JP6514307B2 - Video coding apparatus and method - Google Patents

Description

  The present invention relates to a moving picture coding apparatus and a moving picture decoding apparatus for obtaining a motion vector from an encoded and decoded image and performing motion compensation prediction.

  Motion-compensated prediction is one of the techniques used for coding moving pictures. In motion compensation prediction, a motion vector is obtained using a coding target image to be newly coded in a video coding device and a locally decoded image that has already been obtained, and motion compensation is performed using this motion vector. Thus, a predicted image is generated.

  As one of methods for obtaining a motion vector in motion compensation prediction, there is a direct mode in which a predicted image is generated using a motion vector of an encoding target block derived from a motion vector of an already encoded block (Japanese Patent No. 4020789) And U.S. Patent No. 7,233,621). In the direct mode, since the motion vector is not encoded, the code amount of the motion vector information can be reduced. The direct mode is based on H. Adopted in H.264 / AVC.

  In the direct mode, when the motion vector of the encoding target block is predicted and generated, the motion vector is calculated using a fixed method of calculating the motion vector from the median value of the motion vector of the encoded block adjacent to the encoding target block. Generate Therefore, the degree of freedom of motion vector calculation is low. When the motion vector calculation method of selecting one of a plurality of encoded blocks is used to increase the degree of freedom described above, the position of the block is always selected to indicate the selected encoded block. It must be sent as motion vector selection information. This leads to an increase in code amount.

  The present invention provides a moving picture coding apparatus and a moving picture decoding apparatus which reduce additional information of motion vector selection information while selecting one of encoded blocks to increase the freedom of motion vector calculation. With the goal.

  One aspect of the present invention is a moving picture coding apparatus for performing motion compensation predictive coding on a moving picture, which is an available block which is a block having a motion vector from a coded block adjacent to a coding target block and the use The selected block is obtained using an acquisition unit for obtaining the number of possible blocks, a selection unit for selecting one selected block from the encoded blocks and the available blocks, and a code table according to the number of available blocks. A moving image coding apparatus comprising: a selection information coding unit for coding selection information to be specified; and an image coding unit for performing motion compensation prediction coding on the coding target block using a motion vector of the selected block. I will provide a.

  Another aspect of the present invention is a moving picture decoding apparatus that performs motion compensation prediction decoding on a moving picture, and is a code table according to the number of available blocks that are adjacent to a current block to be decoded and have a motion vector. A selection information decoding unit that decodes selection information by switching the motion information selection unit; a motion vector selection unit that selects one motion vector indicated by the selection information decoded by the selection information decoding unit from the available blocks; Provided is a moving picture decoding apparatus including: an image decoding unit that performs motion compensation predictive decoding on a decoding target image using a motion vector selected by a vector selection unit.

Block diagram of a video encoding apparatus according to an embodiment of the present invention Flow chart showing processing procedure of moving picture coding apparatus Flow chart showing processing procedure of acquisition unit / selection unit Diagram explaining how to determine by block size Diagram explaining how to determine by block size Diagram explaining how to determine by block size Diagram explaining the discrimination method by unidirectional or bidirectional prediction Flow chart showing the processing procedure of the selection information coding unit An example of selection information index Example of code list of selection information Outline of syntax structure Macroblock layer data structure Block diagram of moving picture decoding apparatus according to an embodiment of the present invention Flowchart showing processing procedure of moving picture decoding apparatus

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  A moving picture coding apparatus according to an embodiment will be described with reference to FIG. The subtractor 101 is configured to calculate a difference between the input moving image signal 11 and the predicted image signal 15 and to output a prediction error signal 12. The output terminal of the subtractor 101 is connected to the variable-length encoder 111 via the orthogonal transformer 102 and the quantizer 103. The orthogonal transformer 102 orthogonally transforms the prediction error signal 12 from the subtractor 101 to generate orthogonal transformation coefficients, and the quantizer 103 quantizes the orthogonal transformation coefficients and outputs quantized orthogonal transformation coefficient information 13. The variable-length encoder 111 performs variable-length encoding on the quantized orthogonal transform coefficient information 13 from the quantizer 103.

  The output end of the quantizer 103 is connected to the adder 106 via the inverse quantizer 104 and the inverse orthogonal transformer 105. The inverse quantizer 104 inversely quantizes the quantized orthogonal transformation coefficient information 13 into orthogonal transformation coefficients. The inverse orthogonal transformer 105 converts the orthogonal transformation coefficient into a prediction error signal. The adder 106 adds the prediction error signal of the inverse orthogonal transformer 105 and the prediction image signal 15 to generate a local decoded image signal 14. The output of the adder 105 is connected to the motion compensation predictor 108 via the frame memory 107.

