JP6798598B2 - Image decoding device, image decoding method, image decoding program, receiving device, receiving method, and receiving program - Google Patents

Description

The present invention relates to an image decoding technique, and more particularly to an in-screen decoding technique.

As a typical compression coding method for moving images, MPEG-4 AVC / H. There are 264 standards. MPEG-4 AVC / H. In 264, the picture is encoded in macroblock units divided into a plurality of rectangular blocks. The size of the macroblock is defined as 16 × 16 pixels in the luminance signal regardless of the image size. The macroblock also includes a color difference signal, but the size of the color difference signal included in the macroblock differs depending on the color difference format of the encoded image. When the color difference format is 4: 2: 0, the color difference signal is 8 ×. 8
When the pixel and color difference format is 4: 2: 2, the color difference signal is 8 × 16 pixels, and when the color difference format is 4: 4: 4, the color difference signal is 16 × 16 pixels.

The color difference format represents the ratio of the number of sampled pixels of three signals of one luminance information and two color difference information by X: Y: Z. MPEG-4 AVC / H. The color difference formats of the images to be encoded and decoded in 264 are 4: 2: 0, 4: 2: 2, 4: 4: 4, and monochrome.

FIG. 3 is a diagram illustrating each color difference format of the image. X indicates the position of the pixel of the luminance signal on the screen plane of the image, and ◯ indicates the position of the pixel of the color difference signal.
In 4: 2: 0 shown in FIG. 3A, the color difference signal is 2 in both the horizontal and vertical directions with respect to the luminance signal.
It is a color difference format sampled at a density of 1 /. That is, 4: 2: 0 has the same aspect ratio of the pixels of the luminance signal and the color difference signal. At 4: 2: 0, the color difference signal may be sampled at the position shown in FIG. 3 (e).
4: 2: 2 shown in FIG. 3B is a color difference format in which the color difference signal is sampled at half the density in the horizontal direction and the same density in the vertical direction with respect to the luminance signal. That is, the aspect ratios of the pixels of the luminance signal and the color difference signal are different in 4: 2: 2.
4: 4: 4 shown in FIG. 3C is a color difference format in which both the luminance signal and the color difference signal are sampled at the same density. That is, in 4: 4: 4, the aspect ratios of the pixels of the luminance signal and the color difference signal are the same.
Monochrome shown in FIG. 3D is a color difference format in which there is no color difference signal and only a luminance signal is used.

The luminance signal and the color difference signal are coded and decoded as a set in order to share coding information such as motion compensation, but in 4: 4: 4, one luminance signal and two color difference signals are independently separated. 3
There is also a mechanism for encoding and decoding as one monochrome.

AVC / H. In the 264 method, a method of predicting from already encoded / decoded blocks in the coded / decoded target picture is used. This method is called intra-prediction. Further, a picture that has already been encoded / decoded is used as a reference picture, and motion compensation that predicts motion from the reference picture is used. The method of predicting motion by this motion compensation is called inter-prediction.

First, AVC / H. A unit for switching the intra-prediction mode in the intra-prediction in the intra-coding of the 264 method will be described. 4 (a) to 4 (c) are diagrams for explaining a unit for switching the intra prediction mode. AVC / H. In the 264 method of intra-encoding, "4x4 intra-prediction" and "16x" are used as units for switching the intra-prediction mode.
Three types are available: "16 intra prediction" and "8x8 intra prediction".

In the "4x4 intra-prediction", the luminance signal of the macroblock (luminance signal 16x16 pixel block, color difference signal 8x8 pixel block) is divided into 16 pieces into 4x4 pixel blocks, and the divided 4x4 pixel units. A mode is selected from nine types of 4 × 4 intra-prediction modes, and intra-prediction is sequentially performed (FIG. 4A).
In the "16 x 16 pixel intra prediction", a mode is selected from four types of 16 x 16 intra prediction modes in units of 16 x 16 pixel blocks of the luminance signal, and the intra prediction is performed (FIG. 4 (b)).
In "8x8 pixel intra prediction", the luminance signal of the macro block is divided into 8x8 pixel blocks, and the mode is selected from 9 types of 8x8 intra prediction modes in units of the divided 8x8 pixels. Then, intra-prediction is sequentially performed (FIG. 4 (c)).

In addition, when the color difference format is 4: 2: 0 or 4: 2: 2 for the intra prediction of the color difference signal, the mode is selected from the four types of intra prediction modes of the color difference signal in macroblock units, and the intra prediction is performed. Is done.

Next, AVC / H. The unit for inter-prediction in the inter-coding of the 264 method will be described. 5 (a) to 5 (h) are diagrams for explaining a macroblock partition and a sub-macroblock partition. For the sake of brevity,
Only the pixel block of the luminance signal is drawn. In the MPEG series, macroblocks are defined by square areas. Generally AVC / H. In the MPEG series including the 264 method, 1
A block defined by 6 × 16 pixels (horizontal 16 pixels, vertical 16 pixels) is called a macroblock. In addition, AVC / H. In the 264 method, a block defined by 8 × 8 pixels is called a sub-macroblock. A macroblock partition is a small block obtained by further dividing a macroblock for motion compensation prediction. The sub-macroblock partition is a small block obtained by further dividing the sub-macroblock for motion compensation prediction.

FIG. 5A is a diagram showing that the macroblock is composed of one macroblock partition composed of a luminance signal of 16 × 16 pixels and two color difference signals corresponding thereto. Here, this configuration is referred to as a 16x16 mode macroblock type.
FIG. 5B shows that the macroblock is composed of two macroblock partitions composed of a luminance signal of 16 × 8 pixels (horizontal 16 pixels, vertical 8 pixels) and two corresponding color difference signals. It is a figure which shows. The two macroblock partitions are arranged vertically. Here, this configuration is referred to as a 16x8 mode macroblock type.
FIG. 5C shows that the macroblock is composed of two macroblock partitions composed of a luminance signal of 8 × 16 pixels (horizontal 8 pixels, vertical 16 pixels) and two corresponding color difference signals. It is a figure which shows. The two macroblock partitions are side by side. Here, this configuration is referred to as an 8x16 mode macroblock type.
FIG. 5D is a diagram showing that a macroblock is composed of four macroblock partitions composed of a luminance signal of 8 × 8 pixels and two color difference signals corresponding thereto. These four macroblock partitions are arranged vertically and horizontally two by two. This configuration is called an 8x8 mode macroblock type.
FIG. 5 (e) is a diagram showing that the sub macroblock is composed of one sub macroblock partition composed of a luminance signal of 8 × 8 pixels and two color difference signals corresponding thereto. Here, this configuration is referred to as an 8x8 mode sub-macroblock type.
FIG. 5 (f) shows that the sub-macroblock is composed of two sub-macroblock partitions composed of a luminance signal of 8 × 4 pixels (horizontal 8 pixels, vertical 4 pixels) and two corresponding color difference signals. It is a figure which shows that there is. The two submacroblock partitions are arranged vertically. This configuration is called an 8x4 mode sub-macroblock type.
FIG. 5 (g) shows that the sub-macroblock is composed of two macroblock partitions composed of a luminance signal of 4 × 8 pixels (horizontal 4 pixels, vertical 8 pixels) and two corresponding color difference signals. It is a figure which shows that. The two macroblock partitions are side by side. Here, this configuration is referred to as a 4x8 mode sub-macroblock type.
FIG. 5H is a diagram showing that the sub-macroblock is composed of four sub-macroblock partitions composed of a luminance signal of 4 × 4 pixels and two color difference signals corresponding thereto. These four sub-macroblock partitions are arranged vertically and horizontally two by two. Here, this configuration is referred to as a 4x4 mode sub-macroblock type.

AVC / H. In the 264 coding method, a mechanism that can be selected and used from the above motion compensation block sizes is adopted. First, as the motion compensation block size in macroblock units, one of 16 × 16, 16 × 8, 8 × 16 and 8 × 8 mode macroblock types can be selected. When the 8x8 mode macroblock type is selected, the motion compensation block size for each submacroblock is 8x8.
, 8x4, 4x8, 4x4 mode submacroblock types can be selected.

ISO / IEC 14496-10 Information technology --Coding of audio-visual objects --Part 10: Advanced Video Coding

When encoding the information regarding the intra prediction mode of the image signal, the information regarding the intra prediction mode of the luminance signal and the information regarding the intra prediction mode of the color difference signal are encoded and arranged in the coded stream. If the intra prediction mode is not encoded according to the color difference format, the processing efficiency may deteriorate.

The present invention has been made in view of such a situation, and an object of the present invention is to provide an image decoding technique capable of efficiently decoding an image signal by intra-prediction of a luminance signal and a color difference signal according to a color difference format. is there.

An image decoding device that decodes information about the intra prediction mode in units of prediction blocks and decodes an image signal including a brightness signal and a color difference signal in units of conversion blocks using intra prediction, and is an intra of the prediction block of the brightness signal. An intra-brightness prediction mode decoding unit that decodes the syntax element related to the intra-prediction mode of the brightness signal from the coded stream in which the information about the intra-brightness prediction mode indicating the prediction method is encoded and derives the intra-prediction mode of the brightness signal. , Decoding the syntax element related to the intra color difference prediction mode of the color difference signal from the coded stream in which the information about the intra color difference prediction mode indicating the intra prediction method of the color difference signal prediction block is encoded, and also refer to the intra brightness prediction mode. Then, from the intra-color difference prediction mode decoding unit that derives the first intra-color difference prediction mode, and the brightness signal around the brightness signal conversion block according to the intra-brightness prediction mode specified for each prediction block of the brightness signal. From the color difference signal around the color difference signal conversion block according to the brightness signal intra prediction unit that predicts the brightness signal of the brightness signal conversion block and the intra color difference prediction mode specified for each prediction block of the color difference signal. A color difference signal intra prediction unit that predicts a color difference signal of a color difference signal conversion block is provided, and the intra color difference prediction mode decoding unit has the same aspect ratio when the aspect ratios of the pixels of the brightness signal and the color difference signal are different. The mode number of the first intra color difference prediction mode used in the case is converted, and the second intra is based on the conversion table set as the intra prediction mode of the second color difference signal used when the aspect ratio is different. The color difference prediction mode is derived, and in the conversion table, when the mode number of the first intra color difference prediction mode is a mode number indicating horizontal prediction, the mode number of the second intra color difference prediction mode is also a mode number indicating horizontal prediction. When the mode number of the first intra color difference prediction mode is a mode number indicating vertical prediction, the mode number of the second intra color difference prediction mode is also a mode number indicating vertical prediction. provide.
This is an image decoding method that decodes information about the intra prediction mode in units of prediction blocks and decodes an image signal including a brightness signal and a color difference signal in units of conversion blocks using intra prediction, and is an intra of the prediction block of the brightness signal. With the intra-brightness prediction mode decoding step that decodes the syntax element related to the intra-prediction mode of the brightness signal from the encoded stream in which the information about the intra-brightness prediction mode indicating the prediction method is encoded and derives the intra-prediction mode of the brightness signal. , Decoding the syntax element related to the intra color difference prediction mode of the color difference signal from the coded stream in which the information about the intra color difference prediction mode indicating the intra prediction method of the color difference signal prediction block is encoded, and also refer to the intra brightness prediction mode. Then, according to the intra-color difference prediction mode decoding step for deriving the first intra-color difference prediction mode and the intra-brightness prediction mode specified for each prediction block of the brightness signal, the brightness signals around the conversion block of the brightness signal are used. From the color difference signal around the color difference signal conversion block according to the brightness signal intra prediction step for predicting the brightness signal of the brightness signal conversion block and the intra color difference prediction mode specified for each prediction block of the color difference signal. It has a color difference signal intra prediction step for predicting the color difference signal of the conversion block of the color difference signal, and the intra color difference prediction mode decoding step has the aspect ratio when the aspect ratios of the pixels of the brightness signal and the color difference signal are different. The mode number of the first intra color difference prediction mode used in the same case is converted, and the second is based on the conversion table set as the intra prediction mode of the second color difference signal used when the aspect ratio is different. An intra color difference prediction mode is derived, and in the conversion table, when the mode number of the first intra color difference prediction mode is a mode number indicating horizontal prediction, the mode number of the second intra color difference prediction mode also indicates a mode number indicating horizontal prediction. The image decoding method is characterized in that, when the mode number of the first intra color difference prediction mode is a mode number indicating vertical prediction, the mode number of the second intra color difference prediction mode is also a mode number indicating vertical prediction. I will provide a.
An image decoding program that decodes information about the intra prediction mode in units of prediction blocks and decodes an image signal including a brightness signal and a color difference signal in units of conversion blocks using intra prediction, and is an intra of the prediction block of the brightness signal. With the intra-brightness prediction mode decoding step that decodes the syntax element related to the intra-prediction mode of the brightness signal from the encoded stream in which the information about the intra-brightness prediction mode indicating the prediction method is encoded and derives the intra-prediction mode of the brightness signal. , Decoding the syntax element related to the intra color difference prediction mode of the color difference signal from the coded stream in which the information about the intra color difference prediction mode indicating the intra prediction method of the color difference signal prediction block is encoded, and also refer to the intra brightness prediction mode. Then, according to the intra-color difference prediction mode decoding step for deriving the first intra-color difference prediction mode and the intra-brightness prediction mode specified for each prediction block of the brightness signal, the brightness signals around the conversion block of the brightness signal are used. From the color difference signal around the color difference signal conversion block according to the brightness signal intra prediction step for predicting the brightness signal of the brightness signal conversion block and the intra color difference prediction mode specified for each prediction block of the color difference signal. A computer is made to execute a color difference signal intra prediction step for predicting a color difference signal of a color difference signal conversion block, and the intra color difference prediction mode decoding step is performed when the aspect ratios of the brightness signal and the pixels of the color difference signal are different. Based on the conversion table set as the intra prediction mode of the second color difference signal used when the aspect ratio is different by converting the mode number of the first intra color difference prediction mode used when the ratio is the same. The second intra color difference prediction mode is derived, and in the conversion table, when the mode number of the first intra color difference prediction mode is a mode number indicating horizontal prediction, the mode number of the second intra color difference prediction mode also indicates horizontal prediction. When the mode number of the first intra color difference prediction mode is a mode number and the mode number of the first intra color difference prediction mode is a mode number indicating vertical prediction, the mode number of the second intra color difference prediction mode is also a mode number indicating vertical prediction. Provides a decryption program.
The moving image receives the coded stream encoded, decodes the information about the intra prediction mode in the predicted block unit contained in the received coded stream, and includes the luminance signal and the color difference signal in the converted block unit. A receiving device that decodes an image signal using intra-prediction, and from a coded stream in which information on an intra-luminance prediction mode indicating an intra-prediction method of a luminance signal prediction block is encoded, relates to an intra-prediction mode of the luminance signal. From the intra-luminance prediction mode decoding unit that decodes the syntax element and derives the intra-luminance prediction mode of the luminance signal, and from the coded stream in which the information about the intra-luminance prediction mode indicating the intra-prediction method of the color difference signal prediction block is encoded. , The intra-color difference prediction mode decoding unit that decodes the syntax element related to the intra-color difference prediction mode of the color difference signal and derives the first intra-luminance prediction mode with reference to the intra-luminance prediction mode, and each of the luminance signal prediction blocks. In accordance with the intra-luminance prediction mode specified in, the luminance signal intra-luminance unit that predicts the luminance signal of the luminance signal conversion block from the luminance signals around the luminance signal conversion block, and each of the luminance signal prediction blocks. The intra-luminance prediction mode decoding unit is provided with a color-difference signal intra-prediction unit that predicts the color-difference signal of the color-difference signal conversion block from the color-difference signals around the color-difference signal conversion block according to the specified intra-color difference prediction mode. Is used when the aspect ratios of the pixels of the luminance signal and the color difference signal are different, the mode number of the first intra color difference prediction mode used when the aspect ratios are the same is converted, and the aspect ratios are different. Based on the conversion table set as the intra-prediction mode of the second color difference signal, the second intra-luminance prediction mode is derived, and in the conversion table, the mode number of the first intra-luminance prediction mode indicates horizontal prediction. When it is a mode number, the mode number of the second intra-luminance prediction mode is also a mode number indicating horizontal prediction, and when the mode number of the first intra-luminance prediction mode is a mode number indicating vertical prediction, the second intra-luminance difference. Provided is a receiving device characterized in that the mode number of the prediction mode is also a mode number indicating vertical prediction.
The moving image receives the coded stream encoded, decodes the information about the intra prediction mode in the predicted block unit contained in the received coded stream, and includes the luminance signal and the color difference signal in the converted block unit. It is a receiving method that decodes an image signal using intra-prediction, and is related to an intra-prediction mode of a luminance signal from a coded stream in which information about an intra-luminance prediction mode indicating an intra-prediction method of a luminance signal prediction block is encoded. From the intra-luminance prediction mode decoding step, which decodes the syntax element to derive the intra-luminance signal intra-prediction mode, and the coded stream in which information about the intra-luminance prediction mode indicating the intra-prediction method of the color difference signal prediction block is encoded. , The intra-color difference prediction mode decoding step of decoding the syntax element relating to the intra-color difference prediction mode of the color difference signal and deriving the first intra-luminance prediction mode with reference to the intra-luminance prediction mode, and each of the luminance signal prediction blocks. According to the intra-luminance prediction mode specified in, the luminance signal intra-luminance step of predicting the luminance signal of the luminance signal conversion block from the luminance signal around the luminance signal conversion block, and each of the luminance signal prediction blocks. It has a color difference signal intra-prediction step of predicting the color-difference signal of the color-difference signal conversion block from the color-difference signals around the color-difference signal conversion block according to the specified intra-color difference prediction mode, and the intra-color difference prediction mode decoding. In the step, when the aspect ratios of the pixels of the luminance signal and the color difference signal are different, the mode number of the first intra color difference prediction mode used when the aspect ratios are the same is converted, and when the aspect ratios are different. The second intra-luminance prediction mode is derived based on the conversion table set as the intra-prediction mode of the second color difference signal to be used, and in the conversion table, the mode number of the first intra-luminance prediction mode makes horizontal prediction. When the mode number is indicated, the mode number of the second intra-color difference prediction mode is also a mode number indicating horizontal prediction, and when the mode number of the first intra color difference prediction mode is a mode number indicating vertical prediction, the second intra Provided is a receiving method characterized in that the mode number of the color difference prediction mode is also a mode number indicating vertical prediction.
The moving image receives the coded stream encoded, decodes the information about the intra prediction mode in the predicted block unit contained in the received coded stream, and includes the luminance signal and the color difference signal in the converted block unit. A receiving program that decodes an image signal using intra-prediction, from a coded stream in which information about an intra-luminance prediction mode indicating an intra-prediction method of a luminance signal prediction block is encoded, relating to the intra-prediction mode of the luminance signal. From the intra-luminance prediction mode decoding step, which decodes the syntax element to derive the intra-luminance signal intra-prediction mode, and the coded stream in which information about the intra-luminance prediction mode indicating the intra-prediction method of the color difference signal prediction block is encoded. , The intra-color difference prediction mode decoding step of decoding the syntax element relating to the intra-color difference prediction mode of the color difference signal and deriving the first intra-luminance prediction mode with reference to the intra-luminance prediction mode, and each of the luminance signal prediction blocks. According to the intra-luminance prediction mode specified in, the luminance signal intra-luminance step of predicting the luminance signal of the luminance signal conversion block from the luminance signal around the luminance signal conversion block, and each of the luminance signal prediction blocks. The intra-luminance prediction is performed by causing a computer to execute a color-difference signal intra-prediction step of predicting the color-difference signal of the color-difference signal conversion block from the color-difference signals around the color-difference signal conversion block according to the specified intra-color difference prediction mode. In the mode decoding step, when the aspect ratios of the pixels of the luminance signal and the color difference signal are different, the mode number of the first intra color difference prediction mode used when the aspect ratios are the same is converted, and the aspect ratios are different. The second intra-luminance prediction mode is derived based on the conversion table set as the intra-prediction mode of the second color difference signal used in the case, and the mode number of the first intra-luminance prediction mode is horizontal in the conversion table. When the mode number indicates the prediction, the mode number of the second intra-luminance prediction mode is also the mode number indicating the horizontal prediction, and when the mode number of the first intra-luminance prediction mode is the mode number indicating the vertical prediction, the mode number is the first. 2 Provided is a receiving program characterized in that the mode number of the intra-luminance prediction mode is also a mode number indicating vertical prediction.

