Patent Publication Number: US-11659189-B2

Title: Video encoding device, video decoding device, video encoding method, video decoding method, and program

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     The present application is a continuation application of U.S. patent application Ser. No. 16/910,288 filed on Jun. 24, 2020, which is a continuation application of U.S. patent application Ser. No. 15/146,005, filed on May 4, 2016, which issued as U.S. Pat. No. 10,742,991, which is a continuation application of U.S. patent application Ser. No. 13/881,467, filed on May 3, 2013, which issued as U.S. Pat. No. 10,154,267, which is a National Stage of International Application No. PCT/JP2011/006509 filed on Nov. 22, 2011, claiming priority based on Japanese Patent Application Numbers 2010-264320 filed on Nov. 26, 2010 and 2011-26331 filed on Feb. 9, 2011, the contents of all of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a video encoding device and a video decoding device that use PCM encoding. 
     BACKGROUND ART 
     Patent Literature (PTL) 1 proposes a video encoding method for embedding, in an output bitstream, information indicating a block type that is not subjected to a transform process and an entropy encoding process, in order to guarantee a certain processing time for a video encoding device or a video decoding device. 
     An example of the block type that is not subjected to the transform process and the entropy encoding process is pulse code modulation (PCM) described in Non Patent Literature (NPL) 1. The term block type means an encoding type (below-mentioned intra prediction, inter prediction, and PCM) used for a block. 
     A video encoding device described in NPL 1 has a structure shown in  FIG.  14   . The video encoding device shown in  FIG.  14    is hereafter referred to as a typical video encoding device. 
     A structure and an operation of the typical video encoding device that receives each frame of digitized video as input and outputs a bitstream are described below, with reference to  FIG.  14   . 
     The video encoding device shown in  FIG.  14    includes a transformer/quantizer  102 , an entropy encoder  103 , an inverse transformer/inverse quantizer  104 , a buffer  105 , a predictor  106 , a PCM encoder  107 , a PCM decoder  108 , a multiplex data selector  109 , a multiplexer  110 , a switch  121 , and a switch  122 . 
     The video encoding device shown in  FIG.  14    divides each frame into blocks of 16×16 pixel size called macroblocks (MBs), and encodes each MB sequentially from top left of the frame. In AVC described in NPL 1, each MB is further divided into blocks of 4×4 pixel size, and each block of 4×4 pixel size is encoded. 
       FIG.  15    is an explanatory diagram showing an example of block division in the case where the frame has a spatial resolution of QCIF (Quarter Common Intermediate Format). The following describes an operation of each unit while focusing only on pixel values of luminance, for simplicity&#39;s sake. 
     A prediction signal supplied from the predictor  106  is subtracted from the block-divided input video, and the result is input to the transformer/quantizer  102 . There are two types of prediction signal, namely, an intra prediction signal and an inter-frame prediction signal. Each of the prediction signals is described below. 
     The intra prediction signal is a prediction signal generated based on an image of a reconstructed picture that has the same display time as a current picture and is stored in the buffer  105 . Referring to 8.3.1 Intra 4×4 prediction process for luma samples, 8.3.2 Intra 8×8 prediction process for luma samples, and 8.3.3 Intra 16×16 prediction process for luma samples in NPL 1, intra prediction of three block sizes, i.e. Intra 4×4, Intra 8×8, and Intra 16×16, are available. 
     Intra 4×4 and Intra 8×8 are respectively intra prediction of 4×4 block size and 8×8 block size, as can be understood from (a) and (c) in  FIG.  16   . Each circle (○) in the drawing represents a reference pixel used for intra prediction, i.e. a pixel of the reconstructed picture having the same display time as the current picture. 
     In intra prediction of Intra 4×4, reconstructed peripheral pixels are directly set as reference pixels, and used for padding (extrapolation) in nine directions shown in (b) in  FIG.  16    to form the prediction signal. In intra prediction of Intra 8×8, pixels obtained by smoothing peripheral pixels of the image of the reconstructed picture by low-pass filters (½, ¼, ½) shown under the right arrow in (c) in  FIG.  16    are set as reference signals, and used for extrapolation in the nine directions shown in (b) in  FIG.  16    to form the prediction signal. 
     Similarly, Intra 16×16 is intra prediction of 16×16 block size, as can be understood from (a) in  FIG.  17   . Each circle (○) in the drawing represents a reference pixel used for intra prediction, i.e. a pixel of the reconstructed picture having the same display time as the current picture, as in  FIG.  16   . In intra prediction of Intra 16×16, peripheral pixels of the reconstructed image are directly set as reference pixels, and used for extrapolation in four directions shown in (b) in  FIG.  17    to form the prediction signal. 
     Hereafter, an MB and a block encoded using the intra prediction signal are respectively referred to as an intra MB and an intra block, a block size of intra prediction is referred to as an intra prediction block size, and a direction of extrapolation is referred to as an intra prediction direction. The intra prediction block size and the intra prediction direction are prediction parameters related to intra prediction. 
     The inter-frame prediction signal is a prediction signal generated from an image of a reconstructed picture that has a different display time from the one the current picture has and is stored in the buffer  105 . Hereafter, an MB and a block encoded using the inter-frame prediction signal are respectively referred to as an inter MB and an inter block. A block size of inter prediction (inter prediction block size) can be selected from, for example, 16×16, 16×8, 8×16, 8×8, 8×4, 4×8, and 4×4. 
       FIG.  18    is an explanatory diagram showing an example of inter-frame prediction using 16×16 block size. A motion vector MV=(mv x , mv y ) shown in  FIG.  18    is a prediction parameter of inter-frame prediction, which indicates the amount of parallel translation of an inter-frame prediction block (inter-frame prediction signal) of a reference picture relative to a block to be encoded. In AVC, prediction parameters of inter-frame prediction include not only an inter-frame prediction direction representing a direction of the reference picture of the inter-frame prediction signal relative to a picture to be encoded of the block to be encoded, but also a reference picture index for identifying the reference picture used for inter-frame prediction of the block to be encoded. This is because, in AVC, a plurality of reference pictures stored in the buffer  105  can be used for inter-frame prediction. 
     Inter-frame prediction is described in more detail in 8.4 Inter prediction process in NPL 1. 
     A picture encoded including only intra MBs is called an I picture. A picture encoded including not only intra MBs but also inter MBs is called a P picture. A picture encoded including inter MBs that use not only one reference picture but two reference pictures simultaneously for inter-frame prediction is called a B picture. In the B picture, inter-frame prediction in which the direction of the reference picture of the inter-frame prediction signal relative to the picture to be encoded of the block to be encoded is to the past is called forward prediction, inter-frame prediction in which the direction of the reference picture of the inter-frame prediction signal relative to the picture to be encoded of the block to be encoded is to the future is called backward prediction, and inter-frame prediction involving both the past and the future is called bidirectional prediction. The direction of inter-frame prediction (inter prediction direction) is a prediction parameter of inter-frame prediction. 
     The transformer/quantizer  102  frequency-transforms the image (prediction error image) from which the prediction signal has been subtracted. 
     The transformer/quantizer  102  further quantizes the frequency-transformed prediction error image (frequency transform coefficient), with a predetermined quantization step width Qs. Hereafter, the quantized frequency transform coefficient is referred to as a transform quantization value. 
     The entropy encoder  103  entropy-encodes the prediction parameters and the transform quantization value. The prediction parameters are information related to MB and block prediction, such as block type (intra prediction, inter prediction, and PCM), intra prediction block size, intra prediction direction, inter prediction block size, and motion vector mentioned above. 
     The inverse transformer/inverse quantizer  104  inverse-quantizes the transform quantization value, with the quantization step width Qs. The inverse transformer/inverse quantizer  104  further inverse-frequency-transforms the frequency transform coefficient obtained by the inverse quantization. The prediction signal is added to the reconstructed prediction error image obtained by the inverse frequency transform, and the result is supplied to the switch  122 . 
     The multiplex data selector  109  monitors the amount of input data of the entropy encoder  103  corresponding to the MB to be encoded. In the case where the entropy encoder  103  is capable of entropy-encoding the input data within a processing time of the MB, the multiplex data selector  109  selects the output data of the entropy encoder  103 , and causes the selected data to be supplied to the multiplexer  110  via the switch  121 . The multiplex data selector  109  further selects the output data of the inverse transformer/inverse quantizer  104 , and causes the selected data to be supplied to the buffer  105  via the switch  122 . 
     In the case where the entropy encoder  103  is not capable of entropy-encoding the input data within the processing time of the MB, the multiplex data selector  109  selects the output data of the PCM encoder  107  obtained by PCM encoding the video of the MB, and causes the selected data to be supplied to the multiplexer  110  via the switch  121 . The multiplex data selector  109  further selects the output data of the PCM decoder  108  obtained by PCM decoding the output data of the PCM encoder  107 , and causes the selected data to be supplied to the buffer  105  via the switch  122 . 
