JP6510084B2 - Moving picture decoding method and electronic apparatus - Google Patents

Description

  Embodiments of the present invention relate to a motion information compression method, a moving picture coding method and a moving picture decoding method in coding and decoding of a moving picture.

  In recent years, the ITU-T and ISO / IEC jointly developed ITU-T Rec. H.264 and ISO / IEC 14496-10 (hereinafter referred to as H.264) jointly with ITU-T and ISO / IEC. Is recommended as In H.264, prediction processing, conversion processing, and entropy coding processing are performed in rectangular block units (for example, 16 × 16 pixel block units, 8 × 8 pixel block units, etc.). In the prediction processing, motion compensation is performed to perform prediction in the time direction with reference to a frame (reference frame) that has already been coded for a rectangular block to be coded (coding target block). In such motion compensation, it is necessary to encode motion information including a motion vector as spatial shift information between a current block to be encoded and a block referenced in a reference frame and send it to the decoding side. Furthermore, when motion compensation is performed using a plurality of reference frames, it is necessary to encode reference frame numbers as well as motion information. For this reason, the code amount regarding motion information and a reference frame number may increase. Also, there is a motion information prediction method for deriving prediction motion information of a coding target block with reference to motion information stored in motion information memory of a reference frame (Patent Document 1 and Non-patent Document 2), The capacity of the motion information memory for storing may be increased.

  As an example of a method of reducing the capacity of the motion information memory, (Non-Patent Document 2) derives motion information that is represented in a predetermined block, and stores only the represented motion information in the motion information memory.

Patent No. 4020789 J. Jung et al, “Temporal MV predictor modification for MV-Comp, Skip, Direct and Merge schemes”, Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11 Document, JCTVC-D164, January 20110. Yeping Su et al, “CE9: Reduced resolution storage of motion vector data”, Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11 Document, JCTVC-D072, January 20110.

  However, when the derivation method of predicted motion information shown in Non-Patent Document 1 and the derivation method of representative motion information shown in Non-Patent Document 2 are different, a code related to motion information is reduced because temporal correlation of the predicted motion information is reduced. There is a problem that the amount is increased.

  The problem to be solved by the present invention is to solve the above problems, and a moving picture coding apparatus and a moving picture decoding apparatus including a motion information compression apparatus capable of improving the coding efficiency. It is to provide.

  According to the embodiment, the moving picture coding method is a method of dividing an input image signal into pixel blocks and performing inter prediction on the divided pixel blocks. The method includes: selecting prediction motion information from a motion information buffer that holds motion information in a coded area; and predicting motion information of a current block to be coded using the prediction motion information. Furthermore, this method obtains representative motion information from a plurality of pieces of motion information in the region where encoding is completed according to first information indicating a method for selecting the predicted motion information, and obtains only the representative motion information. Including.

FIG. 1 is a block diagram schematically showing a configuration of an image coding apparatus according to a first embodiment. Explanatory drawing of the prediction encoding order of a pixel block. Explanatory drawing of an example of pixel block size. Explanatory drawing of another example of pixel block size. Explanatory drawing of another example of pixel block size. Explanatory drawing of an example of the pixel block in a coding tree unit. Explanatory drawing of another example of the pixel block in a coding tree unit. Explanatory drawing of another example of the pixel block in a coding tree unit. Explanatory drawing of another example of the pixel block in a coding tree unit. FIG. 2 is a block diagram schematically showing the configuration of the entropy coding unit of FIG. 1; FIG. 2 is an explanatory view schematically showing a configuration of a motion information memory of FIG. 1; Explanatory drawing of an example of the inter prediction process which the inter estimation part of FIG. 1 performs. Explanatory drawing of another example of the inter prediction process which the inter estimation part of FIG. 1 performs. Explanatory drawing of an example of a prediction unit. Explanatory drawing of another example of a prediction unit. Explanatory drawing of another example of a prediction unit. Explanatory drawing of another example of a prediction unit. Explanatory drawing of another example of a prediction unit. Explanatory drawing of another example of a prediction unit. Explanatory drawing of another example of a prediction unit. Explanatory drawing which shows skip mode, merge mode, and inter mode. FIG. 5 is a block diagram schematically showing a configuration of a motion information coding unit of FIG. 4; Explanatory drawing which shows the example of the position of a prediction motion information candidate with respect to an encoding target prediction unit. Explanatory drawing which shows another example of the position of a prediction motion information candidate with respect to an encoding target prediction unit. Explanatory drawing which shows the example of the list | wrist which shows the relationship between the block position of several prediction motion information candidate, and index Mvpidx. Explanatory drawing which shows the example of the reference motion information acquisition position which shows the center of a prediction unit in case the size of a coding object prediction unit is 32x32. Explanatory drawing which shows the example of the reference motion information acquisition position which shows the center of a prediction unit in case the size of a coding object prediction unit is 32x16. Explanatory drawing which shows the example of the reference motion information acquisition position which shows the center of a prediction unit in case the size of a coding object prediction unit is 16x32. Explanatory drawing which shows the example of the reference motion information acquisition position which shows the center of a prediction unit in case the size of a coding object prediction unit is 16x16. Explanatory drawing which shows the example of the reference motion information acquisition position which shows the center of a prediction unit in case the size of a coding object prediction unit is 16x8. Explanatory drawing which shows the example of the reference motion information acquisition position which shows the center of a prediction unit in case the size of a coding object prediction unit is 8x16. FIG. 14 is an explanatory diagram showing still another example of the reference motion information acquisition position indicating the center of the prediction unit when the size of the encoding target prediction unit is 32 × 32; FIG. 14 is an explanatory diagram showing still another example of the reference motion information acquisition position indicating the center of the prediction unit when the size of the encoding target prediction unit is 32 × 16. FIG. 14 is an explanatory diagram showing still another example of the reference motion information acquisition position indicating the center of the prediction unit when the size of the encoding target prediction unit is 16 × 32. FIG. 14 is an explanatory diagram showing still another example of the reference motion information acquisition position indicating the center of the prediction unit when the size of the encoding target prediction unit is 16 × 16. FIG. 14 is an explanatory diagram showing still another example of the reference motion information acquisition position indicating the center of the prediction unit when the size of the encoding target prediction unit is 16 × 8. FIG. 14 is an explanatory diagram showing still another example of the reference motion information acquisition position indicating the center of the prediction unit when the size of the encoding target prediction unit is 8 × 16. Explanatory drawing regarding space direction reference motion information memory 501 and time direction reference motion information memory 502. FIG. 6 is a flowchart showing an example of the operation of the motion information compression unit of FIG. 1; Explanatory drawing which shows the example of the reference motion information acquisition position which shows the upper left end of a prediction unit in case the size of a coding object prediction unit is 32x32. Explanatory drawing which shows the example of the reference motion information acquisition position which shows the upper left end of a prediction unit in case the size of a coding object prediction unit is 32x16. Explanatory drawing which shows the example of the reference motion information acquisition position which shows the upper left end of a prediction unit in case the size of a coding object prediction unit is 16x32. Explanatory drawing which shows the example of the reference motion information acquisition position which shows the upper left end of a prediction unit in case the size of a coding object prediction unit is 16x16. Explanatory drawing which shows the example of the reference motion information acquisition position which shows the upper left end of a prediction unit in case the size of a coding object prediction unit is 16x8. Explanatory drawing which shows the example of the reference motion information acquisition position which shows the upper left end of a prediction unit in case the size of a coding object prediction unit is 8x16. Explanatory drawing which shows the example of a representative motion information position. Explanatory drawing which shows another example of a representative motion information position. Explanatory drawing which shows the example of the center of the prediction unit in each prediction size. Explanatory drawing which shows the example of the representative motion information position at the time of setting the gravity center of several reference motion information acquisition positions for every motion information compression block as a representative motion information position. The explanatory view showing another example of the representative motion information position at the time of setting the gravity center of a plurality of reference motion information acquisition positions for every motion information compression block as a representative motion information position. Explanatory drawing which shows the example of a representative motion information position. Explanatory drawing which shows another example of a representative motion information position. FIG. 2 shows a syntax structure according to one embodiment. FIG. 7 is a diagram illustrating an example of sequence parameter set syntax according to an embodiment. FIG. 7 is a diagram showing another example of sequence parameter set syntax according to one embodiment. FIG. 7 is a diagram illustrating an example of a prediction unit syntax according to an embodiment. FIG. 7 is a block diagram schematically showing an image decoding apparatus according to a second embodiment. FIG. 26 is a block diagram schematically illustrating the entropy decoding unit of FIG. 25. FIG. 27 is a block diagram schematically showing the motion information decoding unit of FIG. 26.

Hereinafter, with reference to the drawings, a moving picture coding apparatus and a moving picture decoding apparatus according to each embodiment will be described in detail. In the following description, the term "image" can be appropriately read as a term such as "image", "pixel", "image signal", "image data" and the like. Further, in the following embodiments, the same operation is performed for the portions given the same numbers, and the overlapping description will be omitted.
First Embodiment
The first embodiment relates to an image coding apparatus. A moving picture decoding apparatus corresponding to the picture coding apparatus according to the present embodiment will be described in the second embodiment. This image coding apparatus can be realized by hardware such as a large-scale integration (LSI) chip, a digital signal processor (DSP), or a field programmable gate array (FPGA). The image coding apparatus can also be realized by causing a computer to execute an image coding program.

  As shown in FIG. 1, the image coding apparatus 100 according to this embodiment includes a subtraction unit 101, an orthogonal transformation unit 102, a quantization unit 103, an inverse quantization unit 104, an inverse orthogonal transformation unit 105, an addition unit 106, and It includes an image memory 107, an inter prediction unit 108, a motion information compression unit 109, a motion information memory 110, and an entropy coding unit 112. The encoding control unit 114 and the output buffer 113 are usually installed outside the image encoding device 100.

