JP5995448B2 - Image decoding apparatus and image encoding apparatus - Google Patents

Description

  The present invention relates to an image decoding apparatus that decodes encoded data representing an image, and an image encoding apparatus that generates encoded data by encoding an image.

  In order to efficiently transmit or record a moving image, a moving image encoding device that generates encoded data by encoding the moving image, and a moving image that generates a decoded image by decoding the encoded data An image decoding device is used.

  As a specific moving picture encoding method, for example, H.264 is used. H.264 / MPEG-4. A method used in KTA software, which is a codec for joint development in AVC and VCEG (Video Coding Expert Group), a method used in TMuC (Test Model under Consideration) software, and a successor codec, HEVC (High- Efficiency Video Coding) (Non-Patent Document 1) and the like can be mentioned.

  In these moving image encoding methods, a prediction image is usually generated based on a local decoded image obtained by encoding / decoding an input image, and the prediction image is subtracted from the input image (original image). The resulting prediction residual (sometimes called a “difference image” or “residual image”) is encoded. In addition, examples of the method for generating a predicted image include inter-screen prediction (inter prediction) and intra-screen prediction (intra prediction).

  In inter prediction, by applying motion compensation using a motion vector to a reference image in a reference frame (decoded image) obtained by decoding the entire frame, a predicted image in a prediction target frame is converted into a prediction unit (for example, Generated every block).

  On the other hand, in intra prediction, based on locally decoded images in the same frame, predicted images in the frame are sequentially generated. Specifically, in intra prediction, usually, any prediction mode is selected and selected from prediction modes included in a predetermined prediction mode group for each prediction unit (for example, block). A prediction image is generated based on the prediction method associated with the prediction mode. Prediction methods include horizontal prediction, vertical prediction, DC prediction, Planar prediction, and Angular prediction. A unique prediction mode number is assigned to each prediction mode, and the video decoding apparatus determines a prediction method to be applied to the prediction target region based on the prediction mode number decoded from the encoded data. Note that prediction modes corresponding to a plurality of prediction directions are associated with Angular prediction, and the video decoding device determines a prediction direction based on the prediction mode number, and the prediction image is based on the determined prediction direction. Generated.

  For the luminance prediction mode, a short code is assigned to the estimated prediction mode derived based on the prediction mode of the adjacent prediction unit. On the other hand, for the color difference prediction mode, a short code is assigned to an estimated prediction mode (luminance prediction mode reuse) that reuses a prediction mode applied to a corresponding luminance prediction unit.

`` WD5: Working Draft 5 of High-Efficiency Video Coding (JCTVC-G1103_d3) '', Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11 7th Meeting: Geneva, CH, 21-30 November, 2011 (released January 9, 2012)

  However, the above-described luminance prediction mode reuse is appropriate when the color format (YUV format) of the input image is 4: 2: 0 format, but when the color format is 4: 2: 2 format, encoding efficiency is improved. Cause a drop in This will be specifically described below.

  In Non-Patent Document 1, when the luminance prediction mode reuse is used, the same prediction mode as the prediction mode applied to the luminance prediction unit is used for prediction image generation in the target prediction unit of color difference. Here, when the color format of the input image is 4: 2: 0 and the prediction mode is directional prediction, the luminance prediction mode reuse indicates that the prediction direction in the luminance region matches the prediction direction in the color difference region. means.

  On the other hand, when the color format of the input image is 4: 2: 2, if the size of the color difference area corresponding to a specific luminance area is expressed by the number of pixels, the size of the luminance area is halved in the horizontal direction. Become. Therefore, the coordinate system of the chrominance pixel has a shape obtained by doubling the coordinate system of the luminance pixel in the horizontal direction, and the prediction direction associated with a certain prediction mode in the luminance region is associated with the same prediction mode in the chrominance region. It does not necessarily match the predicted direction.

  Therefore, in the method of Non-Patent Document 1, when the color format of the input image is 4: 2: 2 format and the prediction mode applied to the luminance prediction unit is direction prediction, the luminance prediction mode is reused. There is a problem that the generated predicted image is inaccurate because it does not reflect the relationship between the size of the luminance area and the color difference area.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to make an accurate prediction image generated by reusing the luminance prediction mode even when the luminance region and the color difference region in the input image are not similar. Thus, an image decoding device or the like that improves the image quality of the decoded image is realized.

  In order to solve the above problems, an image decoding apparatus according to the present invention performs image decoding that restores an image from encoded data by generating a prediction image for luminance and color difference by an intra prediction method associated with a prediction mode. In the apparatus, with respect to the intra prediction method of direction prediction, a prediction mode corresponding to a prediction direction expressed by a gradient from the main direction can be used, and color difference prediction image generation is performed based on the prediction mode used for luminance prediction image generation When performing the above, color difference prediction means for correcting a prediction direction when the shape of the pixel is different between the luminance pixel and the color difference pixel is provided.

  In the above configuration, the prediction mode corresponding to the prediction direction expressed by the gradient from the main direction is used for the intra prediction method of direction prediction. The main direction means a reference direction, for example, a vertical direction and a horizontal direction. Further, the gradient can be defined by the angle formed between the prediction direction and the main direction.

  In the above configuration, a prediction mode is specified for luminance and color difference, and a prediction image is generated based on the specified prediction mode.

  Moreover, the prediction mode used for luminance prediction image generation can be used for color difference prediction image generation. Such a prediction mode performs so-called luminance prediction mode reuse, and is sometimes called a DM mode.

  Here, a case where the shape of the pixel is different between the luminance pixel and the color difference pixel will be described as follows.

  A pixel is represented by a combination of a luminance component (Y) and a color difference component (U, V). In encoding a moving image, the data amount may be reduced by lowering the resolution of the color difference pixels below that of the luminance pixels.

  As described above, examples of an image format for expressing an image with a combination of luminance and color difference of various resolutions include a 4: 4: 4 format, a 4: 2: 2 format, a 4: 1: 1 format, and a 4: 2: format. There are 0 formats.

  In the 4: 4: 4 format, the luminance resolution and the color difference resolution are the same.

  The 4: 2: 2 format is one in which the horizontal resolution is halved in the 4: 4: 4 format.

  The 4: 1: 1 format is a format in which the horizontal resolution is halved in the 4: 2: 2 format.

  In the 4: 2: 0 format, the resolution of the color difference is halved in both the horizontal direction and the vertical direction with respect to the luminance resolution.

  In the 4: 4: 4 format and the 4: 2: 0 format, the aspect ratio is the same between the luminance pixel and the color difference pixel, respectively. In contrast, the 4: 2: 2 format and the 4: 1: 1 format have different aspect ratios between the luminance pixels and the color difference pixels.

  The difference in pixel shape between the luminance pixel and the chrominance pixel means that the luminance pixel and the chrominance pixel have different aspect ratios and are not similar to each other as described above. Furthermore, it means a case where the shape of the luminance pixel and the shape of the color difference pixel do not match even when the pixel is enlarged or reduced.

  According to the above configuration, when generating the color difference prediction image generation using the DM mode, the prediction direction is corrected when the pixel shape is different between the luminance pixel and the color difference pixel. Therefore, in the DM mode, it is possible to correct a prediction direction shift caused by a luminance pixel and a color difference pixel not being similar, and thus a prediction direction more suitable for the color difference region can be obtained. As a result, it is possible to improve the image quality of the decoded image by making the color difference prediction image generated by reusing the luminance prediction mode more accurate.

  In the image decoding apparatus according to the present invention, the color difference prediction means may correct the gradient of the prediction direction based on the main direction and the size ratio of the luminance pixel and the color difference pixel.

  The prediction direction can also be expressed by a two-dimensional vector. If there is a relationship of vxL = α ・ vxC, vyL = β ・ vyC between the prediction direction vector (vxL, vyL) in the luminance space and the prediction direction vector (vxC, vyC) in the color difference space The gradient intraPredAngle value applied to the color difference is (α / β) times larger than the gradient intraPredAngle value applied to the luminance when the main direction is horizontal, and (β / α when the main direction is vertical. ) Is preferably doubled. The coefficient α represents the horizontal size ratio between the luminance pixel and the chrominance pixel, and the coefficient β represents the vertical size ratio between the luminance pixel and the chrominance pixel.

  According to said structure, the gradient of the said prediction direction is correct | amended based on the said main direction and the size ratio of a luminance pixel and a colour-difference pixel. In such correction, an operation for applying the above-described size ratio to a vector representing a luminance prediction direction is performed. By such a calculation, a vector representing the corrected color difference prediction direction can be obtained.

  In this way, the gradient of the prediction direction can be corrected by the calculation, so that it is not necessary to provide a table for associating the luminance prediction direction with the color difference prediction direction. As a result, memory reduction in the color difference predicted image generation process can be achieved.

  In the image decoding apparatus according to the present invention, the color difference prediction means generates a prediction image obtained based on a prediction mode used for luminance prediction image generation, according to the main direction, the shape of the luminance pixel and the shape of the color difference pixel. The prediction direction may be corrected by reducing at a reduction rate determined by the difference between the prediction direction and the prediction direction.

  According to said structure, correction | amendment of a prediction direction is indirectly performed by reducing a brightness | luminance prediction image to the size of a color difference pixel according to the said main direction. Accordingly, the size of the luminance predicted image can be converted into the size of the color difference pixel based on the difference in size (resolution) between the luminance pixel and the color difference pixel.

  For this reason, there is an effect that the color difference prediction pixel can be generated by reusing the luminance prediction image.

  The image decoding apparatus according to the present invention includes a prediction mode conversion table that associates a prediction mode used for luminance prediction image generation with a prediction mode used for color difference prediction image generation, and the color difference prediction means refers to the prediction mode conversion table. Then, the prediction direction may be corrected by converting the prediction mode.

  According to said structure, the prediction mode used for brightness | luminance prediction image generation is converted into the prediction mode used for color difference prediction image generation. In this conversion table, the luminance prediction mode and the color difference prediction mode can be associated with each other so that the prediction directions have substantially the same gradient.

  For example, in the 4: 2: 2 format, the luminance prediction mode VER + 8 may be converted to VER + 5 as the color difference prediction mode. Specifically, it is as follows.

  If the gradient value of VER + 8 is +32 in the horizontal direction, the displacement value corresponding to VER + 8 in the color difference is +16 obtained by dividing +32 by 2.

  Here, it is assumed that the gradient of VER + 5 is +17, which is the horizontal gradient closest to +16. At this time, the prediction mode VER + 8 in luminance may be associated with the prediction mode VER + 5 in color difference.

  With this association, the gradient of the prediction mode VER + 5 is +17 in both luminance and color difference, and the gradient of the prediction mode VER + 8 is +32 in both luminance and color difference.

  In this way, it is possible to unify the correspondence between the prediction mode and the gradient between the luminance and the color difference while improving the accuracy of the prediction direction by correction.

  In the image decoding apparatus according to the present invention, the case where the pixel shape is different between the luminance pixel and the color difference pixel is a case where the color format is 4: 2: 2 format, and the color difference prediction means includes The gradient applied to the color difference is set to twice the gradient value applied to the luminance when the main direction is the horizontal direction, and is halved when the main direction is the vertical direction. It may be set.

  According to said structure, correction | amendment of a prediction direction can be preferably given in 4: 2: 2 format whose horizontal direction resolution is 1/2.

  In order to solve the above-described problem, the image coding apparatus according to the present invention generates a prediction image for luminance and color difference by an intra prediction method associated with a prediction mode, and calculates a difference between the original image and the prediction image. In the image encoding apparatus that encodes the prediction residual obtained by taking the prediction prediction mode corresponding to the prediction direction expressed by the gradient from the main direction can be used for the intra prediction method of direction prediction, and the luminance When color difference prediction image generation is performed based on the prediction mode used for prediction image generation, a color difference prediction unit is provided that corrects the prediction direction when the pixel shape is different between the luminance pixel and the color difference pixel. It is a feature.

  In the above configuration, the prediction mode corresponding to the prediction direction expressed by the gradient from the main direction is used for the intra prediction method of direction prediction. The main direction means a reference direction, for example, a vertical direction and a horizontal direction. Further, the gradient can be defined by the angle formed between the prediction direction and the main direction.

  In the above configuration, a prediction mode is specified for luminance and color difference, and a prediction image is generated based on the specified prediction mode.

  Moreover, the prediction mode used for luminance prediction image generation can be used for color difference prediction image generation. Such a prediction mode performs so-called luminance prediction mode reuse, and is sometimes called a DM mode.

  Depending on the type of image format, the aspect ratio differs between the luminance pixel and the chrominance pixel, and they are not similar, that is, the pixel shape may differ between the luminance pixel and the chrominance pixel. .

  According to the above configuration, when the color difference prediction image generation is generated using the DM mode, the prediction direction is corrected when the pixel shape is different between the luminance pixel and the color difference pixel. Therefore, in the DM mode, it is possible to correct a prediction direction shift caused by a luminance pixel and a color difference pixel not being similar, and thus a prediction direction more suitable for the color difference region can be obtained. As a result, there is an effect that the color difference prediction image generated by reusing the luminance prediction mode can be made more accurate.

