream output from the moving image encoding apparatus, a packet processing unit that packetizes the encoded stream, and transmission that transmits the packetized encoded data via the network. Part. The moving image receiving apparatus generates a coded stream by packetizing the received data, a receiving unit that receives the packetized coded data via a network, a memory that buffers the received coded data, and packet processing. And a packet processing unit provided to the video decoding device.

The above processing relating to encoding and decoding can be realized as a transmission, storage, and reception device using hardware, and is stored in a ROM (Read Only Memory), a flash memory, or the like. It can also be realized by firmware or software such as a computer. The firmware program and software program can be recorded on a computer-readable recording medium, provided from a server through a wired or wireless network, or provided as a data broadcast of terrestrial or satellite digital broadcasting Is also possible.

The present invention has been described based on the embodiments. The embodiments are exemplifications, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. .

101 color difference format setting unit, 102 image memory, 103 intra prediction unit, 104 inter prediction unit, 105 coding method determination unit, 106 residual signal generation unit, 107 orthogonal transform / quantization unit, 108 inverse quantization / inverse orthogonal transform , 109 decoded image signal superimposing unit, 110 encoded information storage memory, 111 decoded image memory, 11
2 1st encoding bit stream production | generation part, 113 2nd encoding bit stream production | generation part, 114
A third encoded bit sequence generation unit; 115 an encoded bit sequence multiplexing unit; 121 a syntax element calculation unit of encoding information in units of encoded blocks; 122 an intra luminance prediction mode syntax element calculation unit; and 123 intra color difference prediction mode Syntax element calculation unit, 124 inter prediction information syntax element calculation unit, 125 intra prediction mode coding control unit, 126 entropy coding unit, 201 coded bit string separating unit, 202 first coded bit string decoding unit, 203 second encoded bit string decoding unit,
204 third coded bit string decoding unit, 205 color difference format management unit, 206
Intra prediction unit, 207 Inter prediction unit, 208 Inverse quantization / inverse orthogonal transform unit, 2
09 decoded image signal superimposing unit, 210 encoded information storage memory, 211 decoded image memory, 212 switch, 213 switch, 221 intra prediction mode decoding control unit, 222 entropy decoding unit, 223 encoded information calculation unit for each encoded block, 224 Intra brightness prediction mode calculation part, 225 Intra color difference prediction mode calculation part, 226 Inter prediction information calculation part.

Claims (6)