  The frame memory 107 stores the local decoded image signal 14. The setting unit 114 sets a motion compensation prediction mode (prediction mode) of the current block. The prediction mode includes unidirectional prediction using one reference image and bidirectional prediction using two reference images. Unidirectional prediction includes AVC L0 prediction and L1 prediction. The motion compensation predictor 108 includes a predictor 109 and an acquisition unit / selection unit 110. The acquisition unit / selection unit 110 obtains an available block that is a block having a motion vector and the number of the available blocks from the encoded block adjacent to the encoding target block, and selects one selected block from the available blocks. select. The motion compensation predictor 108 generates a predicted image signal 15 from the frame memory 107 from the local decoded image signal 14 and the input moving image signal 11. The acquisition unit / selection unit 110 selects one block (selected block) from adjacent blocks adjacent to the current block. For example, a block having an appropriate motion vector among adjacent blocks is selected as a selection block. The acquisition unit / selection unit 110 selects the motion vector of the selected block as the motion vector 16 used for motion compensation prediction, and sends the motion vector to the predictor 109. In addition, the acquisition unit / selection unit 110 generates selection information 17 of the selected block and sends it to the variable-length encoder 111.

  The variable-length encoder 111 has a selection information encoder 112. The selection information coding unit 112 performs variable-length coding of the selection information 17 while switching the code table so that the code table has the same number of entries as the number of encoded block available blocks. The available block is a block having a motion vector among encoded blocks adjacent to the encoding target block. A multiplexer (multiplexer) 113 multiplexes the encoded quantization orthogonal transformation coefficient information and selection information, and outputs encoded data.

  The operation of the moving picture coding apparatus with the above configuration will be described with reference to the flowchart of FIG.

  First, the prediction error signal 12 is generated (S11). In the generation of the prediction error signal 12, a motion vector is selected, and a prediction image is generated using the selected motion vector. A prediction error signal 12 is generated by the subtractor 101 calculating the difference between the signal of the predicted image, that is, the predicted image signal 15 and the input moving image signal 11.

  The orthogonal transformation unit 102 performs orthogonal transformation on the prediction error signal 12 to generate orthogonal transformation coefficients (S12). The orthogonal transformation coefficient is quantized by the quantizer 103 (S13). The quantized orthogonal transformation coefficient information is dequantized by the dequantizer 104 (S14), and then inverse orthogonal transformed by the inverse orthogonal transformer 105 to obtain a reproduced prediction error signal (S15). The adder 106 adds the reproduced prediction error signal and the prediction image signal 15 to generate the local decoded image signal 14 (S16). The local decoded image signal 14 is stored in the frame memory 107 (as a reference image) (S17), and the local decoded image signal read from the frame memory 107 is input to the motion compensation predictor 108.

  The predictor 109 of the motion compensation predictor 108 performs motion compensation prediction of the local decoded image signal (reference image) using the motion vector 16 to generate a predicted image signal 15. The predicted image signal 15 is sent to the subtractor 101 to obtain a difference from the input moving image signal 11, and also sent to the adder 106 to generate the local decoded image signal 14.

  The acquisition unit / selection unit 110 selects one motion vector to be used for motion compensation prediction from adjacent blocks, sends the selected motion vector 16 to the predictor 109, and generates selection information 17. The selection information 17 is sent to the selection information coding unit 112. When selecting a motion vector from an adjacent block, an appropriate motion vector can be selected such that the code amount is small.

  The orthogonal transformation coefficient information 13 quantized by the quantizer 103 is also input to the variable-length encoder 111 and subjected to variable-length encoding (S18). The selection information 16 used for motion compensation prediction is output from the acquisition unit / selection unit 110, and is input to the selection information coding unit 112. The selection information coding unit 112 switches the code table so that the code table has a number of entries equal to the number of available blocks adjacent to the current block and is a coded block having a motion vector. The information 17 is variable-length encoded. The quantization orthogonal transformation coefficient information and selection information from the variable-length encoder 111 are multiplexed by the multiplexer 113, and a bit stream of the encoded data 18 is output (S19). The encoded data 18 is sent to a storage system or a transmission line (not shown).