  As described above, the image decoding apparatus according to the present invention can use the prediction mode corresponding to the prediction direction expressed by the gradient from the main direction with respect to the intra prediction method of direction prediction, and can be used for generating a luminance prediction image. When the color difference prediction image is generated based on the prediction mode, the color difference prediction unit corrects the prediction direction when the pixel shape is different between the luminance pixel and the color difference pixel.

  According to the above configuration, when generating the color difference prediction image generation using the DM mode, the prediction direction is corrected when the pixel shape is different between the luminance pixel and the color difference pixel. Therefore, in the DM mode, it is possible to correct a prediction direction shift caused by a luminance pixel and a color difference pixel not being similar, and thus a prediction direction more suitable for the color difference region can be obtained. As a result, it is possible to improve the image quality of the decoded image by making the color difference prediction image generated by reusing the luminance prediction mode more accurate.

  In addition, the image coding apparatus according to the present invention is obtained by generating a prediction image for luminance and color difference using an intra prediction method associated with a prediction mode, and taking the difference between the original image and the prediction image. In an image encoding apparatus that encodes a prediction residual, a prediction mode corresponding to a prediction direction expressed by a gradient from a main direction can be used for an intra prediction method of direction prediction, and is used for luminance prediction image generation. When the color difference prediction image is generated based on the prediction mode, color difference prediction means for correcting a prediction direction when the pixel shape is different between the luminance pixel and the color difference pixel is provided.

  According to the above configuration, when the color difference prediction image generation is generated using the DM mode, the prediction direction is corrected when the pixel shape is different between the luminance pixel and the color difference pixel. Therefore, in the DM mode, it is possible to correct a prediction direction shift caused by a luminance pixel and a color difference pixel not being similar, and thus a prediction direction more suitable for the color difference region can be obtained. As a result, there is an effect that the color difference prediction image generated by reusing the luminance prediction mode can be made more accurate.

It is a functional block diagram which shows the example of 1 structure of the prediction direction derivation | leading-out part in the moving image decoding apparatus which concerns on one Embodiment of this invention. It is the functional block diagram shown about the schematic structure of the said moving image decoding apparatus. It is a figure which shows the data structure of the encoding data produced | generated by the moving image encoder which concerns on one Embodiment of this invention, and decoded by the said moving image decoder, (a)-(d) is a picture, respectively. It is a figure which shows a layer, a slice layer, a tree block layer, and a CU layer. It is a figure which shows the example of the prediction mode number corresponding to the classification | category of the intra prediction method utilized with the said moving image decoding apparatus. It is a figure which shows the prediction direction corresponding to the identifier of a prediction mode about 33 types of prediction modes which belong to direction prediction. It is a figure which shows an example of the prediction mode definition which is a definition of a response | compatibility with an intra prediction method and a prediction mode number. It is a functional block diagram shown about the structural example of the estimated image generation part with which the said moving image decoding apparatus is provided. It is a figure which shows PU setting order and PU contained in CU when an input image is a YUV format of 4: 2: 0. (A) shows PUs in the CU when the size of the target CU is 8 × 8 pixels and the division type is N × N. (B) shows PUs in the CU when the size of the target CU is 16 × 16 pixels and the division type is 2N × 2N. It is a figure which shows PU setting order and PU contained in CU when an input image is a YUV format of 4: 2: 2. (A) shows PUs in the CU when the size of the target CU is 8 × 8 pixels and the division type is N × N. (B) shows PUs in the CU when the size of the target CU is 16 × 16 pixels and the division type is 2N × 2N. It is a figure which shows PU contained in another setting order of PU, and CU in case an input image is a YUV format of 4: 2: 2. (A) shows PUs in the CU when the size of the target CU is 8 × 8 pixels and the division type is N × N. (B) shows PUs in the CU when the size of the target CU is 16 × 16 pixels and the division type is 2N × 2N. It is a flowchart which shows the outline of the prediction image generation process of the CU unit in the said prediction image generation part. It is a block diagram which shows the detailed structure of the brightness | luminance prediction part with which the said estimated image generation part is provided. It is a table which shows an example of the correspondence of a prediction mode identifier and the value of gradient intraPredAngle. It is a flowchart which shows the Angular prediction process in the said brightness | luminance prediction part. It is a block diagram which shows the detailed structure of the color difference prediction part with which the said estimated image generation part is provided. 10 is a table showing an example of a correspondence relationship between a prediction mode identifier and a gradient intraPredAngle value when a prediction image generation target is a color difference pixel. It is a functional block diagram shown about the structural example of the variable length decoding part with which the said moving image decoding apparatus is provided. It is a figure shown about the derivation method of the MPM candidate in the MPM derivation part with which the above-mentioned variable length decoding part is provided. It is a figure which shows the table which defined matching with intra color difference prediction mode designation | designated information chroma_mode and the prediction mode (IntraPredMode [xB] [yB]) of brightness | luminance, and color difference prediction mode (IntraPredModeC). It is a flowchart which shows an example of the schematic flow of the prediction mode restoration process in the said moving image decoding apparatus. It is a functional block diagram shown about the structure of the moving image encoder which concerns on one Embodiment of this invention. It is a functional block diagram which shows the example of 1 structure of the encoding data generation part with which the said moving image encoder is provided. It is a flowchart which shows an example of the flow of the prediction mode encoding process in the said moving image encoder. It is a figure which shows the modification of the functional block of the prediction direction derivation | leading-out part in the said moving image decoding apparatus. It is a block diagram which shows the modification of the color difference prediction part with which the said prediction image generation part is provided. It is a figure which shows the further modification of the functional block of the prediction direction derivation | leading-out part in the said moving image decoding apparatus. It is a block diagram which shows the further modification of the color difference estimation part with which the said estimated image generation part is provided. It is a figure which shows the table which matched so that the prediction mode of a brightness | luminance prediction mode and the prediction mode of a color difference might become the prediction direction of the substantially same gradient, when a color format is 4: 2: 2. It is a block diagram which shows the further modification of the color difference estimation part with which the said estimated image generation part is provided. It is a figure which shows the example of the prediction mode number corresponding to the classification | category of the intra prediction method utilized with the said moving image decoding apparatus. It is the figure shown about the structure of the transmitter which mounts the said moving image encoder, and the receiver which mounts the said moving image decoder. (A) shows a transmitting apparatus equipped with a moving picture coding apparatus, and (b) shows a receiving apparatus equipped with a moving picture decoding apparatus. It is the figure shown about the structure of the recording device which mounts the said moving image encoder, and the reproducing | regenerating apparatus which mounts the said moving image decoder. (A) shows a recording apparatus equipped with a moving picture coding apparatus, and (b) shows a reproduction apparatus equipped with a moving picture decoding apparatus.

〔Overview〕
An embodiment of the present invention will be described with reference to FIGS. First, an overview of the moving picture decoding apparatus (image decoding apparatus) 1 and the moving picture encoding apparatus (image encoding apparatus) 2 will be described with reference to FIG. FIG. 2 is a functional block diagram showing a schematic configuration of the moving picture decoding apparatus 1.

  The moving picture decoding apparatus 1 and the moving picture encoding apparatus 2 shown in FIG. 264 / MPEG-4 AVC standard technology, VCEG (Video Coding Expert Group) codec for joint development in KTA software, TMuC (Test Model under Consideration) software The technology and the technology proposed by HEVC (High-Efficiency Video Coding), which is the successor codec, are implemented.

  The video encoding device 2 generates encoded data # 1 by entropy encoding a syntax value defined to be transmitted from the encoder to the decoder in these video encoding schemes. .

  As entropy coding methods, context adaptive variable length coding (CAVLC) and context adaptive binary arithmetic coding (CABAC) are known. ing.

  In encoding / decoding by CAVLC and CABAC, processing adapted to the context is performed. The context is an encoding / decoding situation (context), and is determined by past encoding / decoding results of related syntax. Examples of the related syntax include various syntaxes related to intra prediction and inter prediction, various syntaxes related to luminance (Luma) and chrominance (Chroma), and various syntaxes related to CU (Coding Unit coding unit) size. In CABAC, the binary position to be encoded / decoded in binary data (binary string) corresponding to the syntax may be used as the context.

  In CAVLC, various syntaxes are encoded by adaptively changing the VLC table used for encoding. On the other hand, in CABAC, binarization processing is performed on syntax that can take multiple values such as a prediction mode and a conversion coefficient, and binary data obtained by this binarization processing is adaptive according to the occurrence probability. Are arithmetically encoded. Specifically, multiple buffers that hold the occurrence probability of binary values (0 or 1) are prepared, one buffer is selected according to the context, and arithmetic coding is performed based on the occurrence probability recorded in the buffer I do. Further, by updating the occurrence probability of the buffer based on the binary value to be decoded / encoded, an appropriate occurrence probability can be maintained according to the context.

The moving image decoding apparatus 1 receives encoded data # 1 obtained by encoding a moving image by the moving image encoding apparatus 2. The video decoding device 1 decodes the input encoded data # 1 and outputs the video # 2 to the outside. Prior to detailed description of the moving picture decoding apparatus 1, the configuration of the encoded data # 1 will be described below.
[Configuration of encoded data]
A configuration example of encoded data # 1 that is generated by the video encoding device 2 and decoded by the video decoding device 1 will be described with reference to FIG. The encoded data # 1 exemplarily includes a sequence and a plurality of pictures constituting the sequence.

  The hierarchical structure below the picture layer in the encoded data # 1 is shown in FIG. 3A to 3D are included in the picture layer that defines the picture PICT, the slice layer that defines the slice S, the tree block layer that defines the tree block TBLK, and the tree block TBLK, respectively. It is a figure which shows the CU layer which prescribes | regulates a coding unit (Coding Unit; CU).

(Picture layer)
In the picture layer, a set of data referred to by the video decoding device 1 for decoding a picture PICT to be processed (hereinafter also referred to as a target picture) is defined. As shown in FIG. 3A, the picture PICT includes a picture header PH and slices S _{1 to} S _NS (where NS is the total number of slices included in the picture PICT).

Note that, hereinafter, when it is not necessary to distinguish each of the slices S _{1 to} S _NS , the reference numerals may be omitted. The same applies to other data with subscripts included in encoded data # 1 described below.

  The picture header PH includes a coding parameter group that is referred to by the video decoding device 1 in order to determine a decoding method of the target picture. For example, the reference value (pic_init_qp_minus26) in the picture in the quantization step of the prediction residual is an example of a coding parameter included in the picture header PH.

  The picture header PH is also called a picture parameter set (PPS).

(Slice layer)
In the slice layer, a set of data referred to by the video decoding device 1 for decoding the slice S to be processed (also referred to as a target slice) is defined. As shown in FIG. 3B, the slice S includes a slice header SH and tree blocks TBLK _{1 to} TBLK _NC (where NC is the total number of tree blocks included in the slice S).

  The slice header SH includes an encoding parameter group that is referred to by the video decoding device 1 in order to determine a decoding method of the target slice. Slice type designation information (slice_type) for designating a slice type is an example of an encoding parameter included in the slice header SH.

  As slice types that can be specified by the slice type specification information, (1) I slice that uses only intra prediction at the time of encoding, (2) P slice that uses unidirectional prediction or intra prediction at the time of encoding, (3) B-slice using unidirectional prediction, bidirectional prediction, or intra prediction at the time of encoding may be used.

  Further, the slice header SH may include a filter parameter referred to by a loop filter (not shown) included in the video decoding device 1.

(Tree block layer)
In the tree block layer, a set of data referred to by the video decoding device 1 for decoding a processing target tree block TBLK (hereinafter also referred to as a target tree block) is defined.

The tree block TBLK includes a tree block header TBLKH and coding unit information CU _{1 to} CU _NL (NL is the total number of coding unit information included in the tree block TBLK). Here, first, a relationship between the tree block TBLK and the coding unit information CU will be described as follows.

  Tree block TBLK is divided into units for specifying a block size for each process of intra prediction or inter prediction and transformation.

  The unit of the tree block TBLK is divided by recursive quadtree division. The tree structure obtained by this recursive quadtree partitioning is hereinafter referred to as a coding tree.

  Hereinafter, a unit corresponding to a leaf which is a node at the end of the coding tree is referred to as a coding node. In addition, since the encoding node is a basic unit of the encoding process, hereinafter, the encoding node is also referred to as an encoding unit (CU).

That is, coding unit information (hereinafter referred to as CU information) CU _{1 to} CU _NL is information corresponding to each coding node (coding unit) obtained by recursively dividing the tree block TBLK into quadtrees. is there.

  Also, the root of the coding tree is associated with the tree block TBLK. In other words, the tree block TBLK is associated with the highest node of the tree structure of the quadtree partition that recursively includes a plurality of encoding nodes.

  Note that the size of each coding node is half of the size of the coding node to which the coding node directly belongs (that is, the unit of the node one level higher than the coding node).

  The size that each coding node can take depends on the size specification information of the coding node included in the size of the tree block and the sequence parameter set SPS of the coded data # 1. Since the tree block is the root of the encoding node, the maximum size of the encoding node is the size of the tree block. Since the maximum size of the tree block matches the maximum size of the coding node (CU), LCU (Largest CU) may be used as the name of the tree block. Regarding the minimum size, for example, the minimum encoding node size (log2_min_coding_block_size_minus3) and the difference between the maximum and minimum encoding node sizes (log2_diff_max_min_coding_block_size) are used as size designation information. In a general setting, size specification information of a coding node having a maximum coding node size of 64 × 64 pixels and a minimum coding node size of 8 × 8 pixels is used. In this case, the size of the encoding node and the encoding unit CU is 64 × 64 pixels, 32 × 32 pixels, 16 × 16 pixels, or 8 × 8 pixels.