  The image coding apparatus 100 of FIG. 1 divides each frame or each field or each slice constituting the input image signal 151 into a plurality of pixel blocks, performs predictive coding on these divided pixel blocks, and Output the encoded data 163. In the following description, for the sake of simplicity, it is assumed that predictive coding of pixel blocks is performed from upper left to lower right as shown in FIG. 2A. In FIG. 2A, in the frame f to be encoded, the encoded pixel block p is located on the left and upper sides of the pixel block c to be encoded.

  Here, a pixel block refers to a unit that processes an image, for example, a block of M × N size (N and M are natural numbers), a coding unit, a macroblock, a subblock, and one pixel. In the following description, a pixel block is basically used in the meaning of a coding unit, but it is also possible to interpret the pixel block in the above-mentioned meaning by appropriately changing the explanation. The coding unit is typically, for example, a 16 × 16 pixel block shown in FIG. 2B, but may be a 32 × 32 pixel block shown in FIG. 2C or a 64 × 64 pixel block shown in FIG. 2D. Alternatively, it may be an 8 × 8 pixel block or 4 × 4 pixel block. Also, the coding unit does not have to be square. Hereinafter, the encoding target block or coding unit of the input image signal 151 may be referred to as a “prediction target block”. Further, the coding unit is not limited to the pixel block such as the coding unit, and a frame or a field, a slice, or a combination thereof can be used.

  3A to 3D are diagrams showing specific examples of the coding unit. FIG. 3A shows an example in the case where the size of the coding unit is 64 × 64 (N = 32). Here, N represents the size of the coding unit serving as a reference, and the size of the divided case is defined as N, and the case of not divided is defined as 2N. The coding tree unit has a quadtree structure, and when divided, four pixel blocks are indexed in Z scan order. FIG. 3B shows an example in which the 64 × 64 pixel block of FIG. 3A is divided into quadtrees. The numbers shown in the figure represent the order of the Z scan. It is also possible to further divide into quadtrees within the index of one quadtree of the coding unit. Define the depth of division with Depth. That is, FIG. 3A shows an example of Depth = 0. FIG. 3C shows an example of a 32 × 32 (N = 16) -sized coding tree unit in the case of Depth = 1. The largest unit of such a coding tree unit is called a large coding tree unit or tree block, and as shown in FIG. 2A, the input image signal is encoded in raster scan order in this unit.

  The image coding apparatus 100 of FIG. 1 performs inter prediction (also referred to as inter-frame prediction, inter-frame prediction, motion compensation prediction, or the like) on pixel blocks based on the coding parameters input from the coding control unit 114 or Intra prediction (not shown) (also referred to as intra prediction, intra prediction, etc.) is performed to generate a predicted image signal 159. The image coding apparatus 100 orthogonally transforms and quantizes a prediction error signal 152 between a pixel block (input image signal 151) and a predicted image signal 159, performs entropy coding, and generates coded data 163. Output.

  The image coding apparatus 100 of FIG. 1 performs coding by selectively applying a plurality of prediction modes having different block sizes and a method of generating a predicted image signal 159. The method of generating the predicted image signal 159 can be roughly classified into two types: intra prediction that performs prediction within a coding target frame and inter prediction that performs prediction using one or more reference frames that differ in time. is there.

Hereinafter, each element included in the image coding apparatus 100 of FIG. 1 will be described.
The subtraction unit 101 subtracts the corresponding predicted image signal 159 from the encoding target block of the input image signal 151 to obtain a prediction error signal 152. The subtraction unit 101 inputs the prediction error signal 152 to the orthogonal transformation unit 102.

  The orthogonal transformation unit 102 performs orthogonal transformation such as discrete cosine transformation (DCT) on the prediction error signal 152 from the subtraction unit 101 to obtain a transformation coefficient 153. The orthogonal transform unit 102 outputs the transform coefficient 153 to the quantization unit 103.

  The quantization unit 103 quantizes the transform coefficient 153 from the orthogonal transform unit 102 to obtain a quantized transform coefficient 154. Specifically, the quantization unit 103 performs the quantization in accordance with the quantization parameter designated by the coding control unit 114 and the quantization information such as the quantization matrix. The quantization parameter indicates the granularity of the quantization. The quantization matrix is used to weight the granularity of the quantization for each component of the transform coefficient, but the use or non-use of the quantization matrix is not an essential part of the embodiment of the present invention. The quantization unit 103 outputs the quantization transformation coefficient 154 to the entropy coding unit 112 and the dequantization unit 104.

  The entropy coding unit 112 includes the quantization transform coefficient 154 from the quantization unit 103, the motion information 160 from the inter prediction unit 108, the prediction information 165 specified by the coding control unit 114, and the reference from the coding control unit 114. Entropy coding (eg, Huffman coding, arithmetic coding, etc.) is performed on various coding parameters such as position information 164 and quantization information to generate coded data 163. The coding parameters are parameters necessary for decoding the prediction information 165, information on transform coefficients, information on quantization, and the like. For example, the encoding control unit 114 has an internal memory (not shown), the encoding parameter is held in this memory, and the encoding parameter of the already encoded pixel block adjacent to the prediction target block is encoded. Use.

  Specifically, as shown in FIG. 4, the entropy coding unit 112 includes a parameter coding unit 401, a transform coefficient coding unit 402, a motion information coding unit 403, and a multiplexing unit 404. The parameter coding unit 401 codes coding parameters such as the prediction information 165 received from the coding control unit 114 to generate coded data 451A. Transform coefficient coding section 402 encodes quantized transform coefficient 154 received from quantization section 103 to generate encoded data 451B.

  The motion information coding unit 403 refers to the reference motion information 166 received from the motion information memory 110 and the reference position information 164 received from the coding control unit 114, and encodes the motion information 160 received from the inter prediction unit 108. To generate encoded data 451C. The details of the motion information encoding unit 403 will be described later.

  The multiplexing unit 404 multiplexes the encoded data 451A, 451B, and 451C to generate encoded data 163. The generated encoded data 163 includes the motion information 160, the prediction information 165, and all parameters necessary for decoding of information on transform coefficients, information on quantization, and the like.

  The encoded data 163 generated by the entropy encoding unit 112 is temporarily accumulated, for example, in the output buffer 113 through multiplexing, and is output as the encoded data 163 in accordance with the appropriate output timing managed by the encoding control unit 114. Ru. The encoded data 163 is output to, for example, a storage system (storage medium) or a transmission system (communication line) (not shown).

  The inverse quantization unit 104 inversely quantizes the quantized transformation coefficient 154 from the quantization unit 103 to obtain a reconstructed transformation coefficient 155. Specifically, the inverse quantization unit 104 performs inverse quantization in accordance with the quantization information used in the quantization unit 103. The quantization information used in the quantization unit 103 is loaded from the internal memory of the coding control unit 114. The inverse quantization unit 104 outputs the reconstruction transform coefficient 155 to the inverse orthogonal transform unit 105.

  The inverse orthogonal transformation unit 105 performs inverse orthogonal transformation corresponding to orthogonal transformation performed in the orthogonal transformation unit 102, such as inverse discrete cosine transformation, on the restoration transformation coefficient 155 from the inverse quantization unit 104, for example. A reconstructed prediction error signal 156 is obtained. The inverse orthogonal transform unit 105 outputs the restored prediction error signal 156 to the addition unit 106.

  The addition unit 106 adds the restored prediction error signal 156 and the corresponding predicted image signal 159 to generate a local decoded image signal 157. The decoded image signal 157 is subjected to a deblocking filter or a Wiener filter (not shown) and input to the reference image memory 107.

  The reference image memory 107 stores the to-be-filtered image signal 158 after local decoding in the memory, and is referred to as the reference image signal 158 when the inter prediction unit 108 generates a prediction image as needed.

  The inter prediction unit 108 performs inter prediction using the reference image signal 158 stored in the reference image memory 107. Specifically, the inter prediction unit 108 performs block matching processing between the block to be predicted and the reference image signal 158 to derive the amount of movement shift (motion vector). The inter prediction unit 108 performs motion compensation (interpolation processing in the case of motion with decimal precision) based on the motion vector to generate an inter prediction image. H. In H.264, interpolation processing to 1/4 pixel accuracy is possible. The derived motion vector is entropy encoded as part of motion information 160.

  The motion information memory 110 includes a motion information compression unit 109, appropriately performs compression processing on the motion information 160, reduces the amount of information, and temporarily stores the information as reference motion information 166. As shown in FIG. 5, a spatial direction reference motion information memory 501 in which motion information memory 110 is held in frame (or slice) units and stores motion information 160 on the same frame as reference motion information 166, and It further includes a time direction reference motion information memory 502 that stores motion information 160 of the frame for which encoding has been completed as reference motion information 166. The temporal direction reference motion information memory 502 may have a plurality of encoding target frames according to the number of reference frames used for prediction.

  Also, the spatial direction reference motion information memory 501 and the temporal direction reference motion information memory 502 may logically divide the physically same memory. Furthermore, the spatial direction reference motion information memory 501 holds only the spatial direction motion information necessary for the frame currently being encoded, sequentially compresses the spatial direction motion information for which no reference is required, and performs temporal direction reference motion. It may be stored in the information memory 502.