     The buffer  105  stores the reconstructed image supplied via the switch  122 . The reconstructed image per frame is referred to as a reconstructed picture. 
     The multiplexer  110  multiplexes the output data of the entropy encoder  103  and the PCM encoder  107 , and outputs the multiplexing result. 
     Based on the operation described above, the multiplexer  110  in the video encoding device generates the bitstream. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Patent Application Laid-Open No. 2004-135251 
     Non Patent Literatures 
     NPL 1: ISO/IEC 14496-10 Advanced Video Coding 
     NPL 2: “Test Model under Consideration”, Document: JCTVC-B205, Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11 2nd Meeting: Geneva, CH, 21-28 Jul. 2010 
     NPL 3: W.-J. Chen, X. Wang, and M. Karczewicz, “CE5 Improved coding of inter prediction mode with LCEC,” JCTVC-D370 
     NPL 4: S. Liu, Y.-W. Huang, S. Lei, “Remove Partition Size N×N,” JCTVC-D432 
     SUMMARY OF INVENTION 
     Technical Problem 
     The typical technique described above guarantees a certain processing time for a video encoding device or a video decoding device by using, in MBs, PCM that does not involve a transform process and an entropy encoding process. 
     However, the typical technique described above is based on video encoding that uses MBs of a fixed coding unit size (CU size). Accordingly, as described in NPL 2, when the typical technique described above is applied to video encoding (hereafter referred to as Test Model under Consideration scheme (TMuC scheme)) that uses coding units (coding tree blocks (CTBs)) of a quadtree structure shown in  FIG.  19    where the CU size is variable and information (PCM header) indicating PCM is embedded in the output bitstream in CTBs of all layers (i.e. all depths), there is a problem that the ratio of the number of bits of the PCM header included in the bitstream increases and so the quality of compressed video decreases. 
     Here, a maximum CTB is referred to as a largest coding tree block (LCTB), and a minimum CTB is referred to as a smallest coding tree block (SCTB). In this Description, a block corresponding to the CTB is referred to as a coding unit (CU). Moreover, a concept of a prediction unit (PU) (see  FIG.  20   ) as a unit of prediction for the CU is introduced in the TMuC scheme.  FIG.  20    is an explanatory diagram for describing the PU, where only the squares from among the shapes shown in  FIG.  20    are supported as the intra prediction block size. 
     NPL 3 describes improvements in signaling of inter prediction. NPL 4 describes improvements in signaling of inter prediction and intra prediction. 
     To solve the problem of the typical technique described above, the point that PCM may be selected in a higher-layer CU in order to guarantee a certain processing time for a video encoding device or a video decoding device is taken into consideration. The higher-layer CU is a CU of a greater depth value, as can be seen from  FIG.  19   . The number of higher-layer CUs per frame is smaller because their block size is larger. Since the number of higher-layer CUs is smaller, the ratio of the number of bits of the PCM header included in the bitstream can be reduced. 
     In the present invention, the problem is solved by limiting the depth of the CU for which the PCM header is transmitted, in video encoding based on PCM encoding. That is, in the present invention, the CU size for which the PCM header is transmitted is limited to a predetermined size. 
     Solution to Problem 
     A video encoding device according to the present invention includes: transform means for transforming an image block; entropy encoding means for entropy-encoding transformed data of the image block transformed by the transform means; PCM encoding means for encoding by PCM encoding the image block; multiplex data selection means for selecting output data of the entropy encoding means or the PCM encoding means, in a block of a block size set from the outside; and multiplexing means for embedding a PCM header in a bitstream, in the block of the block size set from the outside. 
     A video decoding device according to the present invention includes: de-multiplexing means for de-multiplexing a bitstream including PCM block size information; PCM block size determination means for determining a PCM block size for which a PCM header is parsed based on the PCM block size information de-multiplexed by the de-multiplexing means; PCM header parsing means for parsing from the bitstream the PCM header, in a block of the PCM block size determined by the PCM block size determination means; entropy decoding means for entropy-decoding transformed data of an image included in the bitstream; inverse transform means for inverse-transforming the transformed data entropy-decoded by the entropy decoding means; PCM decoding means for decoding by PCM decoding PCM data of the image in the bitstream; and decoding control means for controlling the entropy decoding means and the PCM decoding means based on the PCM header parsed by the PCM header parsing means. 
     A video encoding method according to the present invention includes: selecting data obtained by entropy-encoding transformed data of an image block or data obtained by PCM encoding the image block, in a unit of a block size set from the outside; and embedding a PCM header in a bitstream, in a block of the block size set from the outside. 
     A video decoding method according to the present invention includes: de-multiplexing a bitstream including PCM block size information; determining a PCM block size for parsing a PCM header based on the de-multiplexed PCM block size information; parsing from the bitstream the PCM header, in a block of the determined PCM block size; controlling an entropy decoding process and a PCM decoding process based on the PCM header: entropy-decoding transformed data of an image in the bitstream and inverse-transforming the entropy-decoded transformed data upon the entropy decoding process being controlled; and decoding by PCM decoding PCM data of the image in the bitstream upon the PCM decoding process being controlled. 
     A video encoding program according to the present invention causes a computer to execute: a selection process of selecting data obtained by entropy-encoding transformed data of an image block or data obtained by PCM encoding the image block, in a unit of a block size set from the outside; and a multiplexing process of embedding a PCM header in a bitstream, in a block of the block size set from the outside. 
     A video decoding program according to the present invention causes a computer to execute: a de-multiplexing process of de-multiplexing a bitstream including PCM block size information; a PCM block size determination process of determining a PCM block size for parsing a PCM header based on the de-multiplexed PCM block size information; a PCM header parsing process of parsing from the bitstream the PCM header, in a block of the determined PCM block size; and a process of controlling an entropy decoding process and a PCM decoding process based on the parsed PCM header: wherein the computer is caused to execute a process of entropy-decoding transformed data of an image in the bitstream and inverse-transforming the entropy-decoded transformed data upon the entropy decoding process being controlled, and wherein the computer is caused to execute a process of decoding by PCM decoding PCM data of the image in the bitstream upon the PCM decoding process being controlled. 
     Advantageous Effects of Invention 
     According to the present invention, the coding unit size for which the PCM header is signaled is limited to the predetermined size, so that the ratio of the number of bits of the PCM header in the bitstream can be kept low and the quality of compressed video can be maintained, while guaranteeing a certain processing time for the video encoding device. 
     Moreover, according to the present invention, the interoperability of the video encoding device and the video decoding device can be enhanced by embedding, in the bitstream, the PCM coding unit size information for signaling the predetermined size to the video decoding device. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a block diagram of a video encoding device in Exemplary Embodiment 1. 
         FIG.  2    is an explanatory diagram of list 1 indicating a PCM header in PU syntax. 
         FIG.  3    is an explanatory diagram of list 2 indicating PCM coding unit size information in a sequence parameter set. 
         FIG.  4    is a flowchart showing a PCM header writing operation. 
         FIG.  5    is a block diagram of a video decoding device in Exemplary Embodiment 2. 
         FIG.  6    is a flowchart showing a PCM header parsing operation. 
         FIG.  7    is an explanatory diagram of list 3 indicating PCM coding unit size information in a picture parameter set. 
         FIG.  8    is an explanatory diagram of list 4 indicating PCM coding unit size information in a slice header. 
         FIG.  9    is an explanatory diagram of list 1 indicating a PCM header in PU syntax in Exemplary Embodiment 3. 
         FIG.  10    is a flowchart showing a PCM header parsing operation in Exemplary Embodiment 3. 
         FIG.  11    is a block diagram showing a structural example of an information processing system capable of realizing functions of a video encoding device and a video decoding device according to the present invention. 
         FIG.  12    is a block diagram showing a main part of a video encoding device according to the present invention. 
         FIG.  13    is a block diagram showing a main part of a video decoding device according to the present invention. 
         FIG.  14    is a block diagram of a typical video encoding device. 
         FIG.  15    is an explanatory diagram showing an example of block division. 
         FIG.  16    is an explanatory diagram for describing prediction types. 
         FIG.  17    is an explanatory diagram for describing prediction types. 
         FIG.  18    is an explanatory diagram showing an example of inter-frame prediction using 16×16 block size as an example. 
         FIG.  19    is an explanatory diagram for describing a CTB. 
         FIG.  20    is an explanatory diagram for describing a PU. 
     