(Tree block header)
The tree block header TBLKH includes an encoding parameter referred to by the video decoding device 1 in order to determine a decoding method of the target tree block. Specifically, as shown in (c) of FIG. 3, tree block division information SP_TBLK that designates a division pattern of the target tree block into each CU, and a quantization parameter difference that designates the size of the quantization step Δqp (qp_delta) is included.

  The tree block division information SP_TBLK is information representing a coding tree for dividing the tree block. Specifically, the shape and size of each CU included in the target tree block, and the position in the target tree block Is information to specify.

  Note that the tree block division information SP_TBLK may not explicitly include the shape or size of the CU. For example, the tree block division information SP_TBLK may be a set of flags (split_coding_unit_flag) indicating whether or not the entire target tree block or a partial area of the tree block is divided into four. In that case, the shape and size of each CU can be specified by using the shape and size of the tree block together.

  The quantization parameter difference Δqp is a difference qp−qp ′ between the quantization parameter qp in the target tree block and the quantization parameter qp ′ in the tree block encoded immediately before the target tree block.

(CU layer)
In the CU layer, a set of data referred to by the video decoding device 1 for decoding a CU to be processed (hereinafter also referred to as a target CU) is defined.

  Here, before describing specific contents of data included in the CU information CU, a tree structure of data included in the CU will be described. The encoding node is a node at the root of a prediction tree (PT) and a transform tree (TT). The prediction tree and the conversion tree are described as follows.

  In the prediction tree, the encoding node is divided into one or a plurality of prediction blocks, and the position and size of each prediction block are defined. In other words, the prediction block is one or a plurality of non-overlapping areas constituting the encoding node. The prediction tree includes one or a plurality of prediction blocks obtained by the above division.

  Prediction processing is performed for each prediction block. Hereinafter, a prediction block that is a unit of prediction is also referred to as a prediction unit (PU).

  Broadly speaking, there are two types of division in the prediction tree: intra prediction and inter prediction.

  In the case of intra prediction, there are 2N × 2N (the same size as the encoding node) and N × N division methods.

  In the case of inter prediction, there are 2N × 2N (the same size as the encoding node), 2N × N, N × 2N, N × N, and the like.

  In the transform tree, the encoding node is divided into one or a plurality of transform blocks, and the position and size of each transform block are defined. In other words, the transform block is one or a plurality of non-overlapping areas constituting the encoding node. The conversion tree includes one or a plurality of conversion blocks obtained by the above division.

  The conversion process is performed for each conversion block. Hereinafter, a transform block that is a unit of transform is also referred to as a transform unit (TU).

(Data structure of CU information)
Next, specific contents of the data included in the CU information CU will be described with reference to FIG. As shown in FIG. 3D, the CU information CU specifically includes a skip flag SKIP, PT information PTI, and TT information TTI.

  The skip flag SKIP is a flag indicating whether or not the skip mode is applied to the target PU. When the value of the skip flag SKIP is 1, that is, when the skip mode is applied to the target CU, PT information PTI and TT information TTI in the CU information CU are omitted. Note that the skip flag SKIP is omitted for the I slice.

  The PT information PTI is information related to the PT included in the CU. In other words, the PT information PTI is a set of information related to each of one or more PUs included in the PT, and is referred to when the moving image decoding apparatus 1 generates a predicted image. As shown in FIG. 3D, the PT information PTI includes prediction type information PType and prediction information PInfo.

  The prediction type information PType is information that specifies whether intra prediction or inter prediction is used as a predicted image generation method for the target PU.

  The prediction information PInfo is configured from intra prediction information or inter prediction information depending on which prediction method is specified by the prediction type information PType. Hereinafter, a PU to which intra prediction is applied is also referred to as an intra PU, and a PU to which inter prediction is applied is also referred to as an inter PU.

  Further, the prediction information PInfo includes information specifying the shape, size, and position of the target PU. As described above, the generation of the predicted image is performed in units of PU. Details of the prediction information PInfo will be described later.

  The TT information TTI is information regarding the TT included in the CU. In other words, the TT information TTI is a set of information regarding each of one or a plurality of TUs included in the TT, and is referred to when the moving image decoding apparatus 1 decodes residual data. Hereinafter, a TU may be referred to as a conversion block.

As shown in FIG. 3D, the TT information TTI includes TT division information SP_TU that designates a division pattern of the target CU into each transform block, and TU information TUI _{1 to} TUI _NT (NT is the target CU). The total number of transform blocks included).

  Specifically, the TT division information SP_TU is information for determining the shape and size of each TU included in the target CU and the position within the target CU. For example, the TT division information SP_TU can be realized from information (split_transform_unit_flag) indicating whether or not the target node is divided and information (trafoDepth) indicating the depth of the division.

  For example, when the size of the CU is 64 × 64, each TU obtained by the division can take a size from 32 × 32 pixels to 4 × 4 pixels.

  The TU partition information SP_TU includes information on whether or not a non-zero transform coefficient exists in each TU. For example, non-zero coefficient existence information (CBP; Coded Block Flag) for individual TUs and non-zero coefficient existence information (no_residual_data_flag) for multiple TUs are included in the TU partition information SP_TU.

The TU information TUI _{1 to} TUI _NT are individual information regarding each of one or more TUs included in the TT. For example, the TU information TUI includes a quantized prediction residual.

  Each quantization prediction residual is encoded data generated by the moving image encoding device 2 performing the following processes 1 to 3 on a target block that is a processing target block.

Process 1: DCT transform (Discrete Cosine Transform) of the prediction residual obtained by subtracting the prediction image from the encoding target image;
Process 2: Quantize the transform coefficient obtained in Process 1;
Process 3: Variable length coding is performed on the transform coefficient quantized in Process 2;
The quantization parameter qp described above represents the magnitude of the quantization step QP used when the moving image coding apparatus 2 quantizes the transform coefficient (QP = 2 ^{qp / 6} ).

(Prediction information PInfo)
As described above, there are two types of prediction information PInfo: inter prediction information and intra prediction information.

  The inter prediction information includes a coding parameter that is referred to when the video decoding device 1 generates an inter prediction image by inter prediction. More specifically, the inter prediction information includes inter PU division information that specifies a division pattern of the target CU into each inter PU, and inter prediction parameters for each inter PU.

  The inter prediction parameters include a reference image index, an estimated motion vector index, and a motion vector residual.

  On the other hand, the intra prediction information includes an encoding parameter that is referred to when the video decoding device 1 generates an intra predicted image by intra prediction. More specifically, the intra prediction information includes intra PU division information that specifies a division pattern of the target CU into each intra PU, and intra prediction parameters for each intra PU. The intra prediction parameter is a parameter for restoring intra prediction (prediction mode) for each intra PU.

  The parameters for restoring the prediction mode include mpm_flag which is a flag related to MPM (Most Probable Mode, the same applies hereinafter), mpm_idx which is an index for selecting the MPM, and an index for designating a prediction mode other than the MPM. Rem_idx is included. Here, MPM is an estimated prediction mode that is highly likely to be selected in the target partition. For example, the MPM may include an estimated prediction mode estimated based on prediction modes assigned to partitions around the target partition, and a DC mode or Planar mode that generally has a high probability of occurrence.

  Further, in the following, when simply described as “prediction mode”, it indicates the luminance prediction mode. The color difference prediction mode is described as “color difference prediction mode” and is distinguished from the luminance prediction mode. The parameter for restoring the prediction mode includes chroma_mode, which is a parameter for designating the color difference prediction mode.

  Details of parameters of mpm_flag, mpm_idx, rem_idx, and chroma_mode will be described later.

Further, mpm_flag and rem_index correspond to “prev_intra_luma_pred_flag” and “rem_intra_luma_pred_mode” in Non-Patent Document 1, respectively. Further, chroma_mode corresponds to “intra_chroma_pred_mode”.
[Video decoding device]
Below, the structure of the moving image decoding apparatus 1 which concerns on this embodiment is demonstrated with reference to FIGS.

(Outline of video decoding device)
The video decoding device 1 generates a predicted image for each PU, generates a decoded image # 2 by adding the generated predicted image and a prediction residual decoded from the encoded data # 1, and generates The decoded image # 2 is output to the outside.

  Here, the generation of the predicted image is performed with reference to an encoding parameter obtained by decoding the encoded data # 1. An encoding parameter is a parameter referred in order to generate a prediction image. In addition to prediction parameters such as a motion vector referred to in inter-screen prediction and a prediction mode referred to in intra-screen prediction, the encoding parameters include PU size and shape, block size and shape, and original image and Residual data with the predicted image is included. Hereinafter, a set of all information excluding the residual data among the information included in the encoding parameter is referred to as side information.

  Also, in the following, a picture (frame), a slice, a tree block, a CU, a block, and a PU to be decoded are a target picture, a target slice, a target tree block, a target CU, a target block, and a target PU, respectively. I will call it.

  The size of the tree block is, for example, 64 × 64 pixels, the size of the CU is, for example, 64 × 64 pixels, 32 × 32 pixels, 16 × 16 pixels, and 8 × 8 pixels, and the size of the PU is For example, 64 × 64 pixels, 32 × 32 pixels, 16 × 16 pixels, 8 × 8 pixels, 4 × 4 pixels, and the like. However, these sizes are merely examples, and the sizes of the tree block, CU, and PU may be other than the sizes shown above. In particular, when the color format is 4: 2: 2, it is preferable to use a PU having a size of 32 × 64 pixels, 16 × 32 pixels, 8 × 16 pixels, 4 × 8 pixels, or the like. This is because the aspect ratio of the chrominance pixels in the 4: 2: 2 color format image is horizontally long, ie, vertical: horizontal = 1: 2, so that the number of pixels in the vertical direction is the horizontal direction in the chrominance region. This is because an area that is twice the number of pixels is visually a square.

(Configuration of video decoding device)
Referring to FIG. 2 again, the schematic configuration of the moving picture decoding apparatus 1 will be described as follows. FIG. 2 is a functional block diagram showing a schematic configuration of the moving picture decoding apparatus 1.

  As illustrated in FIG. 2, the video decoding device 1 includes a variable length decoding unit 11, an inverse quantization / inverse conversion unit 13, a predicted image generation unit 14, an adder 15, and a frame memory 16.

[Variable length decoding unit]
The variable length decoding unit 11 decodes various parameters included in the encoded data # 1 input from the video decoding device 1. In the following description, it is assumed that the variable length decoding unit 11 appropriately decodes a parameter encoded by an entropy encoding method such as CABAC and CAVLC. Specifically, the variable length decoding unit 11 decodes encoded data # 1 for one frame according to the following procedure.

  First, the variable length decoding unit 11 demultiplexes encoded data # 1 for one frame into various types of information included in the hierarchical structure shown in FIG. For example, the variable length decoding unit 11 refers to information included in various headers and sequentially separates the encoded data # 1 into slices and tree blocks.

  Here, the various headers include (1) information about the method of dividing the target picture into slices, and (2) information about the size, shape, and position of the tree block belonging to the target slice. .

  Then, the variable length decoding unit 11 divides the target tree block into CUs with reference to the tree block division information SP_TBLK included in the tree block header TBLKH. Further, the variable length decoding unit 11 decodes the TT information TTI related to the conversion tree obtained for the target CU and the PT information PTI related to the prediction tree obtained for the target CU.

  The TT information TTI includes the TU information TUI corresponding to the TU included in the conversion tree as described above. Further, as described above, the PT information PTI includes the PU information PUI corresponding to the PU included in the target prediction tree.

  The variable length decoding unit 11 supplies the TT information TTI obtained for the target CU to the TU information decoding unit 12. Further, the variable length decoding unit 11 supplies the PT information PTI obtained for the target CU to the predicted image generation unit 14. The configuration of the variable length decoding unit 11 will be described in more detail later.

[Inverse quantization / inverse transform unit]
The inverse quantization / inverse transform unit 13 performs an inverse quantization / inverse transform process on each block included in the target CU based on the TT information TTI. Specifically, for each target TU, the inverse quantization / inverse transform unit 13 performs inverse quantization and inverse orthogonal transform on the quantized prediction residual included in the TU information TUI corresponding to the target TU, so that each pixel is per pixel. Is restored. Here, the orthogonal transform refers to an orthogonal transform from the pixel region to the frequency region. Therefore, the inverse orthogonal transform is a transform from the frequency domain to the pixel domain. Examples of inverse orthogonal transform include inverse DCT transform (Inverse Discrete Cosine Transform), inverse DST transform (Inverse Discrete Sine Transform), and the like. The inverse quantization / inverse transform unit 13 supplies the restored prediction residual D to the adder 15.