  In the flowchart of FIG. 2, the flow of steps S14 to S17 and the flow of steps S18 and S19 can be replaced. That is, the variable length coding step S18 and the multiplexing step S19 can be performed after the quantization step S13, and the inverse quantization step S14 to the storage step S17 can be performed in pair at the multiplexing step S19.

  Next, the operation of the acquisition unit / selection unit 110 will be described using the flowchart shown in FIG.

  First, referring to the frame memory 107, an available block candidate which is an encoded block having a motion vector and is adjacent to the encoding target block is searched (S101). When available block candidates are searched, the block size of motion compensation prediction of these available block candidates is determined (S102). Next, it is determined whether the available block candidate is unidirectional or bidirectional prediction (S103). Based on the determination result and the prediction mode of the current block, an available block is extracted from the available block candidates. One selected block is selected from the extracted available blocks, and information specifying the selected block is obtained as selection information (S104).

  Next, block size determination (S102) will be described with reference to FIGS. 4A to 4C.

  The adjacent block used in the present embodiment is a block located on the left, upper left, upper, upper right of the coding target block. Therefore, when the encoding target block is located at the top left of the frame, the present invention can not be applied to the encoding target block because there is no available block adjacent to the encoding target block. When the encoding target block is at the top of the screen, the available block is only one left block, and when the encoding target block is the left end of the screen and not the right end, the available block is on the encoding target block, It becomes 2 blocks on the upper right.

  When the macroblock size is 16x16, there are four block sizes of motion compensation prediction of adjacent blocks, as shown in FIGS. 4A to 4C, 16x16, 16x8, 8x16, and 8x8. When these four types are considered, there are 20 types of adjacent blocks that can be available blocks as shown in FIGS. 4A to 4C. That is, there are four types at 16x16 size shown in FIG. 4A, ten types at 16x8 size and 8x16 size shown in FIG. 4B, and six types at 8x8 size shown in FIG. 4C. In the block size determination (S102), available blocks are searched from among these 20 types of blocks according to the block size. For example, when the size of the available block is 16x16 only, the available blocks determined with this block size are four types of 16x16 sized blocks as shown in FIG. 4A. That is, the available blocks are the block on the upper left side of the block to be coded, the block above the block to be coded, the block on the left side of the block to be coded, and the block on the upper right side of the block to be coded. Also, even when the macroblock size is expanded to 16 × 16 or more, it can be an available block as in the case of the macroblock size of 16 × 16. For example, when the macroblock size is 32x32, there are four types of motion compensated prediction of adjacent blocks: 32x32, 32x16, 16x32, 16x16, and 20 types of adjacent blocks can be available blocks. It becomes.

  Next, determination of unidirectional or bidirectional prediction (S103) performed by the acquisition unit / selection unit 110 with reference to FIG. 5 will be described using an example.

  For example, it is assumed that the block size is limited to 16 × 16, and uni-directional or bi-directional prediction of an adjacent block is as shown in FIG. In the determination of unidirectional or bidirectional prediction (S103), available blocks are searched according to the direction of prediction. For example, an adjacent block including the prediction direction L0 is an available block determined in the prediction direction. That is, the upper left, upper right blocks of the coding target block shown in FIG. 5A are available blocks determined in the prediction direction. In this case, the upper left block of the current block is not used. Assuming that an adjacent block including the prediction direction L1 is an available block determined by the prediction method, the upper left and upper blocks of the current block to be encoded shown in FIG. 5 (b) are the available blocks determined in the prediction direction. Become. In this case, the left and upper right blocks of the current block are not used. Assuming that the adjacent block including the prediction direction L0 / L1 is the available block determined by the prediction method, the available block shown in FIG. 5C, in which only the block above the coding target block is determined in the prediction direction It becomes. In this case, the left, upper left and upper right blocks of the current block are not used. The prediction direction L0 (L1) corresponds to the prediction direction of L0 prediction (L1 prediction) in AVC.

  Next, the selection information coding unit 112 will be described with reference to the flowchart shown in FIG.

  Among the adjacent blocks adjacent to the current block to be encoded, search for available blocks which are already encoded blocks having motion vectors, and obtain available block information determined by block size and unidirectional or bidirectional prediction To do (S201). Using the available block information, the code table is switched according to the number of available blocks as shown in FIG. 8 (S202). The selection information 17 sent from the acquisition unit / selection unit 110 is variable-length encoded using the switched code table (S203).

  Next, an example of the index of the selection information will be described with reference to FIG.