    
    
     DESCRIPTION OF EMBODIMENT(S) 
     Exemplary Embodiment 1 
     Exemplary Embodiment 1 shows a video encoding device including: means for selecting output data of entropy encoding means or PCM encoding means in a CU size set from the outside; means for embedding, in a bitstream, a PCM header in the CU size set from the outside; and means for embedding, in the bitstream, information related to a PCM coding unit size for signaling the CU size set from the outside to a video decoding device. 
     To provide description using specific examples, in this exemplary embodiment it is assumed that the CU size for which the PCM header is embedded in the bitstream is greater than or equal to a PCM coding unit size set from the outside (pcmCodingUnitSize). It is also assumed that available coding unit sizes are 128, 64, 32, 16, and 8, and pcmCodingUnitSize is 16. It is further assumed that the information related to the PCM coding unit size is base-2 log (logarithm) of a value obtained by dividing the PCM coding unit size by the minimum coding unit size, as described later. Hence, in this exemplary embodiment, block sizes corresponding to CU sizes for which the PCM header is embedded in the bitstream are 128×128, 64×64, 32×32, and 16×16. Moreover, a specific value of the CU size-related information embedded in the bitstream is 1 (=log 2 (16/8)). 
     As shown in  FIG.  1   , the video encoding device in this exemplary embodiment includes a transformer/quantizer  102 , an entropy encoder  103 , an inverse transformer/inverse quantizer  104 , a buffer  105 , a predictor  106 , a PCM encoder  107 , a PCM decoder  108 , a multiplex data selector  109 , a multiplexer  110 , a switch  121 , and a switch  122 , like the typical video encoding device shown in  FIG.  14   . The video encoding device in this exemplary embodiment shown in  FIG.  1    differs from the video encoding device shown in  FIG.  14    in that pcmCodingUnitSize is supplied to the multiplex data selector  109  in order to transmit the PCM header in a CU size smaller than or equal to pcmCodingUnitSize, and pcmCodingUnitSize is also supplied to the multiplexer  110  in order to signal pcmCodingUnitSize to the video decoding device. 
     A prediction signal supplied from the predictor  106  is subtracted from input video of a CU size, and the result is input to the transformer/quantizer  102 . 
     The transformer/quantizer  102  frequency-transforms the image (prediction error image) from which the prediction signal has been subtracted. 
     The transformer/quantizer  102  further quantizes the frequency-transformed prediction error image (frequency transform coefficient), with a quantization step width Qs. 
     The entropy encoder  103  entropy-encodes split coding unit flag (see  FIG.  19   ) for signaling the CU size, prediction parameters supplied from the predictor  106 , and the transform quantization value supplied from the transformer/quantizer  102 . The prediction parameters are information related to prediction of the CU to be encoded, such as block type (intra prediction, inter prediction, and PCM), intra prediction block size, intra prediction direction, inter prediction block size, and motion vector. 
     Based on pcmCodingUnitSize set from the outside via the multiplex data selector  109 , the entropy encoder  103  in this exemplary embodiment entropy-encodes pcm_flag syntax, which indicates ON/OFF of PCM encoding, as OFF, in the case where the CU to be encoded has a size greater than or equal to pcmCodingUnitSize and also has a prediction mode of intra prediction. 
     The inverse transformer/inverse quantizer  104  inverse-quantizes the transform quantization value, with the quantization step width Qs. The inverse transformer/inverse quantizer  104  further inverse-frequency-transforms the frequency transform coefficient obtained by the inverse quantization. The prediction signal is added to the reconstructed prediction error image obtained by the inverse frequency transform, and the result is supplied to the switch  122 . 
     The multiplex data selector  109  monitors the amount of input data of the entropy encoder  103  corresponding to the CU to be encoded that is greater than or equal to pcmCodingUnitSize. In the case where the entropy encoder  103  is capable of entropy-encoding the input data within a processing time of the CU to be encoded that is greater than or equal to pcmCodingUnitSize, the multiplex data selector  109  selects the output data of the entropy encoder  103 , and causes the selected data to be supplied to the multiplexer  110  via the switch  121 . The multiplex data selector  109  further selects the output data of the inverse transformer/inverse quantizer  104 , and causes the selected data to be supplied to the buffer  105  via the switch  122 . 
     In the case where the entropy encoder  103  is not capable of entropy-encoding the input data within the processing time of the CU to be encoded, the multiplex data selector  109  first causes the entropy encoder  103  to entropy-encode and output information indicating that the CU greater than or equal to pcmCodingUnitSize is encoded by PCM encoding. In detail, the multiplex data selector  109  causes the entropy encoder  103  to entropy-encode and output mode_table_idx syntax or pred_mode syntax, which indicates a block type, as intra prediction, and entropy-encode and output the pcm_flag syntax, which indicates ON/OFF of PCM encoding, as ON, in a PU header of the CU. 
     Next, the output bits of the entropy encoder  103  are byte-aligned. In detail, the entropy encoder  103  supplies a predetermined amount of pcm_alignment_zero_bit syntax to the multiplexer  110 . Moreover, an encoding engine of the entropy encoder  103  is initialized for subsequent encoding. 
     After the encoding engine is initialized, the PCM encoder  107  encodes by PCM encoding the input video of the CU. Output data pcm_sample_luma[i] of luminance of the PCM encoder  107  has a pixel bit length bit_depth_luma of luminance of the input video. Here, i (0≤i≤255) is an index in raster scan order within the block of the CU. Likewise, output data pcm_sample_chroma[i] (i: 0≤i≤128) of color difference of the PCM encoder  107  has a pixel bit length bit_depth_chroma of color difference of the input video. 
     After the input video of the CU is encoded by PCM encoding, the PCM decoder  108  decodes by PCM decoding pcm_sample_luma[i] and pcm_sample_chroma[i]. 
     After the PCM decoding, the multiplex data selector  109  selects the output data of the PCM encoder  107 , and causes the selected data to be supplied to the multiplexer  110  via the switch  121 . 
     Lastly, the multiplex data selector  109  selects the output data of the PCM decoder  108 , and causes the selected data to be supplied to the buffer  105  via the switch  122 . 