[Predicted image generator]
The predicted image generation unit 14 generates a predicted image based on the PT information PTI for each PU included in the target CU. Specifically, the predicted image generation unit 14 performs, for each target PU, a local decoded image P ′ that is a decoded image by performing intra prediction or inter prediction according to the parameters included in the PU information PUI corresponding to the target PU. Is used to generate a predicted image Pred. The predicted image generation unit 14 supplies the generated predicted image Pred to the adder 15. The configuration of the predicted image generation unit 14 will be described in more detail later.

[Adder]
The adder 15 adds the predicted image Pred supplied from the predicted image generation unit 14 and the prediction residual D supplied from the inverse quantization / inverse transform unit 13, thereby obtaining the decoded image P for the target CU. Generate.

[Frame memory]
The decoded image P that has been decoded is sequentially recorded in the frame memory 16. In the frame memory 16, at the time of decoding the target tree block, decoded images corresponding to all tree blocks decoded before the target tree block (for example, all tree blocks preceding in the raster scan order) are stored. It is recorded.

  Also, at the time of decoding the target CU, decoded images corresponding to all the CUs decoded before the target CU are recorded.

  In the video decoding device 1, the encoded data for one frame input to the video decoding device 1 at the time when the decoded image generation processing for each tree block is completed for all tree blocks in the image. Decoded image # 2 corresponding to # 1 is output to the outside.

(Definition of prediction mode)
As described above, the predicted image generation unit 14 generates and outputs a predicted image based on the PT information PTI. When the target CU is an intra CU, the PU information PTI input to the predicted image generation unit 14 includes a prediction mode (IntraPredMode) and a color difference prediction mode (IntraPredModeC). Hereinafter, the definition of the prediction mode (luminance / color difference) will be described with reference to FIGS.
(Overview)
FIG. 4 shows an example of the prediction mode number corresponding to the classification of the intra prediction method used in the video decoding device 1. '0' for Planar prediction (Intra_Planar), '1' for vertical prediction (Intra_Vertical), '2' for horizontal prediction (Intra_Horizontal), '3' for DC prediction (Intra_DC), '4' for Angular prediction (Intra_Angular) A prediction mode number of “35” is assigned to “34” and LM prediction (Intra_FromLuma), respectively. The LM prediction is a method for predicting the pixel value of the color difference based on the decoded pixel value of the luminance, and can be selected only when the color difference is predicted. Other prediction modes can be selected for both luminance and color difference. Horizontal prediction, vertical prediction, and angular prediction are collectively referred to as direction prediction. The direction prediction is a prediction method for generating a prediction image by extrapolating adjacent pixel values around the target PU in a specific direction.

  Next, the identifier of each prediction mode included in the direction prediction will be described with reference to FIG. FIG. 5 shows prediction modes corresponding to prediction mode identifiers for 33 types of prediction modes belonging to direction prediction. The direction of the arrow in FIG. 5 represents the prediction direction, but more accurately indicates the direction of the vector from the prediction target pixel to the decoded pixel referred to by the prediction target pixel. In that sense, the prediction direction is also referred to as a reference direction. The identifier of each prediction mode is associated with a code indicating whether the main direction is the horizontal direction (HOR) or the vertical direction (VER) and an identifier composed of a combination of displacements with respect to the main direction. For example, HOR for horizontal prediction, VER for vertical prediction, VER + 8 for prediction mode referring to surrounding pixels in the upper right 45 degree direction, VER-8 for prediction mode referring to surrounding pixels in the upper left 45 degree direction, and lower left 45 A prediction mode that refers to peripheral pixels in the direction of the degree is assigned a code of HOR + 8. In the direction prediction, 17 prediction directions of VER-8 to VER + 8 are defined as a vertical prediction mode, and 16 prediction directions of HOR-7 to HOR + 8 are defined as a prediction mode of horizontal prediction.

  The correspondence between the intra prediction method and the prediction mode number applied in the video decoding device 1 may be defined as shown in FIG. 6, for example. FIG. 6 is a diagram illustrating an example of a prediction mode definition DEFPM1 that is a definition of correspondence between an intra prediction method and a prediction mode number. In the prediction mode definition DEFPM1 shown in FIG. 6, prediction mode numbers “0” for Planar prediction, “1” for vertical prediction, “2” for horizontal prediction, and “3” for DC prediction are assigned. From prediction mode numbers “4” to “18”, the Angular prediction mode in which the displacement from the main direction is an even number is in the order of the prediction mode in which the displacement is small. When the displacements are equal, the main direction is vertical and horizontal The prediction mode numbers are assigned in this order. From prediction mode numbers '19' to '35', the Angular prediction mode in which the displacement from the main direction is an odd number is in the order of the prediction mode in which the displacement is small. When the displacements are equal, the main direction is vertical and horizontal. The prediction mode numbers are assigned in this order.

(Details of predicted image generator)
Next, the configuration of the predicted image generation unit 14 will be described in more detail with reference to FIG. FIG. 7 is a functional block diagram illustrating a configuration example of the predicted image generation unit 14. In addition, this structural example has illustrated the functional block which concerns on the prediction image production | generation of intra CU among the functions of the prediction image production | generation part 14. FIG.

  As illustrated in FIG. 7, the predicted image generation unit 14 includes a prediction unit setting unit 141, a reference pixel setting unit 142, a switch 143, a reference pixel filter unit 144, a luminance prediction unit 145, and a color difference prediction unit 146.

  The prediction unit setting unit 141 sets PUs included in the target CU as target PUs in a prescribed setting order, and outputs information related to the target PU (target PU information). The target PU information includes at least a size of the target PU, a position in the CU of the target PU, and an index (luminance color difference index cIdx) indicating the luminance or color difference plane of the target PU.

  For example, when the input image is in YUV format, the PU setting order is such that PUs corresponding to Y included in the target CU are set in raster scan order, and subsequently, PUs corresponding to the order of U and V are set in raster scan order. Use the order of setting.

  The setting sequence of PUs when the input image is in the 4: 2: 0 YUV format and PUs included in the CU will be described with reference to FIG.

  FIG. 8A illustrates PUs in a CU when the size of the target CU is 8 × 8 pixels and the division type is N × N. First, four 4 × 4 pixel PUs corresponding to the luminance Y are set in the raster scan order (in the order of PU_Y0, PU_Y1, PU_Y2, PU_Y3). Next, one 4 × 4 pixel PU (PU_U0) corresponding to the color difference U is set. Finally, one 4 × 4 pixel prediction unit (PU_V0) corresponding to the color difference V is set.

  (B) of FIG. 8 illustrates PUs in the CU when the size of the target CU is 16 × 16 pixels and the division type is 2N × 2N. First, one 16 × 16 pixel prediction unit (PU_Y0) corresponding to the luminance Y is set. Next, one 8 × 8 pixel prediction unit (PU_U0) corresponding to the color difference U is set. Finally, one 8 × 8 pixel prediction unit (PU_V0) corresponding to the color difference V is set.

  Next, description will be made with reference to FIG. 9 illustrating PU setting order and PUs included in the CU when the input image is in a 4: 2: 2 YUV format.

  FIG. 9A illustrates PUs in a CU when the size of the target CU is 8 × 8 pixels and the division type is N × N. First, four 4 × 4 pixel PUs corresponding to the luminance Y are set in the raster scan order (in the order of PU_Y0, PU_Y1, PU_Y2, PU_Y3). Next, one 4 × 8 pixel PU (PU_U0) corresponding to the color difference U is set. Finally, one 4 × 8 pixel prediction unit (PU_V0) corresponding to the color difference V is set.

  FIG. 9B illustrates PUs in a CU when the size of the target CU is 16 × 16 pixels and the division type is 2N × 2N. First, one 16 × 16 pixel prediction unit (PU_Y0) corresponding to the luminance Y is set. Next, one 8 × 16 pixel prediction unit (PU_U0) corresponding to the color difference U is set. Finally, one 8 × 16 pixel prediction unit (PU_V0) corresponding to the color difference V is set.

  FIG. 10 shows another PU setting. FIG. 10A illustrates another example of PUs in a CU when the size of the target CU is 8 × 8 pixels and the division type is N × N. First, four 4 × 4 pixel PUs corresponding to the luminance Y are set in the raster scan order (in the order of PU_Y0, PU_Y1, PU_Y2, PU_Y3). Next, two 4 × 4 pixel PUs (PU_U0, PU_U1) corresponding to the color difference U are set. Finally, two 4 × 4 pixel PUs (PU_V0, PU_V1) corresponding to the color difference V are set.

  FIG. 10B shows a case where the division type is 2N × 2N, and shows the same PU setting as in FIG. 9B.

  In the following description, the division illustrated in FIG. 9 is used, but the same processing can be applied to each color difference PU even when the division illustrated in FIG. 10 is used.

  The reference pixel setting unit 142 reads a pixel value (decoded pixel value) of a decoded image around the target PU recorded in the frame memory based on the input target PU information, and is referred to when generating a predicted image Set the pixel. The reference pixel value p (x, y) is set by the following equation using the decoded pixel value r (x, y).

p (x, y) = r (xB + x, yB + y) x = -1, y = -1 .. (nS * 2-1) and x = 0 .. (nS * 2-1) , y = -1
Here, (xB, yB) represents the position of the upper left pixel in the target PU, nS represents the size of the target PU, and indicates the larger value of the width or height of the target PU. In the above equation, basically, the decoded pixel value included in the decoded pixel line adjacent to the upper side of the target PU and the decoded pixel column adjacent to the left side of the target PU is copied to the corresponding reference pixel value. Note that when there is no decoded pixel value corresponding to a specific reference pixel position or when reference cannot be made, a predetermined value may be used, or referenceable decoding existing in the vicinity of the corresponding decoded pixel value. Pixel values may be used.

  The switch 143 determines whether the target PU is luminance or color difference based on the input target PU information, and outputs a reference pixel input in the corresponding output direction.

  The reference pixel filter unit 144 applies a filter to the input reference pixel value according to the input prediction mode, and outputs the reference pixel value after the filter application. Specifically, the reference pixel filter unit 144 determines whether to apply the filter according to the target PU size and the prediction mode.

  The luminance prediction unit 145 generates and outputs a luminance prediction image of the target PU based on the input prediction mode and reference pixels. Detailed description of the luminance prediction unit 145 will be described later.

  The color difference prediction unit 146 generates and outputs a color difference prediction image of the target PU based on the input prediction mode and reference pixels. Detailed description of the color difference prediction unit 146 will be described later.

(Flow of predicted image generation processing)
Next, an outline of the prediction image generation processing for each CU in the prediction image generation unit 14 will be described with reference to the flowchart of FIG. When the predicted image generation processing for each CU starts, first, the prediction unit setting unit 141 sets one of the PUs included in the CU as the target PU according to a predetermined order, and sets the target PU information as the reference pixel setting unit 142 and the switch. It outputs to 143 (S11). Next, the reference pixel setting unit 142 sets the reference pixel of the target PU using the decoded pixel value read from the external frame memory (S12). Next, the switch 143 determines whether the target PU is luminance or color difference based on the input target PU information, and switches the output according to the determination result (S13).

  When the target PU is luminance (YES in S13), the output of the switch 143 is connected to the reference pixel filter unit 144. Subsequently, the reference pixel is input to the reference pixel filter unit 144, the reference pixel filter is applied according to the prediction mode separately input, and the reference pixel after the filter application is output to the luminance prediction unit 145 (S14). . Next, the brightness prediction unit 145 generates and outputs a brightness prediction image in the target PU based on the input reference pixel and the prediction mode (S15).

On the other hand, when the target PU is a color difference (NO in S13), the output of the switch 143 is connected to the color difference prediction unit 146. Subsequently, the color difference prediction unit 146 generates and outputs a color difference prediction image in the target PU based on the input reference pixel and the prediction mode (S16). When the generation of the prediction image of the luminance or color difference of the target PU is completed, the prediction unit setting unit 141 determines whether the prediction images of all the PUs in the target CU have been generated (S17). When the prediction image of some PUs in the target CU has not been generated (NO in S17), the process returns to S1, and the prediction image generation process for the next PU in the target CU is executed. If predicted images of all PUs in the target CU have been generated (YES in S17), the predicted images of the luminance and color difference of each PU in the target CU are combined and output as a predicted image of the target CU, and the process ends. To do.
(Details of luminance prediction part)
Next, details of the luminance prediction unit 145 will be described with reference to FIG. FIG. 12 shows a detailed configuration of the luminance prediction unit 145. As illustrated in FIG. 12, the luminance prediction unit 145 includes a prediction method selection unit 1451 and a predicted image derivation unit 1452.

  The prediction method selection unit 1451 selects a prediction method used for prediction image generation based on the input prediction mode and outputs a selection result. The selection of the prediction method is realized by selecting a prediction method corresponding to the prediction mode number of the input prediction mode based on the definition of FIG. 4 described above.

  The prediction image deriving unit 1452 derives a prediction image corresponding to the prediction method selection result output by the prediction method selecting unit 1451. More specifically, the predicted image derivation unit 1452 includes a DC prediction unit 1452D, a Planar prediction unit 1452P, a horizontal prediction unit 1452H, a vertical prediction unit 1452V, an Angular prediction unit 1452A, and a prediction direction derivation unit 1453. Further, when the prediction method is Planer, vertical prediction, horizontal prediction, DC prediction, and Angular, the predicted image derivation unit 1452 is a Planar prediction unit 1452P, a vertical prediction unit 1452V, a horizontal prediction unit 1452H, and an Angular prediction unit, respectively. A prediction image is derived by 1452A.

  The DC prediction unit 1452D derives a DC prediction value corresponding to the average value of the pixel values of the input reference pixels, and outputs a prediction image using the derived DC prediction value as a pixel value.

  The Planar prediction unit 1452P generates and outputs a predicted image based on pixel values derived by linearly adding a plurality of reference pixels according to the distance from the prediction target pixel. For example, the pixel value predSamples [x, y] of the predicted image can be derived by the following equation using the reference pixel value p [x, y] and the size nS of the target PU.

predSamples [x, y] = (
(nS-1-x) * p [-1, y] + (x + 1) * p [nS, -1] +
(nS-1-y) * p [x, -1] + (y + 1) * p [-1, nS] + nS) >> (k + 1)
Here, x, y = 0..nS-1 and it is defined as k = log2 (nS).

  The horizontal prediction unit 1452H generates a predicted image obtained by extrapolating the left side adjacent pixels of the target PU in the horizontal direction based on the input reference pixels, and outputs the result as a predicted image.

  The vertical prediction unit 1452V generates a predicted image obtained by extrapolating the upper side adjacent pixels of the target PU in the vertical direction based on the input reference pixels, and outputs the result as a predicted image.

  When the input prediction mode is the direction prediction mode, the prediction direction deriving unit 1453 determines and outputs a prediction direction (reference direction) associated with the prediction mode. The output prediction direction is expressed by a combination of a main direction flag bRefVer indicating whether or not the main direction is a vertical direction and a gradient (offset) intraPredAngle of the prediction direction with respect to the main direction. When the value of the main direction flag bRefVer is 0, the main direction is the horizontal direction, and when the value is 1, the main direction is the vertical direction.

  A specific configuration of the prediction direction deriving unit 1453 will be described with reference to FIG. FIG. 1 is a functional block diagram illustrating a configuration example of the prediction direction deriving unit 1453. As shown in FIG. 1, more specifically, the prediction direction deriving unit 1453 includes a main direction deriving unit 1453A and a gradient deriving unit 1453B.

  The main direction deriving unit 1453A derives a main direction flag bRefVer. Further, the main direction deriving unit 1453A can refer to the prediction mode definition DEFPM1 of FIG. The main direction flag bRefVer is derived based on the main direction associated with the prediction mode number m.

  The gradient deriving unit 1453B derives the gradient intraPredAngle. Further, the gradient deriving unit 1453B can refer to the gradient definition table DEFANG1 shown in FIG. The gradient definition table DEFANG1 shown in FIG. 13 is a table showing the correspondence between the prediction mode identifier and the value of the gradient intraPredAngle. The gradient deriving unit 1453B may derive the gradient intraPredAngle based on the gradient definition table DEFANG1. The value of the gradient intraPredAngle is a value representing the gradient in the prediction direction. More precisely, when the main direction is the vertical direction, the direction of the vector represented by (intraPredAngle, -32) is the prediction direction. When the main direction is the horizontal direction, the vector direction represented by (−32, intraPredAngle) is the prediction direction. According to the gradient definition table DEFANG1 shown in FIG. 13, the absolute value of the gradient intraPredAngle corresponding to the absolute values 0 to 8 of the displacement with respect to the main direction is 0, 2, 5, 9, 13, 17, 21, 26, 32. The sign of displacement with respect to the main direction and the sign of gradient intraPredAngle are equal. For example, the value of the gradient intraPredAngle corresponding to the identifier HOR-1 is −2 in the luminance region.

  The gradient deriving unit 1453B can also refer to the color difference gradient definition table DEFANG1C shown in FIG. 16 when the prediction image generation target is a color difference pixel. The processing of the gradient deriving unit 1453B when the predicted image generation target is a color difference pixel will be described later.

  The Angular prediction unit 1452A generates and outputs a predicted image corresponding to the target PU using the reference pixels in the input prediction direction (reference direction). In the process of generating a predicted image by Angular prediction, a main reference pixel is set according to the value of the main direction flag bRefVer, and a predicted image is generated by referring to the main reference pixel in units of lines or columns in the PU. When the value of the main direction flag bRefVer is 1 (the main direction is the vertical direction), the prediction image generation unit is set to a line, and the reference pixel above the target PU is set to the main reference pixel. Specifically, the main reference pixel refMain [x] is set using the value of the reference pixel p [x, y] by the following equation.

refMain [x] = p [-1 + x, -1], with x = 0..2 * nS
refMain [x] = p [-1, -1+ ((x * invAngle + 128) >> 8)], with x = -nS ..- 1
Here, invAngle corresponds to a value obtained by scaling (multiplying by 8192) the reciprocal of the displacement intraPredAngle in the prediction direction. According to the above formula, in the range where x is 0 or more, the decoded pixel value of the pixel adjacent to the upper side of the target PU is set as the value of refMain [x]. In the range where x is less than 0, the decoded pixel value of the pixel adjacent to the left side of the target PU is set as a value derived from the prediction direction as the value of refMain [x]. The predicted image predSamples [x, y] is calculated by the following equation.

predSamples [x, y] =
((32-iFact) * refMain [x + iIdx + 1] + iFact * refMain [x + iIdx + 2] + 16) >> 5
Here, iIdx and iFact represent the position of the main reference pixel used for generating the prediction target pixel calculated according to the distance (y + 1) between the prediction target line and the main reference pixel and the gradient intraPredAngle. iIdx corresponds to the position of integer precision in pixel units, and iFact corresponds to the position of decimal precision in pixel units, and is derived by the following equation.

iIdx = ((y + 1) * intraPredAngle) >> 5
iFact = ((y + 1) * intraPredAngle) && 31
When the value of the main direction flag bRefVer is 0 (the main direction is the horizontal direction), the prediction image generation unit is set to a column, and the left reference pixel of the target PU is set to the main reference pixel. Specifically, the main reference pixel refMain [x] is set using the value of the reference pixel p [x, y] by the following equation.

refMain [x] = p [-1, -1 + x], with x = 0..nS
refMain [x] = p [-1+ ((x * invAngle + 128) >> 8), -1], with x = -nS ..- 1
The predicted image predSamples [x, y] is calculated by the following equation.

predSamples [x, y] =
((32-iFact) * refMain [y + iIdx + 1] + iFact * refMain [y + iIdx + 2] + 16) >> 5
Here, iIdx and iFact represent the position of the main reference pixel used for generating the prediction reference pixel calculated according to the distance (x + 1) between the prediction target column and the main reference pixel and the gradient intraPredAngle. iIdx corresponds to an integer-precision position in pixel units, and iFact corresponds to a decimal-precision position in pixel units.

iIdx = ((x + 1) * intraPredAngle) >> 5
iFact = ((x + 1) * intraPredAngle) & 31
Here, “&” is an operator representing a logical bit operation, and the result of “A & 31” means a remainder obtained by dividing the integer A by 32.
(Angular prediction process flow)
Next, a prediction image generation process in the luminance prediction unit 145 when the prediction mode is Angular prediction will be described with reference to the flowchart of FIG. FIG. 14 is a flowchart showing the Angular prediction process in the luminance prediction unit. First, when the prediction mode input to the prediction method selection part 1451 is Angular prediction, the prediction image generation process by Angular prediction is started. The prediction direction deriving unit 1453 determines the main direction of the prediction direction based on the input prediction mode, and outputs it to the Angular prediction unit 1452A (S21). Next, the prediction direction deriving unit 1453 determines an offset intraPredAngle with respect to the main direction of the prediction direction based on the input prediction mode, and outputs it to the Angular prediction unit 1452A (S22). The Angular prediction unit 1452A sets a main reference pixel based on the input main direction (S23). Subsequently, the Angular prediction unit 1452A sets a prediction target line or column (S24), and generates a prediction image for the target line or column (S25). It is confirmed whether predicted image generation for all lines / columns of the target PU has been completed (S26). If not completed (NO in S26), the process of S24 is executed. If completed (YES in S26), the prediction image of the target PU is output and the process is terminated.
(Details of color difference prediction unit)
Next, details of the color difference prediction unit 146 will be described with reference to FIG. FIG. 15 shows a detailed configuration of the color difference prediction unit 146. The color difference prediction unit 146 includes a prediction method selection unit 1451, a predicted image derivation unit 1452, and a prediction direction derivation unit 1453. The predicted image derivation unit 1452 includes a DC prediction unit 1452D, a Planar prediction unit 1452P, a horizontal prediction unit 1452H, a vertical prediction unit 1452V, an Angular prediction unit 1452A, and an LM prediction unit 1452L. Note that the constituent elements other than the LM prediction unit 1452L have the same functions as the corresponding constituent elements included in the luminance prediction unit 145, and thus the same reference numerals are given and description thereof is omitted. However, since the gradient deriving unit 1453B included in the prediction direction deriving unit 1453 operates differently from the luminance image with respect to the color difference image, it will be described here.

  When the predicted image generation target is a color difference pixel, the gradient deriving unit 1453B uses the color difference gradient definition table DEFANG1C shown in FIG. 16 as the gradient definition table. According to the gradient definition table DEFANG1C shown in FIG. 16, the absolute values of the gradient intraPredAngle corresponding to the absolute values 0 to 8 of the displacement with respect to the main direction are 0, 1, 2, 4, 6 in order when the main direction is the vertical direction. , 8, 10, 13, 16, and when the main direction is the horizontal direction, 0, 4, 10, 18, 26, 34, 42, 52, 64 in order. In the color difference gradient definition table DEFANG1C shown in FIG. 16, when the main direction is the vertical direction, half the value of intraPredAngle associated with the same IntraPredMode in the gradient definition table DEFANG1 shown in FIG. When the main direction is the horizontal direction, it is twice the value of intraPredAngle associated with the same IntraPredMode in the gradient definition table DEFANG1 shown in FIG.

  Note that the gradient deriving unit 1453B refers only to the color difference gradient definition table DEFANG1 shown in FIG. 13, and when the predicted image generation target is a color difference pixel, if the main direction is the vertical direction, the gradient definition table shown in FIG. If the value obtained by referring to DEFANG1 is divided by 2, and if the main direction is horizontal, the value obtained by doubling the value obtained by referring to the gradient definition table DEFANG1 shown in FIG. 13 is used as intraPredAngle. Can be realized. At this time, the definition and selective reference of the color difference gradient definition table DEFANG1C shown in FIG. 16 are unnecessary, and the memory can be saved.

  In addition, the relationship of the value of the gradient intraPredAngle between the luminance and the color difference is as follows: in the 4: 2: 2 format image, the vector (vxL, vyL) in the luminance space and the vector (vxC, vyC) in the color difference space Based on the relationship of vxL = 2vxC and vyL = vyC between them. The horizontal gradient of the vector (vxC, vyC) in the color difference space is (vyC / vxC) = 2 (vyL / vxL), which is twice the horizontal gradient of the vector in the luminance space. On the other hand, the vertical gradient of the vector (vxC, vyC) in the color difference space is (vxC / vyC) = 0.5 (vxL / vyL), which is half the vertical gradient of the vector in the luminance space. In general, in the input image, if there is a relationship of vxL = α ・ vxC, vyL = β ・ vyC between the vector (vxL, vyL) in the luminance space and the vector (vxC, vyC) in the color difference space, The value of the gradient intraPredAngle applied to the color difference is (α / β) times when the main direction is horizontal and (β / α) when the main direction is vertical compared to the value of the gradient intraPredAngle applied to the luminance. It is preferable to double.

  The LM prediction unit 1452L estimates a parameter related to the correlation between the luminance pixel value and the chrominance pixel value in the target PU based on the correlation between the luminance decoded pixel value around the target PU and the reference pixel value (color difference decoded pixel value). The correlation parameter includes a correlation coefficient a and an offset b. The prediction target PU, that is, the color difference prediction image predSamuplesC [xC, yC] is calculated by the following equation using the pixel value recY [xL, yL] of the luminance decoded image corresponding to the target PU and the correlation parameter.

predSamplesC [xC, yC] = a * recY [xL, yL] + b
Here, xC and yC are coordinate values in color difference pixel units, and xL and yL are coordinate values in luminance pixel units indicating positions corresponding to xC and yC, respectively. When the 4: 2: 2 YUV format is used, for example, xL = 2 * xC and yL = yC are associated.

  This is the end of the description of the prediction image generation processing of the target CU in the prediction image generation unit 14.

(Details of variable length decoding unit)
Next, the configuration of the variable length decoding unit 11 will be described in more detail with reference to FIG. FIG. 17 is a functional block diagram illustrating a configuration example of the variable length decoding unit 11. In FIG. 17, the configuration for decoding the prediction mode among the configurations of the variable length decoding unit 11 is shown in detail.

  As shown in FIG. 17, the variable length decoding unit 11 includes a prediction set determination unit 111, an MPM derivation unit 112, an MPM determination unit 113, a prediction mode restoration unit 114, a color difference prediction mode restoration unit 116, and a context storage unit 117. .

  The prediction set determination unit 111 determines a prediction set that is a set of prediction modes used for prediction processing. For example, the prediction set determination unit 111 calculates the number of prediction modes used for prediction processing according to the size of the target block, and determines the prediction set by selecting the calculated number of prediction modes from the prediction mode definition. To do. In other words, the prediction set is defined for each size of the target block or for each number of prediction modes available in the target PU.

  The MPM deriving unit 112 derives the MPM based on the prediction mode assigned to the partitions around the target partition.

  For example, the MPM deriving unit 112 derives two MPMs. The MPM deriving unit 112 derives a first MPM candidate (hereinafter referred to as MPM0) and a second MPM candidate (hereinafter referred to as MPM1) as follows.

First, as shown in FIG. 18, the object to PMA PU: Left neighboring adjacent to the left of _{R T} PU: prediction mode _{N A,} subject to PMB PU: adjacent on adjacent on the _{R T} PU: the _{N B} Set the prediction mode. When the prediction mode of the left adjacent PU or the upper adjacent PU is not available, a default prediction mode, for example, “Intra_Planar” is set. The case where the adjacent PU is unavailable includes a case where the prediction mode of the adjacent PU is not decoded, and the case where the adjacent PU is an upper adjacent PU and belongs to a different LCU (tree block).

  Then, the MPM deriving unit 112 derives MPM0 according to the following equation (1).

MPM0 = pmA (1)
Next, the MPM deriving unit 112 derives MPM1 depending on whether pmA and pmB match. If pmA and pmB do not match, MPM1 is derived according to the following equation (2).

MPM1 = pmB (2)
On the other hand, if pmA and pmB match, the MPM deriving unit 112 sets “Intra_Planar” to MPM1 if pmA is “Intra_DC”, and sets “Intra_DC” to MPM1 if pmA is other than “Intra_DC”. Set to.

  The MPM determination unit 113 determines whether or not the prediction mode of the target PU matches the estimated prediction mode MPM based on mpm_flag included in the encoded data. mpm_flag is “1” when the prediction mode of the target PU matches the estimated prediction mode MPM, and “0” when the prediction mode of the target PU does not match the estimated prediction mode MPM. The MPM determination unit 113 notifies the prediction mode restoration unit 114 of the determination result.

  The MPM determination unit 113 decodes mpm_flag from the encoded data in accordance with the context stored in the context storage unit 117.

  The prediction mode restoration unit 114 restores the prediction mode for the target PU. The prediction mode restoration unit 114 restores the prediction mode according to the determination result notified from the MPM determination unit 113.

  When the prediction mode of the target PU matches the estimated prediction mode MPM, the prediction mode restoration unit 114 decodes mpm_idx from the encoded data, and restores the prediction mode based on the value. mpm_idx is “0” when the prediction mode of the target PU matches MPM0, and “1” when the prediction mode of the target PU matches MPM1.

  When the prediction mode of the target PU does not match the estimated prediction mode MPM, the prediction mode restoration unit 114 restores the prediction mode based on rem_idx included in the encoded data. Specifically, first, the values of MPM0 and MPM1 are conditionally swapped so that a smaller prediction mode number of MPM0 and MPM1 is assigned to MPM0. Next, when the value of rem_idx is equal to or greater than the value of MPM0, 1 is added to the value of rem_idx. Next, when the value of rem_idx is equal to or greater than the value of MPM1, 1 is added to the value of rem_idx. Finally, the prediction mode corresponding to the prediction mode number of the value of rem_idx is restored.

  The color difference prediction mode restoration unit 116 restores the color difference prediction mode for the target PU. More specifically, the color difference prediction mode restoration unit 116 restores the color difference prediction mode as follows.

  First, the color difference prediction mode restoring unit 116 decodes intra color difference prediction mode designation information chroma_mode (intra_chroma_pred_mode) included in the encoded data # 1. Then, the color difference prediction mode restoration unit 116 restores the color difference prediction mode based on the restored intra color difference prediction mode designation information chroma_mode and the luminance prediction mode (IntraPredMode [xB] [yB]). This will be described in detail below.

  FIG. 19 is a table in which the intra color difference prediction mode designation information chroma_mode and the luminance prediction mode (IntraPredMode [xB] [yB]) are associated with the color difference prediction mode (IntraPredModeC). In the table, “LM” indicates that the LM mode already described is used. “X” indicates that the value of the luminance prediction mode (IntraPredMode [xB] [yB]) is used as it is. Here, the prediction mode corresponding to “X” is referred to as a DM mode.

[Schematic flow]
First, an example of a schematic flow of a prediction mode restoration process in the video decoding device 1 will be described with reference to a flowchart shown in FIG.

  When the prediction mode restoration process is started in the video decoding device 1, the MPM deriving unit 112 derives MPM0 (S21). Subsequently, the MPM deriving unit 112 derives MPM1 (S22).

  Next, the MPM determination unit 113 determines whether or not the prediction mode of the target PU matches the estimated prediction mode MPM based on mpm_flag (S23).

  When the prediction mode of the target PU matches the estimated prediction mode MPM, that is, MPM0 or MPM1 (YES in S23), the prediction mode restoration unit 114 restores the prediction mode based on mpm_idx. When mpm_idx is “0”, the prediction mode restoration unit 114 sets MPM0 as the prediction mode pmT of the target PU, while when mpm_idx is “1”, sets MPM1 as the prediction mode pmT of the target PU. (S24).

  On the other hand, when the prediction mode of the target PU does not match the estimated prediction mode MPM (NO in S23), the prediction mode restoration unit 114 compares MPM0 and MPM1, and the prediction mode number of MPM1 is greater than the prediction mode number of MPM0. If it is smaller, MPM0 and MPM1 are swapped (S25). Subsequently, the prediction mode restoration unit 114 generates an array of rem_mode (S26). Finally, the prediction mode restoration unit 114 selects the rem_idx-th element from the rem_mode array as the prediction mode (S27).

[Moving picture encoding device]
Hereinafter, the moving picture coding apparatus 2 according to the present embodiment will be described with reference to FIGS.

(Outline of video encoding device)
Generally speaking, the moving image encoding device 2 is a device that generates and outputs encoded data # 1 by encoding the input image # 10.

(Configuration of video encoding device)
First, a configuration example of the video encoding device 2 will be described with reference to FIG. FIG. 21 is a functional block diagram showing the configuration of the moving image encoding device 2. As illustrated in FIG. 21, the moving image encoding device 2 includes an encoding setting unit 21, an inverse quantization / inverse conversion unit 22, a predicted image generation unit 23, an adder 24, a frame memory 25, a subtractor 26, a conversion / A quantization unit 27 and an encoded data generation unit 29 are provided.

  The encoding setting unit 21 generates image data related to encoding and various setting information based on the input image # 10.

  Specifically, the encoding setting unit 21 generates the next image data and setting information.

  First, the encoding setting unit 21 generates the CU image # 100 for the target CU by sequentially dividing the input image # 10 into slice units, tree block units, and CU units.

  Also, the encoding setting unit 21 generates header information H ′ based on the result of the division process. The header information H ′ includes (1) information on the size and shape of the tree block belonging to the target slice and the position in the target slice, and (2) the size, shape and shape of the CU belonging to each tree block. CU information CU ′ for the position at

  Further, the encoding setting unit 21 refers to the CU image # 100 and the CU information CU 'to generate PT setting information PTI'. The PT setting information PTI 'includes information on all combinations of (1) possible division patterns of the target CU for each PU and (2) prediction modes that can be assigned to each PU.

  The encoding setting unit 21 supplies the CU image # 100 to the subtractor 26. In addition, the encoding setting unit 21 supplies the header information H ′ to the encoded data generation unit 29. Also, the encoding setting unit 21 supplies the PT setting information PTI ′ to the predicted image generation unit 23.

  The inverse quantization / inverse transform unit 22 performs inverse quantization and inverse orthogonal transform on the quantized prediction residual for each block supplied from the transform / quantization unit 27, thereby predicting the prediction residual for each block. To restore. The inverse orthogonal transform is as already described for the inverse quantization / inverse transform unit 13 shown in FIG.

  Further, the inverse quantization / inverse transform unit 22 integrates the prediction residual for each block according to the division pattern specified by the TT division information (described later), and generates a prediction residual D for the target CU. The inverse quantization / inverse transform unit 22 supplies the prediction residual D for the generated target CU to the adder 24.

  The predicted image generation unit 23 refers to the locally decoded image P ′ and the PT setting information PTI ′ recorded in the frame memory 25 to generate a predicted image Pred for the target CU. The predicted image generation unit 23 sets the prediction parameter obtained by the predicted image generation process in the PT setting information PTI ′, and transfers the set PT setting information PTI ′ to the encoded data generation unit 29. Note that the predicted image generation process performed by the predicted image generation unit 23 is the same as that performed by the predicted image generation unit 14 included in the video decoding device 1, and thus description thereof is omitted here.

  The adder 24 adds the predicted image Pred supplied from the predicted image generation unit 23 and the prediction residual D supplied from the inverse quantization / inverse transform unit 22 to thereby obtain the decoded image P for the target CU. Generate.

  Decoded decoded images P are sequentially recorded in the frame memory 25. In the frame memory 25, decoded images corresponding to all tree blocks decoded prior to the target tree block (for example, all tree blocks preceding in the raster scan order) at the time of decoding the target tree block. It is recorded.

  The subtractor 26 generates a prediction residual D for the target CU by subtracting the prediction image Pred from the CU image # 100. The subtractor 26 supplies the generated prediction residual D to the transform / quantization unit 27.

  The transform / quantization unit 27 generates a quantized prediction residual by performing orthogonal transform and quantization on the prediction residual D. Here, the orthogonal transformation refers to transformation from the pixel region to the frequency region. Examples of inverse orthogonal transform include DCT transform (Discrete Cosine Transform), DST transform (Discrete Sine Transform), and the like.

  Specifically, the transform / quantization unit 27 refers to the CU image # 100 and the CU information CU ', and determines a division pattern of the target CU into one or a plurality of blocks. Further, according to the determined division pattern, the prediction residual D is divided into prediction residuals for each block.

  The transform / quantization unit 27 generates a prediction residual in the frequency domain by orthogonally transforming the prediction residual for each block, and then quantizes the prediction residual in the frequency domain to Generate quantized prediction residuals.

  In addition, the transform / quantization unit 27 generates the quantization prediction residual for each block, TT division information that specifies the division pattern of the target CU, information about all possible division patterns for each block of the target CU, and TT setting information TTI ′ including is generated. The transform / quantization unit 27 supplies the generated TT setting information TTI ′ to the inverse quantization / inverse transform unit 22 and the encoded data generation unit 29.

  The encoded data generation unit 29 encodes header information H ′, TT setting information TTI ′, and PT setting information PTI ′, and multiplexes the encoded header information H, TT setting information TTI, and PT setting information PTI. Coded data # 1 is generated and output.

(Details of encoded data generator)
Next, details of the encoded data generation unit 29 will be described with reference to FIG. FIG. 22 is a functional block diagram illustrating a configuration example of the encoded data generation unit 29.

  Hereinafter, a configuration for the encoded data generation unit 29 to encode parameters related to the prediction mode (luminance) and the color difference prediction mode among the parameters included in the TT setting information TTI ′ will be described.

  However, the present invention is not limited to this, and the encoded data generation unit 29 can encode data other than transform coefficients included in the TT information TTI ′, for example, side information.

  As illustrated in FIG. 22, the encoded data generation unit 29 includes a context storage unit 117, a prediction set determination unit 291, an MPM derivation unit 292, an MPM determination unit 293, a prediction mode encoding unit 294, and a color difference prediction mode encoding unit. 296.

  Further, for example, the MPM derivation is not different between the video decoding device 1 and the video encoding device 2.

  As described above, the configuration of the video decoding device 1 is the same as the configuration corresponding to the video decoding device 1 and the video encoding device 2 or the configuration that performs the same processing. Can be used.

  Therefore, the prediction set determination unit 291 and the MPM derivation unit 292 are the same as the context storage unit 151, the color difference prediction mode definition storage unit 154, the prediction set determination unit 111, and the MPM derivation unit 112 shown in FIG. Therefore, the description is omitted here.

  Below, the MPM determination part 293, the prediction mode encoding part 294, and the color difference prediction mode encoding part 296 are demonstrated.

  The MPM determination unit 293 determines whether or not the MPM matches the prediction mode, and encodes mpm_flag according to the determination result. Since the encoding process has already been described for the variable length decoding unit 11 shown in FIG. 1, the description thereof is omitted here.

  The prediction mode encoding unit 294 encodes information (mpm_idx, rem_idx) regarding the prediction mode according to the determination result of the MPM determination unit 293. The prediction mode encoding unit 294 encodes mpm_idx when MPM is used, and encodes rem_idx when MPM is not used.

  Since the encoding of mpm_idx has already been described for the variable length decoding unit 11 shown in FIG. 1, the description thereof is omitted here.

  The encoding of rem_idx will be described later.

  The color difference prediction mode encoding unit 296 encodes the color difference prediction mode for the target PU. More specifically, the color difference prediction mode encoding unit 296 encodes the color difference prediction mode as follows.

  First, the color difference prediction mode encoding unit 296 acquires the value of intra color difference prediction mode designation information chroma_mode (intra_chroma_pred_mode) using the prediction mode and the color difference prediction mode for luminance.

  Then, the color difference prediction mode encoding unit 296 encodes the value of the acquired intra color difference prediction mode designation information chroma_mode.

  Next, the flow of the prediction mode encoding process in the moving image encoding device 2 will be described with reference to FIG.

  First, an example of a schematic flow of a prediction mode encoding process in the video encoding device 2 will be described with reference to a flowchart shown in FIG.

  When the prediction mode encoding process is started in the moving image encoding device 2, the MPM deriving unit 292 derives MPM0 (S31). Subsequently, the MPM deriving unit 292 derives MPM1 (S32).

  Next, the MPM determination unit 293 determines whether or not the prediction mode matches the MPM (MPM0 or MPM1) (S33).

  Here, when the prediction mode and the MPM match (YES in S33), the MPM determination unit 293 encodes mpm_flag = 1 (S34), and the prediction mode encoding unit 294 includes MPM0 and MPM1. Of these, mpm_idx is derived for the one that matches the prediction mode (S35).

  On the other hand, when the prediction mode and the MPM do not match (NO in S33), the MPM determination unit 293 encodes mpm_flag = 0 (S36). The prediction mode encoding unit 294 compares MPM0 and MPM1, and if the prediction mode number of MPM1 is smaller than the prediction mode number of MPM0, swaps MPM0 and MPM1 (S37). Subsequently, the prediction mode encoding unit 294 generates an array of rem_mode (S38). Finally, the prediction mode encoding unit 294 derives rem_idx (S39).

(Action / Effect)
As described above, the moving image decoding apparatus 1 decodes image data in 4: 2: 2 YUV format and generates a predicted image by an intra prediction method associated with the prediction mode. When reusing the luminance prediction mode of Angular prediction as the color difference prediction mode, the prediction direction in the luminance image is corrected based on the difference in pixel aspect ratio between the luminance pixel and the color difference pixel to derive the prediction direction in the color difference image. The prediction direction deriving unit is provided.

  Further, as described above, the moving image encoding apparatus 2 decodes image data in 4: 2: 2 YUV format and generates a predicted image by an intra prediction method associated with the prediction mode. In the encoding device 2, when the luminance prediction mode of Angular prediction is reused as the color difference prediction mode, the prediction direction in the luminance image is corrected based on the difference in pixel shape between the luminance pixel and the color difference pixel, and the prediction direction in the color difference image Is provided with a prediction direction deriving unit for deriving.

In the above configuration, by correcting the prediction direction based on the difference in pixel shape between the luminance pixel and the color difference pixel, the difference in angle that occurs when the luminance prediction direction is applied as it is as the color difference prediction direction can be reduced. An accurate predicted image can be generated.
[Modification]
<Modification 1: Correction of prediction direction when generating predicted image>
When the DM mode is used, that is, when the luminance prediction mode is reused and used as the color difference prediction mode, the prediction direction deriving unit 1453 of the video decoding device 1 does not correct the direction, and the Angular prediction unit 1452A performs the correction. Also good. For example, the configuration of the prediction direction deriving unit 1453 of FIG. 1 may be changed as shown in FIG. 24, and the configuration of the color difference prediction unit 146 of FIG. 15 may be changed as shown in FIG.

  Below, this is demonstrated using FIG. 24 and FIG. Components having the same functions as those already described are assigned the same reference numerals and description thereof is omitted.

  FIG. 24 illustrates a prediction direction deriving unit 1453_1 that is a modification of the prediction direction deriving unit 1453 of FIG. The prediction direction deriving unit 1453_1 includes a gradient deriving unit 1453B_1 instead of the gradient deriving unit 1453B of the prediction direction deriving unit 1453. The gradient deriving unit 1453B_1 always uses the gradient definition table DEFANG1 shown in FIG. 13 regardless of whether the processing target is a luminance region or a color difference region. Therefore, the prediction direction deriving unit 1453_1 does not correct the gradient.

  FIG. 25 illustrates a color difference prediction unit 146_1 that is a modification of the color difference prediction unit 146 of FIG. The color difference prediction unit 146_1 includes a prediction direction deriving unit 1453_1 instead of the prediction direction deriving unit 1453 of the color difference prediction unit 146, and an Angular prediction unit 1452A_1 instead of the Angular prediction unit 1452A. In the Angular prediction unit 1452A_1, a color difference prediction image is once generated using the same coordinate system as the luminance image, and is subjected to thinning processing or filtering again according to the color difference coordinate system in the 4: 2: 2 YUV format. to shrink. The reduction ratio in this process is determined by the difference between the shape of the luminance pixel and the shape of the color difference pixel.

  Specifically, in the prediction image generation process in the Angular prediction unit 1452A, intermediate images predSamples ′ [x, y] that have twice the number of pixels necessary for the color difference prediction image in the horizontal direction are generated. To do. That is, if the width and height of the color difference prediction image in the target PU are nWc pixels and nHc pixels, respectively, the size of the intermediate image predSamples ′ [x, y] is 2nWc × nHc pixels. The method for generating the intermediate image predSamples ′ [x, y] will be described in more detail as follows.

  When the value of the main direction flag bRefVer is 1 (the main direction is the vertical direction), the main reference pixel refMain [x] is derived by the following equation.

refMain [2 * x] = p [-1 + x, -1], with x = 0..2 * nWc
refMain [2 * x] = p [-1, -1+ ((x * invAngle + 128) >> 8)], with x = -nWc ..- 1
refMain [2 * x + 1] = (refMain [2 * x] + refMain [2 * x + 2] +1) >> 1, with x = -nWc..2 * nWc-1
Thereby, it is possible to obtain the main reference pixel refMain [x] whose number of pixels in the horizontal direction is double.

  Note that this modification is not necessary when the value of the main direction flag bRefVer is 0 (the main direction is the horizontal direction). This is because when the color format is 4: 2: 2, the resolution in the vertical direction is equal to the luminance and the color difference, and refMain [x] is derived by the following equation.

refMain [x] = p [-1 + x, -1], with x = 0..2 * nHc
refMain [x] = p [-1, -1+ ((x * invAngle + 128) >> 8)], with x = -nHc ..- 1
Next, the prediction image generated from the main reference pixel refMain [x] is stored in the intermediate image predSamples ′ [x, y].

predSamples' [x, y] =
((32-iFact) * refMain [x + iIdx + 1] + iFact * refMain [x + iIdx + 2] + 16) >> 5
Here, the ranges of x and y are x = 0..2 * nWc-1 and y = 0..nHc-1, respectively.

  Finally, the predicted image predSamples [x, y] is derived from the intermediate image predSamples ′ [x, y] by the following equation.

predSamples [x, y] = predSamples' [2 * x, y], with x = 0..nWc, y = 0..nHc
In the above formula, pixels in which x is an odd number in the intermediate image predSamples ′ [x, y] are not referred to, so that derivation of half of the pixels can be omitted. Alternatively, if pixels having an odd number x in the intermediate image predSamples '[x, y] are derived, the intermediate image predSamples' [x, y] is filtered to obtain a more accurate predicted image predSamples [x, y ] Can also be used to generate.

  Note that the generation of the intermediate image predSamples ′ [x, y] is for convenience of explanation. The pixel value derivation result may be directly stored in predSamples [x, y] without going through the intermediate image predSamples ′ [x, y].

In this way, even if the luminance prediction mode is reused in an image having a 4: 2: 2 color format, a predicted image generated intermediately using a coordinate system similar to luminance is used. By converting to a color difference coordinate system and generating a color difference prediction image, the prediction direction can be corrected to match the prediction direction represented by the luminance prediction mode. Thereby, the difference of the prediction direction in the prediction image of a brightness | luminance and a color difference is eliminated, and the accuracy of a color difference prediction image can be improved.
<Modification 2: Correction of prediction direction by mapping of prediction mode>
When the DM mode is used, that is, when the luminance prediction mode is reused and used as the color difference prediction mode, the prediction direction deriving unit 1453 of the video decoding device 1 does not switch the gradient definition table, and the luminance prediction mode is not changed. The prediction direction may be corrected by mapping to the prediction mode. For example, the prediction direction deriving unit 1453 of FIG. 1 may be modified as shown in FIG. 26 and the color difference prediction unit 146 of FIG. 15 may be changed as shown in FIG.

The gradient deriving unit 1453B_2 shown in FIG. 26 does not switch the gradient definition table and always uses the gradient definition table DEFANG1 shown in FIG. 13, while making it possible to refer to the conversion table CNVPM1 shown in FIG. The gradient deriving unit 1453B_2 uses the conversion table CNVPM1 shown in FIG. 28 as the prediction direction (represented by NAME (Luma)) corresponding to the luminance prediction mode (IntraPredMode) according to the prediction mode definition DEFPM1 for the color difference region. To obtain a prediction direction (represented by NAME (Chroma)) corresponding to the color difference prediction mode (IntraPredModeC). The conversion table CNVPM1 shown in FIG. 28 is a table in which the luminance prediction mode and the color difference prediction mode are associated with each other so that the prediction directions have substantially the same gradient when the color format is 4: 2: 2. . For example, the luminance prediction mode VER + 8 is converted to VER + 5 as the color difference prediction mode. The displacement value of VER + 8 is +32 in the horizontal direction, and the displacement value corresponding to VER + 8 in the color difference is +16 obtained by dividing +32 by 2. Here, since the prediction mode having the horizontal displacement closest to +16 is VER + 5 having a displacement of +17, the prediction mode VER + 8 in luminance is associated with the prediction mode VER + 5 in color difference. In another example, the value of displacement of the prediction mode HOR + 8 in luminance is +32 in the vertical direction. However, the prediction mode in which the vertical displacement in the color difference is + 32 * 2 = 64 does not exist as the prediction mode in which the main direction is horizontal. Therefore, it is associated with VER + 5, which has the closest gradient among the prediction modes in which the main direction is vertical. The gradient of VER + 5 is [+17, −32], which is close to the gradient [−32, +64] of HOR + 8.
In the conversion table CNVPM1 shown in FIG. 28, the other prediction modes are similarly associated with prediction modes having similar gradients.

  The color difference predicting unit 146_2 shown in FIG. 27 is provided with a prediction direction deriving unit 1453_2 instead of the prediction direction deriving unit 1453 of FIG.

In this way, even when the luminance prediction mode is reused, it is appropriately converted to the prediction mode indicating the same direction in the color difference area, and the accuracy of the color difference prediction image is improved.
<Modification 3: Restriction of prediction mode in color difference>
As another modification, there is a method of limiting the prediction mode for color difference. For example, the color difference prediction unit 146 in FIG. 15 may be changed as shown in FIG. The color difference prediction unit 146_3 illustrated in FIG. 29 includes a prediction method selection unit 1451_3 instead of the prediction method selection unit 1451 of FIG. In addition, the color difference prediction unit 146_3 illustrated in FIG. 29 does not include a prediction direction deriving unit and an Angular prediction unit.

  The prediction method selection unit 1451_3 illustrated in FIG. 29 selects a prediction method used for prediction image generation based on the input prediction mode and outputs a selection result. The prediction method is selected by selecting the prediction method corresponding to the prediction mode number of the input prediction mode based on the definition shown in FIG. 4 for luminance and the definition shown in FIG. 30 for color difference. It is realized with.

  FIG. 30 is an example of the prediction mode number corresponding to the intra prediction method classification used in the color difference area. Unlike the example shown in FIG. 4, no prediction mode number is assigned to ‘4’ to ‘34’ corresponding to Angular prediction. By using the prediction mode definition shown in FIG. 30 in the color difference region, Angular prediction is not used, and a decrease in the accuracy of the predicted image due to an error in the prediction direction can be avoided.

[Application example]
The above-described moving image encoding device 2 and moving image decoding device 1 can be used by being mounted on various devices that perform transmission, reception, recording, and reproduction of moving images. The moving image may be a natural moving image captured by a camera or the like, or may be an artificial moving image (including CG and GUI) generated by a computer or the like.

  First, it will be described with reference to FIG. 31 that the above-described moving image encoding device 2 and moving image decoding device 1 can be used for transmission and reception of moving images.

  FIG. 31A is a block diagram illustrating a configuration of a transmission device PROD_A in which the moving image encoding device 2 is mounted. As illustrated in (a) of FIG. 31, the transmission device PROD_A modulates a carrier wave with an encoding unit PROD_A1 that obtains encoded data by encoding a moving image and the encoded data obtained by the encoding unit PROD_A1. Thus, a modulation unit PROD_A2 that obtains a modulation signal and a transmission unit PROD_A3 that transmits the modulation signal obtained by the modulation unit PROD_A2 are provided. The moving image encoding apparatus 2 described above is used as the encoding unit PROD_A1.

  The transmission device PROD_A is a camera PROD_A4 that captures a moving image, a recording medium PROD_A5 that records the moving image, and an input terminal PROD_A6 for inputting the moving image from the outside as a supply source of the moving image input to the encoding unit PROD_A1. And an image processing unit A7 for generating or processing an image. FIG. 31A illustrates a configuration in which the transmission apparatus PROD_A includes all of these, but a part of the configuration may be omitted.

  The recording medium PROD_A5 may be a recording of a non-encoded moving image, or a recording of a moving image encoded by a recording encoding scheme different from the transmission encoding scheme. It may be a thing. In the latter case, a decoding unit (not shown) for decoding the encoded data read from the recording medium PROD_A5 according to the recording encoding method may be interposed between the recording medium PROD_A5 and the encoding unit PROD_A1.

  FIG. 31B is a block diagram illustrating a configuration of the receiving device PROD_B in which the video decoding device 1 is mounted. As illustrated in (b) of FIG. 31, the reception device PROD_B includes a reception unit PROD_B1 that receives a modulation signal, a demodulation unit PROD_B2 that obtains encoded data by demodulating the modulation signal received by the reception unit PROD_B1, and a demodulation A decoding unit PROD_B3 that obtains a moving image by decoding the encoded data obtained by the unit PROD_B2. The moving picture decoding apparatus 1 described above is used as the decoding unit PROD_B3.

  The receiving device PROD_B has a display PROD_B4 for displaying a moving image, a recording medium PROD_B5 for recording the moving image, and an output terminal for outputting the moving image to the outside as a supply destination of the moving image output by the decoding unit PROD_B3. PROD_B6 may be further provided. In FIG. 31B, a configuration in which all of these are provided in the receiving device PROD_B is illustrated, but a part may be omitted.

  The recording medium PROD_B5 may be used for recording a non-encoded moving image, or may be encoded using a recording encoding method different from the transmission encoding method. May be. In the latter case, an encoding unit (not shown) for encoding the moving image acquired from the decoding unit PROD_B3 according to the recording encoding method may be interposed between the decoding unit PROD_B3 and the recording medium PROD_B5.

  Note that the transmission medium for transmitting the modulation signal may be wireless or wired. Further, the transmission mode for transmitting the modulated signal may be broadcasting (here, a transmission mode in which the transmission destination is not specified in advance) or communication (here, transmission in which the transmission destination is specified in advance). Refers to the embodiment). That is, the transmission of the modulation signal may be realized by any of wireless broadcasting, wired broadcasting, wireless communication, and wired communication.

  For example, a terrestrial digital broadcast broadcasting station (such as broadcasting equipment) / receiving station (such as a television receiver) is an example of a transmitting device PROD_A / receiving device PROD_B that transmits and receives a modulated signal by wireless broadcasting. Further, a broadcasting station (such as broadcasting equipment) / receiving station (such as a television receiver) of cable television broadcasting is an example of a transmitting device PROD_A / receiving device PROD_B that transmits and receives a modulated signal by cable broadcasting.

  Also, a server (workstation or the like) / client (television receiver, personal computer, smartphone, etc.) such as a VOD (Video On Demand) service or a video sharing service using the Internet transmits and receives a modulated signal by communication. This is an example of PROD_A / reception device PROD_B (usually, either a wireless or wired transmission medium is used in a LAN, and a wired transmission medium is used in a WAN). Here, the personal computer includes a desktop PC, a laptop PC, and a tablet PC. The smartphone also includes a multi-function mobile phone terminal.

  Note that the client of the video sharing service has a function of encoding a moving image captured by a camera and uploading it to the server in addition to a function of decoding the encoded data downloaded from the server and displaying it on the display. That is, the client of the video sharing service functions as both the transmission device PROD_A and the reception device PROD_B.

  Next, the fact that the above-described moving image encoding device 2 and moving image decoding device 1 can be used for recording and reproduction of moving images will be described with reference to FIG.

  FIG. 32A is a block diagram illustrating a configuration of a recording apparatus PROD_C in which the above-described moving picture encoding apparatus 2 is mounted. As shown in (a) of FIG. 32, the recording device PROD_C includes an encoding unit PROD_C1 that obtains encoded data by encoding a moving image, and the encoded data obtained by the encoding unit PROD_C1 on the recording medium PROD_M. A writing unit PROD_C2 for writing. The moving image encoding apparatus 2 described above is used as the encoding unit PROD_C1.

  The recording medium PROD_M may be of a type built in the recording device PROD_C, such as (1) HDD (Hard Disk Drive) or SSD (Solid State Drive), or (2) SD memory. It may be of a type connected to the recording device PROD_C, such as a card or USB (Universal Serial Bus) flash memory, or (3) DVD (Digital Versatile Disc) or BD (Blu-ray Disc: registration) Or a drive device (not shown) built in the recording device PROD_C.

  The recording device PROD_C receives a moving image as a supply source of a moving image to be input to the encoding unit PROD_C1, a camera PROD_C3 that captures a moving image, an input terminal PROD_C4 for inputting a moving image from the outside, and a moving image. May include a receiving unit PROD_C5 and an image processing unit C6 that generates or processes an image. FIG. 32A illustrates a configuration in which the recording apparatus PROD_C includes all of these, but some of them may be omitted.

  The receiving unit PROD_C5 may receive a non-encoded moving image, or may receive encoded data encoded by a transmission encoding scheme different from the recording encoding scheme. You may do. In the latter case, a transmission decoding unit (not shown) that decodes encoded data encoded by the transmission encoding method may be interposed between the reception unit PROD_C5 and the encoding unit PROD_C1.

  Examples of such a recording device PROD_C include a DVD recorder, a BD recorder, and an HD (Hard Disk) recorder (in this case, the input terminal PROD_C4 or the receiving unit PROD_C5 is a main supply source of moving images). In addition, a camcorder (in this case, the camera PROD_C3 is a main source of moving images), a personal computer (in this case, the receiving unit PROD_C5 is a main source of moving images), a smartphone (in this case, the camera PROD_C3 or The receiving unit PROD_C5 or the image processing unit C6 is a main supply source of moving images) is also an example of such a recording apparatus PROD_C.

  (B) of FIG. 32 is a block showing a configuration of a playback device PROD_D in which the above-described video decoding device 1 is mounted. As shown in (b) of FIG. 32, the playback device PROD_D reads a moving image by decoding a read unit PROD_D1 that reads encoded data written on the recording medium PROD_M and a coded data read by the read unit PROD_D1. And a decoding unit PROD_D2 to be obtained. The moving picture decoding apparatus 1 described above is used as the decoding unit PROD_D2.

  Note that the recording medium PROD_M may be of the type built into the playback device PROD_D, such as (1) HDD or SSD, or (2) such as an SD memory card or USB flash memory, It may be of a type connected to the playback device PROD_D, or (3) may be loaded into a drive device (not shown) built in the playback device PROD_D, such as DVD or BD. Good.

  In addition, the playback device PROD_D has a display PROD_D3 that displays a moving image, an output terminal PROD_D4 that outputs the moving image to the outside, and a transmission unit that transmits the moving image as a supply destination of the moving image output by the decoding unit PROD_D2. PROD_D5 may be further provided. FIG. 32B illustrates a configuration in which the playback apparatus PROD_D includes all of these, but some of them may be omitted.

    The transmission unit PROD_D5 may transmit an unencoded moving image, or transmits encoded data encoded by a transmission encoding method different from the recording encoding method. You may do. In the latter case, it is preferable to interpose an encoding unit (not shown) that encodes a moving image with an encoding method for transmission between the decoding unit PROD_D2 and the transmission unit PROD_D5.

  Examples of such a playback device PROD_D include a DVD player, a BD player, and an HDD player (in this case, an output terminal PROD_D4 to which a television receiver or the like is connected is a main supply destination of moving images). . In addition, a television receiver (in this case, the display PROD_D3 is a main supply destination of moving images), a digital signage (also referred to as an electronic signboard or an electronic bulletin board), and the display PROD_D3 or the transmission unit PROD_D5 is the main supply of moving images. Desktop PC (in this case, the output terminal PROD_D4 or the transmission unit PROD_D5 is the main video image supply destination), laptop or tablet PC (in this case, the display PROD_D3 or the transmission unit PROD_D5 is a moving image) A smartphone (which is a main image supply destination), a smartphone (in this case, the display PROD_D3 or the transmission unit PROD_D5 is a main moving image supply destination), and the like are also examples of such a playback device PROD_D.

(Hardware implementation and software implementation)
Each block of the moving picture decoding apparatus 1 and the moving picture encoding apparatus 2 described above may be realized in hardware by a logic circuit formed on an integrated circuit (IC chip), or may be a CPU (Central Processing). Unit) may be implemented in software.

  In the latter case, each device includes a CPU that executes instructions of a program that realizes each function, a ROM (Read Only Memory) that stores the program, a RAM (Random Access Memory) that expands the program, the program, and various types A storage device (recording medium) such as a memory for storing data is provided. An object of the present invention is to provide a recording medium in which a program code (execution format program, intermediate code program, source program) of a control program for each of the above devices, which is software that realizes the above-described functions, is recorded so as to be readable by a computer. This can also be achieved by supplying each of the above devices and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include tapes such as magnetic tape and cassette tape, magnetic disks such as floppy (registered trademark) disks / hard disks, CD-ROM (Compact Disc Read-Only Memory) / MO disks (Magneto-Optical discs), and the like. ) / MD (Mini Disc) / DVD (Digital Versatile Disc) / CD-R (CD Recordable) / Blu-ray Disc (Blu-ray Disc: registered trademark) and other optical discs, IC cards (including memory cards) / Cards such as optical cards, mask ROM / EPROM (Erasable Programmable Read-Only Memory) / EEPROM (Electrically Erasable and Programmable Read-Only Memory) / Semiconductor memories such as flash ROM, or PLD (Programmable Logic Device) or FPGA Logic circuits such as (Field Programmable Gate Array) can be used.

  Further, each of the above devices may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited as long as it can transmit the program code. For example, Internet, Intranet, Extranet, LAN (Local Area Network), ISDN (Integrated Services Digital Network), VAN (Value-Added Network), CATV (Community Antenna television / Cable Television) communication network, Virtual Private Network (Virtual Private Network) Network), telephone line network, mobile communication network, satellite communication network, and the like. The transmission medium constituting the communication network may be any medium that can transmit the program code, and is not limited to a specific configuration or type. For example, infra-red such as IrDA (Infrared Data Association) or remote control even with wired such as IEEE (Institute of Electrical and Electronic Engineers) 1394, USB, power line carrier, cable TV line, telephone line, ADSL (Asymmetric Digital Subscriber Line) line, etc. , Bluetooth (registered trademark), IEEE 802.11 wireless, HDR (High Data Rate), NFC (Near Field Communication), DLNA (Digital Living Network Alliance), mobile phone network, satellite line, terrestrial digital network, etc. Is possible. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  The present invention can be suitably applied to an image decoding apparatus that decodes encoded data obtained by encoding image data and an image encoding apparatus that generates encoded data obtained by encoding image data. Further, the present invention can be suitably applied to the data structure of encoded data generated by an image encoding device and referenced by the image decoding device.

1 video decoding device (image decoding device)
14 prediction image generation unit 141 prediction unit setting unit 142 reference pixel setting unit 143 switch 144 reference pixel filter unit 145 luminance prediction unit 146 color difference prediction unit 1451 prediction method selection unit 1452 prediction image derivation unit 1452D DC prediction unit 1452P Planar prediction unit 1452H horizontal Prediction unit 1452V Vertical prediction unit 1452A Angular prediction unit 1452L LM prediction unit 1453 Prediction direction deriving unit 1453A Main direction deriving unit 1453B Gradient deriving unit (color difference prediction means)
2 Video encoding device (image encoding device)
23 Predicted image generator (color difference predicting means)

Claims (2)

In an image decoding apparatus that restores an image from encoded data by generating a prediction image for luminance and color difference by an intra prediction method associated with a prediction mode,
A color difference prediction unit that corrects a prediction direction when the color format of the image is 4: 2: 2 when the color difference prediction image is generated based on the prediction mode used for luminance prediction image generation;
The color difference prediction means derives a second prediction mode used for color difference prediction image generation based on an intra color difference prediction mode designation index having a smaller number than at least the first prediction mode used for luminance prediction image generation,
When the value of the intra color difference prediction mode designation index is the first value and the first prediction mode is the Planar prediction mode, the color difference prediction means sets the diagonal prediction mode as the second prediction mode. Derive the corresponding index value ,
When the value of the intra color difference prediction mode designation index is a first value and the first prediction mode is other than the Planar prediction mode, the color difference prediction means sets the Planar prediction mode as the second prediction mode. An image decoding apparatus characterized by deriving a corresponding index value . An image decoding method for restoring an image from encoded data by generating a predicted image for luminance and color difference by an intra prediction method associated with a prediction mode,
A color difference prediction step of correcting a prediction direction when the color format of the image is 4: 2: 2 when generating a color difference prediction image based on the prediction mode used for luminance prediction image generation;
The color difference prediction step derives a second prediction mode used for color difference prediction image generation based on an intra color difference prediction mode designation index having a smaller number than at least the first prediction mode used for luminance prediction image generation,
When the value of the intra color difference prediction mode designation index is the first value and the first prediction mode is the Planar prediction mode, the color difference prediction step is changed to the oblique direction prediction mode as the second prediction mode. Derive the corresponding index value ,
When the value of the intra color difference prediction mode designation index is a first value and the first prediction mode is other than the Planar prediction mode, the color difference prediction step sets the Planar prediction mode as the second prediction mode. An image decoding method characterized by deriving a corresponding index value .

Images