An image decoding apparatus that decodes information related to an intra prediction mode and performs intra prediction decoding of an image signal including a luminance signal and a color difference signal in units of blocks,
Intra luminance prediction mode deriving means for deriving a value of the intra luminance prediction mode;
When the color difference format is 4: 2: 2, the color difference format is 4: based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal derived by the intra luminance prediction mode deriving unit. When the value of the intra color difference prediction mode is derived from the conversion table indicating the value of the 2: 2 intra color difference prediction mode, and the color difference format is not 4: 2: 2, the color difference signal prediction block is used without using the conversion table. Intra prediction mode deriving means for deriving the value of the intra color difference prediction mode based on the value of the intra luminance prediction mode of the prediction block at the same position,
The conversion table includes a plurality of intra prediction directions closest to each of a plurality of directions derived by scaling a prediction direction of a plurality of intra luminance prediction modes whose reference destinations are arranged in the vertical direction to twice the vertical direction. At least a value representing the color difference prediction mode is shown,
An image decoding apparatus characterized by that. An image decoding method for decoding information on an intra prediction mode and performing intra prediction decoding on an image signal including a luminance signal and a color difference signal in units of blocks,
An intra luminance prediction mode deriving step for deriving a value of the intra luminance prediction mode;
When the color difference format is 4: 2: 2, the color difference format is 4 based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal derived in the intra luminance prediction mode deriving step. A value of the intra color difference prediction mode is derived from the conversion table indicating the value of the 2: 2 intra color difference prediction mode, and when the color difference format is not 4: 2: 2, the color difference signal prediction block is used without using the conversion table. An intra color difference prediction mode deriving step for deriving a value of the intra color difference prediction mode based on the value of the intra luminance prediction mode of the prediction block at the same position as
The conversion table includes a plurality of intra prediction directions closest to each of a plurality of directions derived by scaling a prediction direction of a plurality of intra luminance prediction modes whose reference destinations are arranged in the vertical direction to twice the vertical direction. At least a value representing the color difference prediction mode is shown,
An image decoding method characterized by the above. An image decoding program for causing a computer to decode information related to an intra prediction mode and performing intra prediction decoding of an image signal including a luminance signal and a color difference signal in units of blocks,
An intra luminance prediction mode deriving step for deriving a value of the intra luminance prediction mode;
When the color difference format is 4: 2: 2, the color difference format is 4 based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal derived in the intra luminance prediction mode deriving step. A value of the intra color difference prediction mode is derived from the conversion table indicating the value of the 2: 2 intra color difference prediction mode, and when the color difference format is not 4: 2: 2, the color difference signal prediction block is used without using the conversion table. Causing the computer to execute an intra color difference prediction mode deriving step for deriving a value of the intra color difference prediction mode based on the value of the intra luminance prediction mode of the prediction block at the same position as
The conversion table includes a plurality of intra prediction directions closest to each of a plurality of directions derived by scaling a prediction direction of a plurality of intra luminance prediction modes whose reference destinations are arranged in the vertical direction to twice the vertical direction. At least a value representing the color difference prediction mode is shown,
An image decoding program characterized by the above. A reception device that decodes information related to an intra prediction mode from an encoded stream and performs intra prediction decoding of an image signal including a luminance signal and a color difference signal in units of blocks,
A receiving unit that receives encoded data in which a moving image is encoded;
A packet processing unit that packet-processes the encoded data to generate the encoded stream;
Intra luminance prediction mode deriving means for deriving a value of the intra luminance prediction mode from the encoded stream;
When the color difference format is 4: 2: 2, the color difference format is 4: based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal derived by the intra luminance prediction mode deriving unit. When the value of the intra color difference prediction mode is derived from the conversion table indicating the value of the 2: 2 intra color difference prediction mode, and the color difference format is not 4: 2: 2, the color difference signal prediction block is used without using the conversion table. Intra color difference prediction mode deriving means for deriving the value of the intra color difference prediction mode based on the value of the intra luminance prediction mode of the prediction block at the same position,
The conversion table includes a plurality of intra prediction directions closest to each of a plurality of directions derived by scaling a prediction direction of a plurality of intra luminance prediction modes whose reference destinations are arranged in the vertical direction to twice the vertical direction. At least a value representing the color difference prediction mode is shown,
A receiving apparatus. A reception method for decoding intra-prediction mode information from an encoded stream and intra-prediction decoding an image signal including a luminance signal and a color difference signal in units of blocks,
A reception step of receiving encoded data in which a moving image is encoded;
A packet processing step of packet-processing the encoded data to generate the encoded stream;
An intra luminance prediction mode deriving step for deriving a value of the intra luminance prediction mode from the encoded stream;
When the color difference format is 4: 2: 2, the color difference format is 4 based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal derived in the intra luminance prediction mode deriving step. A value of the intra color difference prediction mode is derived from the conversion table indicating the value of the 2: 2 intra color difference prediction mode, and when the color difference format is not 4: 2: 2, the color difference signal prediction block is used without using the conversion table. An intra color difference prediction mode deriving step for deriving a value of the intra color difference prediction mode based on the value of the intra luminance prediction mode of the prediction block at the same position as
The conversion table includes a plurality of intra prediction directions closest to each of a plurality of directions derived by scaling a prediction direction of a plurality of intra luminance prediction modes whose reference destinations are arranged in the vertical direction to twice the vertical direction. At least a value representing the color difference prediction mode is shown,
And a receiving method. A reception program for causing a computer to decode information related to an intra prediction mode from an encoded stream and to perform intra prediction decoding of an image signal including a luminance signal and a color difference signal in units of blocks.
A reception step of receiving encoded data in which a moving image is encoded;
A packet processing step of packet-processing the encoded data to generate the encoded stream;
An intra luminance prediction mode deriving step for deriving a value of the intra luminance prediction mode from the encoded stream;
When the color difference format is 4: 2: 2, the color difference format is 4 based on the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal derived in the intra luminance prediction mode deriving step. A value of the intra color difference prediction mode is derived from the conversion table indicating the value of the 2: 2 intra color difference prediction mode, and when the color difference format is not 4: 2: 2, the color difference signal prediction block is used without using the conversion table. Causing the computer to execute an intra color difference prediction mode deriving step for deriving a value of the intra color difference prediction mode based on the value of the intra luminance prediction mode of the prediction block at the same position as
The conversion table includes a plurality of intra prediction directions closest to each of a plurality of directions derived by scaling a prediction direction of a plurality of intra luminance prediction modes whose reference destinations are arranged in the vertical direction to twice the vertical direction. At least a value representing the color difference prediction mode is shown,
A receiving program characterized by the above.

Images