  The reference motion information 166 is held in the space direction reference motion information memory 501 and the time direction reference motion information memory 502 in predetermined area units (for example, 4 × 4 pixel block units). The reference motion information 166 further includes information indicating whether the region is encoded by inter prediction described later or encoded by intra prediction described later. In addition, the coding unit (or prediction unit) is H. As in the skip mode, the direct mode or the merge mode described later, the value of the motion vector in the motion information 160 is not encoded, and the motion information 160 predicted from the encoded area is used for inter Even when predicted, motion information of the coding unit (or prediction unit) is held as reference motion information 166.

  When the encoding process of the frame or slice to be encoded is completed, the spatial direction reference motion information memory 501 of the frame is changed as the temporal direction reference motion information memory 502 used for the next frame to be encoded. Ru. At this time, in order to reduce the memory capacity of the time direction reference motion information memory 502, the motion information 160 compressed by the motion information compression unit 109 described later is stored in the time direction reference motion information memory 502.

  The prediction information 165 follows the prediction mode controlled by the coding control unit 114, and as described above, it is possible to select inter prediction or intra prediction not shown for generation of the predicted image signal 159, but it is possible to select A plurality of modes can be further selected for each of and inter prediction. The coding control unit 114 determines one of a plurality of prediction modes of intra prediction and inter prediction as an optimum prediction mode, and sets prediction information 165.

  For example, the coding control unit 114 determines the optimal prediction mode using the cost function shown in the following equation (1).

  In Equation (1) (hereinafter referred to as simplified coding cost), OH indicates a code amount related to prediction information 160 (for example, motion vector information, prediction block size information), SAD indicates a prediction target block and a prediction image signal 159 The difference absolute value sum (ie, the cumulative sum of the absolute values of the prediction error signal 152) between In addition, λ indicates a Lagrange undetermined multiplier determined based on the value of quantization information (quantization parameter), and K indicates a coding cost. When Equation (1) is used, the prediction mode that minimizes the coding cost K is determined as the optimum prediction mode from the viewpoint of the generated code amount and the prediction error. As a modification of Equation (1), the coding cost may be estimated from only OH or only SAD, or the coding cost may be estimated using a value obtained by performing Hadamard transformation on SAD or an approximation thereof.

  Moreover, it is also possible to determine the optimal prediction mode by using a temporary coding unit (not shown). For example, the coding control unit 114 determines the optimal prediction mode using the cost function shown in the following equation (2).

  In Equation (2), D indicates the sum of squared errors (ie, coding distortion) between the block to be predicted and the local decoded image, and R indicates the prediction between the block to be predicted and the predicted image signal 159 in the prediction mode. Indicate the amount of code estimated for the error by provisional coding, and J indicates the coding cost. In the case of deriving the coding cost J of equation (2) (hereinafter referred to as the detailed coding cost), the circuit size or the amount of operation increases because temporary coding processing and local decoding processing are required for each prediction mode. . On the other hand, since the coding cost J is derived based on the more accurate coding distortion and the code amount, it is easy to determine the optimum prediction mode with high accuracy and maintain high coding efficiency. As a modification of Equation (2), the coding cost may be estimated from only R or D alone, or the coding cost may be estimated using an approximate value of R or D. Also, these costs may be used hierarchically. The encoding control unit 114 performs determination using Equation (1) or Equation (2) based on information (a prediction mode of surrounding pixel blocks, a result of image analysis, and the like) obtained in advance with respect to a prediction target block. The number of prediction mode candidates may be narrowed down in advance.

  As a modified example of the present embodiment, by performing two-step mode determination combining Equation (1) and Equation (2), it is possible to further reduce the number of prediction mode candidates while maintaining encoding performance. It becomes. Here, the simplified coding cost represented by the equation (1) can be calculated at high speed because the local decoding process is not necessary unlike the equation (2). In the moving picture coding apparatus of the present embodiment, H.264 is used. Since the number of prediction modes is large compared to H.264, mode determination using detailed coding cost is not realistic. Therefore, as a first step, mode determination using a simple coding cost is performed on a prediction mode available for the pixel block to derive prediction mode candidates.

  Here, the number of prediction mode candidates is changed using the property that the correlation between the simplified coding cost and the detailed coding cost increases as the value of the quantization parameter that defines the quantization roughness increases.

Next, the prediction processing of the image coding apparatus 100 will be described.
Although not shown, a plurality of prediction modes are prepared in the image coding apparatus 100 of FIG. 1, and in each prediction mode, the method of generating the prediction image signal 159 and the motion compensation block size are different from each other. As a method of generating the predicted image signal 159, the prediction unit 108 roughly divides the method into intra prediction (in frame, in which a predicted image is generated using the reference image signal 158 of the encoding target frame (or field). Prediction) and inter prediction (interframe prediction) in which a prediction image is generated using the reference image signal 158 of one or more encoded reference frames (or reference fields). The prediction unit 108 selectively switches between intra prediction and inter prediction to generate a predicted image signal 159 of the current block.

  FIG. 6A shows an example of inter prediction. Inter prediction is typically performed in units of prediction units, and it is possible to have different motion information 160 in units of prediction units. In inter prediction, as shown in FIG. 6A, it is a pixel block in a reference frame that has already been encoded (eg, an encoded frame one frame before), and a prediction unit to be encoded and From the block 601 at the same position, the predicted image signal 159 is generated using the reference image signal 158 of the block 602 at the position spatially shifted according to the motion vector included in the motion information 160. That is, in the generation of the predicted image signal 159, the reference image signal 158 of the block 602 in the reference frame specified by the position (coordinates) of the current block and the motion vector included in the motion information 160 is used.

  In inter prediction, motion compensation with low pixel accuracy (for example, 1/2 pixel accuracy or 1/4 pixel accuracy) is possible, and interpolation pixel values are generated by performing filtering processing on the reference image signal 158. Be done. For example, H. In H.264, interpolation processing up to 1⁄4 pixel accuracy is possible for luminance signals. The interpolation process is performed according to H.1. In addition to the filtering defined in H.264, it can be implemented by using arbitrary filtering.

  In addition, in inter prediction, not only the example which uses the reference frame of 1 frame before as shown to FIG. 6A but as shown to FIG. 6B, any reference frame of encoded may be used. When reference image signals 158 of a plurality of reference frames having different time positions are held, information indicating which time position of the reference image signal 158 from which the predicted image signal 159 is generated is represented by a reference frame number. The reference frame number is included in the motion information 160. The reference frame number can be changed in area units (picture, slice, block units, etc.). That is, different reference frames may be used for each prediction unit. As an example, when the reference frame of 1 frame before encoding is used for prediction, the reference frame number of this area is set to 0, and when the reference frame of 2 frames before encoding is used for prediction, The reference frame number in this area is set to 1. As another example, when the reference image signal 158 for one frame is held in the reference image memory 107 (only one reference frame is held), the reference frame number is always 0. It is set.

  Furthermore, in inter prediction, it is possible to select and use a size suitable for a target block to be coded from among sizes of a plurality of prediction units prepared in advance. For example, motion compensation can be performed for each prediction unit obtained by dividing a coding tree unit as shown in FIGS. 7A to 7G. In addition, it is possible to perform motion compensation for each prediction unit obtained by dividing it into a non-rectangular shape as shown in FIGS. 7F and 7G.

  As described above, since the motion information 160 of the encoded pixel block (for example, 4 × 4 pixel block) in the encoding target frame used for inter prediction is held as the reference motion information 166, the input image signal According to the local nature of 151, optimal motion compensation block shapes and motion vectors, reference frame numbers can be used. Also, the coding unit and the prediction unit can be arbitrarily combined. When the coding tree unit is a 64 × 64 pixel block, further divide the coding tree unit into four for each of four coding tree units (32 × 32 pixel blocks) obtained by dividing the 64 × 64 pixel block. Hierarchically from 64 × 64 pixel blocks to 16 × 16 pixel blocks. Similarly, hierarchically 64 × 64 pixel blocks to 8 × 8 pixel blocks can be used. Here, assuming that the prediction unit is a coding tree unit divided into four, it is possible to execute hierarchical motion compensation processing from 64 × 64 pixel blocks to 4 × 4 pixel blocks. .

  Further, in inter prediction, bi-directional prediction using two types of motion compensation can be performed on a pixel block to be encoded. H. In H.264, two types of motion compensation are performed on the encoding target pixel block, and two types of predicted image signals are weighted and averaged to obtain a new predicted image signal (not shown). Two types of motion compensation in bidirectional prediction are referred to as list 0 prediction and list 1 prediction, respectively.

<Description of skip mode, merge mode, inter mode>
The image coding apparatus 100 according to the present embodiment uses a plurality of prediction modes with different coding processes shown in FIG. The skip mode in the drawing is a mode in which only the syntax related to the predicted motion information position 954 described later is encoded, and the other syntax is a mode not encoded. The merge mode is a mode in which only the syntax relating to the predicted motion information position 954, the transform coefficient information 153 is encoded, and the other syntax is not encoded. The inter mode is a mode in which the syntax relating to the predicted motion information position 954, the differential motion information 953 to be described later, and the transform coefficient information 153 are encoded. These modes are switched by the prediction information 165 controlled by the coding control unit 114.

<Motion Information Encoding Unit 403>
The motion information encoding unit 403 will be described below with reference to FIG.

  The motion information coding unit 403 includes a reference motion vector acquisition unit 901, a predicted motion vector selection switch (also referred to as a predicted motion information selection switch) 902, a subtraction unit 903, a differential motion information coding unit 904, and predicted motion information position coding. A unit 905 and a multiplexing unit 906 are included.