It should be noted that any combination of the above components and the conversion of the expression of the present invention between methods, devices, systems, recording media, computer programs and the like are also effective as aspects of the present invention.

According to the present invention, an image signal can be efficiently decoded by intra-prediction of a luminance signal and a color difference signal according to a color difference format.

It is a block diagram which shows the structure of the image coding apparatus of embodiment. It is a block diagram which shows the structure of the image decoding apparatus of embodiment. It is a figure explaining the color difference format of an image. AVC / H. It is a figure explaining the unit which switches the intra prediction mode of a 264 system. AVC / H. It is a figure explaining the unit of inter-prediction of 264 method. It is a figure explaining the tree block and the coding block defined in this Example. It is a figure explaining the division mode defined in this Example. It is a figure explaining the value and the prediction direction of the intra prediction mode defined in this Example. It is a figure of an example for demonstrating the position of the block specified in this Example. It is a figure explaining an example of the definition of syntax at the time of encoding the color difference format information by the sequence parameter set which becomes the header which encodes the information concerning the coding of the whole sequence defined in this Example. It is a figure explaining the division method of the color difference signal of the coded block in N × N division at the time of intra prediction defined in this Example. It is a block diagram which shows the structure of the 2nd coded stream generation part of the image coding apparatus of embodiment. It is a block diagram which shows the structure of the 2nd coded stream decoding part of the image decoding apparatus of embodiment. It is a table that derives the value of the intra-color difference prediction mode from the value of the syntax element used on the decoding side defined in this embodiment and the value of the intra-luminance prediction mode of the prediction block of the luminance signal at the same position as the prediction block of the color difference signal. .. The color difference format defined in this embodiment is 4: 2: 2, and this is an example of a conversion table for converting from the intra-luminance prediction mode or the first intra-color difference prediction mode to the second intra-color difference prediction mode. The color difference format defined in this embodiment is 4: 2: 2, and it is a conversion table for converting from the intra-luminance prediction mode or the first intra-color difference prediction mode to the second intra-color difference prediction mode. The color difference format defined in this embodiment is 4: 2: 2, which is another example of a conversion table for converting from the intra-luminance prediction mode or the first intra-color difference prediction mode to the second intra-color difference prediction mode. It is a figure explaining the value and the prediction direction of the intra prediction mode of the conversion table of FIG. 15 defined in this Example. It is a figure explaining the value and the prediction direction of the intra prediction mode of the conversion table of FIG. 16 defined in this Example. It is a figure explaining the value and the prediction direction of the intra prediction mode of the conversion table of FIG. 17 defined in this Example. It is a figure explaining the correspondence | correspondence of the luminance signal when the color difference format is 4: 2: 2, and the prediction direction of the intra prediction of a color difference signal. It is a figure explaining the correspondence of the luminance signal when the color difference format is 4: 2: 0, and the prediction direction of the intra prediction of the color difference signal. The figure explaining the derivation processing procedure at the time of conversion from the intra-luminance prediction mode or the first intra-color difference prediction mode to the second intra-color difference prediction mode corresponding to the conversion tables of FIGS. 15 and 16 defined in this embodiment. Is. It is a figure explaining the derivation processing procedure at the time of conversion from the 1st intra-color difference prediction mode to the 2nd intra-color difference prediction mode corresponding to the conversion table of FIG. 17 defined in this Example. From the value of the intra-color difference prediction mode used on the coding side specified in this embodiment and the value of the intra-luminance prediction mode of the prediction block of the luminance signal at the same position as the prediction block of the color difference signal, the value of the syntax element related to the intra-color difference prediction mode. It is a table to derive. It is a figure explaining the processing procedure of the decoding and the intra prediction of the intra prediction mode on the decoding side. This is an example of a table for deriving the angle of the intra prediction for the color difference format 4: 2: 2 from the first intra color difference prediction mode. This is another example of a table for deriving the intra-prediction angle for the color difference format 4: 2: 2 from the first intra-color difference prediction mode. It is a figure explaining the derivation processing procedure which derives the angle of the intra prediction for the color difference format 4: 2: 2 from the 1st intra color difference prediction mode corresponding to the table of FIG. 28 defined in this Example. The color difference format defined in this embodiment is 4: 2: 2, and it is a conversion table for converting from the intra-luminance prediction mode or the first intra-color difference prediction mode to the second intra-color difference prediction mode. It is a figure explaining the value and the prediction direction of the intra prediction mode of the conversion table of FIG. 30 defined in this Example. It is a figure explaining the derivation processing procedure at the time of conversion from the 1st intra color difference prediction mode to the 2nd intra color difference prediction mode corresponding to the conversion table of FIG. 30 defined in this Example. The color difference format defined in this embodiment is 4: 2: 2, and it is a conversion table for converting from the intra-luminance prediction mode or the first intra-color difference prediction mode to the second intra-color difference prediction mode. It is a figure explaining the value and the prediction direction of the intra prediction mode of the conversion table of FIG. 33 defined in this Example. It is a figure explaining the derivation processing procedure at the time of conversion from the 1st intra color difference prediction mode to the 2nd intra color difference prediction mode corresponding to the conversion table of FIG. 33 defined in this Example.

In this embodiment, regarding the coding and decoding of moving images, in particular, the picture is of any size.
Intra-prediction that predicts from the pixel values of the surrounding blocks that have already been encoded and decoded in coding and decoded (hereinafter referred to as decoded) in decoding, and already decoded in block units divided into rectangular shapes. The amount of code is reduced by using inter-prediction by motion compensation from the completed picture.

First, the technology and technical terms used in this embodiment are defined.

(Color difference format)
The color difference format of the image to be encoded and decoded in the description of the embodiment is monochrome, 4: 2: 0, 4: 2: 2, 4: 4: 4, and the luminance signal and the color difference signal are set as a set. It shall be encoded and decoded. However, the description of the color difference signal will be omitted in the case of monochrome. When the color difference format is 4: 4: 4, RGB signals can be encoded and decoded. In that case, the G (green) signal is regarded as the luminance signal, and the B (blue) signal,
The R (red) signal is regarded as a color difference signal and encoded and decoded. The method of independently encoding and decoding the luminance signal and the color difference signal at 4: 4: 4 is regarded as monochrome in this embodiment.

(About tree blocks and coded blocks)
In the embodiment, as shown in FIG. 6, the screen is evenly divided into units of arbitrary rectangular rectangles of the same size. This unit is defined as a tree block, and is used as a basic unit of address management for specifying a coding / decoding target block (encoding target block in coding, decoding target block in decoding) in an image. Except for monochrome, the tree block is composed of one luminance signal and two color difference signals. The size of the tree block can be freely set to the power of 2 according to the picture size and the texture in the screen. The tree block hierarchically divides the luminance signal and the color difference signal in the tree block into four (two in each of the vertical and horizontal directions) in order to optimize the coding process according to the texture in the screen. It can be a block with a small block size. Each of these blocks is defined as a coded block, and is used as a basic unit of processing when encoding and decoding. Except for monochrome, the coded block is also composed of one luminance signal and two color difference signals. The maximum size of the coded block is the same as the size of the tree block. The coded block having the minimum size of the coded block is called the minimum coded block, and can be freely set by the size of a power of 2.

In FIG. 6, the coded block A is a single coded block without dividing the tree block. The coded block B is a coded block formed by dividing the tree block into four parts. The coded block C is a coded block formed by further dividing a block formed by dividing a tree block into four. The coded block D has 4 tree blocks.
It is a coded block made by dividing a block made by dividing it into four layers twice.
The smallest coded block.

In the description of the embodiment, the color difference format is 4: 2: 0, the size of the tree block is set to 64 × 64 pixels for the luminance signal, and 32 × 32 pixels for the color difference signal, and the minimum coded block size is set. It is assumed that the luminance signal is set to 8 × 8 pixels and the color difference signal is set to 4 × 4 pixels.
In FIG. 6, the size of the coded block A is 64 × 64 pixels for the luminance signal and 32 × 3 for the color difference signal.
It has 2 pixels, and the size of the coded block B is 32 × 32 pixels for the luminance signal and 16 for the color difference signal.
The size of the coding block C is 16 × 16 pixels for the luminance signal and 8 × 8 pixels for the color difference signal, and the size of the coding block D is 8 × 8 pixels for the luminance signal and 4 × for the color difference signal.
It becomes 4 pixels. When the color difference format is 4: 4: 4, the size of the luminance signal and the color difference signal of each coded block are equal. When the color difference format is 4: 2: 2, the size of the coded block A is 32 × 64 pixels for the color difference signal, the size of the coded block B is 16 × 32 pixels for the color difference signal, and the size of the coded block C is The color difference signal has 8 × 16 pixels, and the size of the coded block D, which is the smallest coded block, is 4 × 8 pixels for the color difference signal.

(About prediction mode)
For each coded block, the intra prediction that makes a prediction from the surrounding image signal that has been coded / decoded and the inter prediction that makes a prediction from the image signal of the coded / decoded image are switched.
The mode that distinguishes between intra-prediction and inter-prediction is defined as a prediction mode (PredMode). The prediction mode (PredMode) is intra prediction (MODE_INTRA) or inter prediction (MODE_I).
It has NTER) as a value and can be selected and encoded.

(About split mode and prediction block)
When the screen is divided into blocks for intra-prediction and inter-prediction, the coded blocks are divided and predicted as necessary in order to make the unit for switching the intra-prediction and inter-prediction methods smaller. A mode for identifying the method of dividing the luminance signal and the color difference signal of this coded block is defined as a division mode (PartMode). Further, this divided block is defined as a prediction block. As shown in FIG. 7, four types of division modes (PartMode) are defined according to the division method of the luminance signal of the coded block. The division mode (PartMode) of the coded block whose luminance signal is regarded as one prediction block without being divided (FIG. 7A) is set to 2N ×.
2N division (PART_2Nx2N), the division mode (PartMode) of the two prediction blocks (Fig. 7 (b)) obtained by dividing the luminance signal of the coded block into two in the horizontal direction is divided into 2N x N (PART_2Nx).
N), the luminance signal of the coded block is divided in the vertical direction, and the coded block is divided into two prediction blocks (FIG. 7 (c)). The division mode (PartMode) is N × 2N division (PART_Nx2N).
The division mode (PartMode) of the four prediction blocks (FIG. 7 (d)) in which the luminance signal of the coded block is divided horizontally and vertically is defined as N × N division (PART_NxN), respectively. Except for the N × N division (PART_NxN) of the intra prediction (MODE_INTRA), the color difference signal is also divided in the same manner as the vertical and horizontal division ratio of the luminance signal for each division mode (PartMode). The vertical and horizontal division ratio of the color difference signal of the N × N division (PART_NxN) coding block of the intra prediction (MODE_INTRA) differs depending on the type of the color difference format, and will be described later.

Inside the coded block, in order to identify each predicted block, numbers starting from 0 are assigned to the predicted blocks existing inside the coded block in the coding order. This number is defined as the split index PartIdx. The numbers described in each prediction block of the coded block of FIG. 7 represent the division index PartIdx of the prediction block. FIG. 7 (b
In the 2N × N division (PART_2NxN) shown in), the division index PartIdx of the upper prediction block is set to 0, and the division index PartIdx of the lower prediction block is set to 1. N shown in FIG. 7 (c)
In the × 2N division (PART_Nx2N), the division index PartIdx of the left prediction block is set to 0, and the division index PartIdx of the right prediction block is set to 1. N × N division (P) shown in FIG. 7 (d)
In ART_NxN), the split index PartIdx of the upper left prediction block is set to 0, the split index PartIdx of the upper right prediction block is set to 1, and the split index Par of the lower left prediction block.
Let tIdx be 2, and let the split index PartIdx of the lower right prediction block be 3.

When the prediction mode (PredMode) is intra-prediction (MODE_INTRA), the division mode (Part) is used except for the coding block D (in this embodiment, the luminance signal is 8 × 8 pixels), which is the smallest coding block.
Mode) defines 2N × 2N division (PART_2Nx2N), only the coding block D which is the smallest coding block, and the division mode (PartMode) is 2N × 2N division (PART_2Nx2N) and N × N division (PART_2Nx2N).
PART_NxN) is defined.

When the prediction mode (PredMode) is inter-prediction (MODE_INTER), the division mode (PartMode) is 2N × 2N division (PART_2Nx2N) except for the coding block D, which is the smallest coding block.
), 2N × N division (PART_2NxN), and N × 2N division (PART_Nx2N) are defined, only the coding block D which is the smallest coding block, and the division mode (PartMode) is 2N × 2N division (PA
RT_2Nx2N), 2NxN division (PART_2NxN), and Nx2N division (PART_Nx2N) plus Nx
Define N division (PART_NxN). In addition to the smallest coded block, N × N division (PART_N)
The reason why xN) is not defined is that the coded block can be divided into four to represent a small coded block except for the minimum coded block.

(About intra prediction and intra prediction mode)
In the intra prediction, the value of the pixel of the conversion block to be processed is predicted from the value of the pixel of the conversion block described later that has been decoded around the same screen. In the coding device and the decoding device of this embodiment, each prediction block is selected from 35 types of intra prediction modes, and intra prediction is performed for each conversion block. The size of the prediction block and the conversion block may be different, but when the conversion block is intra-predicted, the intra-prediction mode of the prediction block including the conversion block is used. FIG. 8 is an explanatory diagram of the value and the prediction direction of the intra prediction mode defined in this embodiment. The value of the intra prediction mode is defined by a mode number from 0 to 34. Intrapredmode (intraPredMode) is a plane prediction (intrapredmode mode intraPredMode = 0) that predicts by interpolating pixel values from the surrounding decoded blocks, and by deriving the mean value from the surrounding decoded blocks. Predicting mean value prediction (intra prediction mode intraPredMod
In addition to e = 1), 33 different angle predictions (intraPredMode = 2 ... 34) are defined to predict at various angles from the surrounding decoded blocks.

(Conversion block)
Similar to the conventional case, in this embodiment as well, the amount of code is reduced by using orthogonal transforms such as DCT (discrete cosine transform) and DST (discrete sine transform) that convert discrete signals into the frequency domain and vice versa. .. Conversion or inverse conversion is performed in units of conversion blocks in which the coded blocks are hierarchically divided into four. In the embodiment, 32 × 32 pixels, 16 × 16 pixels, 8 × 8 pixels, 4 ×
Define 4 conversion sizes of 4 pixels, 32x32 conversion, 16x16 conversion, 8x8 conversion,
It is assumed that 4 × 4 conversion and the inverse conversion of each are performed.

(Position of tree block, coded block, predicted block, conversion block)
The position of each block including the tree block, the coding block, the prediction block, and the conversion block described in this embodiment is the origin (0,0) of the position of the pixel of the luminance signal at the upper left of the screen of the luminance signal. The position of the upper left luminance signal pixel included in the area of each block is represented by the two-dimensional coordinates of (x, y). The directions of the coordinate axes are positive in the horizontal direction to the right and in the vertical direction to the bottom, and the unit is one pixel unit of the luminance signal. Not only when the color difference format in which the image size (number of pixels) is the same in the luminance signal and the color difference signal is 4: 4: 4, but also in the case where the image size (number of pixels) is different in the luminance signal and the color difference signal is 4:
Even in the case of 2: 0, 4: 2: 2, the position of each block of the color difference signal is represented by the coordinates of the pixels of the luminance signal included in the area of the block, and the unit is one pixel of the luminance signal. By doing so, not only the position of each block of the color difference signal can be specified, but also the relationship between the position of the block of the luminance signal and the block of the color difference signal becomes clear only by comparing the coordinate values. FIG. 9 is a diagram of an example for explaining the position of the block defined in this embodiment when the color difference format is 4: 2: 0. In FIG. 9, x indicates the position of the pixel of the luminance signal on the screen plane of the image, and ◯ indicates the position of the pixel of the color difference signal. The dotted quadrangle of FIG. 9 is a block E of a luminance signal of 8 × 8 pixels and at the same time a block F of a color difference signal of 4 × 4 pixels. ▲ is the position of the upper left luminance signal pixel of the block E of the 8 × 8 luminance signal indicated by the dotted line. Therefore, ▲ is the position of the block E of the 8 × 8 pixel luminance signal indicated by the dotted line, and the coordinates of the pixel luminance signal indicated by ▲ are the coordinates of the block E of the 8 × 8 pixel luminance signal indicated by the dotted line. Become. Similarly, ▲ is also the position of the upper left luminance signal pixel included in the area of the block F of the 4 × 4 pixel color difference signal indicated by the dotted line. Therefore, ▲ is also the position of the block F of the color difference signal of 4 × 4 pixels indicated by the dotted line, and the coordinates of the luminance signal of the pixel indicated by ▲ are 4 × 4 indicated by the dotted line.
It becomes the coordinates of the block F of the color difference signal of the pixel. In the embodiment, when the values of the x component and the y component of the defined luminance signal block coordinates and the color difference signal block coordinates are the same regardless of the type of color difference format, the shape and size of the block. Only define that these blocks are in the same position.