  If there is no available block as shown in FIG. 7 (a), no selection information is sent since the present invention is not applicable to this block. As shown in FIG. 7B, when there is one available block, the selection vector is not sent because the motion vector of the available block used for motion compensation of the current block is uniquely determined. As shown in FIG. 7C, when there are two available blocks, selection information of index 0 or 1 is sent. As shown in FIG. 7D, when there are three available blocks, selection information of index 0, 1 or 2 is sent. As shown in FIG. 7E, when there are four available blocks, selection information of index 0, 1, 2 or 3 is sent.

  Further, as an example of indexing of usable blocks, FIG. 7 shows an example in which usable blocks are indexed in the order of left, upper left, upper and upper right of the coding target block. That is, the blocks to be used except for the blocks not used are indexed sequentially.

  Next, the code table of the selection information 17 will be described with reference to FIG.

  The selection information coding unit 112 switches the code table in accordance with the number of available blocks (S202). As described above, the selection information 17 needs to be encoded when there are two or more available blocks.

  First, in the case where there are two available blocks, the index needs 0 and 1 and the code table is the one shown on the left side of FIG. In the case of three available blocks, the index needs 0, 1, 2 and the code table is the one shown in the center of FIG. If there are four available blocks, the index needs 0, 1, 2, 3 and the code table is as shown on the right side of FIG. These codebooks are switched according to the number of available blocks.

  Next, an encoding method of selection information will be described.

  FIG. 9 shows an outline of the structure of syntax used in the present embodiment. The syntax mainly consists of three parts, and High Level Syntax 801 is packed with syntax information of upper layers above slices. In Slice Level Syntax 804, information necessary for each slice is described, and in Macroblock Level Syntax 807, a variable-length encoded error signal and mode information required for each macroblock are specified.

  Each of these syntaxes is configured in more detailed syntax, and the High Level Syntax 801 is composed of a sequence such as Sequence parameter set syntax 802 and Picture parameter set syntax 803, and syntax of picture level. The Slice Level Syntax 804 includes Slice header syntax 405, Slice data syntax 406, and the like. Furthermore, Macroblock Level Syntax 807 is configured of macroblock layer syntax 808, macroblock prediction syntax 809, and the like.

  The syntax information required in the present embodiment is macroblock layer syntax 808, and the syntax will be described below.

  Available_block_num shown in FIGS. 10 (a) and 10 (b) indicates the number of available blocks, and if this is 2 or more, it is necessary to encode selection information. Also, mvcopy_flag is a flag indicating whether or not to use the motion vector of the available block in motion compensated prediction, and when the available block is 1 or more and this flag is 1, the available block of motion compensated prediction is Motion vectors can be used. Furthermore, mv_select_info indicates selection information, and the code table is as described above.

  FIG. 10A shows a syntax in the case of encoding selection information after mb_type. For example, when the block size is only 16x16, mvcopy_flag and mv_select_info do not need to be encoded unless mb_type is 16x16. If mb_type is 16x16, mvcopy_flag and mv_select_info are encoded.

  FIG. 10 (b) shows the syntax in the case of encoding selection information before mb_type. For example, if mvcopy_flag is 1, it is not necessary to encode mb_type. If mv_copy_flag is 0, encode mb_type.

  In the present embodiment, any order may be used for the scan order of encoding. For example, the present invention is also applicable to line scan and Z scan.

  A moving picture decoding apparatus according to another embodiment will be described with reference to FIG.

  The encoded data 18 output from the moving picture encoding apparatus of FIG. 1 is input to the demultiplexer 201 of the moving picture decoding apparatus as encoded data 21 to be decoded via a storage system or a transmission system. A demultiplexer 201 demultiplexes the coded data 21 and separates the coded data 21 into quantized orthogonal transform coefficient information and selection information. The output of the demultiplexer 201 is connected to a variable length decoder 202. The variable length decoder 202 decodes the quantized orthogonal transform coefficient information and the selection information. An output end of the variable length decoder 202 is connected to the inverse quantizer 204 and the inverse orthogonal transformer 205 to the adder 206. The inverse quantizer 204 inversely quantizes the quantized orthogonal transformation coefficient information and converts it into orthogonal transformation coefficients. The inverse orthogonal transformer 205 inverse orthogonal transforms the orthogonal transform coefficients to generate a prediction error signal. The adder 206 adds the prediction error signal to the prediction image signal from the prediction image generator 207 to generate a moving image signal.