  The reference motion vector acquisition unit 901 receives at least the reference motion information 166 and the reference position information 164, and generates at least one or more prediction motion information candidates (also referred to as motion motion vector candidates) 951 (951A, 951B, ...). . 10 and 11 show an example of the position of the predicted motion information candidate 951 with respect to the target prediction unit. FIG. 10 shows the position of the prediction unit spatially adjacent to the target prediction unit. AX (X = 0 to nA-1) is a prediction unit adjacent on the left with respect to the target prediction unit, and BY (Y = 0 to nB-1) is a prediment adjacent on the target prediction unit. , C, D, and E indicate the prediction units adjacent to the upper right, upper left, and lower left, respectively, with respect to the target prediction unit. Further, FIG. 11 shows the position of the prediction unit in the reference frame which has already been coded, with respect to the prediction target prediction unit. Col in FIG. 11 indicates a prediction unit in the reference frame and at the same position as the prediction unit to be coded. FIG. 12 shows an example of a list showing the relationship between block positions of a plurality of motion prediction information candidates 951 and an index Mvpidx. Mvpidx 0 to 2 indicates a motion vector predictor candidate 951 located in the space direction, and Mvpidx 3 indicates a motion vector predictor candidate 951 located in the time direction. The prediction unit position A is inter prediction among AX shown in FIG. 10, that is, the prediction unit having the reference motion information 166 and the position where the value of X is the smallest is taken as the prediction unit position A. Further, the prediction unit position B is inter prediction among BY shown in FIG. 10, that is, it is a prediction unit having the reference motion information 166 and a position where the value of Y is smallest is taken as the prediction unit position A and Do. When the prediction unit position C is not inter prediction, the reference motion information 166 of the prediction unit position D is replaced as the reference motion information 166 of the prediction unit position C. When the prediction unit positions C and D are not inter predictions, the reference motion information 166 of the prediction unit position E is replaced as the reference motion information 166 of the prediction unit position C.

  When the size of the encoding target prediction unit is larger than the minimum prediction unit, the prediction unit position Col may hold a plurality of pieces of reference motion information 166 in the temporal direction reference motion information memory 502. In this case, reference motion information 166 in the prediction unit at the position Col is acquired according to the reference position information 164. Hereinafter, the acquisition position of the reference motion information 166 in the prediction unit at the position Col will be referred to as a reference motion information acquisition position. 13A to 13F illustrate an example of the reference motion information acquisition position in the case where the reference position information 164 indicates the center of the prediction unit at the position Col for each size (32 × 32 to 16 × 16) of the encoding target prediction unit. Each block in the figure indicates a 4 × 4 prediction unit, and a circle indicates the position of the 4 × 4 prediction unit to be acquired as the prediction motion information candidate 951. Another example of the reference motion information acquisition position is shown in FIGS. In FIGS. 14A to 14F, since the position of the circle is not 4x4 prediction unit, the predetermined method such as the average value or the median value of the reference motion information 166 in the four 4x4 prediction units adjacent to the circle is Predictive motion information candidate 951 is generated. As another example of the reference motion information acquisition position, the reference motion information 166 of the 4x4 prediction unit located at the upper left end of the prediction unit at the position Col may be used as the prediction motion information candidate 951. Even if other than the above example, the predicted motion information candidate 951 may be generated using any position and method as long as it is a predetermined method.

  When the reference motion information 166 does not exist, the motion information 160 having a zero vector is output as the predicted motion information candidate 951.

  By the above, at least one or more prediction motion information candidates 951 are output from the reference motion block. When the reference frame number of the prediction motion information candidate 951 is different from the reference frame number of the encoding target prediction unit, the reference frame number of the prediction motion information candidate 951 and the encoding target prediction of the prediction motion information candidate 951 It may be scaled according to the unit's reference frame number.

  The prediction motion information selection switch 902 selects one of the plurality of prediction motion information candidates 951 in response to a command from the coding control unit 114, and outputs prediction motion information 952. Also, the predicted motion information selection switch 902 may output predicted motion information position information 954 described later. The selection may be made using an evaluation function such as Equation (1) or (2). Subtraction unit 903 subtracts prediction motion vector information 952 from motion information 160, and outputs difference motion information 953 to difference motion information coding unit 904. The differential motion information encoding unit 904 encodes the differential motion information 953 and outputs encoded data 960A. In the skip mode and the merge mode, encoding of the differential motion information 953 is unnecessary in the differential motion information encoding unit 904.

  The prediction motion information position coding unit 905 codes prediction motion information position information 954 (Mvpidx) indicating which prediction motion information candidate 951 is selected from the list shown in FIG. 12, and outputs the coded data 960B. Do. The prediction motion information position information 954 is encoded using isometric coding or variable length coding generated from the total number of prediction motion information candidates 951. Variable-length coding may be performed using correlation with adjacent blocks. Furthermore, when there is information overlapping in a plurality of prediction motion information candidates 951, a code table is created from the total number of prediction motion information candidates 951 from which overlapping prediction motion information candidates 951 have been deleted, and prediction motion information position information 954 is encoded It does not matter. In addition, when the total number of prediction motion information candidates 951 is one type, the prediction motion information candidates 951 are determined to be prediction motion information 952, so it is not necessary to encode the prediction motion information position information 954.

  Further, in each of the skip mode, the merge mode and the inter mode, it is not necessary to derive the prediction motion information candidate 951 in the same derivation method, and the derivation method of the prediction motion information candidate 951 may be set independently. In this embodiment, the method of deriving prediction motion information candidate 951 in the skip mode and the inter mode is the same, and the method of deriving prediction motion information candidate 951 in the merge mode is different.

<Details of Motion Information Compression Unit 109>
First, motion information compression processing will be described using FIG. FIG. 15 compresses the reference motion information 166 of the space direction reference motion information memory 501 and stores it in the time direction reference motion information memory 502. In the spatial direction reference motion information memory 501, the reference motion information 166 held at the representative motion information position is stored in the time direction reference motion information memory 502 for each motion information compression block (16 × 16 pixel blocks in the figure). When the above-described motion information coding process is performed, the reference motion information 166 held at the above-described reference motion information acquisition position is set as a predicted motion information candidate 951. At this time, the reference motion information 166 held at the above-described reference motion information acquisition position may be set as the predicted motion information candidate 951 as the motion information compression block virtually has the same reference motion information 166. None (the same prediction motion information candidate 951 is derived)
Next, the motion information compression unit 109 will be described using the flowchart shown in FIG.
The motion information compression unit 109 compresses the motion information 160 and stores the motion information 160 in the time direction reference motion information memory 502 when the encoding process of a frame (or an arbitrary unit such as a slice or a coding unit) is completed. .

  First, reference position information 164 is acquired from the encoding control unit 114 (step S1601), and a frame is divided into motion information compression blocks which are compression units of the motion information 160 (step S1602). The motion information compression block is a pixel block larger than a unit (typically 4 × 4 pixel block) in which motion information 160 is held by motion compensation processing, and is typically a 16 × 16 pixel block. The motion information compression block may be a 64x64 pixel block, a 32x32 pixel block, an 8x8 pixel block, a rectangular pixel block, or a pixel region of any shape.

  Next, a representative motion information position is generated according to the reference position information 164 (step S1603). As an example of generating a representative motion information position, when the motion information compression block is a 16 × 16 pixel block, the reference motion information acquisition position is representatively represented when the size of the prediction unit shown in FIGS. 13D, 14D, and 17D is 16 × 16. The motion information position. Next, reference motion information 166 of the generated representative motion information position is set as representative motion information (step S1604), and the representative motion information is stored in the time direction reference motion information memory (step S1605). The above steps S1604 to S1605 are performed on all motion information compression blocks.

  Assuming that the unit in which the motion information 160 is held is MxM blocks and the size of the motion information compression block is NxN (N is a multiple of M), the capacity of the reference motion information memory is reduced to (MxM ) / (NxN) can be reduced.

Another Embodiment of Representative Motion Information Position
As another example of generating a representative motion information position, the central position of a plurality of reference motion information acquisition positions may be used as the representative motion information position. FIGS. 18A and 18B show representative motion information positions for each motion compression block whose size is 16 × 16. FIG. 18A is a representative motion information position when the reference motion information acquisition position is the position shown in FIG. 13D, and similarly FIG. 18B is a representative motion information when the reference motion information acquisition position is the position shown in FIG. The position is shown respectively. Circles in FIG. 18A and FIG. 18B indicate reference motion information acquisition positions when the prediction unit is a 16 × 16 block, and are located at the center positions (also referred to as center of gravity positions) of four reference motion information acquisition positions. The representative motion information positions indicated by crosses are arranged.

  As another example of generating a representative motion information position, a reference motion information acquisition position for each size of a plurality of prediction units is included as the reference position information 164, and a representative motion information position is generated from the plurality of reference motion information acquisition positions It does not matter.

  As an example of generating a representative motion information position, a reference motion information acquisition position for each size of a plurality of prediction units is included as the reference position information 164, and even if a representative motion information position is generated from a plurality of reference motion information acquisition positions I do not care. FIG. 19 shows the centers (reference motion information acquisition positions) of the prediction units at each size of the prediction unit of 16 × 16 or more when the tree block is a 64 × 64 pixel block.

  As another example of generating a representative motion information position, the representative motion information position may be set using a reference motion information acquisition position arranged for each motion information compression block. FIG. 20A shows an example where the center of gravity of a plurality of reference motion information acquisition positions for each motion information compression block is set as a representative motion information position. If the position of the center of gravity does not coincide with the position of the 4x4 block, the nearest 4x4 block may be used as the representative motion information position, or a reference motion vector 166 of the center of gravity position is obtained using interpolation such as bilinear interpolation. You may generate it.

  Further, FIG. 20B shows an example where one of a plurality of reference motion information acquisition positions is selected for each motion information compression block, and a representative motion information position is set.

  Further, FIGS. 21A and 21B further show an example in which reference motion information acquisition positions are made identical in each motion information compression block in a tree block. Since the representative motion information positions are the same in all the motion information compression blocks, it is not necessary to switch the representative motion information positions according to the position in the tree block. Further, the representative motion information position may be located at any position, such as the upper left end or the upper right end in the motion information compression block, as well as in FIGS. 21A and 21B.

  The representative motion information position may be indicated using BlkIdx indicating the 4x4 block position in the motion information compression block in Z scan order as an example of generating the representative motion information position. When the size of the motion information compression block is 16 × 16, the representative motion information position shown in FIG. 21A corresponds to the position of BlkIdx = 12. The representative motion information position shown in FIG. 21B corresponds to the position of BlkIdx = 15.

  As another example of the motion information compression process, the reference information may be included in the motion information compression process in order to reduce the memory capacity of the reference frame number. In this case, the reference frame number held at the representative motion information position is stored in the memory capacity related to the reference frame number. Therefore, the spatial direction reference motion information memory 501 and the spatial direction reference motion information memory 502 shown in FIG. 5 store the reference frame number in addition to the motion vector information.

  As another example of the motion information compression processing, when the motion information compression processing does not include the reference frame number, the motion vector information in the motion information at the representative motion information position is subjected to scaling processing using the reference frame number May be stored in the motion information memory 110. As a typical example of the scaling process, there is a linear scaling process based on the reference frame number zero. This is to perform linear scaling processing so that motion vector information refers to a reference frame corresponding to the reference frame number zero when the reference frame number is a value other than zero. The reference of the scaling process described above may be a value other than zero for the reference frame number. When division occurs when the above-described linear scaling processing is performed, the division processing may be previously made into a table, and the division may be realized by drawing a table each time.

  When the size of the motion information compression block is other than 16 × 16 blocks, the representative motion information position is generated using the same process as described above. In one example, when the size of the motion information compression block is 64x64, the reference motion information acquisition position where the size of the prediction unit is 64x64 is taken as the representative motion information position. In yet another example, the motion information compression block size shown in FIG. 21A, FIG. 21B, etc. represents the representative motion information position in the 16x16 block, and the horizontal and vertical scaled position according to the motion information compression block size represents the representative motion It does not matter as an information position.

  If the reference motion information does not exist because the representative motion information position is outside the picture or slice, a new representative motion is a position where the reference motion information can be acquired in the motion information compression block, such as the upper left end of the motion information compression block. It may be replaced as an information position. Also, even when the representative motion information position is an area to which intra prediction is applied and there is no reference motion information, the same processing may be performed to replace it as a new representative motion information position.

<Syntax configuration>
Hereinafter, the syntax used by the image coding apparatus 100 of FIG. 1 will be described.
The syntax indicates the structure of encoded data (for example, encoded data 163 in FIG. 1) when the image encoding apparatus encodes moving image data. When decoding this encoded data, the moving picture decoding apparatus performs syntax interpretation with reference to the same syntax structure. A syntax 2200 used by the moving picture coding apparatus of FIG. 1 is illustrated in FIG.

  The syntax 2200 includes three parts of high level syntax 2201, slice level syntax 2202 and coding tree level syntax 2203. The high level syntax 2201 includes syntax information of a layer higher than the slice. A slice refers to a rectangular area or continuous area included in a frame or field. The slice level syntax 2202 includes information necessary to decode each slice. The coding tree level syntax 2203 includes information necessary to decode each coding tree (ie, each coding tree unit). Each of these parts contains further detailed syntax.

  High level syntax 2201 includes sequence and picture level syntax, such as sequence parameter set syntax 2204 and picture parameter set syntax 2205. The slice level syntax 2202 includes a slice header syntax 2206, a slice data syntax 2207, and the like. The coding tree level syntax 2203 includes a coding tree unit syntax 2208, a transform unit syntax 2209, a prediction unit syntax 2210, and the like.

The coding tree unit syntax 2208 can have a quadtree structure.
Specifically, coding tree unit syntax 2208 can be further recursively called as a syntax tree unit syntax 2208 syntax element. That is, one coding tree unit can be subdivided into quadtrees. In addition, transform unit syntax 2209 and pre-discussion unit syntax 2210 are included in coding tree unit syntax 2208. Transform unit syntax 2209 and Predi Cushion unit syntax 2210 are called in each coding tree unit syntax 2208 at the end of the quadtree. Information related to prediction is described in the pre-de-cushion unit syntax 2210, and information related to inverse orthogonal transformation, quantization, etc. is described in the transform unit syntax 2209, respectively.

FIG. 23 exemplifies a sequence parameter set syntax 2204 according to the present embodiment. Motion_vector_buffer_comp_flag shown in FIG. 23A and FIG. 23B is syntax that indicates validity / invalidity of motion information compression according to the present embodiment with respect to the sequence. When motion_vector_buffer_comp_flag is 0, the motion information compression according to the present embodiment is invalid for the sequence. Therefore, the processing of the motion information compression unit shown in FIG. 1 is skipped. As an example, when motion_vector_buffer_comp_flag is 1, motion information compression according to the present embodiment is effective for the sequence. Motion_vector_buffer_comp_ratio_log 2 shown in FIG. 23 and FIG. 23B is information indicating a unit of motion information compression processing, and is shown when motion_vector_buffer_comp_flag is 1. motion_vector_buffer_comp_ratio_log2 indicates, for example, information on the size of the motion information compression block according to the present embodiment, and motion_vector_buffer_comp_ratio_log2 is the motion information compression block size obtained by multiplying the minimum unit of motion compensation by 2 ^{(motion_vector_buffer_comp_ratio_log2)} . An example in which the minimum unit of motion compensation is a 4 × 4 pixel block, that is, the reference motion information memory is held in 4 × 4 pixel block units, will be shown below. When motion_vector_buffer_comp_ratio_log2 is 1, the size of the motion information compression block according to the present embodiment is an 8 × 8 pixel block. Similarly, when motion_vector_buffer_comp_ratio_log2 is 2, the size of the motion information compression block according to the present embodiment is a 16 × 16 pixel block. Motion_vector_buffer_comp_position shown in FIG. 23B is information indicating a representative motion information position in a motion information compression block, and is shown when motion_vector_buffer_comp_flag is 1. motion_vector_buffer_comp_position indicates, for example, the reference motion information position in the motion information compression block as shown in FIGS. 21A and 21B, or indicates the reference motion information position for each motion information compression block as shown in FIGS. 20A and 20B. It does not matter. Also, it may be at the center of a plurality of blocks.

  Further, as another example, in the syntax of layers lower than motion_vector_buffer_comp_flag, motion_vector_buffer_comp_ratio_log2, motion_vector_buffer_comp_position (picture parameter set syntax, slice level syntax, coding tree unit, transform unit, etc.) The validity / invalidity of such prediction may be defined.

  FIG. 24 shows an example of the prediction unit syntax. The skip_flag in the drawing is a flag indicating whether the prediction mode of the coding unit to which the prediction unit syntax belongs is the skip mode. If skip_flag is 1, it indicates that syntax (coding unit syntax, prediction unit syntax, transform unit syntax) other than predicted motion information position information 954 is not encoded. NumMVPCand (L0) and NumMVPCand (L1) indicate the number of prediction motion information candidates 951 in list 0 prediction and list 1 prediction, respectively. When a prediction motion information candidate 951 exists (NumMVPCand (LX)> 0, X = 0 or 1), mvp_idx_lX indicating prediction motion information position information 954 is encoded.

  When skip_flag is 0, it indicates that the prediction mode of the coding unit to which the prediction unit syntax belongs is not the skip mode. NumMergeCandidates indicates the number of prediction motion information candidates 951 derived in FIG. If a prediction motion information candidate 951 exists (NumMergeCandidates> 0), merge_flag, which is a flag indicating whether the prediction unit is in merge mode, is encoded. merge_flag indicates that the prediction unit is in merge mode when the value is 1, and indicates that the prediction unit uses inter mode when the value is 0. When merge_flag is 1 and there are two or more prediction motion information candidates 951 (NumMergeCandidates> 1), merge_idx which is prediction motion information 952 indicating which block of prediction motion information candidates 951 is to be merged is encoded .

  When merge_flag is 1, prediction unit syntaxes other than merge_flag and merge_idx do not need to be encoded.

  If merge_flag is 0, it indicates that the prediction unit is in the inter mode. In inter mode, in the case of mvd_lX (X = 0 or 1) indicating difference motion vector information included in the difference motion information 953, reference frame number ref_idx_lX, and B slice, the prediction unit is unidirectional prediction (list 0 or list 1) Inter_pred_idc indicating whether it is bi-directional prediction is encoded. Also, as in the skip mode, NumMVPCand (L0) and NumMVPCand (L1) are acquired, and when there is a predicted motion information candidate 951 (NumMVPCand (LX)> 0, X = 0 or 1), predicted motion information position information 954 Mvp_idx_lX indicating is encoded.

  The above is the syntax configuration according to the present embodiment.

Second Embodiment
The second embodiment relates to a moving picture decoding apparatus. The moving picture coding apparatus corresponding to the moving picture decoding apparatus according to the present embodiment is as described in the first embodiment. That is, the moving picture decoding apparatus according to the present embodiment decodes, for example, coded data generated by the moving picture coding apparatus according to the first embodiment.

  As shown in FIG. 25, the moving picture decoding apparatus according to this embodiment includes an entropy decoding unit 2501, an inverse quantization unit 2502, an inverse orthogonal transformation unit 2503, an addition unit 2504, a reference image memory 2505, and an inter prediction unit 2506. , A reference motion information memory 2507, a reference motion information compression unit 2508, and a decoding control unit 2510.

  The moving picture decoding apparatus shown in FIG. 25 decodes the encoded data 2550, stores the decoded picture signal 2554 in the output buffer 2511 and outputs it as an output picture. The encoded data 2550 is output from, for example, the moving picture coding apparatus shown in FIG. 1, and is input to the moving picture decoding apparatus 2500 through a storage system or a transmission system (not shown).

  The entropy decoding unit 2501 performs decoding based on the syntax to decode the encoded data 2550. The entropy decoding unit 2501 performs entropy decoding on the code sequence of each syntax sequentially to reproduce the coding parameters of the current block, such as the motion information 2559 and the quantization transformation coefficient 2551. The coding parameter is a parameter necessary for decoding prediction information, information on transform coefficients, information on quantization, and the like.

  Specifically, as shown in FIG. 26, the entropy decoding unit 2501 includes a separation unit 2601, a parameter decoding unit 2602, a transform coefficient decoding unit 2603 and a motion information decoding unit 2604. A separating unit 2601 separates the encoded data 2550, and encodes the encoded data 2651A relating to parameters into a parameter decoding unit 2602, the encoded data 2651B relating to transform coefficients into a transform coefficient decoding unit 2603, and the encoded data 2651C relating to motion information into motion information It outputs to the decoding unit 2604 respectively. The parameter decoding unit 2602 decodes the coding parameter 2570 such as prediction information and outputs the coding parameter 2570 to the decoding control unit 2510. Transform coefficient decoding section 2603 receives as input encoded data 2651 B, decodes transform coefficient information 2551, and outputs the result to inverse quantization section 2502.

  The motion information decoding unit 2604 receives the encoded data 2651 C from the separation unit 2601, the reference position information 2560 from the decoding control unit 2510, and the reference motion information 2558 from the reference motion information memory 2507, and outputs the motion information 2559. The output motion information 2559 is input to the inter prediction unit 2506.

  The motion information decoding unit 2604 is, as shown in FIG. 27, a separation unit 2701, a differential motion information decoding unit 2702, a predicted motion information position decoding unit 2503, a reference motion information acquisition unit 2704, a predicted motion information selection switch 2705, An adder 2706 is included.

  The encoded data 2651 C relating to motion information is input to the separation unit 2701, and is separated into encoded data 2751 relating to differential motion information and encoded data 2752 relating to the predicted motion information position. The differential motion information encoding unit 2702 receives the encoded data 2751 related to differential motion information, and decodes the differential motion information 2753. The differential motion information 2753 is added to predicted motion information 2756 to be described later by the addition unit 2706, and motion information 2759 is output. The prediction motion information position decoding unit 2703 receives the coded data 2752 related to the prediction motion information position, and decodes the prediction motion information position 2754.

  The prediction motion information position 2754 is input to the prediction motion information selection switch 2705, and selects prediction motion information 2756 from among the prediction motion information candidates 2755. The predicted motion information position information 2560 is decoded using isometric decoding or variable length decoding generated from the number of predicted motion information candidates 2755. Variable length decoding may be performed using the correlation with the adjacent block. Furthermore, when a plurality of prediction motion information candidates 2755 overlap, prediction motion information position information 2560 may be decoded from a code table generated from the total number of prediction motion information candidates 2755 from which duplication has been deleted. Further, when the total number of prediction motion information candidates 2755 is one type, the prediction motion information candidate 2755 is determined to be prediction motion information 2556, and therefore there is no need to decode the prediction motion information position information 2754.

  The reference motion information acquisition unit 2704 has the same configuration and processing content as the reference motion information acquisition unit 901 described in the first embodiment.

The reference motion information acquisition unit 2704 receives the reference motion information 2558 and the reference position information 2560, and generates at least one or more predicted motion information candidates 2755 (2755A, 2755B,...). FIGS. 10 and 11 show an example of the position of the predicted motion information candidate 2755 with respect to the prediction target prediction unit. FIG. 10 shows the position of the prediction unit spatially adjacent to the decoding target prediction unit. AX (X = 0 to nA-1) is a prediction unit adjacent on the left with respect to the target prediction unit, and BY (Y = 0 to nB-1) is a prediment adjacent on the target prediction unit. , C, D, and E indicate prediction units adjacent to the upper right, upper left, and lower left, respectively, for the prediction target prediction unit.
Further, FIG. 11 shows the position of the prediction unit in the reference frame that has already been decoded, with respect to the prediction target prediction unit. Col in the figure indicates a prediction unit in the reference frame and at the same position as the prediction unit to be decoded. FIG. 12 shows an example of a list showing the relationship between the block positions of the plurality of predicted motion information candidates 2755 and the index Mvpidx. Mvpidx of 0 to 2 indicates a predicted motion information candidate 2755 located in the space direction, and Mvpidx of 3 indicates a motion estimation vector candidate 2755 located in the time direction. The prediction unit position A is inter prediction among AX shown in FIG. 10, that is, the prediction unit having the reference motion information 2558, and the position at which the value of X is smallest is taken as the prediction unit position A. Further, the prediction unit position B is inter prediction among BY shown in FIG. 10, that is, it is a prediction unit having the reference motion information 2558 and a position where the value of Y is the smallest is the prediction unit position A Do. When the prediction unit position C is not inter prediction, the reference motion information 2558 of the prediction unit position D is replaced as the reference motion information 2558 of the prediction unit position C. When the prediction unit positions C and D are not inter prediction, the reference motion information 2558 of the prediction unit position E is replaced as the reference motion information 2558 of the prediction unit position C.

  When the size of the prediction target prediction unit is larger than the minimum prediction unit, the prediction unit position Col may hold a plurality of reference motion information 2558 in the temporal direction reference motion information memory 2507. In this case, reference motion information 2558 in the prediction unit at position Col is obtained in accordance with reference position information 2560. Hereinafter, the acquisition position of the reference motion information 2558 in the prediction unit at the position Col will be referred to as a reference motion information acquisition position. 13A to 13F show an example of the reference motion information acquisition position when the reference position information 2560 indicates the center of the prediction unit at the position Col, for each size (32 × 32 to 16 × 16) of the decoding target prediction unit. Each block in the figure indicates a 4 × 4 prediction unit, and a circle indicates the position of the 4 × 4 prediction unit to be acquired as the predicted motion information candidate 2755. Another example of the reference motion information acquisition position is shown in FIGS. In FIGS. 14A to 14F, since the position of the circle is 4 × 4 prediction unit not present, the predetermined method such as the average value or the median value of the reference motion information 2558 in the four x4 prediction units adjacent to the circle is Predictive motion information candidate 2755 is generated. As another example of the reference motion information acquisition position, the reference motion information 2558 of the 4x4 prediction unit located at the upper left end of the prediction unit at the position Col may be used as the prediction motion information candidate 2755. Even if other than the above example, the predicted motion information candidate 2755 may be generated using any position and method as long as it is a predetermined method.

  When the reference motion information 2558 does not exist, motion information 2559 having a zero vector is output as a predicted motion information candidate 2755.

  By the above, at least one or more prediction motion information candidates 2755 are output from the reference motion block. When the reference frame number of the above prediction motion information candidate 2755 is different from the reference frame number of the decoding target prediction unit, the reference frame number of the prediction motion information candidate 2755 and the decoding target prediction unit of the prediction motion information candidate 2755 It may be scaled according to the reference frame number of. The prediction motion information selection switch 2705 selects one of the plurality of prediction motion information candidates 2755 according to the prediction motion information position 2754, and outputs prediction motion information 952.

  The inverse quantization unit 2502 performs inverse quantization on the quantized transformation coefficient 2551 from the entropy decoding unit 2501 to obtain a reconstructed transformation coefficient 2552. Specifically, the inverse quantization unit 2502 performs inverse quantization in accordance with the information on the quantization decoded by the entropy decoding unit 2501. The inverse quantization unit 2502 outputs the restoration transform coefficient 2552 to the inverse orthogonal transformation unit 2503.

  The inverse orthogonal transformation unit 2503 performs inverse orthogonal transformation corresponding to the orthogonal transformation performed on the encoding side on the reconstruction transform coefficient 2552 from the inverse quantization unit 2502 to obtain a reconstruction prediction error signal 2553. The inverse orthogonal transform unit 2503 inputs the restored prediction error signal 2553 to the addition unit 2504.

  The addition unit 2504 adds the restored prediction error signal 2553 and the corresponding predicted image signal 2556 to generate a decoded image signal 2554. Decoded image signal 2554 is subjected to a deblocking filter, a Wiener filter, etc., not shown, and temporarily stored in output buffer 2511 for an output image, and also stored in reference image memory 2505 for reference image signal 2555. Ru. The decoded image signal 2554 stored in the reference image memory 2505 is referred to as a reference image signal 2555 by the inter prediction unit 2506 in units of frames or fields as necessary. The decoded image signal 2554 temporarily stored in the output buffer 2511 is output according to the output timing managed by the decoding control unit 2510.

  The inter prediction unit 2506 performs inter prediction using the reference image signal 2555 stored in the reference image memory 2505. Specifically, the inter prediction unit 2506 obtains, from the entropy decoding unit 2501, motion information 2559 including the shift amount (motion vector) of motion between the block to be predicted and the reference image signal 2555, and uses this motion vector. Interpolation processing (motion compensation) is performed to generate an inter prediction image. The generation of the inter prediction image is the same as that of the first embodiment, and thus the description thereof is omitted.

  The decoding control unit 2510 controls each element of the moving picture decoding apparatus shown in FIG. Specifically, the decoding control unit 2510 outputs reference position information 2560 to be described later to the entropy decoding unit 2501, and performs various controls for the decoding process including the above-described operation.

<Description of skip mode, merge mode, inter mode>
The image decoding apparatus 2500 according to the present embodiment uses a plurality of different prediction modes of the decoding process shown in FIG. The skip mode in the drawing is a mode in which only the syntax related to the predicted motion information position 2754 described later is decoded, and the other syntaxes are not decoded. The merge mode is a mode in which only the syntax related to the predicted motion information position 2754 and the transform coefficient information 2551 are decoded, and the other syntax is not decoded. The inter mode is a mode for decoding syntax relating to the predicted motion information position 2754, differential motion information 2753 described later, and transform coefficient information 2551. These modes are switched by prediction information 2571 controlled by the decoding control unit 2510.

  Further, since the moving picture decoding apparatus shown in FIG. 25 uses syntax the same as or similar to the syntax described in FIG. 28, its detailed description will be omitted.

<Details of Motion Information Compression Unit 2508>
Next, the motion information compression unit 2508 will be described using the flowchart shown in FIG. The motion information compression unit 2508 compresses the motion information 2559 and stores the motion information 2559 in the time direction reference motion information memory 502 when the decoding processing of a frame (or an arbitrary unit such as a slice or a coding unit) is completed. .

  First, reference position information 2560 is acquired from the decoding control unit 2510 (step S1601), and the frame is divided into motion information compression blocks which are compression units of the motion information 2559 (step S1602). The motion information compression block is a pixel block larger than a unit (typically, 4 × 4 pixel block) in which motion information 2559 is held by motion compensation processing, and is typically a 16 × 16 pixel block. The motion information compression block may be a 32 × 32 pixel block, an 8 × 8 pixel block, a rectangular pixel block, or a pixel region of any shape.

Next, the representative motion information position is generated according to the reference position information 2560 (step S1603). As an example of generating a representative motion information position, when the motion information compression block is a 16 × 16 pixel block, the reference motion information acquisition position is representatively represented when the size of the prediction unit shown in FIG. 13D, FIG. The motion information position.
Next, reference motion information 2558 of the generated representative motion information position is set as representative motion information (step S1605), and the representative motion information is stored in the time direction reference motion information memory (step S1606). The above steps S1604 to S1605 are performed on all motion information compression blocks.

  Assuming that the unit in which the motion information 2559 is held is MxM blocks and the size of the motion information compression block is NxN (N is a multiple of M), the capacity of the reference motion information memory is reduced to (MxM ) / (NxN) can be reduced.

Another Embodiment of Representative Motion Information Position
As another example of generating a representative motion information position, the central position of a plurality of reference motion information acquisition positions may be used as the representative motion information position. FIGS. 18A and 18B show representative motion information positions for each motion compression block whose size is 16 × 16. FIG. 18A is a representative motion information position when the reference motion information acquisition position is the position shown in FIG. 13D, and similarly FIG. 18B is a representative motion information when the reference motion information acquisition position is the position shown in FIG. The position is shown respectively. Circles in FIGS. 18A and 18B indicate reference motion information acquisition positions when the prediction unit is 16 × 16, and representative motions indicated by crosses at the center positions of the four reference motion information acquisition positions It arranges the information position.

  As another example of generating a representative motion information position, a reference motion information acquisition position for each size of a plurality of prediction units is included as reference position information 2560, and a representative motion information position is generated from the plurality of reference motion information acquisition positions It does not matter. FIG. 19 shows the centers (reference motion information acquisition positions) of the prediction units at each size of the prediction unit of 16 × 16 or more when the tree block is a 64 × 64 pixel block.

  As another example of generating a representative motion information position, the representative motion information position may be set using a reference motion information acquisition position arranged for each motion information compression block. FIG. 20A shows an example where the center of gravity of a plurality of reference motion information acquisition positions for each motion information compression block is set as a representative motion information position. If the position of the center of gravity does not coincide with the position of the 4x4 block, the nearest 4x4 block may be used as the representative motion information position, or a reference motion vector 166 of the center of gravity position is obtained using interpolation such as bilinear interpolation. You may generate it.

  Further, FIG. 20B shows an example where one of a plurality of reference motion information acquisition positions is selected for each motion information compression block, and a representative motion information position is set.

  Further, FIGS. 21A and 21B further show an example in which the reference motion information acquisition position is made the same in each motion information compression block in the tree block. Since the representative motion information positions are the same in all the motion information compression blocks, it is not necessary to switch the representative motion information positions according to the position in the tree block. Further, the representative motion information position may be located at any position, such as the upper left end or the upper right end in the motion information compression block, as well as in FIGS. 21A and 21B.

  The representative motion information position may be indicated using BlkIdx indicating the 4x4 block position in the motion information compression block in Z scan order as an example of generating the representative motion information position. When the size of the motion information compression block is 16 × 16, the representative motion information position shown in FIG. 21A corresponds to the position of BlkIdx = 12. The representative motion information position shown in FIG. 21B corresponds to the position of BlkIdx = 15.

  As another example of the motion information compression process, the reference information may be included in the motion information compression process in order to reduce the memory capacity of the reference frame number. In this case, the reference frame number held at the representative motion information position is stored in the memory capacity related to the reference frame number. Therefore, the spatial direction reference motion information memory 501 and the spatial direction reference motion information memory 502 shown in FIG. 5 store the reference frame number in addition to the motion vector information.

  As another example of the motion information compression processing, when the motion information compression processing does not include the reference frame number, the motion vector information in the motion information at the representative motion information position is subjected to scaling processing using the reference frame number May be stored in the motion information memory 110. As a typical example of the scaling process, there is a linear scaling process based on the reference frame number zero. This is to perform linear scaling processing so that motion vector information refers to a reference frame corresponding to the reference frame number zero when the reference frame number is a value other than zero. The reference of the scaling process described above may be a value other than zero for the reference frame number. When division occurs when the above-described linear scaling processing is performed, the division processing may be previously made into a table, and the division may be realized by drawing a table each time.

  When the size of the motion information compression block is other than 16 × 16 blocks, the representative motion information position is generated using the same process as described above. In one example, when the size of the motion information compression block is 64x64, the reference motion information acquisition position where the size of the prediction unit is 64x64 is taken as the representative motion information position. In yet another example, the motion information compression block size shown in FIG. 21A, FIG. 21B, etc. represents the representative motion information position in the 16x16 block, and the horizontal and vertical scaled position according to the motion information compression block size represents the representative motion It does not matter as an information position.

  If the reference motion information does not exist because the representative motion information position is outside the picture or slice, a new representative motion is a position where the reference motion information can be acquired in the motion information compression block, such as the upper left end of the motion information compression block. It may be replaced as an information position. Also, even if the representative motion information position is an area to which intra prediction is applied and there is no reference motion information, the same processing may be performed to replace it as a new representative motion information position.

Hereinafter, modifications of each embodiment will be listed and introduced.
In the first and second embodiments, an example in which a frame is divided into rectangular blocks having a size of 16 × 16 pixels, and encoding / decoding is sequentially performed from the block on the upper left of the screen to the lower right is described. See Figure 2A). However, the coding order and the decoding order are not limited to this example. For example, encoding and decoding may be sequentially performed from the lower right to the upper left, or may be performed so as to draw a spiral from the center of the screen to the edge of the screen. Furthermore, encoding and decoding may be sequentially performed from the upper right to lower left, or may be performed so as to draw a spiral from the screen edge toward the screen center.

  The first and second embodiments have been described by exemplifying the block sizes to be predicted such as 4 × 4 pixel blocks, 8 × 8 pixel blocks, and 16 × 16 pixel blocks, but the blocks to be predicted are uniform blocks It does not have to be in shape. For example, the size of the block to be predicted (prediction unit) may be 16 × 8 pixel block, 8 × 16 pixel block, 8 × 4 pixel block, 4 × 8 pixel block, or the like. Moreover, it is not necessary to unify all block sizes in one coding tree unit, and a plurality of different block sizes may be mixed. When a plurality of different block sizes are mixed in one coding tree unit, the amount of code for encoding or decoding division information also increases as the number of divisions increases. Therefore, it is desirable to select the block size in consideration of the balance between the code amount of the division information and the quality of the local decoded image or the decoded image.

  In the first and second embodiments, for the sake of simplicity, the luminance signal and the color difference signal are not distinguished, and a comprehensive description is described regarding color signal components. However, if the prediction process is different between the luminance signal and the color difference signal, the same or different prediction methods may be used. If a different prediction method is used between the luminance signal and the chrominance signal, the selected prediction method for the chrominance signal can be encoded or decoded in the same manner as the luminance signal.

In the first and second embodiments, for the sake of simplicity, the luminance signal and the color difference signal are not distinguished, and a comprehensive description is described regarding color signal components. However, if orthogonal transform processing differs between the luminance signal and the color difference signal, the same or different orthogonal transform method may be used.
If a different orthogonal transformation method is used between the luminance signal and the chrominance signal, the orthogonal transformation method selected for the chrominance signal can be encoded or decoded in the same manner as the luminance signal.

  In the first and second embodiments, syntax elements not defined in the embodiment can be inserted between the rows of the table shown in the syntax configuration, and the descriptions regarding other conditional branches are included. It does not matter. Alternatively, the syntax table can be divided and integrated into a plurality of tables. Further, the same term need not necessarily be used, and may be arbitrarily changed depending on the form to be used.

  As described above, each embodiment can realize highly efficient orthogonal transformation and inverse orthogonal transformation while alleviating the difficulty in hardware implementation and software implementation. Therefore, according to each embodiment, the coding efficiency is improved, and the subjective image quality is also improved.

Also, the instructions shown in the processing procedure shown in the above-described embodiment can be executed based on a program that is software. A general-purpose computer system can store this program in advance and read this program to obtain the same effects as those of the moving picture coding apparatus and the moving picture decoding apparatus according to the above-described embodiment. is there.
The instructions described in the above-described embodiment are a program that can be executed by a computer, such as a magnetic disk (flexible disk, hard disk, etc.), an optical disk (CD-ROM, CD-R, CD-RW, DVD-ROM, DVD ± R, DVD ± RW, etc.), semiconductor memory, or similar recording media. The storage format may be any form as long as the storage medium is readable by a computer or an embedded system. If a computer reads a program from the recording medium and causes the CPU to execute an instruction described in the program based on the program, the computer is similar to the video encoding device and the video decoding device according to the above-described embodiment. The operation can be realized. Of course, when a computer acquires or loads a program, it may acquire or load through a network.
In addition, an operating system (OS) operating on a computer based on instructions of a program installed in a computer or an embedded system from a recording medium, database management software, MW (middleware) such as a network, etc. realize this embodiment. You may perform a part of each process for doing.
Furthermore, the recording medium in the embodiment of the present invention is not limited to a medium independent of a computer or an embedded system, and includes a recording medium downloaded and stored or temporarily stored a program transmitted by a LAN, the Internet or the like. Further, the program for realizing the processing of each of the above embodiments may be stored on a computer (server) connected to a network such as the Internet, and downloaded to the computer (client) via the network.
Further, the recording medium is not limited to one, and even when the processing in the present embodiment is executed from a plurality of media, it is included in the recording medium in the embodiment of the present invention, and the configuration of the medium is any configuration. Good.

The computer or the embedded system in the embodiment of the present invention is for executing each process in the present embodiment based on the program stored in the recording medium, and is an apparatus comprising one of a personal computer, a microcomputer and the like. The configuration may be any system such as a system in which a plurality of devices are connected to a network.
Further, the computer in the embodiment of the present invention is not limited to a personal computer, but includes an arithmetic processing unit, a microcomputer and the like included in an information processing device, and a device capable of realizing the function in the embodiment of the present invention by a program. It is a generic term for the device.

  While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

DESCRIPTION OF SYMBOLS 100 ... Image coding apparatus, 101 ... Subtraction part, 102 ... Orthogonal transformation part, 103 ... Quantization part, 104, 2502 ... Dequantization part, 105, 2503 ... Inverse orthogonal transformation part, 106, 2504, 2706 ... Addition part 107, 2505 Reference image memory 108, 2506 Inter prediction unit 109 Motion information compression unit 110 Motion information memory 112 Entropy coding unit 113 Output buffer 114 Coding control unit 401 ... Parameter coding unit 402 ... Transform coefficient coding unit 403 ... Motion information coding unit 404 ... Multiplexing unit 901 ... Reference motion vector acquisition unit 902 ... Predicted motion vector selection switch 903 ... Subtraction unit 904 ... Differential motion information coding unit, 905 ... Predictive motion information position coding unit, 906 ... Multiplexing unit, 2500 ... Moving picture decoding apparatus, 250 ... Entropy decoding unit, 2507 ... Reference motion information memory, 2508 ... Reference motion information compression unit, 2510 ... Decoding control unit, 2601, 2701 ... Separation unit, 2602 ... Parameter decoding unit, 2603 ... Transform coefficient decoding unit, 2604 ... motion information decoding unit, 2702 ... differential motion information decoding unit, 2503 ... predicted motion information position decoding unit, 2704 ... reference motion information acquisition unit, 2705 ... prediction motion information selection switch.

Claims (18)

A method for decoding encoded data having at least a decoding target block in a first frame, the method comprising:
Decode a merge flag indicating whether at least motion vectors for inter prediction are derived from the merge block,
The first motion vector candidate is derived from at least one adjacent block of the block to be decoded in the first frame, when the merge flag indicates that at least a motion vector for inter prediction is derived from the merge block,
The second motion vector candidate is derived from the representative position of the reference block in a second frame different from the first frame when the merge flag indicates that at least a motion vector involved in the inter prediction is derived from the merge block. ,
Decoding a merge index identifying the merge block from among the at least one neighboring block and the reference block;
Deriving a first motion vector of the current block from any one of the first motion vector candidate and the second motion vector candidate according to the merge index,
The reference block is determined based on a first position on the first frame of the decoding target block, and is a block having the first position on the second frame,
The representative position is a position determined in accordance with the second position and the size of the reference block, the representative position is a position of the center of the said reference block, and one of the positions other than the center of the reference block To be determined,
Information specifying which of the position of the center of the reference block and the position other than the center of the reference block is the representative position is determined based on at least the second position or the size. . Derive a reference image according to the first motion vector;
The method according to claim 1, further comprising generating a predicted image by the inter prediction using the reference image. Decoding transform coefficients from the encoded data;
Deriving a prediction error value by at least an inverse transformation of the transformation coefficients;
3. The method of claim 2, further comprising: deriving a decoded image by addition of at least the prediction error value and the predicted image.   The at least one adjacent block is (1) a block on the lower left side of the block to be decoded, (2) a block on the left side of the block to be decoded, (3) a block on the upper right side of the block to be decoded, The method according to any one of claims 1 to 3, which is at least one of an upper block of a block to be decoded and (5) a block on the upper left side of the block to be decoded.   The first number of merge indices indicating the first motion vector candidate as the merge block is smaller than the second number of the merge indices indicating the second motion vector candidate as the merge block. The method according to any one of the preceding claims.   The method according to any one of claims 1 to 5, wherein the reference block is a block including a position determined according to a position of the block to be decoded.   The method according to any one of claims 1 to 6, wherein the representative position is a block including not only the center of the reference block but also a position determined according to an end position of the reference block. Receiving the encoded data via a communication link;
Temporarily storing at least a portion of the encoded data in a buffer;
Reading at least a part of the encoded data from the buffer by a central processing unit (CPU);
The method according to any of the preceding claims, further comprising: deriving the first motion vector from the encoded data by the central processing unit. Receiving the encoded data via a communication link;
Temporarily storing at least a portion of the encoded data in a buffer;
Reading at least a part of the encoded data from the buffer by an electronic circuit;
The electronic circuit may further derive the first motion vector from the encoded data.
The method according to any one of claims 1 to 7, wherein the electronic circuit is a field programmable gate array (FPGA) or a digital signal processor (DSP). An electronic apparatus for decoding encoded data having at least a decoding target block in a first frame, the electronic apparatus comprising:
Decode a merge flag indicating whether at least motion vectors for inter prediction are derived from the merge block,
The first motion vector candidate is derived from at least one adjacent block of the block to be decoded in the first frame, when the merge flag indicates that at least a motion vector for inter prediction is derived from the merge block,
The second motion vector candidate is derived from the representative position of the reference block in a second frame different from the first frame when the merge flag indicates that at least a motion vector involved in the inter prediction is derived from the merge block. ,
Decoding a merge index identifying the merge block from among the at least one neighboring block and the reference block;
The decoder is configured to derive a first motion vector of the current block from any one of the first motion vector candidate and the second motion vector candidate according to the merge index.
The reference block is determined based on a first position on the first frame of the decoding target block, and is a block having the first position on the second frame,
The representative position is a position determined in accordance with the second position and the size of the reference block, the representative position is a position of the center of the said reference block, and one of the positions other than the center of the reference block To be determined,
Information specifying which of the position of the center of the reference block and the position other than the center of the reference block is the representative position is determined based on at least the second position or the size. apparatus. The decoder further comprises
Derive a reference image according to the first motion vector;
The electronic device according to claim 10, wherein a predicted image is generated by the inter prediction using the reference image. The decoder further comprises
Decoding transform coefficients from the encoded data;
Deriving a prediction error value by at least an inverse transformation of the transformation coefficients;
The electronic device according to claim 11, wherein a decoded image is derived by adding at least the prediction error value and the predicted image.   The at least one adjacent block is (1) a block on the lower left side of the block to be decoded, (2) a block on the left side of the block to be decoded, (3) a block on the upper right side of the block to be decoded, The electronic device according to any one of claims 10 to 12, wherein the electronic device is at least one of an upper block of a block to be decoded and (5) a block on the upper left side of the block to be decoded.   The first number of merge indices indicating the first motion vector candidate as the merge block is smaller than the second number of the merge indices indicating the second motion vector candidate as the merge block. Electronic device given in any 1 paragraph.   The electronic device according to any one of claims 10 to 14, wherein the reference block is a block including a position determined according to a position of the block to be decoded.   The electronic device according to any one of claims 10 to 15, wherein the representative position is a block including not only the center of the reference block but also a position determined according to an end position of the reference block. . A communication circuit for receiving the encoded data via a communication link;
A buffer for temporarily storing at least a part of the encoded data;
The decoder further comprises
Reading at least a part of the encoded data from the buffer by a central processing unit (CPU);
The electronic device according to any one of claims 10 to 16, wherein the central processing unit derives the first motion vector from the encoded data. A communication circuit for receiving the encoded data via a communication link;
A buffer for temporarily storing at least a part of the encoded data;
The decoder further comprises
Read at least a part of the encoded data from the buffer;
Deriving the first motion vector from the encoded data;
The electronic device according to any one of claims 10 to 16, wherein the decoder is a field programmable gate array (FPGA) or a digital signal processor (DSP).