     When complying with Specification of syntax functions, categories, and descriptors in NPL 1 and 4.1.10 Prediction unit syntax in NPL 2, the above-mentioned mode_table_idx syntax, pred_mode syntax, pcm_flag syntax, and pcm_alignment_zero_bit syntax can be signaled as represented in list 1 shown in  FIG.  2   . In list 1, a variable pcm_unit_flag which is a signaling condition of the pcm_alignment_zero_bit syntax is ON only in the case where the pcm_flag syntax for PCM encoding ON is signaled. Otherwise, the variable pcm_unit_flag is OFF. This exemplary embodiment has a feature that, in list 1, the pcm_flag syntax is signaled only in the PU header of the CU of the size greater than or equal to pcmCodingUnitSize, according to the condition “if(currPredUnitSize&gt;=pcmCodingUnitSize)”. 
     The multiplexer  110  multiplexes the information (max_pcm_coding_unit_hierarchy_depth) related to the PCM coding unit size and the output data of the entropy encoder  103  and the PCM encoder  107 , and outputs the multiplexing result. When complying with 4.1.2 Sequence parameter set RBSP syntax in NPL 2, max_pcm_coding_unit_hierarchy_depth syntax (base-2 log (logarithm) of a value obtained by dividing the PCM coding unit size by the minimum coding unit size, “1” in this exemplary embodiment) is multiplexed following log2_min_coding_unit_size_minus3 syntax and max_coding_unit_hierarchy_depth syntax of a sequence parameter set, as represented in list 2 shown in  FIG.  3   . Here, max_pcm_coding_unit_hierarchy_depth may be called min_pcm_coding_unit_hierarchy_depth. The log2_min_coding_unit_size_minus3 syntax and the max_coding_unit_hierarchy_depth syntax are information for determining a SCU size (MinCodingUnitSize) and a LCU size (MaxCodingUnitSize), respectively. MinCodingUnitSize and MaxCodingUnitSize are respectively computed as follows. 
     MinCodingUnitSize=1«(log2_min_coding_unit_size_minus3+3) 
     MaxCodingUnitSize=1«(log2_min_coding_unit_size_minus3+3+max_coding_unit_hierarchy_depth) 
     The max_coding_unit_hierarchy_depth syntax and MinCodingUnitSize have the following relation. 
     max_pcm_coding_unit_hierarchy_depth=log 2 (pcmCodingUnitSize/MinCodingUnitSize) 
     Based on the operation described above, the video encoding device according to the present invention generates the bitstream. 
     The following describes a PCM header writing operation which is a feature of the present invention, with reference to the flowchart in  FIG.  4   . 
     As shown in  FIG.  4   , in the case of not being capable of entropy-encoding within the processing time of the CU to be encoded, the entropy encoder  103  entropy-encodes the block type as intra prediction in step S 101 . That is, the entropy encoder  103  entropy-encodes the mode_table_idx syntax or the pred_mode syntax as intra prediction. In step S 102 , the entropy encoder  103  entropy-encodes the PCM header. In detail, the entropy encoder  103  entropy-encodes the pcm_flag syntax as ON. In step S 103 , the entropy encoder  103  byte-aligns the output bits by supplying the predetermined amount of the pcm_alignment_zero_bit syntax to the multiplexer  110 . That is, the entropy encoder  103  outputs the predetermined amount of the pcm_alignment_zero_bit syntax. The entropy encoder  103  also initializes the encoding engine. In step  5104 , the PCM encoder  107  encodes by PCM encoding the input video of the CU. 
     The video encoding device in this exemplary embodiment includes: multiplex data selection means for selecting output data of entropy encoding means or PCM encoding means in a coding unit size set from the outside; and multiplexing means for embedding, in a bitstream, a PCM header in the coding unit size set from the outside. Therefore, the ratio of the number of bits of the PCM header in the bitstream can be kept low and the quality of compressed video can be maintained, while guaranteeing a certain processing time for the video encoding device. 
     Moreover, the multiplexing means embeds, in the bitstream, PCM coding unit size information for signaling the CU size set from the outside to the video decoding device, where the CU size information can be expressed by, for example, a depth difference relative to a depth of a LCU or a SCU. For instance, in the case of expression relative to the depth of the LCU (LCU_depth), a CU size of a predetermined depth can be expressed as ½ (depth−LCU_depth)  of the LCU size (¼ (depth−LCU_depth)  when converted to block size). In the case of expression relative to the depth of the SCU (SCU_depth), a CU size of a predetermined depth can be expressed as 2 (SCU_depth−depth)  times the SCU size (4 (SCU_depth−depth)  times when converted to block size). 
     By the inclusion of the multiplexing means having the above-mentioned feature, the present invention can enhance the interoperability of the video encoding device and the video decoding device. 
     The video encoding device in this exemplary embodiment includes means for embedding, in the bitstream, the information related to the coding unit size for which the PCM header is provided, so as to enable the PCM header to be parsed from the bitstream and switching between entropy decoding means and PCM decoding means to be performed equally in video decoding. The interoperability of the video encoding device and the video decoding device can thus be enhanced. 
     Exemplary Embodiment 2 
     Exemplary Embodiment 2 shows a video decoding device that decodes the bitstream generated by the video encoding device in Exemplary Embodiment 1. 
     The video decoding device in this exemplary embodiment includes: means for de-multiplexing PCM coding unit size information multiplexed in the bitstream; block size means for determining a predetermined block size for which a PCM header is parsed, based on the de-multiplexed PCM coding unit size information; parsing means for parsing the PCM header from the bitstream in the coding unit size determined by the block size means; and decoding control means for controlling entropy decoding means and PCM decoding means based on the PCM header parsed by the parsing means. 
     As shown in  FIG.  5   , the video decoding device in this exemplary embodiment includes a de-multiplexer  201 , a decoding controller  202 , a PCM decoder  203 , an entropy decoder  204 , an inverse transformer/inverse quantizer  206 , a predictor  207 , a buffer  208 , a switch  221 , and a switch  222 . 
     The de-multiplexer  201  de-multiplexes the input bitstream, and extracts the PCM coding unit size information and the entropy-encoded or PCM-encoded video bitstream. The de-multiplexer  201  de-multiplexes the max_pcm_coding_unit_hierarchy_depth syntax following the log2_min_coding_unit_size_minus3 syntax and the max_coding_unit_hierarchy_depth syntax in the sequence parameters, as represented in list 2 shown in  FIG.  3   . The de-multiplexer  201  then determines, using the de-multiplexed syntax values, the PCM coding unit size pcmCodingUnitSize for which pcm_flag as the PCM header is transmitted, as follows.
         pcmCodingUnitSize=1«(log2_min_coding_unit_size_minus3+3+max_pcm_coding_unit_hierarchy_depth)       