  The predicted image generator 207 includes a predictor 208 and a selection unit 209. The selection unit 209 selects a motion vector according to the selection information 23 decoded by the selection information decoder 203 of the variable-length decoder 202, and sends the selected motion vector 25 to the predictor 208. The predictor 208 motion compensates the reference image stored in the frame memory 210 with the motion vector 25 to generate a predicted image.

  The operation of the moving picture decoding apparatus with the above configuration will be described with reference to the flowchart of FIG.

  The encoded data 21 is demultiplexed by the demultiplexer 201 (S31), and is decoded by the variable-length decoder 202 to generate quantized orthogonal transform coefficient information 22 (S32). Also, the state of the adjacent block adjacent to the current block is examined by the selection information decoder 203, and the selection information of the encoding apparatus according to the number of available blocks which are adjacent encoded blocks having a motion vector. Similar to the coding unit 112, the code table is switched as shown in FIG. 8 and decoded. Thus, the selection information 23 is output (S33).

  The quantized orthogonal transformation coefficient information 22, which is information output from the variable decoder 202, is information output from the selection information decoding unit 203 to the dequantizer 204, and the selection information 23 is a selection unit 209. Sent to

  The quantized orthogonal transform coefficient information 22 is dequantized by the dequantizer 204 (S34), and then inverse orthogonal transformed by the inverse orthogonal transformer 205 (S35). Thereby, a prediction error signal 24 is obtained. The adder 206 adds the predicted image signal to the prediction error signal 24 to reproduce the moving image signal 26 (S36). The moving image signal 27 to be reproduced is stored in the frame memory 210 (S37).

  The predicted image generator 207 generates a predicted image 26 using the motion vector of the available block which is a decoded block adjacent to the current block to be decoded and has a motion vector, which is selected by the decoded selection information 23 Do. The selection unit 209 investigates the state of the adjacent block, and from the available block information of the adjacent block and the selection information 23 decoded by the selection information decoding unit 203, a motion vector used for motion compensation prediction is acquired by the acquisition unit Similar to the selection unit 110, one adjacent block is selected. The predicted image 26 is generated by the predictor 208 using the selected motion vector 25, and is sent to the adder 206 to obtain a moving image signal 27.

  According to the present invention, by encoding selection information according to the number of available blocks, selection information can be sent using an appropriate encoding table, and additional information of the selection information can be reduced. .

  Further, by using the motion vector of the available block for motion compensation prediction of the coding target block, it is possible to reduce the additional information on the motion vector information.

  Furthermore, the motion vector calculation method is not fixed, and by selecting an appropriate one from available blocks, the degree of freedom of motion vector calculation becomes higher than that in the direct mode.

  The method of the present invention described in the embodiment of the present invention can be executed by a computer, and as a program that can be executed by a computer, a magnetic disk (flexible disk, hard disk, etc.), an optical disk (CD-ROM) , DVD, etc.), semiconductor memory, etc. can also be stored and distributed.

  The present invention is not limited to the above embodiment as it is, and in the implementation stage, the constituent elements can be modified and embodied without departing from the scope of the invention. In addition, various inventions can be formed by appropriate combinations of a plurality of constituent elements disclosed in the above embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components in different embodiments may be combined as appropriate.

  The apparatus of the present invention is used for image compression processing in communication, storage and broadcasting.

Claims (4)

From encoded blocks adjacent to the coding target block, according to the direction of unidirectional and bidirectional least one prediction, an acquisition unit for obtaining an available block is a block having a motion vector,
An image coding unit that performs motion compensation prediction coding on the coding target block using a motion vector of the available block;
A video coding apparatus comprising: A moving picture coding method for performing motion compensation predictive coding on a moving picture,
From encoded blocks adjacent to the coding target block, according to the direction of unidirectional and bidirectional least one prediction, determining an available block is a block having a motion vector,
Motion-compensated predictive coding of the current block using the motion vector of the available block,
A moving picture coding method comprising: An obtaining unit for obtaining an available block that is a block having a motion vector according to at least one of unidirectional and bidirectional prediction from a decoded block adjacent to a decoding target block;
An image decoding unit that performs motion compensation prediction decoding on the decoding target block using a motion vector of the available block;
A video decoding apparatus comprising: A moving picture decoding method for performing motion compensation predictive decoding on a moving picture,
Determining an available block, which is a block having a motion vector, from the decoded block adjacent to the block to be decoded according to the direction of at least one prediction in one direction and two directions.
Motion compensated predictive decoding of the block to be decoded using the motion vector of the available block;
A moving picture decoding method comprising: