JP2019054517A - Encoding device, decoding device, and program - Google Patents

Abstract

To provide a coding efficiency while reducing information amount transferred by a decoding device 1 and reducing a computing time on the decoding device.SOLUTION: An encoding device 1 according to the present invention comprises: a coding processing order determination part 11 that determines a coding processing order of a coding target block; an intra-prediction mode candidate generation part 12 that generates an intra-prediction mode candidate of a coding target block on the basis of the coding processing order; an intra-prediction mode determination part 13 that determines the intra-prediction mode adapted to the coding target block from the intra-prediction mode candidate; an intra-prediction part 14 that executes an intra-prediction processing for the coding target block on the basis of the determined coding processing order and the intra-prediction mode; and an entropy coding part 15 that executes the entropy coding processing to the coding processing order and the intra-prediction mode.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an encoding device, a decoding device, and a program.

  In the H.265 / HEVC (High Efficiency Video Coding) video (video) coding system represented by next-generation video compression technology, inter prediction using temporal correlation between frames and spatial correlation within the frames are performed. After performing prediction while switching between two types of intra prediction used, a residual signal is generated, and then orthogonal transform processing, loop filter processing, and entropy coding processing are performed. And it is comprised so that the stream obtained by this entropy encoding process may be output.

  For intra prediction in HEVC, a total of 35 types of intra prediction modes including Planar prediction, DC prediction, direction prediction, and the like are prepared. The decoding device is configured to perform intra prediction using adjacent decoded reference pixels according to the intra prediction mode determined by the encoding device (encoder), and generate a prediction image. Hereinafter, unless otherwise specified, the “reference pixel” refers to a decoded reference pixel.

  In the conventional HEVC, a frame-unit original image constituting a moving image is divided into a plurality of blocks having a fixed size (hereinafter referred to as CTU: Coding Tree Unit), and then divided into hierarchical quadrants for each CTU. It is configured to encode by applying tree partitioning.

  The encoding apparatus performs encoding processing while switching between intra prediction and inter prediction on a divided encoding target block (hereinafter referred to as CU: Coding Unit). This encoding process is performed in a predetermined encoding process order from the upper left to the lower right (the upper left CU → the upper right CU → the lower left CU → the lower right CU, for example, This is called Z scan).

  As described above, in the intra prediction mode, a prediction image is generated using reference pixels. However, in this intra prediction mode, the order of the encoding process is advanced by a Z scan described later, and therefore the upper right and lower left reference pixels of the CU may not be decoded.

  In such a case, the predicted image is generated using a value obtained by extrapolating the nearest decoded reference pixel as a reference pixel (see, for example, Non-Patent Document 1).

  Also, in HEVC, in a block where there is no adjacent decoded reference pixel, such as a block located at the upper left in a frame, a specified value (for example, “512” for a 10-bit moving image) is filled. Thus, the reference pixel used when generating the predicted image is created.

  As described above, when there is a reference pixel that has not been decoded, if the direction prediction is performed from the direction in which the reference pixel that has not been decoded is located, the prediction accuracy is lowered, and thus the coding efficiency is reduced.

  Therefore, in intra prediction, in addition to Z scan, inverse N scan (encoding processing order such as upper right CU → lower right CU → upper left CU → lower left CU) or reverse Z scan (lower left CU → lower right) There is known a technique for improving the prediction accuracy by providing a degree of freedom in the order of encoding processing, such as CU → upper left CU → upper right CU) (see Non-Patent Document 2). ).

  In the technique defined in Non-Patent Document 2, a flag indicating what encoding processing order is used for each CU is transmitted, and then a flag indicating an intra prediction mode applicable to each CU is transmitted. It is configured.

  Further, in the technology defined in Non-Patent Document 2, the intra prediction mode of each CU is configured to be selected from among 35 fixed intra prediction modes, as in HEVC, and is transmitted. The entropy encoding process in the prediction mode is the same as in HEVC.

Supervised by Satoshi Okubo, “Impress Standard Textbook Series H.265 / HEVC Textbook” Xiulian Peng et al., “Improved intra frame coding by PU / TU reordering”, JVTVC-C275, October 2010

  However, as in Non-Patent Document 2, when the encoding processing order (scan order) can be selected and the reverse Z scan or N scan is selected, the accuracy of intra prediction is reduced. There was a problem that it might end.

  For example, as shown in FIG. 9, when the reverse Z scan is selected in the encoding processing order for the divided CU, CU # 3 (lower left CU) → CU # 4 (lower right CU) → CU # 1 Intra prediction processing is performed in the order of (upper left CU) → CU # 2 (upper right CU).

  Here, when the intra prediction mode of each CU is an intra prediction mode using reference pixels adjacent to the left side or the upper side as in the example of FIG. 9, the encoding process is performed by inverse Z scan. Done. For this reason, in CU # 4 (lower right CU) and CU # 3 (lower left CU), an upper reference pixel that can be referred to in the case of Z scan cannot be used.

  That is, as in the example of FIG. 9, when the inverse Z scan is selected, the possibility of selecting an intra prediction mode using reference pixels located on the left side or the upper side is low.

  As described above, in Non-Patent Document 2, the entropy encoding of the flag indicating the intra prediction mode is the same as in HEVC even though there is a bias in the probability of the intra prediction mode selected according to the encoding processing order. The probability bias in the intra prediction mode is not taken into consideration.

  Further, in Non-Patent Document 2, it is necessary to try all combinations on the encoding device side as to what intra prediction mode is selected for each CU in all selectable encoding processing orders. There is a problem that the calculation time on the converter side increases.

  Therefore, the present invention has been made to solve the above-described problem, and reduces the amount of information transmitted by the encoding device and improves the encoding efficiency while reducing the calculation time on the encoding device side. An object of the present invention is to provide an encoding device, a decoding device, and a program.

  A first feature of the present invention is an encoding apparatus configured to divide a frame-unit original image constituting a moving image into blocks and encode them, and to perform encoding processing sequence of encoding target blocks. An encoding processing order determining unit configured to determine the encoding processing block, a generating unit configured to generate an intra prediction mode candidate for the encoding target block based on the encoding processing order, and the intra Based on the intra prediction mode determination unit configured to determine the intra prediction mode to be applied to the encoding target block from among the prediction mode candidates, the determined encoding processing order, and the intra prediction mode, An intra prediction unit configured to perform an intra prediction process on the encoding target block, the encoding processing order, and the intra prediction mode; And, a gist that includes an entropy encoding unit is configured to perform entropy coding process.

  A second feature of the present invention is a decoding device configured to decode each block obtained by dividing a frame unit image constituting a moving image, and entropy is applied to a stream output from the encoding device. An encoding process order decoding unit configured to acquire the encoding process order of the encoding target block by performing a decoding process; and the intra prediction mode of the encoding target block based on the encoding process order An intra prediction mode to be applied to the encoding target block is obtained by performing entropy decoding processing on the stream based on the generation unit configured to generate a candidate and the intra prediction mode candidate. Based on the intra prediction mode decoding unit configured as described above, the encoding processing order and the intra prediction mode And gist by comprising an intra prediction unit is configured to perform the intra prediction process for the encoding target block.

  The gist of a third feature of the present invention is a program for causing a computer to function as the encoding device described in the first feature.

  The gist of the fourth feature of the present invention is that it is a program for causing a computer to function as the decoding device described in the second feature.

  According to the present invention, there are provided an encoding device, a decoding device, and a program capable of improving the encoding efficiency while reducing the amount of information transmitted by the encoding device and reducing the calculation time on the encoding device side. be able to.

FIG. 1 is a diagram illustrating an example of functional blocks of the encoding device 1 according to the first embodiment.

FIG. 2 is a diagram illustrating an example of the encoding processing order (scan order) used in the encoding device 1 and the decoding device 3 according to the first embodiment.

FIG. 3 is a diagram illustrating an example of the encoding processing order (scan order) used in the encoding device 1 and the decoding device 3 according to the first embodiment.

FIG. 4 is a diagram illustrating an example of the entire range of intra prediction modes used in the encoding device 1 and the decoding device 3 according to the first embodiment.

FIG. 5 is a diagram illustrating an example of intra prediction processing in the encoding device 1 and the decoding device 3 according to the first embodiment.

FIG. 6 is a diagram illustrating an example of functional blocks of the decoding device 3 according to the first embodiment.

FIG. 7 is a diagram for explaining the first modification.

FIG. 8 is a diagram for explaining the prior art.

(First embodiment)
Hereinafter, the encoding device 1 and the decoding device 3 according to the first embodiment of the present invention will be described with reference to FIGS.

  Here, the encoding device 1 and the decoding device 3 according to the present embodiment are configured to support intra prediction in a moving image encoding scheme such as HEVC. Note that the encoding device 1 and the decoding device 3 according to the present embodiment are configured to be compatible with any video encoding scheme as long as the video encoding scheme performs intra prediction.

  The encoding device 1 according to the present embodiment is configured to divide and encode a frame-unit original image constituting a moving image into encoding target CUs. Hereinafter, in the present embodiment, an example will be described in which a frame-unit original image constituting a moving image is hierarchically divided into quadtrees and encoded.

  As illustrated in FIG. 1, the encoding device 1 according to the present embodiment includes an encoding processing order determination unit 11, an intra prediction mode candidate generation unit 12, an intra prediction mode determination unit 13, an intra prediction unit 14, And an entropy encoding unit 15.

  The encoding process order determination unit 11 is configured to determine (select) the encoding process order (hereinafter, scan order) of an encoding target CU (encoding target block).

  Specifically, the encoding process order determination unit 11 is configured to determine in what order the divided CUs should be encoded.

  FIG. 2 shows an example of scan order that can be selected by the encoding process order determination unit 11. The scan order shown in FIG. 2A is called Z scan (upper left CU → upper right CU → lower left CU → lower right CU), and the encoding processing order shown in FIG. It is called a scan (lower left CU → lower right CU → upper left CU → upper right CU), and the scan order shown in FIG. 2B is N scan (upper right CU → lower right CU → upper left CU → It shall be called CU in the lower left.

  In the present specification, hereinafter, a case where the Z scan, the reverse Z scan, and the N scan can be selected by the encoding process order determination unit 11 will be described as an example. In addition, the present invention can be applied to the scan order shown in FIG.

  Here, when the scan order shown in FIG. 3A is applied, the same processing as N scan can be applied, and when the scan order shown in FIG. A process similar to the Z scan can be applied.

  The intra prediction mode candidate generation unit 12 is configured to generate intra prediction mode candidates for the encoding target CU based on the scan order determined (selected) by the encoding process order determination unit 11.

  Hereinafter, the intra prediction mode applicable to HEVC will be described as an example.

  As shown in FIG. 4, the 35 intra prediction modes are categorized into A, B, and C for each reference direction.

  In the present embodiment, HEVC intra prediction mode will be described as an example, but the present invention can be applied to any encoding process that performs intra prediction using adjacent decoded reference pixels.

  In HEVC, a total of 9 intra prediction modes from mode 2 to mode 10 are set as category A, a total of 15 intra prediction modes from mode 11 to mode 25 are set as category B, and a total of 9 from mode 26 to mode 34 is set as 9 categories. Let each intra prediction mode be category C.

  It should be noted that, in a method other than HEVC or the like, among the applicable intra prediction modes, a mode for performing direction prediction uses an intra prediction mode group that does not use upper reference pixels as category A and uses reference pixels located on the left side. The intra prediction mode group not to be used is set as category C, and the intra prediction mode group using both the upper and left reference pixels is set to be category B.

  The intra prediction mode candidate generation unit 12 is configured to generate intra prediction mode candidates for the encoding target CU based on the scan order determined by the encoding process order determination unit 11.

  For example, when the scan order determined by the encoding process order determination unit 11 is a Z scan, the intra prediction mode candidate generation unit 12 uses the three categories A, B, and C as in the case of HEVC. The DC mode and the Planar mode are configured as selectable intra prediction mode candidates for each CU.

  On the other hand, when the order of the encoding processes determined by the encoding process order determination unit 11 is an inverse Z scan, the intra prediction mode candidate generation unit 12 performs the intra prediction mode, DC mode, and Planar mode belonging to the category A. Are set as intra prediction mode candidates that can be selected for each CU.

  Further, when the scan order determined by the encoding processing order determination unit 11 is N scan, the intra prediction mode candidate generation unit 12 sets the intra prediction mode, the DC mode, and the Planar mode belonging to the category C to each CU. Are selected as intra prediction mode candidates.

  The intra prediction mode determination unit 13 is configured to determine an intra prediction mode to be applied to the encoding target CU from the intra prediction mode candidates generated by the intra prediction mode candidate generation unit 12.

  For example, the intra prediction mode determination unit 13 applies the intra prediction mode to be applied to each CU by optimization on the encoding device 1 side among the intra prediction modes belonging to the category determined by the intra prediction mode candidate generation unit 12. Is configured to determine.

  The intra prediction unit 14 is configured to perform an intra prediction process on the encoding target CU based on the scan order determined by the encoding process order determination unit 11 and the intra prediction mode determined by the intra prediction mode determination unit 13. Has been.

  Specifically, the intra prediction unit 14 is configured to perform an intra prediction process on the CU to be encoded according to an intra prediction mode applied to each CU and a position where a decoded reference pixel adjacent to each CU exists. ing.

  Hereinafter, an example of the intra prediction process according to the present embodiment will be described with reference to FIG.

  As described above, the intra prediction mode candidate generation unit 12 determines the intra prediction mode, the DC mode, and the Planar mode belonging to the category A when the scan order is the reverse Z scan determined by the encoding processing order determination unit 11. The intra prediction mode candidates that can be selected for each CU.

  As shown in FIG. 5A and FIG. 5B, the intra prediction unit 14 performs the intra prediction for CU # 3 (lower left CU) and CU # 4 (lower right CU) as in the case of conventional HEVC. It is comprised so that a prediction process may be performed. In the HEVC, when intra prediction processing is performed, the decoded image is sequentially generated so that the decoded image can be reused in the intra prediction processing in the CU that performs subsequent encoding processing.

  Therefore, as shown in FIGS. 5C and 5D, the intra prediction unit 14 performs intra prediction for CU # 1 (upper left CU) and CU # 2 (upper right CU). Since the lower CUs (CU # 3 and CU # 4) have been decoded, the decoded images of these CUs can be reused as reference pixels.

  Therefore, when the scan order of each CU is a reverse Z scan, the intra prediction unit 14 replaces an intra prediction process performed in normal HEVC for a CU that has already been decoded by the lower CU. The intra prediction process is performed using reference pixels adjacent to at least the lower side and the left side.

  Similarly, when the scanning order of each CU is N scans, the intra prediction unit 14 does not perform intra prediction processing performed in normal HEVC for a CU that has already been decoded on the right CU. An intra prediction process is performed using reference pixels adjacent to at least the right side and the upper side.

  The entropy encoding unit 15 is configured to perform entropy encoding processing on the scan order determined by the encoding processing order determination unit 11 and the intra prediction mode determined by the intra prediction mode determination unit 13. .

  Specifically, as illustrated in FIG. 1, the entropy encoding unit 15 includes an encoding processing order encoding unit 151 and an intra prediction mode encoding unit 152.

  The encoding process order encoding unit 151 is configured to perform entropy encoding processing on the scan order determined by the encoding process order determination unit 11.

  The intra prediction mode encoding unit 152 generates an entropy code for the intra prediction mode based on the intra prediction mode candidate generated by the intra prediction mode candidate generation unit 12 and the intra prediction mode determined by the intra prediction mode determination unit 13. It is comprised so that a process may be performed.

  In the conventional HEVC, among the 35 intra prediction modes, 32 intra prediction modes other than the three intra prediction modes registered in MPM (Most Probable Mode) having a higher probability of being selected are selected. It is configured to output 5-bit flag information as a stream.

  On the other hand, in the present embodiment, the intra prediction mode encoding unit 152 determines that only the intra prediction mode, the DC mode, and the Planar mode belonging to the category A can be selected by the intra prediction mode candidate generation unit 12 (that is, If it is determined that the inverse Z scan is applied to the encoding target CU), or only the intra prediction mode, the DC mode, and the Planar mode belonging to the category C can be selected by the intra prediction mode candidate generation unit 12. When it is determined (that is, when it is determined that N-scan is applied to the encoding target CU), there are a total of 10 intra prediction modes that may be selected. 3 bits flag information for 7 modes excluding 3 intra prediction modes Can be configured to stream output. According to this configuration, it is possible to reduce the amount of information necessary for encoding in the intra prediction mode, and improve the encoding efficiency.

  In the above example, the case of fixed-length encoding has been described as an example of 3 bits. However, when entropy encoding is performed using variable-length encoding, context adaptive arithmetic encoding (CABAC), or the like, a stream is output. The number of bits that are not necessarily 3 bits.

  In addition, the decoding device 3 according to the present embodiment is configured to decode for each CU obtained by dividing a frame unit image constituting a moving image. Here, the decoding device 3 according to the present embodiment is configured so as to be able to hierarchically divide the frame-by-frame images constituting the moving image into quadtrees, similarly to the encoding device 1 according to the present embodiment. Has been.

  As illustrated in FIG. 6, the decoding device 3 according to the present embodiment includes an entropy decoding unit 31, an intra prediction mode candidate generation unit 32, and an intra prediction unit 33.

  The entropy decoding unit 31 is configured to obtain the encoding processing order of the encoding target CU by performing entropy decoding processing on the stream output from the encoding device 1.

  Specifically, the entropy decoding unit 31 includes an encoding processing order decoding unit 311 and an intra prediction mode decoding unit 312.

  The encoding processing order decoding unit 311 is configured to obtain flag information indicating the scanning order for each CU by performing entropy decoding processing on the stream output from the encoding device 1.

  The intra prediction mode candidate generation unit 32 is configured to generate an intra prediction mode candidate of the encoding target CU based on the scan order indicated by the flag information decoded by the encoding processing order decoding unit 311. .

  Specifically, the intra-prediction mode candidate generation unit 32, as with the intra-prediction mode candidate generation unit 12 included in the encoding device 1, is based on the categories A and B shown in FIG. 4 based on the scan order applied to each CU. , C, DC mode, and Planar mode are configured to generate intra prediction mode candidates applicable to each CU.

  The intra prediction mode decoding unit 312 performs entropy decoding processing on the stream output from the encoding device 1 based on the intra prediction mode candidate generated by the intra prediction mode candidate generation unit 32, thereby causing each CU to perform It is comprised so that the intra prediction mode to apply may be acquired.

  The intra prediction unit 33 is configured to perform an intra prediction process on the encoding target CU based on the scan order acquired by the encoding process order decoding unit 311 and the intra prediction mode acquired by the intra prediction mode decoding unit 312. Has been.

  Specifically, the intra prediction unit 33, according to the intra prediction mode applied to each CU and the position where the decoded reference pixel adjacent to each CU exists, similarly to the intra prediction unit 14 configuring the encoding device 1. Thus, the intra prediction process is performed.

  According to the encoding device 1 and the decoding device 3 according to the present embodiment, the intra prediction efficiency can be improved by controlling the scan order by the encoding device 1, and transmission is performed based on the applied scan order. The amount of information in the intra prediction mode can be reduced, and the encoding efficiency can be improved.

(Second Embodiment)
Hereinafter, with reference to FIG. 7, the encoding apparatus 1 and the decoding apparatus 3 according to the second embodiment of the present invention are different from the above-described encoding apparatus 1 and the decoding apparatus 3 according to the first embodiment. This will be explained with a focus on.

  The encoding apparatus 1 according to the present embodiment is configured to divide and encode a frame-unit original image constituting a moving image into CUs by hierarchical binary tree division.

  In the first embodiment described above, determination of scan order for CUs divided by quadtree partitioning, generation of intra prediction mode candidates, and entropy coding processing for intra prediction mode and scan order have been described. In the form, a case where binary tree division is applied to a CU will be described.

  When binary tree division is applied to a CU, it is possible to further select from two types of division methods: division into two vertically long CUs and division into two horizontally long CUs.

  Furthermore, in the case of dividing into two vertically long CUs, a left-right sequential scan of CU # 1 (left CU) → CU # 2 (right CU) shown in FIG. 7A and FIG. It is possible to select two types of scan order: left-right reverse scan of CU # 2 (right CU) → CU # 1 (left CU).

  On the other hand, in the case of dividing into two horizontally long CUs, a vertical order scan of CU # 1 (upper CU) → CU # 2 (lower CU) shown in FIG. 7C, and FIG. Can be selected from two types of scan order: CU # 2 (lower CU) → CU # 1 (upper CU).

  The encoding process order determination unit 11 is configured to determine which encoding process to apply, that is, a left-right forward scan or a left-right reverse scan, when dividing a CU into two vertically long CUs. Yes.

  On the other hand, the encoding process order determination unit 11 is configured to determine which scan order to apply, that is, a vertical scan or a reverse scan, when dividing a CU into two horizontally long CUs. ing.

  The intra prediction mode candidate generation unit 12 is configured to generate intra prediction mode candidates applicable to each CU based on the scan order determined by the encoding processing order determination unit 11.

  Hereinafter, the intra prediction process according to the present embodiment will be described.

  When the scan order determined by the encoding processing order determination unit 11 is the left-right order scan and the up-down order scan, the intra prediction mode candidate generation unit 12 includes the three categories A, B, and C, the DC mode, and the Planar. The mode is configured to be a selectable intra prediction mode candidate of each CU (that is, similar to the intra prediction mode candidates in HEVC).

  On the other hand, when the scan order determined by the encoding process order determination unit 11 is the left-right reverse scan, the intra prediction mode candidate generation unit 12 sets the intra prediction mode, DC mode, and Planar mode belonging to the category C to each The CU is configured to be a selectable intra prediction mode candidate.

  Furthermore, when the scan order determined by the encoding process order determination unit 11 is the upside down scan order, the intra prediction mode candidate generation unit 12 selects the intra prediction mode, the DC mode, and the Planar mode belonging to the category A, Each CU is configured to be a selectable intra prediction mode candidate.

  In the first embodiment, the case of hierarchical quadtree partitioning has been described. In the present embodiment, the case of hierarchical binary tree partitioning has been described. The present invention can also be applied to an encoding method that can be divided by switching according to whether each CU selects a quadtree partition or a binary tree partition.

  That is, the encoding target CU may be configured to be obtained by hierarchically applying at least one of quadtree division and binary tree division to the original image.

(Other embodiments)
As described above, the present invention has been described by using the above-described embodiment. However, it should not be understood that the description and drawings constituting a part of the disclosure in the embodiment limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  Further, although not particularly mentioned in the above-described embodiment, a program for causing a computer to execute each process performed by the above-described encoding device 1 and decoding device 3 may be provided. Such a program may be recorded on a computer-readable medium. If a computer readable medium is used, such a program can be installed in the computer. Here, the computer-readable medium on which such a program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or a DVD-ROM.

  Alternatively, a chip configured by a memory that stores a program for realizing at least a part of the functions in the encoding device 1 and the decoding device 3 and a processor that executes the program stored in the memory may be provided. Good.

DESCRIPTION OF SYMBOLS 1 ... Encoding apparatus 11 ... Encoding process order determination part 12 ... Intra prediction mode candidate production | generation part 13 ... Intra prediction mode determination part 14 ... Intra prediction part 15 ... Entropy encoding part 151 ... Encoding process order encoding part 152 ... Intra prediction mode encoding unit 3 ... decoding device 31 ... entropy decoding unit 311 ... encoding processing order decoding unit 312 ... intra prediction mode decoding unit 32 ... intra prediction mode candidate generation unit 33 ... intra prediction unit

Claims (6)

An encoding device configured to divide and encode an original image of a frame unit constituting a moving image into blocks,
An encoding processing order determination unit configured to determine the encoding processing order of the encoding target block;
A generating unit configured to generate an intra prediction mode candidate of the encoding target block based on the encoding processing order;
An intra prediction mode determination unit configured to determine an intra prediction mode to be applied to the encoding target block from among the intra prediction mode candidates;
An intra prediction unit configured to perform an intra prediction process on the encoding target block based on the determined encoding processing order and the intra prediction mode;
An encoding apparatus comprising: an entropy encoding unit configured to perform entropy encoding processing on the encoding processing order and the intra prediction mode.   The encoding target block is configured to be obtained by hierarchically applying at least one of quadtree division and binary tree division to the original image. Encoding device. A decoding device configured to decode each block obtained by dividing a frame-unit image constituting a moving image,
An encoding processing order decoding unit configured to obtain an encoding processing order of a block to be encoded by performing entropy decoding processing on the stream output from the encoding device;
A generating unit configured to generate an intra prediction mode candidate of the encoding target block based on the encoding processing order;
An intra prediction mode decoding unit configured to acquire an intra prediction mode to be applied to the encoding target block by performing an entropy decoding process on the stream based on the intra prediction mode candidates;
A decoding apparatus comprising: an intra prediction unit configured to perform an intra prediction process on the encoding target block based on the encoding processing order and the intra prediction mode.   The encoding target block is configured to be obtained by hierarchically applying at least one of quadtree division and binary tree division to the original image. Decoding device.   A program for causing a computer to function as the encoding device according to claim 1 or 2.   The program for functioning a computer as a decoding apparatus of Claim 3 or 4.

Images