     Thus, the de-multiplexer  201  in this exemplary embodiment also has a function of determining the block size of the coding unit for which the PCM header is parsed, based on the de-multiplexed PCM coding unit size information. 
     The entropy decoder  204  entropy-decodes the video bitstream. 
     In the case where the coding unit (CU) to be entropy-decoded is not a PCM-encoded CU, the entropy decoder  204  entropy-decodes the prediction parameters and the transform quantization value of the CU, and supplies them to the inverse transformer/inverse quantizer  206  and the predictor  207 . 
     Note that a CU is PCM-encoded in the case where, after split_coding_unit_flag (see  FIG.  19   ) is entropy-decoded and the CU size is determined, the pcm_flag syntax indicating PCM encoding ON in the PU header is entropy-decoded. Thus, the entropy decoder  204  in this exemplary embodiment also has a function of parsing the PCM header including the pcm_flag syntax from the bitstream in the CU of the size greater than or equal to pcmCodingUnitSize. 
     The inverse transformer/inverse quantizer  206  inverse-quantizes the transform quantization value of luminance and color difference, with a quantization step width. The inverse transformer/inverse quantizer  206  further inverse-frequency-transforms the frequency transform coefficient obtained by the inverse quantization. 
     After the inverse frequency transform, the predictor  207  generates a prediction signal using an image of a reconstructed picture stored in the buffer  208 , based on the entropy-decoded prediction parameters. 
     After the prediction signal generation, the prediction signal supplied from the predictor  207  is added to the reconstructed prediction error image obtained by the inverse frequency transform by the inverse transformer/inverse quantizer  206 , and the result is supplied to the switch  222 . 
     After the addition of the prediction signal, the decoding controller  202  switches the switch  222  to supply the reconstructed prediction error image to which the prediction signal has been added to the buffer  208  as the reconstructed image. 
     In the case where the CU is PCM-encoded, the decoding controller  202  causes a decoding engine of the entropy decoder  204  to be initialized. 
     The decoding controller  202  then causes the video bitstream which is in the middle of entropy decoding, to be byte-aligned. The decoding controller  202  causes pcm_alignment_zero_bit to be parsed from the video bitstream until byte-aligned. 
     Following this, the decoding controller  202  switches the switch  221  to supply the byte-aligned video bitstream to the PCM decoder  203 . 
     The PCM decoder  203  decodes by PCM decoding PCM-encoded luminance data pcm_sample_luma[i] and color difference data pcm_sample_chroma[i] corresponding to the block size of the CU, from the byte-aligned video bitstream. 
     After the PCM decoding, the decoding controller  202  switches the switch  222  to supply the PCM decoded coding unit image to the buffer  208  as the reconstructed image. The decoding controller  202  switches the switch  221  to the entropy decoder  204 , for decoding of a next macroblock. 
     The reconstructed picture stored in the buffer  208  is then output as a decoded image. 
     Based on the operation described above, the video decoding device in this exemplary embodiment generates the decoded image. 
     The following describes a PCM header parsing operation which is a feature of the present invention, with reference to the flowchart in  FIG.  6   . 
     As shown in  FIG.  6   , in the case where the CU is PCM-encoded, the entropy decoder  204  entropy-decodes split_coding_unit_flag and determines the CU size in step S 201 . In step  5202 , the entropy decoder  204  entropy-decodes the block type. That is, the entropy decoder  204  entropy-decodes the mode_table_idx syntax or the pred_mode syntax. In steps S 203  and S 204 , the entropy decoder  204  entropy-decodes the pcm_flag syntax only in the case where the block type is intra prediction and the CU size is a size greater than or equal to pcmCodingUnitSize. In the case where the pcm_flag syntax is ON, in step  5205  the entropy decoder  204  initializes the decoding engine. The entropy decoder  204  also byte-aligns the video bitstream by parsing the predetermined amount of the pcm_alignment_zero_bit_syntax from the de-multiplexer  201 . The PCM decoder  203  decodes by PCM decoding the PCM-encoded luminance data pcm_sample_luma[i] and color difference data pcm_sample_chroma[i] corresponding to the CU block size, from the byte-aligned video bitstream. In the case where the CU is not a PCM-encoded CU (step  5203 ) or in the case where the entropy decoder  204  does not entropy-decode the pcm_flag syntax indicating PCM encoding ON in the PU header (step S 204 ), the entropy decoder  204  entropy-decodes the prediction parameters and the transform quantization value of the following CU, and supplies them to the inverse transformer/inverse quantizer  206  and the predictor  207 . 
     The video decoding device in this exemplary embodiment can parse, based on the de-multiplexed PCM coding unit size information, the PCM header from the bitstream in the coding unit of the determined PCM coding unit size, and switch between the entropy decoding means and the PCM decoding means. Therefore, the bitstream in which the ratio of the number of bits of the PCM header is low to thereby maintain video quality can be decoded while guaranteeing a certain processing time for the video decoding device. 
     Note that the video encoding device may multiplex the PCM coding unit size information (max_pcm_coding_unit_hierarchy_depth) used in Exemplary Embodiment 1, in a picture parameter set or a slice header as represented in list 3 shown in  FIG.  7    or list 4 shown in  FIG.  8   . Similarly, the video decoding device may de-multiplex the max_pcm_coding_unit_hierarchy_depth syntax from the picture parameter set or the slice header. 
     Moreover, the max_pcm_coding_unit_hierarchy_depth syntax may be base-2 log (logarithm) of a value obtained by dividing the maximum coding unit size (MaxCodingUnitSize) by the PCM coding unit size (pcmCodingUnitSize). That is, the following expression may be used.
         max_pcm_coding_unit_hierarchy_depth=log 2 (MaxCodingUnitSize/pcmCodingUnitSize)       