FIG. 1 is a block showing a configuration of an image coding device according to an embodiment. The image coding apparatus of the embodiment includes a color difference format setting unit 101, an image memory 102, and an intra prediction unit 1.
03, inter-prediction unit 104, coding method determination unit 105, residual signal generation unit 106, orthogonal conversion / quantization unit 107, inverse quantization / inverse orthogonal conversion unit 108, decoded image signal superimposition unit 109, decoded image memory 111. , A first coded stream generation unit 112, a second coded stream generation unit 113, a third coded stream generation unit 114, and a coded stream multiplexing unit 115.

The color difference format setting unit 101 sets the color difference format of the image signal to be encoded. The color difference format may be set by determining the color difference format from the coded image signal supplied to the color difference format setting unit 101, or may be set from the outside. Only the brightness signal, the information of the color difference format set to 4: 2: 0, 4: 2: 2, or 4: 4: 4 is supplied to the first coded stream generator 112 and the second code. It is supplied to the conversion stream generation unit 113, and coding processing based on the color difference format is performed. Although not shown, the image memory 102, the intra prediction unit 103, and the inter prediction unit 104 in FIG. 1 are shown.
, Coding method determination unit 105, residual signal generation unit 106, orthogonal conversion / quantization unit 107, inverse quantization / inverse orthogonal conversion unit 108, decoded image signal superimposition unit 109, third coded stream generation unit 1
In 14, the coding process is performed based on the set color difference format, and the coding information storage memory 110 and the decoded image memory 111 are managed based on the set color difference format.

The image memory 102 temporarily stores the image signals to be encoded, which are supplied in chronological order. The image signals to be encoded stored in the image memory 102 are rearranged in the coding order, divided into each coding block unit by a plurality of combinations according to the settings, and further divided into each prediction block unit. Then, it is supplied to the intra prediction unit 103 and the inter prediction unit 104.

The intra prediction unit 103 includes each division mode (Pa) in a plurality of coded block units.
Multiple intra-luminance prediction modes and intra-color difference prediction modes for each of the luminance signal and color difference signal of the prediction block to be encoded from the decoded image signal stored in the decoded image memory 111 in units of prediction blocks according to rtMode). Set the intra-brightness prediction mode,
And each intra prediction according to the intra color difference prediction mode is performed for each conversion block.
Get the intra prediction signal. The intra color difference prediction mode is a value predicted from the intra brightness prediction mode, or 0 (plane prediction), 1 (average value prediction), 10 (horizontal prediction), 26 (vertical prediction), which are typical intra prediction modes. ) And 34 (diagonal prediction) can be selected for each prediction block. However, in this embodiment, the color difference format is 4.
A second intra-color difference prediction mode, which will be described later, is used for the 2: 2 intra-prediction. The intra-prediction of the color difference signal and the intra-prediction mode will be described in detail later.

From the signal to be encoded supplied in the prediction block unit, the intra prediction signal in the prediction block unit is subtracted for each pixel to obtain the prediction residual signal. The evaluation value for evaluating the code amount and the distortion amount is derived using the predicted residual signal, and the code amount and the distortion are the most among the plurality of intra-brightness prediction modes and the intra-color difference prediction modes for each prediction block. The optimum mode is selected in terms of quantity, and the intra prediction information, the intra prediction signal, and the evaluation value of the intra prediction corresponding to the selected intra prediction mode are encoded as candidates for the intra prediction of the prediction block. Supply to 105.

The inter-prediction unit 104 has a division mode (Pa) in a plurality of coded block units.
In units according to rtMode), that is, in units of prediction blocks, a plurality of inter-prediction modes (L0 prediction, L1 prediction, both predictions) from the decoded image signal stored in the decoded image memory 111, and each according to the reference image. Inter-prediction is performed and an inter-prediction signal is obtained. At that time, a motion vector search is performed, and inter-prediction is performed according to the searched motion vector. In the case of both predictions, the inter-prediction of both predictions is performed by averaging or weighting the two inter-prediction signals for each pixel. From the signal to be encoded supplied in the prediction block unit, the inter-prediction signal in the prediction block unit is subtracted for each pixel to obtain the prediction residual signal. The evaluation value for evaluating the code amount and the distortion amount is derived using the predicted residual signal, and the most suitable mode from the viewpoint of the code amount and the distortion amount from among a plurality of inter-prediction modes for each prediction block. Is selected, and the inter-prediction information, the inter-prediction signal, and the evaluation value of the inter-prediction corresponding to the selected inter-prediction mode are supplied to the coding method determination unit 105 as candidates for the inter-prediction of the prediction block.

The coding method determination unit 105 determines the optimum code based on the intra prediction evaluation value corresponding to the intra prediction information selected for each prediction block in each of the plurality of coding block units and the inter prediction evaluation value corresponding to the inter prediction information. How to divide the conversion block, prediction mode (
PredMode) and division mode (PartMode) are determined, and the intra prediction information or the coding information including the inter prediction information according to the decision is supplied to the second coded stream generation unit 113, and the coded information storage memory 110 The intra-predicted or inter-predicted predicted signal according to the determination is supplied to the residual signal generation unit 106 and the decoded image signal superimposing unit 109.

The residual signal generation unit 106 generates a residual signal by subtracting the intra-predicted or inter-predicted predicted signal from the encoded image signal for each pixel, and supplies the residual signal to the orthogonal conversion / quantization unit 107.

The orthogonal conversion / quantization unit 107 performs orthogonal conversion and quantization to convert the supplied residual signal into a frequency region such as DCT or DST according to the quantization parameter, and the orthogonal conversion / quantization residual. A signal is generated and supplied to a third coded stream generation unit 114 and an inverse quantization / inverse orthogonal conversion unit 108.

The first coded stream generation unit 112 derives and derives the values of the syntax elements related to the coding information of the sequence, the picture, and the slice unit according to the semantic rules that define the meaning of the syntax elements and the derivation method. The value of the syntax element is entropy-coded by variable-length coding, arithmetic coding, etc. according to the syntax rules, a first coded stream is generated, and the coded first coded stream is coded. It is supplied to the stream multiplexing unit 115. The value of the syntax element related to the color difference format is also derived by the first coded stream generation unit 112. The syntax element related to the color difference format is derived from the color difference format information supplied from the color difference format setting unit 101. Figure 1
0 is an example of the syntax definition when encoding the color difference format information with the sequence parameter set which is the header for encoding the information related to the coding of the entire sequence specified in this embodiment. The syntax element chroma_format_idc indicates the type of color difference format. The meaning of the syntax element chroma_format_idc is that 0 is monochrome and 1 is 4: 2:
0 and 2 represent 4: 2: 2, and 3 represents 4: 4: 4. Also, the syntax element separate_colour_
The meaning of plane_flag indicates whether the luminance signal and the color difference signal are encoded separately, and separate.
When the value of _colour_plane_flag is 0, it means that the luminance signal is encoded by associating two color difference signals. When the value of the syntax element chroma_format_idc is 1, the luminance signal and 2
Indicates that two color difference signals are encoded separately. The value of chroma_format_idc can be set to 0 or 1 only when the value of the syntax element chroma_format_idc is 3, that is, the color difference format is 4: 4: 4, and in other color difference formats, the syntax element is always set.
It is encoded assuming that the value of separate_colour_plane_flag is 0.

The second coded stream generation unit 113 is determined by the coding method determination unit 105 for each prediction block in addition to the coding information for each coding block according to the semantic rules that define the meaning of the syntax element and the derivation method. Derivation of the value of the syntax element related to the coded information. Specifically, in addition to the coding information of each coding block such as the division method of the coding block, the prediction mode (PredMode), and the division mode (PartMode), the value of the syntax element related to the coding information of the prediction block unit. Is derived. When the prediction mode (PredMode) is intra prediction, the values of the syntax elements related to the intra brightness prediction mode and the intra prediction mode including the intra color difference prediction mode are derived, and when the prediction mode (PredMode) is inter prediction, the inter prediction mode is derived. , Information that identifies the reference image, and the value of the syntax element related to the inter-prediction information such as the motion vector are derived. The value of each derived syntax element is entropy-coded by variable-length coding, arithmetic coding, etc. according to the syntax rules, a second coded stream is generated, and the coded second coded code is generated. The stream is supplied to the coded stream multiplexing unit 115. The details of the processing related to the derivation of the syntax elements related to the intra-luminance prediction mode and the intra-color difference prediction mode performed by the second coded stream generation unit 113 will be described later.

The third coded stream generation unit 114 performs entropy coding by variable length coding, arithmetic coding, etc. according to the specified syntax rules for the orthogonal conversion and the quantized residual signal, and the third coded stream. Is generated to supply a third coded stream to the coded stream multiplexing unit 115.

In the coded stream multiplexing unit 115, the first coded stream, the second coded stream, and the third coded stream are multiplexed according to the specified syntax rules to generate a bit stream, and the bits are multiplexed. Output a bitstream.

The inverse quantization / inverse orthogonal conversion unit 108 derives the residual signal by inverse quantization and inverse orthogonal conversion of the orthogonal conversion / quantization residual signal supplied from the orthogonal transformation / quantization unit 107, and decodes the residual signal. It is supplied to the image signal superimposing unit 109. The decoded image signal superimposition unit 109 is a residual that is inversely quantized and inversely orthogonalized by the inverse quantization / inverse orthogonal conversion unit 108 with the prediction signal that is intra-predicted or inter-predicted according to the determination by the coding method determination unit 105. The signals are superimposed to generate a decoded image, which is stored in the decoded image memory 111. The decoded image may be stored in the decoded image memory 111 after being subjected to a filtering process for reducing block distortion or the like due to encoding.

FIG. 2 is a block showing a configuration of an image decoding device according to an embodiment corresponding to the image coding device of FIG. The image decoding apparatus of the embodiment includes a coded stream separation unit 201, a first coded stream decoding unit 202, a second coded stream decoding unit 203, a third coded stream decoding unit 204, and a color difference format management unit. It includes 205, an intra prediction unit 206, an inter prediction unit 207, an inverse quantization / inverse orthogonal conversion unit 208, a decoded image signal superimposing unit 209, a coded information storage memory 210, a decoded image memory 211, and switches 212 and 213.

The bit stream supplied to the coded stream separation unit 201 is separated according to a specified syntax rule, and a first sequence, a picture, and a slice-based coding information are shown.
The coded stream of is supplied to the first coded stream decoding unit 202, and the second coded stream containing the coded information in units of coded blocks is the second coded stream decoding unit 203.
A third coded stream containing the orthogonally transformed and quantized residual signal is supplied to the third coded stream decoding unit 204.

The first coded stream decoding unit 202 is supplied according to the syntax rules.
The coded stream of is entropy-decoded to obtain the respective values of the syntax elements for sequence, picture, and slice-by-slice coding information. Decoded sequences, pictures, according to semantic rules that define the meaning of syntax elements and how they are derived.
And the coded information of the sequence, the picture, and the slice unit is derived from the value of the syntax element related to the coded information of the slice unit. The first coded stream decoding unit 202 is a coded stream decoding unit corresponding to the first coded stream generation unit 112 on the coding side, and is a sequence encoded by the first coded stream generation unit 112. It has a function of returning to each coded information from the first coded stream including the coded information of each picture and slice. The color difference format information encoded by the first coded stream generation unit 112 is a syntax element relating to the color difference format information obtained by entropy decoding the second coded stream by the first coded stream decoding unit 202. Derived from the value. According to the syntax rule and the syntax rule shown in FIG. 10, the type of the color difference format is specified from the value of the syntax element chroma_format_idc, and the syntax element chrom.
When the value of a_format_idc is 0, it is monochrome, 1 is 4: 2: 0, 2 is 4: 2: 2, and 3 is 4: 4: 4. Further, when the value of the syntax element chroma_format_idc is 3, that is, when the color difference format is 4: 4: 4, the syntax element separate_colour_plane_flag is decoded to determine whether the luminance signal and the color difference signal are encoded separately. The derived color difference format information is supplied to the color difference format management unit 205.

The color difference format management unit 205 manages the supplied color difference format information. The supplied color difference format information is supplied to the second coded stream decoding unit 203, and the coding information of the coding block and the prediction block based on the color difference format information is derived. Although not explicitly shown in the figure, the third coded stream decoding unit 204, the intra prediction unit 206 in FIG. 2, the inter prediction unit 207, the inverse quantization / inverse orthogonal conversion unit 208, and the decoded image signal superimposition unit 209 also Decoding processing is performed based on the color difference format information, and the coding information storage memory 210 and the decoded image memory 211 are managed based on the color difference format information.

The second coded stream decoding unit 203 is supplied with the first coded stream according to the syntax rules.
The coded stream of is entropy-decoded to obtain the respective values of the syntax element for the coded block and the coded information in the predicted block unit. The meaning of the syntax element,
According to the semantic rules that define the derivation method, the coded information of the coded block unit and the coded information of the predicted block unit is derived from the values of the syntax elements related to the coded information of the supplied coded block unit and the predicted block unit. Second coded stream decoding unit 203
Is a coded stream decoding unit corresponding to the second coded stream generation unit 113 on the coding side, the coded block encoded by the second coded stream generation unit 113, and the coding in units of predicted blocks. It has a function of returning each coded information from the second coded stream containing the information. Specifically, from each syntax element obtained by decoding the second coded stream according to a specified syntax rule, in addition to the coded block division method, prediction mode (PredMode), and division mode (PartMode). When the prediction mode (PredMode) is intra prediction, an intra brightness prediction mode and an intra prediction mode including an intra color difference prediction mode are obtained. On the other hand, when the prediction mode (PredMode) is inter-prediction, inter-prediction information such as inter-prediction mode, information for specifying a reference image, and motion vector is obtained. When the prediction mode (PredMode) is intra prediction, the intra brightness prediction mode and the intra prediction mode including the intra color difference prediction mode are supplied to the intra prediction unit 206 through the switch 212, and when the prediction mode (PredMode) is inter prediction, Through the switch 212, inter-prediction information such as an inter-prediction mode, information for identifying a reference image, and a motion vector is supplied to the inter-prediction unit 207. Details regarding the entropy decoding process performed by the second coded stream decoding unit 203, the intra-luminance prediction mode, the intra-luminance prediction mode from the syntax elements related to the intra-color difference prediction mode, and the derivation process of the intra-color difference prediction mode. The processing will be described later.

The third coded stream decoding unit 204 decodes the supplied third coded stream to derive an orthogonally converted / quantized residual signal, and reverses the orthogonally converted / quantized residual signal. It is supplied to the quantization / inverse orthogonal conversion unit 208.

The intra prediction unit 206 generates a prediction image signal by intra prediction from the decoded peripheral blocks stored in the decoded image memory 211 according to the supplied intra brightness prediction mode and the intra color difference prediction mode, and switches 213. The predicted image signal is supplied to the decoded image signal superimposing unit 209 via the above. However, in this embodiment, the color difference format is 4.
A second intra-color difference prediction mode, which will be described later, is used for the 2: 2 intra-prediction. The intra-prediction of the color difference signal and the intra-prediction mode will be described in detail later.

The inter-prediction unit 207 uses motion compensation from the decoded reference picture stored in the decoded image memory 211 using the supplied inter-prediction mode, the information for identifying the reference picture, the inter-prediction information such as the motion vector, and the like. A predicted image signal is generated by inter-prediction, and the predicted image signal is supplied to the decoded image signal superimposing unit 209 via the switch 213. In the case of both predictions, the two motion compensation prediction image signals of L0 prediction and L1 prediction are adaptively multiplied by a weighting coefficient and superposed to generate a final prediction image signal.

The inverse quantization / inverse orthogonal conversion unit 208 performs inverse orthogonal conversion and inverse quantization on the orthogonal conversion / quantization residual signal decoded by the third coded stream decoding unit 204, and performs inverse orthogonal conversion and inverse orthogonal conversion.・
Obtain an inversely quantized residual signal.

The decoded image signal superimposition unit 209 includes a predicted image signal predicted by the intra prediction unit 206 or the inter prediction unit 207, and a residual signal that is inversely orthogonally converted and inversely quantized by the inversely quantized / inversely orthogonalized conversion unit 208. The decoded image signal is decoded by superimposing the above, and the decoded image memory 211
Store in. When the decoded image is stored in the decoded image memory 211, the decoded image may be stored in the decoded image memory 211 after being subjected to a filtering process for reducing block distortion or the like due to coding. The decoded image signals stored in the decoded image memory 211 are output in the output order.

Next, it is used in the intra prediction and the intra prediction performed by the intra prediction unit 103 of the image encoding device of FIG. 1 and the intra prediction unit 206 of the image decoding device of FIG. 2, and the second reference numeral of FIG. The intra prediction mode encoded by the conversion stream generation unit 113 and decoded by the second encoded stream decoding unit 203 of FIG. 2 will be described.