     In this case, in the video decoding device, the PCM coding unit size can be computed based on the max_pcm_coding_unit_hierarchy_depth syntax as follows.
         pcmCodingUnitSize=1«(log2_min_coding_unit_size_minus3+3+max_coding_unit_hierarchy_depth−max_pcm_coding_unit_hierarchy_depth)       

     Note that the video encoding device may concatenate and encode the pcm_flag syntax with the mode_table_idx syntax or the pred_mode syntax. For example, in a CU of a size greater than or equal to the PCM coding unit size, mode_table_idx=0 (codeword 1) may be set as inter prediction, mode_table_idx=1 (codeword 00) as intra prediction with pcm_flag=OFF, and mode_table_idx=2 (codeword 01) as PCM. In a CU of a size less than the PCM coding unit size, mode_table_idx=0 (codeword 0) may be set as inter prediction, and mode_table_idx=1 (codeword 1) as intra prediction with pcm_flag=OFF. 
     In this case, in the CU of the size greater than or equal to the PCM coding unit size, the video decoding device interprets codeword 1 (mode_table_idx=0) as inter prediction, codeword 00 (mode_table_idx=1) as intra prediction with pcm_flag=OFF, and codeword 01 (mode_table_idx=2) as PCM. In the CU of the size less than the PCM coding unit size, the video decoding device interprets codeword 0 (mode_table_idx=0) as inter prediction, and codeword 1 (mode_table_idx=1) as intra prediction with pcm_flag=OFF. 
     Exemplary Embodiment 3 
     In each of the exemplary embodiments described above, PCM is selected in a higher-layer CU in order to guarantee a certain processing time for the video encoding device or the video decoding device. However, in the case of taking into consideration that PCM tends to be selected in an image block having low inter-pixel correlation, i.e. PCM tends to be selected in a lower-layer CU of a divided small region, it is also significant to limit to a predetermined size or less the CU size for which PCM is selected. Based on such consideration, the ratio of the number of bits of the PCM header in the bitstream can also be reduced. The lower-layer CU mentioned here is a CU having a larger depth value, as can be seen from  FIG.  19   . 
     In Exemplary Embodiment 3, a video encoding device limits the CU size for which PCM is selected, to the predetermined size or less. The video encoding device has the same structure as shown in  FIG.  1   . 
     In the case of limiting the CU size for which PCM is selected to the predetermined size or less, the CU size for which the PCM header is embedded in the bitstream is set to be less than or equal to the PCM coding unit size set from the outside (pcmCodingUnitSize), as an example. It is also assumed that available coding unit sizes are 128, 64, 32, 16, and 8, and pcmCodingUnitSize is 16. 
     In the video encoding device, the multiplex data selector  109  monitors the amount of input data of the entropy encoder  103  corresponding to the CU to be encoded that is less than or equal to pcmCodingUnitSize. In the case where the entropy encoder  103  is capable of entropy-encoding the input data within a processing time of the CU to be encoded that is less than or equal to pcmCodingUnitSize, the multiplex data selector  109  selects the output data of the entropy encoder  103 , and causes the selected data to be supplied to the multiplexer  110  via the switch  121 . In the case where the entropy encoder  103  is not capable of entropy-encoding the input data within the processing time of the CU to be encoded, the multiplex data selector  109  first causes the entropy encoder  103  to entropy-encode and output information indicating that the CU whose size is less than or equal to pcmCodingUnitSize is PCM-encoded. In detail, the multiplex data selector  109  causes the entropy encoder  103  to entropy-encode and output the mode_table_idx syntax or the pred_mode syntax, which indicates the block type, as intra prediction, and entropy-encode and output the pcm_flag syntax, which indicates ON/OFF of PCM encoding, as ON, in the PU header of the CU. 
     In this exemplary embodiment, when complying with Specification of syntax functions, categories, and descriptors in NPL 1 and 4.1.10 Prediction unit syntax in NPL 2, the video encoding device can signal the above-mentioned mode_table_idx syntax, pred_mode syntax, pcm_flag syntax, and pcm_alignment_zero_bit syntax as represented in list 1 shown in  FIG.  9   . In list 1 shown in  FIG.  9   , the variable pcm_unit_flag which is a signaling condition of the pcm_alignment_zero_bit syntax is ON only in the case where the pcm_flag syntax for PCM encoding ON is signaled. Otherwise, the variable pcm_unit_flag is OFF. This exemplary embodiment has a feature that, in list 1, the pcm_flag syntax is signaled only in the PU header of the CU whose size is less than or equal to pcmCodingUnitSize, according to the condition “if(currPredUnitSize«pcmCodingUnitSize)”. The other processes of the video encoding device are the same as the processes in Exemplary Embodiment 1. Besides, the contents of list 1 in this exemplary embodiment are the same as the contents of list 1 shown in  FIG.  2    in Exemplary Embodiment 1. 
     Exemplary Embodiment 4 
     Exemplary Embodiment 4 shows a video decoding device that decodes the bitstream generated by the video encoding device in Exemplary Embodiment 3. 
     The video decoding device in Exemplary Embodiment 4 has the same structure as shown in  FIG.  5   . In Exemplary Embodiment 4, however, the video decoding device performs a PCM header parsing operation as shown in the flowchart in  FIG.  10   . In the case where the CU is PCM-encoded, the entropy decoder  204  entropy-decodes split_coding_unit_flag and determines the CU size in step S 201 . In step S 202 , the entropy decoder  204  entropy-decodes the block type. That is, the entropy decoder  204  entropy-decodes the mode_table_idx syntax or the pred_mode syntax. In steps S 203 B and S 204 , the entropy decoder  204  entropy-decodes the pcm_flag syntax only in the case where the block type is intra prediction and the CU size is a size less than or equal to pcmCodingUnitSize. In the case where the pcm_flag syntax is ON, in step S 205  the entropy decoder  204  initializes the decoding engine. The entropy decoder  204  also byte-aligns the video bitstream by parsing the predetermined amount of the pcm_alignment_zero_bit syntax from the de-multiplexer  201 . The PCM decoder  203  decodes by PCM decoding the PCM-encoded luminance data pcm_sample_luma[i] and color difference data pcm_sample_chroma[i] corresponding to the CU block size, from the byte-aligned video bitstream. The other processes of the video decoding device are the same as the processes in Exemplary Embodiment 2. 
     In the case of limiting to the predetermined size or less the CU size for which PCM is selected, the entropy decoder  204  in the video decoding device also has a function of parsing the PCM header including the pcm_flag syntax from the bitstream in the CU whose size is less than or equal to pcmCodingUnitSize. 
     In this exemplary embodiment, the bitstream in which the ratio of the number of bits of the PCM header is low to thereby maintain video quality can be decoded while guaranteeing a certain processing time for the video decoding device. 
     Note that the video encoding device in Exemplary Embodiment 3 may concatenate and encode the pcm_flag syntax with the mode_table_idx syntax or the pred_mode syntax. For example, in a CU of a size less than or equal to the PCM coding unit size, mode_table_idx=0 (codeword 0) may be set as intra prediction with pcm_flag=OFF, mode_table_idx=1 (codeword 10) as inter prediction, and mode_table_idx=2 (codeword 11) as PCM. In a CU of a size greater than the PCM coding unit size, mode_table_idx=0 (codeword 0) may be set as intra prediction with pcm_flag=OFF, and mode_table_idx=1 (codeword 1) as inter prediction. 
     In this case, in the CU of the size less than or equal to the PCM coding unit size, the video decoding device in Exemplary Embodiment 4 interprets codeword 0 (mode_table_idx=0) as intra prediction with pcm_flag=OFF, codeword 10 (mode_table_idx=1) as inter prediction, and codeword 11 (mode_table_idx=2) as PCM. In the CU of the size greater than the PCM coding unit size, the video decoding device interprets codeword 0 (mode_table_idx=0) as intra prediction with pcm_flag=OFF, and codeword 1 (mode_table_idx=1) as inter prediction. 
     The pcm_flag syntax may be concatenated and encoded with the pred_mode syntax, in the same manner as in the example of the mode_table_idx syntax. 
     In the exemplary embodiments described above, in the case of limiting the PCM coding unit size to the maximum coding unit size, the PCM block size information need not be explicitly embedded in the bitstream. This is because the information related to the maximum coding unit size implicitly includes the PCM block size information in such a case. 
     In the exemplary embodiments described above, in the case of limiting the PCM coding unit size to the minimum coding unit size, the PCM block size information need not be explicitly embedded in the bitstream. This is because the information related to the minimum coding unit size implicitly includes the PCM block size information in such a case. 
     The pcm_flag syntax may be concatenated and encoded with the pred_mode syntax, in the same manner as in the above-mentioned example of the mode_table_idx syntax. For instance, in an intra slice, syntax and codeword can be associated as follows, as described in NPL 3 (note that this is based on an assumption that no N×N partition (intra prediction and inter prediction) exists in a coding unit other than a minimum coding unit as described in NPL 4). 
     [Correspondence Between Syntax and Codeword in Minimum Coding Unit Including PCM Encoding] 
                                             Syntax   Codeword                                                    Intra 2N × 2N   1           Intra N × N   01           PCM   00                        
[Correspondence Between Syntax and Codeword in CU Other Than Minimum Coding Unit Including PCM Encoding]
 
                                             Syntax   Codeword                          Intra 2N × 2N   1           PCM   0                        
[Correspondence Between Syntax and Codeword in Minimum Coding Unit Not Including PCM Encoding]
 
                                             Syntax   Codeword                          Intra 2N × 2N   1           Intra N × N   0                        
[Correspondence Between Syntax and Codeword in Minimum Coding Unit Not Including PCM Encoding]
 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Syntax 
                 Codeword 
               
               
                   
                   
               
             
            
               
                   
                 Intra 2N × 2N 
                 none 
               
               
                   
                   
               
            
           
         
       
     
     Note that “CU including PCM encoding” is a CU of the PCM coding unit size, and “CU not including PCM encoding” is a CU of not the PCM coding unit size. In this case, for example in the minimum coding unit including PCM encoding in the intra slice, the video decoding device interprets codeword 1 as 2N×2N intra prediction, codeword 01 as N×N intra prediction, and codeword 00 as PCM. 
     Likewise, in a non-intra slice, syntax and codeword can be associated as follows. 
     [Correspondence Between Syntax and Codeword Common to All CUs] 
                                             Syntax   Codeword                                                    Split   1           Skip   01           Inter 2N × 2N_MRG   001           Inter 2N × 2N   0001           Others   0000                        
[Correspondence Between Syntax and Codeword in Minimum Coding Unit Including PCM Encoding, Following Others]
 
                                             Syntax   Codeword                                                    Inter 2N × N   0           Inter N × 2N   01           Inter N × N   001           Intra 2N × 2N   0001           Intra N × N   00001           PCM   00000                        
[Correspondence Between Syntax and Codeword in CU Other Than Minimum Coding Unit Including PCM Encoding, Following Others]
 
                                             Syntax   Codeword                                                    Inter 2N × N   0           Inter N × 2N   01           Intra 2N × 2N   001           PCM   000                        
[Correspondence Between Syntax and Codeword in Minimum Coding Unit Not Including PCM Encoding, Following Others]
 
                                             Syntax   Codeword                                                    Inter 2N × N   0           Inter N × 2N   01           Inter N × N   001           Intra 2N × 2N   0001           Intra N × N   0000                        
[Correspondence Between Syntax and Codeword in CU Other Than Minimum Coding Unit Not Including PCM Encoding, Following Others]
 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Syntax 
                 Codeword 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Inter 2N × N 
                 0 
               
               
                   
                 Inter N × 2N 
                 01 
               
               
                   
                 Intra 2N × 2N 
                 00 
               
               
                   
                   
               
            
           
         
       
     
     In this case, for example in the minimum coding unit including PCM encoding, the video decoding device interprets codeword 0 following Others as 2N×N inter prediction, codeword 01 as N×2N inter prediction, codeword 001 as N×N inter prediction, codeword 0001 as 2N×2N intra prediction, codeword 00001 as N×N intra prediction, and codeword 00000 as PCM. 
     Note that the intra slice is a slice composed of only coding units encoded by intra prediction, and the non-intra slice is a slice including coding units encoded by inter prediction. 
     Each of the exemplary embodiments described above may be realized by hardware, or may be realized by a computer program. 
     An information processing system shown in  FIG.  11    includes a processor  1001 , a program memory  1002 , a storage medium  1003  for storing video data, and a storage medium  1004  for storing a bitstream. The storage medium  1003  and the storage medium  1004  may be separate storage media, or may be storage areas included in the same storage medium. As a storage medium, a magnetic storage medium such as a hard disk is applicable. 
     In the information processing system shown in  FIG.  11   , a program for realizing the functions of the blocks (except the block of the buffer) shown in each of  FIGS.  1  and  5    is stored in the program memory  1002 . The processor  1001  realizes the functions of the video encoding device or the video decoding device shown in  FIG.  1  or  5   , by executing processing according to the program stored in the program memory  1002 . 
       FIG.  12    is a block diagram showing a main part of a video encoding device according to the present invention. As shown in  FIG.  12   , the video encoding device according to the present invention includes: transform means  11  (e.g. the transformer/quantizer  102  shown in  FIG.  1   ) for transforming an image block; entropy encoding means  12  (e.g. the entropy encoder  103  shown in  FIG.  1   ) for entropy-encoding transformed data of the image block transformed by the transform means  11 ; PCM encoding means  13  (e.g. the PCM encoder  107  shown in  FIG.  1   ) for encoding by PCM encoding the image block; multiplex data selection means  14  (e.g. the multiplex data selector  109  and the switch  121 ) for selecting output data of the entropy encoding means  12  (e.g. the entropy encoder  103  shown in  FIG.  1   ) or the PCM encoding means  13 , in a block of a block size set from the outside; and multiplexing means  15  (e.g. the multiplexer  110  shown in  FIG.  1   ) for embedding a PCM header in a bitstream, in the block of the block size set from the outside. 
       FIG.  13    is a block diagram showing a main part of a video decoding device according to the present invention. As shown in  FIG.  13   , the video decoding device according to the present invention includes: de-multiplexing means  21  (e.g. the de-multiplexer  201  shown in  FIG.  5   ) for de-multiplexing a bitstream including PCM block size information; PCM block size determination means  22  (e.g. the de-multiplexer  201  shown in  FIG.  5   ) for determining a PCM block size for which a PCM header is parsed, based on the PCM block size information de-multiplexed by the de-multiplexing means  21 ; PCM header parsing means  23  (e.g. the entropy decoder  204  shown in  FIG.  5   ) for parsing the PCM header from the bitstream, in a block of the PCM block size determined by the PCM block size determination means  22 ; entropy decoding means  24  (e.g. the entropy decoder  204  shown in  FIG.  5   ) for entropy-decoding transformed data of an image in the bitstream; inverse transform means  25  (e.g. the inverse transformer/inverse quantizer  206  shown in  FIG.  5   ) for inverse-transforming the transformed data entropy-decoded by the entropy decoding means  24 ; PCM decoding means  26  (e.g. the PCM decoder  203  shown in  FIG.  5   ) for decoding by PCM decoding PCM data of the image in the bitstream; and decoding control means  27  (e.g. the decoding controller  202  shown in  FIG.  5   ) for controlling the entropy decoding means  24  and the PCM decoding means  26 , based on the PCM header parsed by the PCM header parsing means  23 . 
     The exemplary embodiments described above may be partly or wholly described in the following supplementary notes, though the present invention is not limited to the following structures. 
     (Supplementary note 1) A video encoding device wherein the multiplexing means embeds, in the bitstream, information related to N as PCM block size information, in the case where the externally-set block size is greater than or equal to ¼N of a block size corresponding to a maximum coding unit size or in the case where the externally-set block size is greater than or equal to 4N times a block size corresponding to a minimum coding unit size. 
     (Supplementary note 2) A video decoding device wherein the de-multiplexing means obtains information related to N as the PCM block size information, in the case where the block size is greater than or equal to ¼N of a block size corresponding to a maximum coding unit size or in the case where the block size is greater than or equal to 4N times a block size corresponding to a minimum coding unit size. 
     (Supplementary note 3) A video encoding device wherein the multiplexing means embeds, in the bitstream, information related to N as PCM block size information, in the case where the externally-set block size is less than or equal to ¼N of a block size corresponding to a maximum coding unit size or in the case where the externally-set block size is less than or equal to 4N times a block size corresponding to a minimum coding unit size. 
     (Supplementary note 4) A video decoding device wherein the de-multiplexing means obtains information related to N as the PCM block size information, in the case where the block size is less than or equal to ¼N of a block size corresponding to a maximum coding unit size or in the case where the block size is less than or equal to 4N times a block size corresponding to a minimum coding unit size. 
     Though the present invention has been described with reference to the above exemplary embodiments and examples, the present invention is not limited to the above exemplary embodiments and examples. Various changes understandable by those skilled in the art within the scope of the present invention can be made to the structures and details of the present invention. 
     This application claims priority based on Japanese Patent Application No. 2010-264320 filed on Nov. 26, 2010 and Japanese Patent Application No. 2011-026331 filed on Feb. 9, 2011, the disclosures of which are incorporated herein in their entirety. 
     REFERENCE SIGNS LIST 
       11  transform means 
       12  entropy encoding means 
       13  PCM encoding means 
       14  multiplex data selection means 
       15  multiplexing means 
       21  de-multiplexing means 
       22  block size determination means 
       23  PCM header parsing means 
       24  entropy decoding means 
       25  inverse transform means 
       26  PCM decoding means 
       27  decoding control means 
       102  transformer/quantizer 
       103  entropy encoder 
       104  inverse transformer/inverse quantizer 
       105  buffer 
       106  predictor 
       107  PCM encoder 
       108  PCM decoder 
       109  multiplex data selector 
       110  multiplexer 
       121  switch 
       122  switch 
       201  de-multiplexer 
       202  decoding controller 
       203  PCM decoder 
       204  entropy decoder 
       206  inverse transformer/inverse quantizer 
       207  predictor 
       208  buffer 
       221  switch 
       222  switch 
       1001  processor 
       1002  program memory 
       1003  storage medium 
       1004  storage medium