In intra-prediction, the value of the pixel of the conversion block to be processed is predicted from the value of the pixel of the surrounding decoded conversion block in the same screen. In the coding device and the decoding device of this embodiment, the intra prediction mode is selected from 35 types of intra prediction modes to perform intra prediction. FIG. 8 is an explanatory diagram showing the values and prediction directions of the intra prediction mode defined in this embodiment. The direction indicated by the arrow indicates the prediction direction of each intra prediction, that is, the direction referred to in the intra prediction. In each intra prediction mode, each pixel (FIG. 8) refers to the pixels of the decoded boundary in the prediction direction of the intra prediction (direction indicated by the arrow in FIG. 8) included in the conversion block adjacent to the conversion block to be the target of the intra prediction. Intra-prediction of (the pixel at the start point of the arrow 8) is performed. The numbers on the left and upper sides indicate the values of the intra prediction mode. The numbers on the right and bottom indicate the angles of intra prediction corresponding to the intra prediction modes on the left and top, respectively. IntrapredMode is a plane prediction mode that predicts by interpolating pixel values from the pixels of the surrounding decoded conversion block (intrapredmode).
intraPredMode = 0), in addition to the mean value prediction (intrapredmode mode intraPredMode = 1) that predicts by deriving the mean value from the pixels of the surrounding decoded conversion block, it varies from the pixels of the surrounding decoded conversion block. 33 kinds of angle predictions (intraPredMode = 2 ... 34) are defined. For this angle prediction, vertical prediction (intrapredMode = 26) that predicts in the vertical direction from the pixels of the above decoded conversion block.
), Horizontal prediction (intrapredMode = 10) that predicts in the horizontal direction from the pixels of the decoded conversion block on the left is also included. In this embodiment, the angle of the intra prediction is represented by the length in the vertical direction with respect to the unit length 32 in the horizontal direction or the length in the horizontal direction with respect to the unit length 32 in the vertical direction. The angle of the intra prediction corresponding to the intra prediction mode of the horizontal prediction for horizontal prediction is set to 0, and the length in the vertical direction with respect to the unit length 32 in the horizontal direction is represented by a positive value in the downward direction and a negative value in the upward direction. The angle of intra prediction. Alternatively, the angle of the intra prediction corresponding to the intra prediction mode of the vertical prediction that predicts in the vertical direction is set to 0, and the horizontal length with respect to the unit length 32 in the vertical direction is set to a positive value in the right direction and a negative value in the left direction. Represented as the angle of the intra prediction. For example, an intra-prediction angle of 32 represents 45 ° in the degree method, and −32 represents −45 ° in the power method.

The intra-prediction mode is prepared for each of the luminance signal and the color difference signal, and the intra-luminance prediction mode for the luminance signal is defined as the intra-luminance prediction mode and the intra-prediction mode for the color difference signal is defined as the intra-color difference prediction mode. In the coding and decoding of the intra-luminance prediction mode, the correlation with the intra-luminance prediction mode of the surrounding blocks is used, and if it is determined on the coding side that the prediction can be performed from the intra-luminance prediction mode of the surrounding blocks. When it is determined that it is better to set a different value in the intra-luminance prediction mode than to transmit the information that identifies the block to be referred to and predict from the intra-luminance prediction mode of the surrounding blocks, the intra-luminance prediction mode is further executed. Use a mechanism to encode or decode the value of. By predicting the intra-luminance prediction mode of the block to be encoded / decoded from the intra-luminance prediction mode of the surrounding blocks, the amount of code to be transmitted can be reduced. On the other hand, in the coding and decoding of the intra-color difference prediction mode, the intra-luminance prediction mode is used on the coding side by utilizing the correlation between the color difference signal prediction block and the intra-luminance prediction block of the luminance signal prediction block at the same position. If it is judged that it can be predicted from, the value of the intra-color difference prediction mode is predicted from the value of the intra-luminance prediction mode.
When it is determined that it is better to set an original value in the intra color difference prediction mode than to predict from the intra brightness prediction mode, a mechanism for encoding or decoding the value in the intra color difference prediction mode is used. By predicting the intra-color difference prediction mode from the intra-luminance prediction mode, the amount of code to be transmitted can be reduced.

Next, regarding the coding block performed by the second coded stream generation unit 113 in FIG. 1 and the coding processing of the coding information in units of prediction blocks, the points related to the intra prediction mode, which is a feature of the embodiment, are described. I will explain mainly. FIG. 12 is a block diagram showing the configuration of the second coded stream generation unit 113 of FIG.

As shown in FIG. 12, the second coded stream generation unit 113 of FIG. 1 includes a syntax element derivation unit 121 for coding information in units of coded blocks, a syntax element derivation unit 122 for the intra-brightness prediction mode, and an intra. It is composed of a syntax element derivation unit 123 related to a color difference prediction mode, a syntax element derivation unit 124 related to inter-prediction information, an intra prediction mode coding control unit 125, and an entropy coding unit 126. In each unit constituting the second coded stream generation unit 113, the color difference format setting unit 101
Processing is performed according to the color difference format information supplied from the above, and processing is performed according to the coding information such as the prediction mode and the division mode (PartMode) of each coding block.

The syntax element derivation unit 121 relating to the coding information of the coding block unit derives the value of the syntax element relating to the coding information of the coding block unit, and the value of each derived syntax element is transmitted to the entropy coding unit 126. Supply. Intra-prediction of coded blocks (
MODE_INTRA), or prediction mode (PredMode) to determine inter-prediction (MODE_INTER),
The value of the syntax element relating to the division mode (PartMode) for determining the shape of the prediction block is derived by the syntax element deriving unit 121 relating to the coding information of each coded block.

The syntax element derivation unit 122 regarding the intra-luminance prediction mode sets the values of the syntax elements regarding the intra-luminance prediction mode of the luminance signal prediction block when the prediction mode (PredMode) of the coding block is intra-prediction (MODE_INTRA). It is derived, and the value of each derived syntax element is supplied to the entropy coding unit 126. The syntax element related to the intra-brightness prediction mode is a flag indicating whether or not it can be predicted from the intra-brightness prediction mode of the surrounding blocks. Syntax element prev_intra_luma_pred_flag [x0] [y0
], Syntax element mpm_idx [x0], which is an index that points to the prediction block of the prediction source
[y0], and the syntax element rem_in indicating the intra-brightness prediction mode for each prediction block.
tra_luma_pred_mode [x0] [y0]. Note that x0, and y0 are coordinates indicating the position of the prediction block. In deriving the value of the syntax element for the intra-brightness prediction mode,
It is a flag indicating that the correlation with the intra-luminance prediction mode of the peripheral block stored in the coding information storage memory 110 is used, and that value is used when the prediction can be made from the intra-luminance prediction mode of the peripheral block. Syntax element prev_intra_luma_pred_flag [x0
] [Y0] is set to 1 (true), and the syntax element mpm_idx [x0] [y0], which is an index indicating the prediction block of the prediction source, is set to a value that specifies the reference destination. , Prev_intra_luma_pred_flag [x0] [y0] is set to 0 (false), and the syntax element rem_intra_luma_pred_mode [x0] [y0] indicating the intra-luminance prediction mode to be encoded is set to a value that specifies the intra-luminance prediction mode.

The number of intra-luminance prediction modes of the prediction blocks in the coded block differs depending on the division block. When the division mode (PartMode) is 2N × 2N division, the intra-luminance of one set of prediction blocks for each coded block. The value of the syntax element related to the prediction mode is derived, and when the division mode is N × N division, the value of the syntax element related to the intra-luminance prediction mode of 4 sets of prediction blocks is derived for each coded block.

The syntax element derivation unit 123 relating to the intra-color difference prediction mode is a syntax element intra_chroma_pred_mode [x0] relating to the intra-color difference prediction mode of the color difference signal prediction block when the prediction mode (PredMode) of the coding block is intra prediction (MODE_INTRA). [
The value of [y0] is derived, and the derived value of the syntax element intra_chroma_pred_mode [x0] [y0] is supplied to the entropy encoding unit 126. In the determination of the intra color difference prediction mode by the intra prediction unit 103 and the derivation of the value of the syntax element related to the intra color difference prediction mode of the intra color difference prediction mode of the intra color difference prediction mode 123, the position is the same as the prediction block of the color difference signal. Utilizing the correlation with the intra-brightness prediction mode of the brightness signal prediction block, the value predicted from the intra-brightness prediction mode of the brightness signal prediction block at the same position as the color difference signal prediction block in the intra-color difference prediction mode is most suitable. If so, predict the value of the intra-color difference prediction mode from the value of the intra-brightness prediction mode, and if it is determined that it is better to set an original value rather than the predicted value from the intra-brightness prediction mode, switch to the intra-color difference prediction mode. Use a mechanism to set any of 0 (plane prediction), 1 (average value prediction), 10 (horizontal prediction), 26 (vertical prediction), and 34 (diagonal prediction), which are typical intra prediction modes. Therefore, the amount of code is reduced.

Here, a method of deriving the value of the intra-color difference prediction mode from the value of the intra-luminance prediction mode and the value of the syntax element related to the intra-color difference prediction mode will be described by the intra-color difference prediction mode derivation unit 225 described later on the decoding side. In this embodiment, in order to distinguish from the intra color difference prediction mode for the color difference format 4: 2: 2 described later, FIG. 14 described later
The intra-color difference prediction mode for 4: 2: 0 or 4: 4: 4 derived from the table of is defined as the first intra-color difference prediction mode. FIG. 14 shows the first intra from the values of the syntax element intra_chroma_pred_mode [x0] [y0] relating to the intra color difference prediction mode defined in this embodiment and the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal. It is a table for deriving the value of the color difference prediction mode, and using this table, on the decoding side,
The value of the first intra color difference prediction mode is derived.
When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0, the value of the first intra-color difference prediction mode unless the value of the intra-luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal is 0. Takes a value of 0 (plane prediction), and if the value of the intra-luminance prediction mode is 0, the value of the first intra-color difference prediction mode takes a value of 34 (diagonal prediction).

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 1, the value of the first intra-color difference prediction mode unless the value of the intra-luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal is 1. Takes a value of 26 (vertical prediction), and if the value of the intra-luminance prediction mode is 1, the value of the first intra-color difference prediction mode takes a value of 34 (diagonal prediction).

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 2, the value of the first intra-color difference prediction mode unless the value of the intra-luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal is 2. Takes a value of 10 (horizontal prediction), and if the value of the intra-luminance prediction mode is 2, the value of the first intra-color difference prediction mode takes a value of 34 (diagonal prediction).

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 3, the value of the first intra-color difference prediction mode is 1 unless the intra-luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal is 3. If the value of the intra-luminance prediction mode is 3, the value of the first intra-color difference prediction mode is 34 (diagonal prediction).

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 4, the value of the first intra-color difference prediction mode takes the same value as the intra-luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal.

When the color difference format is 4: 2: 0 or 4: 4: 4, the first intra color difference prediction mode derived from FIG. 14 is the intra color difference signal for the color difference format of 4: 2: 0 or 4: 4: 4. Used as a prediction mode. In the intra prediction unit 103 of the image encoding device of FIG. 1 and the intra prediction unit 206 of the image decoding device of FIG. 2, the first intra color difference is obtained when the color difference format is 4: 2: 0 or 4: 4: 4. Intra-prediction of the color difference signal is performed using the prediction mode.

When the color difference format is 4: 2: 2, the value of the intra color difference prediction mode for the color difference format 4: 2: 2 is derived from the first intra color difference prediction mode derived in FIG. 14 from the conversion table. In the coding and decoding of the present embodiment, FIGS. 15 and 16 described later,
Color difference format 4: 2 derived from the conversion table of FIG. 17, FIG. 30, or FIG.
: The intra color difference prediction mode for 2 is defined as the second intra color difference prediction mode. The intra prediction unit 103 of the image coding device of FIG. 1 and the intra prediction unit 206 of the image decoding device of FIG.
Then, when the color difference format is 4: 2: 2, the intra prediction of the color difference signal is performed using the second intra color difference prediction mode. 15, FIG. 16, FIG. 17, FIG. 30, and FIG. 33 have a color difference format of 4: 2 from the intra-luminance prediction mode defined in this embodiment or the first intra-color difference prediction mode derived from the table of FIG. This is a conversion table for deriving the value of the second intra-color difference prediction mode for the color difference format 4: 2: 2 used for intra-prediction of the color difference signal of: 2. FIG. 18 is a diagram for explaining the value and the prediction direction of the intra-prediction mode derived from the conversion table of FIG. 15 defined in this embodiment, and FIG. 19 is derived from the conversion table of FIG. 16 defined in this embodiment. FIG. 20 is a diagram for explaining the value and the prediction direction of the intra prediction mode, and FIG. 20 is a diagram for explaining the value and the prediction direction of the intra prediction mode derived from the conversion table of FIG. 17 defined in this embodiment. 31 is a diagram for explaining the value and the prediction direction of the intra prediction mode derived in the conversion table of FIG. 30 defined in this embodiment, and FIG. 34 is derived in the conversion table of FIG. 33 defined in this embodiment. It is a figure explaining the value of the intra prediction mode and the prediction direction.

In the present embodiment, the second intra color difference prediction for the color difference format 4: 2: 2 from the intra brightness prediction mode according to FIGS. 15, 16, 17, 30, and 33 or the first intra color difference prediction mode. The process of deriving the mode is performed by the intra prediction unit 103 of the coding device on the coding side, and is performed by the second coded stream decoding unit 203 of the decoding device or the intra prediction unit 206 on the decoding side.

In the coding and decoding of the present embodiment, when the color difference format is 4: 2: 2, 4
Instead of using the first intra-color difference prediction mode derived from the table of FIG. 14 as it is as in: 2: 0 or 4: 4: 4, FIG. 15, FIG. 16, FIG. 17, FIG. 30, or FIG. 33
The reason for deriving the second intra-color difference prediction mode for the color difference format 4: 2: 2 will be described using the conversion table of. When the color difference format is 4: 2: 2, as shown in FIG. 3B, the color difference signal is sampled at half the density in the horizontal direction and the same density in the vertical direction with respect to the luminance signal. is there. Therefore, the intra-brightness prediction mode or the first
When intra-prediction of the color difference signal is performed in the prediction direction scaled by half in the horizontal direction or in the prediction direction in the vicinity of each prediction direction in the intra-color difference prediction mode of
It is equivalent to or close to the intra-prediction of the luminance signal of the prediction block at the same position as the prediction block of the color difference signal.

This will be described in more detail with reference to FIG. In FIG. 21, the color difference format is 4: 2.
: 2 is a diagram for explaining the correspondence between the luminance signal in the case of 2 and the prediction direction of the intra-prediction of the color difference signal. In FIG. 21, x indicates the position of the pixel of the luminance signal, and ◯ indicates the position of the pixel of the color difference signal. In 4: 2: 2, the color difference signal is sampled (sampled) at 1/2 in the horizontal direction with respect to the luminance signal, and the aspect ratios of the pixels of the luminance signal and the color difference signal are different. FIG. 21 (a) is 4
: Indicates the positions of the sampled pixels of the 2: 2 luminance signal and the color difference signal. The reference numeral P1 is a pixel that is predicted to be intra-predicted, and the reference numeral P2 is a pixel that is referred to during intra-prediction (because it is actually filtered, the pixel next to it is also referred to). The arrow from the pixel P1 to the pixel P2 shown by reference numeral 2701 indicates the intra prediction direction of the pixel P1 of the luminance signal and the pixel P1 of the color difference signal.
Intra prediction direction of.

FIG. 21B shows an array of pixels of a color difference signal sampled at 1/2 in the horizontal direction. Here, if the intra-prediction of the color difference signal is not scaled by 1/2 in the horizontal direction, the intra-prediction direction of the pixel P1 of the color difference signal will be the direction of the arrow indicated by the reference numeral 2702, and the color difference signal In the pixel arrangement of, the pixel of reference numeral P3 is erroneously referred to. However, the correct reference is the pixel of reference numeral P2. Therefore, by scaling the intra prediction direction of the luminance signal by 1/2 times in the horizontal direction and setting it as the intra prediction direction of the color difference signal, the correct intra prediction direction in the arrangement of the color difference signals is derived as shown by reference numeral 2703. Then, the pixel adjacent to the upper side, which is the correct reference destination in the intra prediction direction (actually, the filtering is performed, so the pixel next to the pixel is also referred to) is acquired.

Although FIGS. 21A and 21B have described the case where the pixels adjacent to the upper side of the prediction block are referred to, the same applies to the case where the pixels adjacent to the upper side of the prediction block are referred to. In the case of pixels adjacent to the left side, the intra prediction direction of the brightness signal is scaled twice in the vertical direction (this is equivalent to scaling in the horizontal direction by 1/2 times in the sense of finding the direction of intra prediction. By doing so, the correct intra prediction direction in the color difference signal array is derived, and the pixels adjacent to the left side (including some pixels adjacent to the upper side), which is the correct reference destination in the intra prediction direction, are acquired. To do.

Therefore, in the conversion tables of FIGS. 15 and 16, the intra-luminance prediction mode or the intra-luminance prediction mode arranged in the horizontal direction (on the horizontal axis), as shown by the dotted arrows in FIGS. 18 and 19, respectively,
The values of the first intracolor difference prediction mode derived from the table of are 18, 19, 20, and 2.
1, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34
At the time of, the value of the intra prediction mode in the prediction direction close to the prediction direction derived by scaling the angle of the prediction direction to half in the horizontal direction around the vertical prediction (intra prediction mode 26) is used as the second value. Select as the value of the intra color difference prediction mode, and set the value of the second intra color difference prediction mode to 21, 22, 23, 23, 24, 24, 25, 25, 26, 27, respectively.
27, 28, 28, 29, 29, 30, 31. Further, scaling the prediction direction of the intra prediction by a factor of 2 in the horizontal direction is equivalent to scaling by a factor of 2 in the vertical direction. Therefore, for each prediction direction of the intra-brightness prediction mode or the first intra-color difference prediction mode, the prediction direction is scaled twice in the vertical direction with respect to the horizontal prediction (intra prediction mode 10), or the prediction in the vicinity thereof. When the intra prediction of the color difference signal is performed in the direction, it is equivalent to or close to the intra prediction of the brightness signal of the prediction block at the same position as the prediction block of the color difference signal. Therefore, in the conversion tables of FIGS. 15 and 16, as shown in FIGS. 18 and 19, of the intra-prediction mode (intra-luminance prediction mode or first intra-color difference prediction mode) arranged in the vertical direction (on the vertical axis), respectively. Values are 2, 3, 4
When 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 and 17, the angle of the prediction direction is doubled in the vertical direction centered on the horizontal prediction (intra prediction mode 10). The value of the intra prediction mode in the prediction direction close to the prediction direction derived by scaling to is selected as the value of the second intra color difference prediction mode, and the value of the second intra color difference prediction mode is set to 2, 2, 2 respectively. 2,3,5,7,8,10,12,13,15,17,18,18,18
, 18, and 2,2,2,2,3,5,7,8,10,12,13,15,17,18,
Let it be 18, 19, 20.

Further, it is also possible to convert from the intra prediction mode (intra brightness prediction mode or the first intra color difference prediction mode) to the second intra color difference prediction mode by using the conversion table of FIG. In the conversion table of FIG. 17, as shown by the dotted arrow of FIG. 20, the intra-luminance prediction mode in which the reference destinations are arranged in the horizontal direction (on the horizontal axis) or the first intra-color difference prediction mode derived from the table of FIG. 14 Values are 18, 19, 20, 21, 22, 23, 24, 2
When 5, 26, 27, 28, 29, 30, 31, 32, 33, 34, the intra-brightness prediction mode or the first intra-color difference prediction mode is set to 2 in the horizontal direction centered on the vertical prediction (intra-prediction mode 26). The value derived by scaling to 1/1 is used as the value of the second intra color difference prediction mode, and the value of the second intra color difference prediction mode is 22, 22, 2 respectively.
3, 23, 24, 24, 25, 25, 26, 27, 27, 28, 28, 29, 29, 30
, 30. Further, scaling the prediction direction of the intra prediction by a factor of 2 in the horizontal direction is equivalent to scaling by a factor of 2 in the vertical direction. Therefore, for each prediction direction of the intra-brightness prediction mode or the first intra-color difference prediction mode, the prediction direction is scaled twice in the vertical direction with respect to the horizontal prediction (intra prediction mode 10), or the prediction in the vicinity thereof. When the intra prediction of the color difference signal is performed in the direction, it is equivalent to or close to the intra prediction of the brightness signal of the prediction block at the same position as the prediction block of the color difference signal.
Therefore, in the conversion table of FIG. 17, as shown by the dotted line arrow of FIG. 20, the values of the intra-luminance prediction mode or the first intra-color difference prediction mode in which the reference destinations are arranged in the vertical direction (on the vertical axis) are 2, 3 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
At 17, the intra-luminance prediction mode or the first intra-color difference prediction mode is horizontally predicted (
The value derived by scaling twice in the vertical direction around the intra prediction mode 10) and limiting it to 2 or more and 18 or less is used as the value of the intra color difference prediction mode, and the value of the second intra color difference prediction mode is set to 2. 2,2,2,2,4,6,8,10,12,14,16,18,1
Let it be 8, 18 and 18.

Further, it is also possible to convert from the intra prediction mode (intra brightness prediction mode or the first intra color difference prediction mode) to the second intra color difference prediction mode by using the conversion table of FIG. In the conversion table of FIG. 30, as shown by the dotted arrow in FIG. 31, the values of the intra-luminance prediction mode or the first intra-color difference prediction mode derived from the table of FIG. 14 are 16, 17, 18, 19, 20. , 21, 22, 23, 24, 25, 26, 27, 28,
When 29, 30, 31, 32, 33, 34, the intra-luminance prediction mode or the first intra-color difference prediction mode is halved in the horizontal direction centered on the vertical prediction (intra-prediction mode 26).
The value derived by scaling twice is used as the value of the second intra-color difference prediction mode.
The values of the second intra color difference prediction mode are 21, 21, 22, 22, 23, 23, respectively.
24, 24, 25, 25, 26, 27, 27, 28, 28, 29, 29, 30, 30. Further, the values of the intra-luminance prediction mode or the first intra-color difference prediction mode are 2, 3,
At 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15, the intra-luminance prediction mode or the first intra-color difference prediction mode is centered on horizontal prediction (intra-prediction mode 10). The value derived by scaling twice in the vertical direction and limiting it to 2 or more is the second value.
The value of the intra-color difference prediction mode of, and the value of the second intra-color difference prediction mode are 2, 2, 2,
2, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20.

Further, it is also possible to convert from the intra prediction mode (intra brightness prediction mode or the first intra color difference prediction mode) to the second intra color difference prediction mode by using the conversion table of FIG. 33. In the conversion table of FIG. 33, as shown by the dotted arrow in FIG. 34, the values of the intra-brightness prediction mode or the first intra-color difference prediction mode derived from the table of FIG. 14 are 21, 22, 23, 24, 25. , 26, 27, 28, 29, 30, 31, the intra-brightness prediction mode or the first intra-color difference prediction mode is scaled by half in the horizontal direction centered on the vertical prediction (intra-prediction mode 26). The value derived by this is used as the value of the second intra-color difference prediction mode, and the value of the second intra-color difference prediction mode is set to 23, respectively.
, 24, 24, 25, 25, 26, 27, 27, 28, 28, 29. Further, the values of the intra-luminance prediction mode or the first intra-color difference prediction mode are 7, 8, 9, 10, 11,
In the case of 12 and 13, the value derived by doubling the intra-brightness prediction mode or the first intra-color difference prediction mode in the vertical direction with respect to the horizontal prediction (intra-prediction mode 10) is used for the second intra-color difference prediction. The value of the mode is set, and the value of the second intra color difference prediction mode is set to 4, 6, 8, 10, 12, 14, and 16. Further, when the values of the intra-brightness prediction mode or the first intra-color difference prediction mode are 2, 3, 4, 5, and 6, subtract 3 from the intra-brightness prediction mode or the first intra-color difference prediction mode to make it 2 or more. The value derived by limiting is used as the value of the second intra-color difference prediction mode, and the value of the second intra-color difference prediction mode is set as 2, 2, 2, 2, 3. Further, when the values of the intra-brightness prediction mode or the first intra-color difference prediction mode are 14, 15, 16, 17, 18, 19, and 20, 3 is added to the intra-brightness prediction mode or the first intra-color difference prediction mode. The value derived by this is used as the value of the second intra-color difference prediction mode, and the value of the second intra-color difference prediction mode is set to 17,1.
Let it be 8, 19, 20, 21, 22. Further, when the values of the intra-luminance prediction mode or the first intra-color difference prediction mode are 32, 33, and 34, the intra-luminance prediction mode or the first intra-luminance prediction mode or the first
The value derived by subtracting 3 from the intra-color difference prediction mode of is used as the value of the second intra-color difference prediction mode, and the values of the second intra-color difference prediction mode are set to 29, 30, and 31.

When the color difference format is 4: 2: 2, the first intra color difference prediction mode corresponding to the conversion table of FIGS. 15 and 16 when converting from the first intra color difference prediction mode to the second intra color difference prediction mode to the first. The derivation processing procedure when converting to the intra-color difference prediction mode of No. 2 will be described with reference to the flowchart of FIG.

For each value from 0 to 34 of the first intra prediction mode IntraPredMode1, the second intra prediction mode IntraPredMode2 is derived by the procedure of the flowchart of FIG.

First, when it is not angle prediction, that is, when the first intra prediction mode IntraPredMode1 is 1 or less (NO in step S3001 in FIG. 23), the first intra prediction mode IntraPredMod
The value of e1 is set as the second intracolor difference prediction mode IntraPredMode2 (step S3002 in FIG. 23), and the derivation process is completed. 1st IntraPredMode1 is 1
The following are plane prediction predicted by interpolating pixel values from the surrounding decoded blocks (intraPredMode1 = 0), and mean value prediction predicted by deriving the mean value from the surrounding decoded blocks (intraPredMode1 = 0). IntrapredMode1 = 1).

On the other hand, when the first intra color difference prediction mode IntraPredMode1 is angle prediction, that is, when it is larger than 1 (YES in step S3001 in FIG. 23), the first intra color difference prediction mode to the second intra color difference prediction mode after step S3003. Performs conversion processing to.
When IntraPredMode1 is smaller than 18 (step S3 in FIG. 23).
003 YES), the angle of the first intraprediction corresponding to the first intracolor difference prediction mode IntraPredMode1 IntraPredAngle1 is doubled to obtain the angle of intraprediction IntraPredAngle2'(step S3004 in FIG. 23). Further, the value of the intra-brightness prediction mode or the first intra-color difference prediction mode IntraPredMode1 corresponding to the first intra-prediction angle IntraPredAngle1 close to the intra-prediction angle IntraPredAngle2'is set to the second intra-prediction mode IntraPre.
Set to dMode2 (step S3005 in FIG. 23), and end the derivation process. However, the first
If the intra prediction mode of is 2, 3, 4 and 5, the angle of intra prediction IntraPredAngle2'
The value of is −32 or less, the angle of intra prediction at that time is −32, and the second intra color difference prediction mode is 2. When the first intra prediction mode is 15, 16 and 17, the value of the intra prediction angle IntraPredAngle2'is 32 or more, but the intra prediction angle at that time is 32 and the second intra color difference prediction mode is 18. And. As shown in FIG. 19, when the angle of the intra prediction corresponding to 16 in the first intra prediction mode is doubled in the vertical direction, the intra prediction mode takes a value close to the angle of the intra prediction corresponding to 19. When the angle of the intra prediction corresponding to 17 in the first intra prediction mode is doubled in the vertical direction, the intra prediction mode takes a value close to the angle of the intra prediction corresponding to 20. Therefore, as shown in FIG. 19, when the first intra prediction mode is 16, the second intra prediction mode is set to 19.
When the first intra prediction mode is 17, the second intra prediction mode can be set to 20.

On the other hand, when the intra color difference prediction mode IntraPredMode1 is not smaller than 18, that is, when it is 18 or more (NO in step S3003 in FIG. 23), the first intra color difference prediction mode IntraP
The first intra-prediction angle IntraPredAngle1 corresponding to redMode1 is multiplied by 1/2 to obtain the intra-prediction angle IntraPredAngle2'(steps S3006 to S3007 in FIG. 23). In this embodiment, it has a value of -1 when it is negative and 1 when it is positive or the variable a is 0, depending on the positive and negative signs of the angle IntraPredAngle1 of the first intra prediction corresponding to the first intracolor difference prediction mode IntraPredMode1. Set a value in the variable SignIntraPredAngle (step S3006 in FIG. 23).
The absolute value of the first intracolor difference prediction mode IntraPredMode1 is multiplied by the variable SignIntraPredAngle by the result of performing a 1-bit right shift operation equivalent to 1/2 times, and the angle of intraprediction IntraPre
Set to dAngle2'(step S3007 in FIG. 23). The variable SignIntraPredAngle is multiplied by the result of performing a 1-bit right shift operation equivalent to 1/2 times after adding 1 to the absolute value of the first intra-color difference prediction mode IntraPredMode1, and set to the intra-prediction angle IntraPredAngle2'. You may. Further, the intra-prediction mode (upper part of FIG. 8) corresponding to the intra-prediction angle (lower part of FIG. 8) prepared in the intra-luminance prediction mode close to the intra-prediction angle IntraPredAngle2'and the first intra-color difference prediction mode. Set the value to the second intra prediction mode In
Set to traPredMode2 (step S3008 in FIG. 23), and end this derivation process. Intra Prediction Angle When rounding the value of IntraPredAngle2'to the Intra Prediction Angle provided in the Intra Luminance Prediction Mode and the First Intra Color Difference Prediction Mode, the Intra Prediction Angle Intr
It may be rounded to the value closest to aPredAngle2', rounded, rounded up, or rounded down. Further, the same positive and negative signs as the intraprediction angle IntraPredAngle2'may be set in the value obtained by rounding, rounding up, or rounding down the absolute value of the intraprediction angle IntraPredAngle2'.

If the first intra-color difference prediction mode doubles the angle of 25 intra-prediction by 1/2,-
It becomes 1, and -1 can be rounded (converted) to both the value of -2 corresponding to the value of the intra prediction mode of 25 and the value of 0 corresponding to the value of the intra prediction mode of 26, but the vertical prediction is performed. Since 26 shown can always be encoded, it is set to 25 when the first intra-color difference prediction mode converts 25 to the second intra-color difference prediction mode. The first intra-color difference prediction mode becomes 1 when the angle of the intra-prediction of 27 is multiplied by 1/2, and either the value of the intra-prediction mode is 0 corresponding to 26 or the value of the intra-prediction mode is 2 corresponding to 27. Can be rounded (converted) to, but 26, which indicates a vertical prediction, can always be encoded, so
When the first intra-color difference prediction mode converts 27 to the second intra-color difference prediction mode, it is set to 27. That is, when converting from the first intra color difference prediction mode to the second intra color difference prediction mode using the conversion tables shown in FIGS. 15, 16, 17, 30, and 33, the first intra color difference is used. When the prediction mode is not 26, which is the vertical prediction, the second intra color difference prediction mode is derived from the first intra color difference prediction mode by converting the vertical prediction 26 into a value that avoids it. That is, it can be derived from the syntax elements of the intra-color difference prediction mode (0, 1, 2, 3 in FIGS. 14 and 25) selected when the value of the intra-luminance prediction mode and the value of the intra-color difference prediction mode do not match. Values (0, 1, 10, 26, 34)
Convert to avoid. By setting in this way, the range of selection of the intra color difference prediction mode is widened, and the coding efficiency can be improved.

In steps S3005 and S3008, the angle of intra prediction IntraPredA
By setting the value of the intra-brightness prediction mode or the first intra-color difference prediction mode IntraPredMode1 corresponding to the first intra-prediction angle IntraPredAngle1 close to ngle2'to the second intra-prediction mode IntraPredMode2, the color difference format 4: 2: When the intra prediction calculation of the color difference signal in 2 is implemented by hardware, the intra prediction calculation using the second intra color difference prediction mode is performed in the intra luminance prediction mode or the first intra color difference prediction mode IntraPre.
Since it can be realized only by the intra-prediction angle corresponding to dMode1, it can be performed without adding hardware by a new intra-prediction angle.

For this angle prediction, vertical prediction that predicts vertically from the above decoded block (intrapredMode1 = 26) and horizontal prediction that predicts horizontally from the left decoded block (intrapredMode1 = 26) 10) is also included. However, vertical prediction,
And the horizontal prediction does not change even if the conversion process from the first intra color difference prediction mode to the second intra color difference prediction mode after step S3003 is performed. Therefore, step S3
In the condition determination of 001, the process may proceed to step S3002 in the case of vertical prediction and horizontal prediction.

When the color difference format is 4: 2: 2, the derivation processing procedure for converting from the first intra color difference prediction mode corresponding to the conversion table of FIG. 17 to the second intra color difference prediction mode will be described with reference to the flowchart of FIG. To do.

When it is not angle prediction, that is, when the first intra prediction mode IntraPredMode1 is 1 or less (NO in step S3101 in FIG. 24), the value of the first intra prediction mode IntraPredMode1 is used as it is as the second intracolor difference prediction mode IntraPredMode2 (NO in step S3101 of FIG. 24). Step S3 of FIG. 24
102), the present derivation process is terminated.

On the other hand, when the first intra color difference prediction mode IntraPredMode1 is angle prediction, that is, when it is larger than 1 (YES in step S3101 in FIG. 24), the first intra color difference prediction mode to the second intra color difference prediction mode after step S3103. Performs conversion processing to.
When the first intra color difference prediction mode IntraPredMode1 is smaller than 18 (YES in step S3103 of FIG. 24), the first intra color difference prediction mode derived from the table of FIG. 14 is centered on the horizontal prediction (intra prediction mode 10). The value derived by scaling twice in the vertical direction is used as the value of the second intra-color difference prediction mode (step S in FIG. 32).
3304 to S3307). A value obtained by subtracting 10 indicating horizontal prediction from the first intracolor difference prediction mode IntraPredMode1 is set in the variable a (step S3104 in FIG. 24). Subsequently, the value obtained by doubling the variable a is set in the variable b (step S3105 in FIG. 24).
.. Subsequently, the value obtained by adding 10 indicating the horizontal prediction to b is set in the variable c (step S3106 in FIG. 24). Subsequently, the value obtained by limiting the value of the variable c to 2 or more and 18 or less is set in the second intra prediction mode IntraPredMode2 (step S3107 in FIG. 24), and the derivation process is terminated. Specifically, when the variable c is 2 or more and less than 18, the intra prediction mode In
Set the variable c as it is to the value of traPredMode2, if the variable c is less than 2, set the intrapredmode mode IntraPredMode2 to 2, and if the variable c exceeds 18, the intra prediction mode IntraP
Set redMode2 to 18. That is, when the value derived by scaling the mode number of the angle prediction of the first intra-color difference prediction mode is out of the range of the mode number of the angle prediction defined in the intra-prediction mode, the derived value is used. Set the value within that range. As a result, when the intra prediction calculation of the color difference signal in the color difference format 4: 2: 2 is implemented by hardware, the intra prediction calculation using the second intra color difference prediction mode can be performed without adding hardware. Can be done.

On the other hand, when the first intra color difference prediction mode IntraPredMode1 is not smaller than 18, that is, 18 or more (NO in step S3103 of FIG. 24), the first intra color difference prediction mode derived from the table of FIG. 14 is vertically predicted. The value derived by scaling the (intra-prediction mode 26) in the horizontal direction by half is used as the value of the second intra-color difference prediction mode (steps S3108 to S3112 in FIG. 24). A value obtained by subtracting 26 indicating vertical prediction from the first intracolor difference prediction mode IntraPredMode1 is set in the variable a (step S3108 in FIG. 24). Then, depending on the positive and negative signs of the variable a, if it is negative-1,
Set a value to the variable SignIntraPredMode, which has a value of 1 when it is positive or the variable a is 0 (FIG. 24).
Step S3109). Subsequently, the value obtained by multiplying the absolute value of the variable a by the variable SignIntraPredMode with the result of performing a 1-bit right shift operation equivalent to 1/2 times is set in the variable b (step S3110 in FIG. 24). Note that the variable b may be set to a value obtained by multiplying the result of performing a 1-bit right shift operation equivalent to 1/2 times the absolute value of the variable a by the variable SignIntraPredMode. Then, the value obtained by adding 26 indicating the vertical prediction to b is the variable c.
Is set to (step S3111 in FIG. 24). Subsequently, the value of the variable c is set to the second intra prediction mode IntraPredMode2 (step S3112 in FIG. 24), and the derivation process is terminated. When the value of the variable c corresponding to 25 in the first intra-color difference prediction mode is 26, the first intra-color difference prediction mode is set to avoid 26, which indicates vertical prediction that can always be encoded. When converting 25 to the second intra color difference prediction mode, it is set to 25. 1st
When the value of the variable c corresponding to the intra color difference prediction mode of 27 is 26, the first intra color difference prediction mode is 27 to the second, avoiding 26 indicating the vertical prediction that can always be encoded. When converting to the intra-color difference prediction mode of, 27 is set. That is, it can be derived from the syntax elements of the intra-color difference prediction mode (0, 1, 2, 3 in FIGS. 14 and 25) selected when the value of the intra-luminance prediction mode and the value of the intra-color difference prediction mode do not match. Round (convert) to avoid values (0, 1, 10, 26, 34).
By setting in this way, the range of selection of the intra color difference prediction mode is widened, and the coding efficiency can be improved. In this derivation processing procedure, a value that can be derived from the syntax element of the intra color difference prediction mode (1 of FIGS. 14 and 25) selected when the value of the intra brightness prediction mode and the value of the intra color difference prediction mode do not match. In order to convert so as to avoid 26, 1 is added to the absolute value of the variable a in step S3110 before the 1-bit right shift operation is performed on the absolute value of the variable a.

When the color difference format is 4: 2: 2, the derivation processing procedure for converting from the first intra color difference prediction mode corresponding to the conversion table of FIG. 30 to the second intra color difference prediction mode will be described with reference to the flowchart of FIG. To do.

When it is not angle prediction, that is, when the first intra prediction mode IntraPredMode1 is 1 or less (NO in step S3301 in FIG. 32), the value of the first intra prediction mode IntraPredMode1 is used as it is as the second intracolor difference prediction mode IntraPredMode2 (NO). Step S3 of FIG.
302), the present derivation process is terminated.

On the other hand, when the first intra color difference prediction mode IntraPredMode1 is angle prediction, that is, when it is larger than 1 (YES in step S3301 in FIG. 32), the first intra color difference prediction mode to the second intra color difference prediction mode after step S3303 Performs conversion processing to.
When the first intracolor difference prediction mode IntraPredMode1 is smaller than 16, that is, 15 or less (YES in step S3303 in FIG. 32), the first derived from the table in FIG.
Intra color difference prediction mode of 2 in the vertical direction centered on horizontal prediction (intra prediction mode 10)
The value derived by scaling to a factor of 2 and limiting to 2 or more is used as the value of the second intra-color difference prediction mode (steps S3304 to S3307 in FIG. 32). A value obtained by subtracting 10 indicating horizontal prediction from the first intracolor difference prediction mode IntraPredMode1 is set in the variable a (step S3304 in FIG. 32). Subsequently, the value obtained by doubling the variable a is set in the variable b (step S3305 in FIG. 32). Subsequently, the value obtained by adding 10 indicating the horizontal prediction to b is set in the variable c (step S3306 in FIG. 32). Then, the value of the variable c is set to 2.
The value obtained by limiting the above is set to the second intra prediction mode IntraPredMode2 (FIG. 32).
Step S3307), the present derivation process is completed. Specifically, when the variable c is 2 or less,
The value of IntraPredMode2 is set to 2. That is, when the value derived by scaling the mode number of the angle prediction of the first intra-color difference prediction mode is out of the range of the mode number of the angle prediction defined in the intra-prediction mode, the derived value is used. Set the value within that range. As a result, when the intra prediction calculation of the color difference signal in the color difference format 4: 2: 2 is implemented by hardware, the intra prediction calculation using the second intra color difference prediction mode can be performed.
It can be done without adding any hardware.

On the other hand, when the first intra color difference prediction mode IntraPredMode1 is not smaller than 16, that is, 16 or more (NO in step S3303 in FIG. 32), the first intra color difference prediction mode derived from the table in FIG. 14 is vertically predicted. The value derived by scaling the (intra-prediction mode 26) in the horizontal direction by half is used as the value in the second intra-color difference prediction mode (steps S3308 to S3312 in FIG. 32). A value obtained by subtracting 26 indicating vertical prediction from the first intracolor difference prediction mode IntraPredMode1 is set in the variable a (step S3308 in FIG. 32). Then, depending on the positive and negative signs of the variable a, if it is negative-1,
Positive or when the variable a is 0 Set the value to the variable SignIntraPredMode which has a value of 1 (FIG. 32).
Step S3309). Subsequently, the value obtained by multiplying the absolute value of the variable a by the variable SignIntraPredMode with the result of performing a 1-bit right shift operation equivalent to 1/2 times is set in the variable b (
Step S3310 in FIG. 32). Note that the variable b may be set to a value obtained by multiplying the result of performing a 1-bit right shift operation equivalent to 1/2 times the absolute value of the variable a by the variable SignIntraPredMode. Subsequently, the value obtained by adding 26 indicating the vertical prediction to b is set in the variable c (step S3311 in FIG. 32). Subsequently, the value of the variable c is set to the second intra prediction mode IntraPredMode2 (step S3312 in FIG. 32), and the derivation process is terminated. When the value of the variable c corresponding to 25 in the first intra-color difference prediction mode is 26, the first intra-color difference prediction mode is set to avoid 26, which indicates vertical prediction that can always be encoded. When converting 25 to the second intra color difference prediction mode, it is set to 25.
When the value of the variable c corresponding to 27 in the first intra-color difference prediction mode is 26, the first intra-color difference prediction mode is 27, avoiding 26, which indicates a vertical prediction that can always be encoded. When converting to the second intra color difference prediction mode, it is set to 27. That is, FIG.
5. When converting from the first intra color difference prediction mode to the second intra color difference prediction mode using the conversion tables shown in FIGS. 16, 17, 30, and 33, the first intra color difference prediction mode is selected. If it is not the vertical prediction 26, the second intra color difference prediction mode is derived from the first intra color difference prediction mode by converting the vertical prediction 26 into a value that avoids it. That is, the syntax element of the intra-color difference prediction mode selected when the value of the intra-luminance prediction mode and the value of the intra-color difference prediction mode do not match (0 in FIGS. 14 and 25,
Round to avoid values (0, 1, 10, 26, 34) that can be derived from 1, 2, 3) (
Convert). In this derivation processing procedure, a value that can be derived from the syntax element of the intra-color difference prediction mode (1 of FIGS. 14 and 25) selected when the value of the intra-luminance prediction mode and the value of the intra-color difference prediction mode do not match. To convert to avoid 26
In step S3310, 1 is added to the absolute value of the variable a before the 1-bit right shift operation is performed on the absolute value of the variable a.

In the step S3303 of this derivation processing procedure, the intra color difference prediction mode IntraP
When redMode1 is less than 16, that is, 15 or less, the first intracolor difference prediction mode is derived by scaling twice in the vertical direction around the horizontal prediction (intra prediction mode 10) and limiting it to 2 or more. Let the value be the value of the second intra color difference prediction mode (steps S3304 to S3307 in FIG. 32), and when the intra color difference prediction mode IntraPredMode1 is not smaller than 16, that is, 16 or more, the first intra color difference prediction mode is vertically predicted. The value derived by scaling in the horizontal direction by half with respect to (Intra prediction mode 26) was used as the value of the second intra color difference prediction mode (steps S3308 to S3 in FIG. 32).
312) Intra color difference prediction mode When IntraPredMode1 is smaller than 15, that is, 14 or less, the first intra color difference prediction mode is derived by doubling the horizontal prediction (intra prediction mode 10) in the vertical direction. The value obtained is used as the value of the second intra color difference prediction mode (steps S3304 to S3307 in FIG. 32), and the intra color difference prediction mode Intr is used.
When aPredMode1 is not less than 15, that is, 15 or more, the value derived by scaling the first intra-color difference prediction mode by half in the horizontal direction around the vertical prediction (intra-prediction mode 26) is obtained. It may be used as the value of the second intra-color difference prediction mode (FIG. 32).
Steps S3308 to S3312), the conversion result is the same. This is because when the intracolor difference prediction mode IntraPredMode1 is 15, the value derived by doubling the first intracolor difference prediction mode in the vertical direction centering on the horizontal prediction (intra prediction mode 10) and the first intracolor difference. This is because the values derived by scaling the prediction mode by half in the horizontal direction around the vertical prediction (intra prediction mode 26) are equal.

Next, in the color difference format of 4: 2: 2, the first one corresponding to the conversion table of FIG. 33.
The derivation processing procedure when converting from the intra-color difference prediction mode to the second intra-color difference prediction mode will be described with reference to the flowchart of FIG. 35.

When it is not angle prediction, that is, when the first intra prediction mode IntraPredMode1 is 1 or less (NO in step S3401 in FIG. 35), the value of the first intra prediction mode IntraPredMode1 is used as it is as the second intracolor difference prediction mode IntraPredMode2 (NO in step S3401 of FIG. 35). Step S3 of FIG. 35
402), this derivation process is terminated.

On the other hand, when the first intra color difference prediction mode IntraPredMode1 is angle prediction, that is, when it is larger than 1 (YES in step S3401 in FIG. 35), the first intra color difference prediction mode to the second intra color difference prediction mode after step S3403 Performs conversion processing to.
When the first intra color difference prediction mode IntraPredMode1 is smaller than 7, that is, 6 or less (YES in step S3403 in FIG. 35), the first intra color difference prediction mode IntraPredMod
The value obtained by subtracting 3 indicating the horizontal prediction from e1 is set in the variable c (step S in FIG. 35).
3407). Subsequently, the value obtained by limiting the value of the variable c to 2 or more is set in the second intra prediction mode IntraPredMode2 (step S3408 in FIG. 35), and this derivation process is terminated.
Specifically, when the variable c is 2 or more, the variable c is set as it is in the intrapredation mode IntraPredMode2, and when the variable c is less than 2, the intraprediction mode IntraPredMode2 is set to 2. That is, when the value derived by scaling the mode number of the angle prediction of the first intra-color difference prediction mode is out of the range of the mode number of the angle prediction defined in the intra-prediction mode, the derived value is used. Set the value within that range. As a result, when the intra prediction calculation of the color difference signal in the color difference format 4: 2: 2 is implemented by hardware, the intra prediction calculation using the second intra color difference prediction mode can be performed without adding hardware. Can be done.

On the other hand, when the first intra color difference prediction mode IntraPredMode1 is not smaller than 7, and the first intra color difference prediction mode IntraPredMode1 is smaller than 14, that is, 7 or more and 13 or less (
NO in step S3403 of FIG. 35 and YES in step S3404), horizontal prediction of the first intra color difference prediction mode derived from the table of FIG. 14 (intra prediction mode 10).
The value derived by doubling in the vertical direction with respect to the center is used as the value of the second intra-color difference prediction mode (steps S3409 to S3412 in FIG. 35). A value obtained by subtracting 10 indicating horizontal prediction from the first intracolor difference prediction mode IntraPredMode1 is set in the variable a (step S3409 in FIG. 35). Then, the value obtained by doubling the variable a is the variable b.
Is set to (step S3410 in FIG. 35). Subsequently, the value obtained by adding 10 indicating the horizontal prediction to b is set in the variable c (step S3411 in FIG. 35). Subsequently, the value of the variable c is set to the second intra prediction mode IntraPredMode2 (step S3412 in FIG. 35).
This derivation process ends.

On the other hand, when the first intra color difference prediction mode IntraPredMode1 is not smaller than 14, but smaller than 21, that is, 14 or more and 20 or less (NO in step S3404 in FIG. 35 and YES in step S3405), the first intra color difference prediction mode The value obtained by adding 3 to IntraPredMode1 is set in the variable c (step S3413 in FIG. 35). Subsequently, the value of the variable c is set to the second intra prediction mode IntraPredMode2 (step S3414 in FIG. 35), and the derivation process is terminated.

On the other hand, when the first intracolor difference prediction mode IntraPredMode1 is not smaller than 21, but smaller than 32, that is, 21 or more and 31 or less (NO in step S3405 in FIG. 35 and YES in step S3406), it is derived from the table in FIG. The value derived by scaling the first intra-color difference prediction mode by half in the horizontal direction around the vertical prediction (intra-prediction mode 26) is used as the value of the second intra-color difference prediction mode (Fig.). 35 steps S3415 to S3419). The value obtained by subtracting 26 indicating vertical prediction from the first intracolor difference prediction mode IntraPredMode1 is set in the variable a (step S3415 in FIG. 35).
). Subsequently, a value is set in the variable SignIntraPredMode having a value of -1 when negative and 1 when positive or variable a is 0 according to the positive and negative signs of the variable a (step S3416 in FIG. 35). Then, the variable SignIn is the result of performing a 1-bit right shift operation equivalent to half the absolute value of the variable a.
The value obtained by multiplying traPredMode is set in the variable b (step S3417 in FIG. 35).
.. Note that the variable b may be set to a value obtained by multiplying the result of performing a 1-bit right shift operation equivalent to 1/2 times the absolute value of the variable a by the variable SignIntraPredMode. Subsequently, the value obtained by adding 26 indicating the vertical prediction to b is set in the variable c (step S3418 in FIG. 35). Subsequently, the value of the variable c is set to the second intra prediction mode IntraPredMode2 (step S3419 in FIG. 35), and the derivation process is terminated. When the value of the variable c corresponding to 25 in the first intra-color difference prediction mode is 26, the first intra-color difference prediction mode is set to avoid 26, which indicates vertical prediction that can always be encoded. 25 second
When converting to the intra-color difference prediction mode of, 25 is set. When the value of the variable c corresponding to 27 in the first intra-color difference prediction mode is 26, the first intra-color difference prediction mode is 27, avoiding 26, which indicates a vertical prediction that can always be encoded. When converting to the second intra color difference prediction mode, it is set to 27. That is, it can be derived from the syntax elements of the intra-color difference prediction mode (0, 1, 2, 3 in FIGS. 14 and 25) selected when the value of the intra-luminance prediction mode and the value of the intra-color difference prediction mode do not match. Values (0, 1, 10,
Round (convert) to avoid 26, 34). In this derivation processing procedure, a value that can be derived from the syntax element of the intra color difference prediction mode (1 of FIGS. 14 and 25) selected when the value of the intra brightness prediction mode and the value of the intra color difference prediction mode do not match. In order to convert so as to avoid 26, 1 is added to the absolute value of the variable a in step S3417 before the 1-bit right shift operation is performed on the absolute value of the variable a.

On the other hand, when the first intra color difference prediction mode IntraPredMode1 is not smaller than 32, that is, 32 or more (NO in step S3416 of FIG. 35), the first intra color difference prediction mode
The value obtained by subtracting 3 from IntraPredMode1 is set in the variable c (step S3 in FIG. 35).
420). Subsequently, the value of the variable c is set to the second intra prediction mode IntraPredMode2 (step S3421 in FIG. 35), and this derivation process is terminated.

In the step S3403 of this derivation processing procedure, the intra color difference prediction mode IntraP
When redMode1 is 6 or less, the value obtained by subtracting 3 from the first intra color difference prediction mode is limited to 2 or more to set the second intra color difference prediction mode. However, for simplification, step S
By omitting the condition judgment of 3403, the intracolor difference prediction mode IntraPredMode1 is 7 or more and 13 or less, and the intracolor difference prediction mode IntraPredMode1 is 6 or less.
The value derived by scaling the first intra-color difference prediction mode twice in the vertical direction around the horizontal prediction (intra-prediction mode 10) can also be used as the value of the second intra-color difference prediction mode (FIG. 35). Steps S3409 to S3412). However, step S3
In 412, as in S3408, the variable c derived in step S3411 is limited to 2 or more to set the second intra color difference prediction mode.

Further, in step S3406 of this derivation processing procedure, the intra color difference prediction mode Intr
When aPredMode1 is 32 or more, the value obtained by subtracting 3 from the first intra color difference prediction mode is set as the second intra color difference prediction mode, but for the sake of simplification, the condition determination in step S3406 is omitted. , Intra color difference prediction mode IntraPredMode1 is 21 or more and 31 or less, and even when the intra color difference prediction mode IntraPredMode1 is 32 or more, the first intra color difference prediction mode is horizontal centering on vertical prediction (intra prediction mode 26). The value derived by scaling in half in the direction can also be used as the value of the second intra-color difference prediction mode (steps S3415 to S3419 in FIG. 35).

On the other hand, when the color difference format is 4: 2: 0 or 4: 4: 4, the ratio of the intra-prediction direction of the luminance signal and the horizontal and vertical sampling ratios of the color difference signal match, so the table of FIG. 14 is used. It is not necessary to convert the derived first intra-color difference prediction mode to the second intra-color difference prediction mode. This will be described with reference to FIG. FIG. 22 is a diagram for explaining the correspondence between the luminance signal when the color difference format is 4: 2: 0 and the prediction direction of the intra prediction of the color difference signal. FIG. 22A shows the arrangement of the brightness signal and the color difference signal when the color difference format is 4: 2: 0, and the color difference signal is sampled at 1/2 both horizontally and vertically with respect to the brightness signal ( It is sampled), and the aspect ratio of the pixels of the brightness signal and the color difference signal is the same. The arrow from the pixel P4 to the pixel P5 shown by reference numeral 2704 indicates the intra prediction direction of the pixel P4 of the luminance signal. The arrow from pixel P1 to pixel P2 shown by reference numeral 2705 indicates the intra prediction direction of pixel P1 of the color difference signal. The arrow from pixel P4 to pixel P5 shown by reference numeral 2704 and the arrow from pixel P1 to pixel P2 shown by reference numeral 2705 point in the same direction, and the intra prediction directions are the same. In this case, even in the arrangement of the color difference signals shown in FIG. 22B, the intra prediction direction of the luminance signal is the same as the intra prediction direction of the color difference signal as shown by reference numeral 2706, and the reference destination of the pixel P1 of the color difference signal. Pixel P2 can be referred to correctly.

In addition, when the intra prediction unit 103 also predicts the value of the intra color difference prediction mode in consideration of the above points, the value of the intra brightness prediction mode of the prediction block at the same position as the prediction block of the color difference signal according to the color difference format. Predict the value of the intra color difference prediction mode from. That is, the color difference format in which the aspect ratios of the pixels of the luminance signal and the color difference signal are the same is 4: 2: 0.
Or, when predicting the value of the intra color difference prediction mode in 4: 4: 4, the value of the intra color difference prediction mode obtained from the table of FIG. 14 is used as it is, and the color difference format is 4: 2: 0 or 4.
The value of the intra-color difference prediction mode for 4: 4 is used, and the intra-prediction of the color difference signal is performed according to this intra-color difference prediction mode. When predicting the value of the intra color difference prediction mode with a color difference format of 4: 2: 2, the intra obtained from the table of FIG. 14 by the conversion table shown in FIGS. 15, 16, 17, 30, or 33. The value of the intra color difference prediction mode for the color difference format 4: 2: 2 is derived from the value of the color difference prediction mode, and the intra prediction of the color difference signal is performed according to this intra color difference prediction mode.

FIG. 25 shows the values of the intra_chroma_pred_mode [x0] [y0] syntax elements related to the intra-color difference prediction mode from the values of the intra-color difference prediction mode and the intra-luminance prediction mode values of the luminance signal prediction block at the same position as the color difference signal prediction block. It is a table to be derived, and the table of FIG. 25 used on the coding side corresponds to the table of FIG. 14 used on the decoding side. Using the table shown in FIG. 25, on the encoding side, the syntax element intra_chroma_pred_mo
Derive the values of de [x0] [y0].

When the value of the first or second intra-color difference prediction mode is 0, if the value of the intra-luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal is not 0, the syntax element intra_chroma_pred_mode [x0] [y0] ] Value takes a value of 0, and if the value of the intra-luminance prediction mode is 0, the value of the syntax element intra_chroma_pred_mode [x0] [y0] takes a value of 4.

When the value of the first or second intra-color difference prediction mode is 26, the syntax element intra_chroma_pred_mode [x0] [y0] unless the value of the intra-luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal is 26. ] Is a value of 1, and if the value of the intra-brightness prediction mode is 26, the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 4.
Take the value of.

When the value of the first or second intra-color difference prediction mode is 10, the value of the intra-luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal is not 10, the syntax element intra_chroma_pred_mode [x0] [y0] ] Is a value of 2, and if the value of the intra-brightness prediction mode is 10, the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 4.
Take the value of.

When the value of the first or second intra-color difference prediction mode is 1, the value of the intra-luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal is not 10, the syntax element intra_chroma_pred_mode [x0] [y0] ] Values take a value of 3, and if the value of the intra-luminance prediction mode is 10, the value of the syntax element intra_chroma_pred_mode [x0] [y0] takes a value of 4.

When the value of the first intra-color difference prediction mode is 34, the syntax element intra_ unless the value of the intra-luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal is 0.
The value of chroma_pred_mode [x0] [y0] takes a value of 0, and if the value of the intra-luminance prediction mode is 1, the value of the syntax element intra_chroma_pred_mode [x0] [y0] takes a value of 1 and the intra-luminance prediction. If the mode value is 2, the syntax element intra_chroma_pred_mode [x0
] [Y0] has a value of 2 and if the value of the intra-brightness prediction mode is 3, the value of the syntax element intra_chroma_pred_mode [x0] [y0] has a value of 3 and the value of the intra-brightness prediction mode If is 34, the value of the syntax element intra_chroma_pred_mode [x0] [y0] takes a value of 4.

If the value of the first intra-color difference prediction mode is the same as the value of the intra-luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal, the syntax element intra_chroma_pred_mode
The value of [x0] [y0] takes a value of 4. However, when the color difference format is 4: 2: 2 and the value of the intra color difference prediction mode is predicted, the intra prediction unit 103 uses FIGS. 15, 16, and 17.
, From the first intracolor difference prediction mode for color difference format 4: 2: 0 or 4: 4: 4 to the second for color difference format 4: 2: 2, according to the conversion table shown in FIG. 30 or FIG.
The intra color difference prediction mode is derived, and the second intra color difference prediction mode is used for the intra prediction of the color difference signal for the color difference format 4: 2: 2.

When specifying the prediction block of the luminance signal at the same position as the prediction block of the color difference signal, it may be specified by referring to the division index PartIdx that specifies each prediction block, or of each prediction block. It may be specified by referring to the coordinates indicating the position.

The number of intra color difference prediction modes of the prediction block in the coding block differs depending on the combination of the division mode and the color difference format supplied from the color difference format setting unit 101. When the division mode is 2N × 2N division, the value of the syntax element related to the intra color difference prediction mode of one prediction block is derived for each coding block regardless of the type of color difference format.

When the division mode is N × N division and the color difference format is 4: 2: 0, the value of the syntax element related to the intra color difference prediction mode of one prediction block for each coded block is derived. When the division mode is N × N division and the color difference format is 4: 2: 2, the values of the syntax elements related to the intra color difference prediction mode of two prediction blocks are derived for each coded block. When the division mode is N × N division and the color difference format is 4: 4: 4, the values of the syntax elements related to the intra color difference prediction mode of four prediction blocks are derived for each coded block. FIG. 11 is a diagram illustrating a method of dividing a color difference signal of a coded block into a prediction block by N × N division at the time of intra prediction. FIG. 11 (a) shows the luminance signal in the N × N division, and FIG. 11 (b) shows the color difference signal in the N × N division when the color difference format is 4: 2: 0.
FIG. 11C shows a color difference signal in N × N division when the color difference format is 4: 2: 2, and FIG. 11 (d) shows N × N when the color difference format is 4: 4: 4. The color difference signal in the division is shown. When the color difference format is 4: 2: 0, 4: 4: 4, the coded block of the luminance signal and the coded block of the color difference signal are similar, and the aspect ratios of both blocks are the same. When the color difference format is 4: 2: 2, the coded block of the luminance signal and the coded block of the color difference signal are not similar, and the aspect ratios of both coded blocks are different. The color difference format is 4: 2: 0
Similar to the case of, even when the color difference format is 4: 2: 2 or 4: 4: 4, the coded block is not divided into one prediction block in the color difference signal whose division mode is N × N division. You can also do it. As in the case where the color difference format is 4: 0: 0, even when the color difference format is 4: 2: 2 or 4: 4: 4, the coding block is used in the color difference signal whose division mode is N × N division. It is also possible to make one prediction block without dividing it.

The syntax element derivation unit 124 related to the inter-prediction information derives and derives the value of the syntax element related to the inter-prediction information for each prediction block when the prediction mode (PredMode) of the coded block is inter-prediction (MODE_INTER). The value of each syntax element is supplied to the entropy encoding unit 126. The inter-prediction information for each prediction block includes information such as an inter-prediction mode (L0 prediction, L1 prediction, both predictions), an index for identifying a plurality of reference images, and a motion vector.

The entropy coding unit 126 derives the value of the syntax element related to the coding information of the coding block unit supplied from the syntax element derivation unit 121 related to the coding information of the coding block unit, and the syntax element derivation of the intra-luminance prediction mode. The value of the syntax element for the intra-luminance prediction mode of the luminance signal prediction block supplied by unit 122,
The value of the syntax element related to the intra color difference prediction mode of the prediction block of the color difference signal supplied from the syntax element derivation unit 123 related to the intra color difference prediction mode, and the prediction block unit supplied from the syntax element derivation unit 124 related to the inter prediction information. Entropy-encodes the value of the syntax element for the inter-prediction information in according to the default syntax rules. At that time, the intra prediction mode coding control unit 125 controls the order of entropy coding in the intra brightness prediction mode and the intra color difference prediction mode according to the division mode and the color difference format, and the entropy coding unit 126 controls the entropy coding order. The entropy coding processing of the intra-brightness prediction mode and the intra-color difference prediction mode is performed in the order specified by the coding control unit 125.

Next, regarding the coding block performed by the second coded stream decoding unit 203 of FIG. 2 and the decoding process of the coded information in units of prediction blocks, focusing on the points related to the intra prediction mode, which is a feature of the embodiment. Explain to. FIG. 13 is a block diagram showing the configuration of the second coded stream decoding unit 203 of FIG.

As shown in FIG. 13, the second coded stream decoding unit 203 of FIG. 2 includes an intra prediction mode decoding control unit 221, an entropy decoding unit 222, a coded information derivation unit 223 for each coded block, and an intra-luminance prediction mode. Derivation unit 224, intra-color difference prediction mode derivation unit 22
5. It is composed of an inter-prediction information derivation unit 226. In each unit constituting the second coded stream decoding unit 203, processing is performed according to the color difference format information supplied from the color difference format management unit 205, and codes such as a prediction mode and a division mode for each coded block are performed. Processing is performed according to the conversion information.

The entropy decoding unit 222 entropy-decodes the coded block supplied from the coded stream separation unit 201 and the second coded stream including the coded information in units of predicted blocks according to a predetermined syntax rule, and encodes the coded block. The value of the syntax element for the coded information in block units, the value of the syntax element for the intra-luminance prediction mode of the luminance signal prediction block, the value of the syntax element for the intra-luminance prediction mode of the color difference signal prediction block, and the prediction block. Get the value of the syntax element for the unit inter-prediction information. At that time, the intra prediction mode decoding control unit 221 controls the order of entropy decoding of the intra brightness prediction mode and the intra color difference prediction mode according to the division mode and the color difference format, and the entropy decoding unit 222 controls the intra prediction mode decoding control unit. The entropy decoding processing of the intra-brightness prediction mode and the intra-color difference prediction mode is performed in the order specified in 221. The intra prediction mode decoding control unit 221 is a control unit corresponding to the intra prediction mode coding control unit 125 on the coding side, and is an intra prediction mode set by the intra prediction mode coding control unit 125 according to the division mode and the color difference format. The decoding order of the intra prediction mode, which is the same as the coding order of, is set, and the decoding order of the intra prediction mode of the entropy decoding unit 222 is controlled. The entropy decoding unit 222 is the entropy coding unit 126 on the coding side.
It is a decoding unit corresponding to the above, and the entropy decoding process is performed according to the same rules as the syntax rules used in the entropy coding unit 126.

The value of the syntax element related to the coded information in the coded block unit obtained by decoding is supplied to the coded information derivation unit 223 in the coded block unit, and the value of the syntax element related to the intra-luminance prediction mode of the luminance signal prediction block The value is the intra-brightness prediction mode derivation unit 224.
The value of the syntax element related to the intra color difference prediction mode of the prediction block of the color difference signal is supplied to the intra color difference prediction mode derivation unit 225, and the value of the syntax element related to the inter prediction information of the prediction block unit is derived from the inter prediction information. It is supplied to unit 226.

The coded information derivation unit 223 of the coded block unit derives the coded information of the coded block unit from the value of the syntax element related to the coded information of the coded block unit supplied.
It is supplied to the intra prediction unit 206 or the inter prediction unit 207 via the switch 212.

The coded information derivation unit 223 for each coded block is a coded information derivation unit corresponding to the syntax element derivation unit 121 for the coded information for each coded block on the coding side, and is common to both the coding side and the decoding side. The coding information is derived according to the rules of. Prediction mode (PredMode) that determines the intra prediction (MODE_INTRA) or inter prediction (MODE_INTER) of the coded block.
) And the value related to the division mode (PartMode) for discriminating the shape of the prediction block are derived by the coding information derivation unit 223 for each coding block.

The intra-luminance prediction mode derivation unit 224 is a coding information derivation unit 22 for each coding block.
The prediction mode (PredMode) of the coded block derived in 3 is intra prediction (MODE_INTRA).
In the case of, the intra-luminance prediction mode of the luminance signal prediction block is derived from the value of the syntax element related to the intra-luminance prediction mode of the supplied luminance signal prediction block, and is supplied to the intra-color difference prediction mode derivation unit 225. It is supplied to the intra prediction unit 206 via the switch 212. The intra-luminance prediction mode derivation unit 224 is a derivation unit corresponding to the syntax element derivation unit 122 regarding the intra-luminance prediction mode on the coding side, and is derived according to a common rule on the coding side and the decoding side. The syntax element related to the intra-luminance prediction mode is the syntax element prev_intra_luma_pred_flag [x0] [y0], which is a flag indicating whether or not it can be predicted from the intra-luminance prediction mode of the surrounding blocks, and the syntax, which is an index indicating the prediction block of the prediction source. Element mpm_idx [x0] [y0], and syntax element rem_intra_luma_pred_mode [x0] indicating the intra-brightness prediction mode for each prediction block.
[Y0]. In the derivation of the intra-luminance prediction mode, the coded information storage memory 210
A syntax element prev_intra_luma_pred_flag [x0] that is a flag indicating that the correlation with the intra-luminance prediction mode of the surrounding blocks stored in is used and that value is used when the prediction can be made from the intra-luminance prediction mode of the surrounding blocks. ] [Y0] is 1 (true), and the syntax element mpm_idx [x] is an index that points to the prediction block of the prediction source.
The intra-luminance prediction mode of the surrounding prediction block indicated by [0] [y0] is set as the intra-luminance prediction mode of the prediction mode. Syntax element prev_intra_luma_pred_flag [
When x0] [y0] is 0 (false), the syntax element rem_intr indicates the decoded intra-luminance prediction mode instead of predicting the intra-luminance prediction mode from the surrounding prediction blocks.
The intra-luminance prediction mode is derived from the values of a_luma_pred_mode [x0] [y0].

The number of intra-brightness prediction modes of the prediction blocks in the coded block differs depending on the division mode. When the division mode is 2N × 2N division, the intra-brightness prediction mode of one set of prediction blocks for each coded block is used. The value is derived, and when the division mode is N × N division, the value of the intra-brightness prediction mode of 4 sets of prediction blocks is derived for each coded block.

The intra-color difference prediction mode derivation unit 225 is a coding information derivation unit 22 for each coding block.
The prediction mode (PredMode) of the coded block derived in 3 is intra prediction (MODE_INTRA).
In the case of, the value of the syntax element intra_chroma_pred_mode [x0] [y0] and the intra-luminance prediction mode derivation unit 2 regarding the intra-color difference prediction mode of the prediction block of the supplied color difference signal.
From the value of the intra-luminance prediction mode supplied from No. 24, the value of the first intra-color difference prediction mode is derived according to the table of FIG. Color difference format is 4: 2: 0 or 4: 4: 4
In the case of, the first intra color difference prediction mode is supplied to the intra prediction unit 206 via the switch 212 as the intra prediction mode of the color difference signal. Also, the color difference format is 4: 2:
In the case of 2, the second intra color difference prediction mode is derived from the first intra color difference prediction mode from the conversion table of FIG. 15, FIG. 16, FIG. 17, FIG. 30, or FIG. 33, and the second intra color difference prediction is performed. The mode is supplied to the intra prediction unit 206 via the switch 212 as the intra prediction mode of the color difference signal. The intra color difference prediction mode derivation unit 225 is a coding information derivation unit corresponding to the syntax element derivation unit 123 regarding the intra color difference prediction mode on the coding side, and is derived according to a common rule on the coding side and the decoding side. On the coding side, in the coding of the intra color difference prediction mode, the correlation between the color difference signal prediction block and the intra-brightness prediction mode of the brightness signal prediction block at the same position is used, and the intra-color difference prediction is performed on the coding side. If it is determined that the predicted value from the intra-brightness prediction mode of the brightness signal prediction block at the same position as the color difference signal prediction block is the most suitable, the value of the intra-color difference prediction mode is changed from the value of the intra-brightness prediction mode. When it is predicted and it is judged that it is better to set an original value in the intra color difference prediction mode rather than predicting from the intra brightness prediction mode, 0 (plane prediction) which is a typical intra prediction mode in the intra color difference prediction mode ), 1 (average value prediction), 10
The amount of code is reduced by using a mechanism for setting any value of (horizontal prediction), 26 (vertical prediction), and 34 (diagonal prediction).

The inter-prediction information derivation unit 226 derives and derives inter-prediction information from the value of the syntax element related to the inter-prediction information for each prediction block when the prediction mode (PredMode) of the coded block is inter-prediction (MODE_INTER). The value of the inter-prediction information is supplied to the inter-prediction unit 207 via the switch 212. The inter-prediction information derivation unit 226 is an inter-prediction information derivation unit corresponding to the syntax element derivation unit 124 related to the inter-prediction information on the coding side, and derives according to a common rule on the coding side and the decoding side. The derived inter-prediction information for each prediction block includes information such as an inter-prediction mode (L0 prediction, L1 prediction, both predictions), an index for identifying a plurality of reference images, and a motion vector.

Next, the procedure for decoding the intra prediction mode and processing the intra prediction on the decoding side will be described. FIG. 26 shows the second coded stream decoding unit 203 and the intra prediction unit 206 on the decoding side.
It is a figure explaining the processing procedure of the decoding of the intra prediction mode and the intra prediction carried out in. First, the intra-luminance prediction mode derivation unit 224 of the second coded stream decoding unit 203 decodes the intra-luminance prediction mode (step S4001 in FIG. 26). Subsequently, the intra-color difference prediction mode derivation unit 225 of the second coded stream decoding unit 203 decodes the first intra-color difference prediction mode according to the table of FIG. 14 (step S4002 of FIG. 26).
.. Subsequently, when the color difference format is not 4: 2: 2 (N in step S4003 of FIG. 26).
O), in the case where the color difference format is 4: 2: 2 (YES in step S4003 in FIG. 26), the process proceeds to step S4004, and the intra color difference prediction mode derivation unit 225 of the second coded stream decoding unit 203 is shown in FIG. A second intra-color difference prediction mode is derived from the first intra-color difference prediction mode by the conversion table of 16, 17, 30, or 33 (FIG. 2).
Step 6 S4004). Subsequently, the intra prediction unit 206 performs intra prediction of the luminance signal and the color difference signal (step S4004 in FIG. 26). In addition, step S40 of FIG.
The process of deriving the second intra color difference prediction mode from the first intra color difference prediction mode of 04 is performed by the intra prediction unit 206 instead of the intra color difference prediction mode derivation unit 225 of the second coded stream decoding unit 203. May be good.

When the intra prediction mode for plane prediction is 0 and the intra prediction mode for mean value prediction is 1, the color difference format is 4: 2: 2, as in the color difference format 4: 2: 0 and the color difference format 4: 4: 4. At this time, the intra prediction mode of the plane prediction is 0 and the intra prediction mode of the mean value prediction is 1, so that the intra prediction is performed.
7. In the conversion table of FIG. 30, or FIG. 33, the values are the same even if the first intra color difference prediction mode is converted to the second intra color difference prediction mode. Therefore, in the case of intra prediction modes 0 and 1 that are not angle prediction, the second intra from the value of the first intra color difference prediction mode using the conversion table of FIGS. 15, 16, 17, 30, or 33. Intra-prediction may be performed after deriving the value of the color difference prediction mode, or FIG. 15, FIG. 16, and FIG.
7. Intra prediction may be performed as it is according to the first intra color difference prediction mode without deriving the second intra color difference prediction mode using the conversion table of FIG. 30 or FIG. 33.

In the image coding device and the image decoding device of the present embodiment, the color difference format is 4.
In the case of: 2: 2, the value of the first intra color difference prediction mode is changed to the value of the second intra color difference prediction mode using the conversion table of FIGS. 15, 16, 17, 30, or 33. Although described as being derived, the value of the second intra-color difference prediction mode may be derived from the value of the first intra-color difference prediction mode by a calculation formula instead of the conversion table.

In the image encoding device and the image decoding device of the present embodiment, when the color difference format in which the aspect ratios of the pixels of the luminance signal and the color difference signal are different is 4: 2: 2, FIGS. 15 and 16
, The conversion table of FIG. 17, FIG. 30, or FIG. 33 has been described as deriving the value of the second intra color difference prediction mode from the value of the first intra color difference prediction mode. However, the intra prediction of the encoding device has been described. In the intra prediction unit 206 of the unit 103 and the decoding device, instead of converting to the second intra color difference prediction mode, the intra prediction mode shown in FIG. 27 or 28 is converted to an intra other than the color difference signal of the color difference format 4: 2: 2. In addition to the prediction angle (intra prediction angle for the brightness signal and intra prediction angle for the color difference format 4: 2: 0, 4: 4: 4), the color difference in the color difference format 4: 2: 2. Prepare a table that corresponds to the angle of the intra prediction for the signal, and when the color difference format is 4: 2: 2, use this table to change the color difference from the first intra color difference prediction mode to the color difference format 4: 2: 2. It is also possible to derive the intra-prediction angle for the signal and use this angle to perform the intra-prediction of the color difference signal. 27 and 28 show the angles of the intra prediction other than the color difference signal of the color difference format 4: 2: 2 from the intra prediction mode (the angle of the intra prediction for the luminance signal, and the color difference format 4: 2: 0, 4: 4: 4: This is a table used when deriving the intra-prediction angle of the color difference signal for the color difference format 4: 2: 2 in addition to the intra-prediction angle for the color difference signal of 4. FIG. 27 shows the second value from the value of the first intra-color difference prediction mode using the conversion table of FIG.
It is a table in which the angle of the intra-prediction for the color-difference signal of the color-difference format 4: 2: 2 is set so as to obtain the same result as the intra-prediction of the color-difference signal by deriving the value of the intra-color difference prediction mode of. When the color difference format is 4: 2: 2, the angle of the intra prediction for the color difference signal is derived according to the table of FIG. 27, and the intra prediction is performed, so that the conversion table of FIG. 15 is used to determine the first intra color difference prediction mode. The result is the same as when the value of the second intra-color difference prediction mode is derived from the value and the intra-prediction of the color difference signal is performed.

Further, FIG. 28 is a table in which the result of doubling the angle of the intra prediction in the vertical direction and halving in the horizontal direction is set. The derivation processing procedure of the table of FIG. 28 when converting the angle of the first intra-color difference prediction to the angle of the second intra-color difference prediction in the color difference format of 4: 2: 2 will be described with reference to the flowchart of FIG. 29.

For each value from 0 to 34 of the first intra-prediction mode IntraPredMode1, the angle IntraPredMode2 of the second intra-prediction used for the intra-prediction of the color difference signal of the color difference format 4: 2: 2 is derived by the procedure of the flowchart of FIG. To do.

First, when the angle prediction is not performed, that is, when the first intra prediction mode IntraPredMode1 is 1 or less (NO in step S3201 in FIG. 29), the derivation process is terminated. The reason why the first intra prediction mode IntraPredMode1 is 1 or less is that the plane prediction is predicted by interpolating the pixel value from the surrounding decoded blocks (intrapredmode1 = 0), and the average value is derived from the surrounding decoded blocks. Mean value prediction predicted by doing (intra prediction mode)
intraPredMode1 = 1).

On the other hand, when the first intracolor difference prediction mode IntraPredMode1 is angle prediction, that is, when it is larger than 1 (YES in step S3201 in FIG. 29), the angle of the second intra prediction from the angle of the first intra prediction after step S3202. Performs conversion processing to.

When IntraPredMode1 is smaller than 18 (step S3 in FIG. 29).
202 YES), the angle of the first intraprediction corresponding to the first intracolor difference prediction mode IntraPredMode1 IntraPredAngle1 is doubled, and the angle of the second intraprediction IntraPredAngle2
(Step S3203 in FIG. 29). In addition, the angle of the second intra prediction IntraPredA
Limit ngle2 to −32 or more and 32 or less (step S3204 in FIG. 29), and end the derivation process. Specifically, when the angle of the second intra-prediction IntraPredAngle2 is smaller than −32, the angle of the second intra-prediction IntraPredAngle2 is set to −32, and the angle of the second intra-prediction IntraPredAngle2 is larger than 32. If the angle of the second intra prediction Intra
Set PredAngle2 to 32. When the intra prediction mode IntraPredMode2 is 2 or more and less than 18, the intra prediction mode IntraPredMode2 remains as it is.

On the other hand, when the intra color difference prediction mode IntraPredMode1 is not smaller than 18, that is, when it is 18 or more (NO in step S3202 in FIG. 29), the first intra color difference prediction mode IntraP
The angle of the first intra prediction corresponding to redMode1 IntraPredAngle1 is multiplied by half, and the second
The angle of IntraPredAngle2 is set to IntraPredAngle2 (step S3205 in FIG. 29), and this derivation process is completed. In this embodiment, the result of performing a 1-bit right shift operation equivalent to 1/2 times the angle IntraPredAngle1 of the first intraprediction is obtained as the angle IntraPredAngle of the second intraprediction.
Set to 2.

In the above, when the color difference format is 4: 2: 2, the angle of the second intra prediction is derived from the angle of the first intra prediction using the table of FIG. 28. In the intra prediction unit 103 of the above and the intra prediction unit 206 of the decoding device,
Instead of the table of FIG. 28, the angle of the second intra prediction may be derived from the value of the first intra color difference prediction mode by the derivation method according to the processing procedure of FIG.

The moving image coding stream output by the image coding apparatus of the above-described embodiment has a specific data format so that it can be decoded according to the coding method used in the embodiment. An image decoding device corresponding to the image coding device can decode the coded stream of this particular data format.

When a wired or wireless network is used to exchange the coded stream between the image encoding device and the image decoding device, the coded stream is converted into a data format suitable for the transmission form of the communication path and transmitted. You may. In that case, the image transmission device that converts the coded stream output by the image coding device into coded data in a data format suitable for the transmission form of the communication path and transmits it to the network, and the image transmitting device that receives the coded data from the network and receives the coded data. An image receiving device that restores the coded stream and supplies it to the image decoding device is provided.

The image transmission device includes a memory that buffers the coded stream output by the image coding device, a packet processing unit that packets the coded stream, and a transmission unit that transmits the packetized coded data via the network. including. The image receiving device generates a coded stream by packet-processing the coded data and a receiver that receives the packetized coded data via the network, a memory that buffers the received coded data, and a packet process. It includes a packet processing unit provided to the image decoding device.

The above processing related to coding and decoding can be realized as a transmission, storage, and receiving device using hardware, and is stored in a ROM (read-only memory), a flash memory, or the like. It can also be realized by firmware or software such as a computer. The firmware program and software program may be recorded on a recording medium readable by a computer or the like and provided, or provided from a server via a wired or wireless network, or provided as terrestrial or satellite digital broadcasting data broadcasting. Is also possible.

The present invention has been described above based on the embodiments. Embodiments are examples, and it is understood by those skilled in the art that various modifications are possible for each of these components and combinations of each processing process, and that such modifications are also within the scope of the present invention. ..

101 Color difference format setting unit, 102 image memory, 103 intra prediction unit, 104 inter prediction unit, 105 coding method determination unit, 106 residual signal generation unit, 107 orthogonal conversion / quantization unit, 108 inverse quantization / inverse orthogonal conversion Unit, 109 Decoded image signal superimposition part, 110 Coding information storage memory, 111 Decoded image memory, 11
2 1st coded stream generator, 113 2nd coded stream generator, 11
4 Third coded stream generator, 115 coded stream multiplexing unit, 121
Syntax element derivation section for coding information in coded block units, 122 Syntax element derivation section for intra-brightness prediction mode, 123 Syntax element derivation section for intra-color difference prediction mode, 124 Syntax element derivation section for inter-prediction information, 125 Intra-prediction mode coding control unit, 126 entropy coding unit, 201 coded stream separation unit, 202 1st coded stream decoding unit, 2
03 2nd coded stream decoding unit, 204 3rd coded stream decoding unit, 2
05 Color difference format management unit, 206 intra prediction unit, 207 inter prediction unit, 208 inverse quantization / inverse orthogonal conversion unit, 209 decoded image signal superimposition unit, 210 encoded information storage memory, 211 decoded image memory, 212 switch, 213 switch , 221 Intra-prediction mode decoding control unit, 222 Entropy decoding unit, 22
3 Coding information derivation unit for each coded block 223, 224 intra-luminance prediction mode derivation unit, 225 intra-color difference prediction mode derivation unit, 226 inter-prediction information derivation unit.

Claims (6)

An image decoding device that decodes information related to the intra prediction mode in units of prediction blocks and decodes an image signal including a luminance signal and a color difference signal in units of conversion blocks using intra prediction.
Decoding the syntax element related to the intra-prediction mode of the luminance signal from the encoded stream in which the information about the intra-luminance prediction mode indicating the intra-prediction method of the prediction block of the luminance signal is encoded to derive the intra-prediction mode of the luminance signal. Intra-brightness prediction mode decoding unit and
Decode the syntax element related to the intra color difference prediction mode of the color difference signal from the encoded stream in which the information about the intra color difference prediction mode indicating the intra prediction method of the color difference signal prediction block is encoded, and also refer to the intra brightness prediction mode. The intra-color difference prediction mode decoding unit that derives the first intra-color difference prediction mode,
A luminance signal intra-prediction unit that predicts the luminance signal of the luminance signal conversion block from the luminance signals around the luminance signal conversion block according to the intra-luminance prediction mode specified for each luminance signal prediction block.
It is provided with a color difference signal intra prediction unit that predicts the color difference signal of the color difference signal conversion block from the color difference signal around the color difference signal conversion block according to the intra color difference prediction mode specified for each color difference signal prediction block. ,
When the aspect ratios of the pixels of the brightness signal and the color difference signal are different, the intra-color difference prediction mode decoding unit converts the mode number of the first intra-color difference prediction mode to be used when the aspect ratios are the same, and the above-mentioned The second intra color difference prediction mode is derived based on the conversion table set as the intra prediction mode of the second color difference signal used when the aspect ratios are different.
In the conversion table, when the mode number of the first intra color difference prediction mode is a mode number indicating horizontal prediction, the mode number of the second intra color difference prediction mode is also a mode number indicating horizontal prediction, and the first intra color difference When the mode number of the prediction mode is a mode number indicating vertical prediction, the mode number of the second intra-color difference prediction mode is also a mode number indicating vertical prediction. This is an image decoding method that decodes information about the intra prediction mode in units of prediction blocks and decodes an image signal including a luminance signal and a color difference signal in units of conversion blocks using intra prediction.
Decoding the syntax element related to the intra-prediction mode of the luminance signal from the encoded stream in which the information about the intra-luminance prediction mode indicating the intra-prediction method of the prediction block of the luminance signal is encoded to derive the intra-prediction mode of the luminance signal. Intra-brightness prediction mode decoding step and
Decode the syntax element related to the intra color difference prediction mode of the color difference signal from the encoded stream in which the information about the intra color difference prediction mode indicating the intra prediction method of the color difference signal prediction block is encoded, and also refer to the intra brightness prediction mode. Then, the intra-color difference prediction mode decoding step for deriving the first intra-color difference prediction mode, and
A luminance signal intra-prediction step for predicting the luminance signal of the luminance signal conversion block from the luminance signals around the luminance signal conversion block according to the intra-luminance prediction mode specified for each luminance signal prediction block.
According to the intra color difference prediction mode specified for each prediction block of the color difference signal, there is a color difference signal intra prediction step of predicting the color difference signal of the conversion block of the color difference signal from the color difference signal around the conversion block of the color difference signal. And
The intra-color difference prediction mode decoding step converts the mode number of the first intra-color difference prediction mode to be used when the aspect ratios of the pixels of the brightness signal and the color difference signal are different and the aspect ratios are the same. The second intra color difference prediction mode is derived based on the conversion table set as the intra prediction mode of the second color difference signal used when the aspect ratios are different.
In the conversion table, when the mode number of the first intra color difference prediction mode is a mode number indicating horizontal prediction, the mode number of the second intra color difference prediction mode is also a mode number indicating horizontal prediction, and the first intra color difference An image decoding method characterized in that when the mode number of the prediction mode is a mode number indicating vertical prediction, the mode number of the second intra-color difference prediction mode is also a mode number indicating vertical prediction. An image decoding program that decodes information about the intra prediction mode in units of prediction blocks and decodes an image signal including a luminance signal and a color difference signal in units of conversion blocks using intra prediction.
Decoding the syntax element related to the intra-prediction mode of the luminance signal from the encoded stream in which the information about the intra-luminance prediction mode indicating the intra-prediction method of the prediction block of the luminance signal is encoded to derive the intra-prediction mode of the luminance signal. Intra-brightness prediction mode decoding step and
Decode the syntax element related to the intra color difference prediction mode of the color difference signal from the encoded stream in which the information about the intra color difference prediction mode indicating the intra prediction method of the color difference signal prediction block is encoded, and also refer to the intra brightness prediction mode. Then, the intra-color difference prediction mode decoding step for deriving the first intra-color difference prediction mode, and
A luminance signal intra-prediction step for predicting the luminance signal of the luminance signal conversion block from the luminance signals around the luminance signal conversion block according to the intra-luminance prediction mode specified for each luminance signal prediction block.
A computer performs a color difference signal intra prediction step of predicting the color difference signal of the color difference signal conversion block from the color difference signal around the color difference signal conversion block according to the intra color difference prediction mode specified for each color difference signal prediction block. To execute,
The intra-color difference prediction mode decoding step converts the mode number of the first intra-color difference prediction mode to be used when the aspect ratios of the pixels of the brightness signal and the color difference signal are different and the aspect ratios are the same. The second intra color difference prediction mode is derived based on the conversion table set as the intra prediction mode of the second color difference signal used when the aspect ratios are different.
In the conversion table, when the mode number of the first intra color difference prediction mode is a mode number indicating horizontal prediction, the mode number of the second intra color difference prediction mode is also a mode number indicating horizontal prediction, and the first intra color difference An image decoding program characterized in that when the mode number of the prediction mode is a mode number indicating vertical prediction, the mode number of the second intra-color difference prediction mode is also a mode number indicating vertical prediction. The moving image receives the encoded stream, decodes the information about the intra prediction mode in the predicted block unit contained in the received coded stream, and includes the luminance signal and the color difference signal in the converted block unit. A receiver that decodes an image signal using intra-prediction.
Decoding the syntax element related to the intra-prediction mode of the luminance signal from the encoded stream in which the information about the intra-luminance prediction mode indicating the intra-prediction method of the prediction block of the luminance signal is encoded to derive the intra-prediction mode of the luminance signal. Intra-brightness prediction mode decoding unit and
Decode the syntax element related to the intra color difference prediction mode of the color difference signal from the encoded stream in which the information about the intra color difference prediction mode indicating the intra prediction method of the color difference signal prediction block is encoded, and also refer to the intra brightness prediction mode. The intra-color difference prediction mode decoding unit that derives the first intra-color difference prediction mode,
A luminance signal intra-prediction unit that predicts the luminance signal of the luminance signal conversion block from the luminance signals around the luminance signal conversion block according to the intra-luminance prediction mode specified for each luminance signal prediction block.
It is provided with a color difference signal intra prediction unit that predicts the color difference signal of the color difference signal conversion block from the color difference signals around the color difference signal conversion block according to the intra color difference prediction mode specified for each color difference signal prediction block. ,
When the aspect ratios of the pixels of the brightness signal and the color difference signal are different, the intra color difference prediction mode decoding unit converts the mode number of the first intra color difference prediction mode to be used when the aspect ratios are the same, and the above-mentioned The second intra color difference prediction mode is derived based on the conversion table set as the intra prediction mode of the second color difference signal used when the aspect ratios are different.
In the conversion table, when the mode number of the first intra color difference prediction mode is a mode number indicating horizontal prediction, the mode number of the second intra color difference prediction mode is also a mode number indicating horizontal prediction, and the first intra color difference When the mode number of the prediction mode is a mode number indicating vertical prediction, the mode number of the second intra-color difference prediction mode is also a mode number indicating vertical prediction. The moving image receives the encoded stream, decodes the information about the intra prediction mode in the predicted block unit contained in the received coded stream, and includes the luminance signal and the color difference signal in the converted block unit. A receiving method that decodes an image signal using intra-prediction.
Decoding the syntax element related to the intra-prediction mode of the luminance signal from the encoded stream in which the information about the intra-luminance prediction mode indicating the intra-prediction method of the prediction block of the luminance signal is encoded to derive the intra-prediction mode of the luminance signal. Intra-brightness prediction mode decoding step and
Decode the syntax element related to the intra color difference prediction mode of the color difference signal from the encoded stream in which the information about the intra color difference prediction mode indicating the intra prediction method of the color difference signal prediction block is encoded, and also refer to the intra brightness prediction mode. Then, the intra-color difference prediction mode decoding step for deriving the first intra-color difference prediction mode, and
A luminance signal intra-prediction step for predicting the luminance signal of the luminance signal conversion block from the luminance signals around the luminance signal conversion block according to the intra-luminance prediction mode specified for each luminance signal prediction block.
According to the intra color difference prediction mode specified for each prediction block of the color difference signal, there is a color difference signal intra prediction step of predicting the color difference signal of the conversion block of the color difference signal from the color difference signal around the conversion block of the color difference signal. And
The intra-color difference prediction mode decoding step converts the mode number of the first intra-color difference prediction mode to be used when the aspect ratios of the pixels of the brightness signal and the color difference signal are different and the aspect ratios are the same. The second intra color difference prediction mode is derived based on the conversion table set as the intra prediction mode of the second color difference signal used when the aspect ratios are different.
In the conversion table, when the mode number of the first intra color difference prediction mode is a mode number indicating horizontal prediction, the mode number of the second intra color difference prediction mode is also a mode number indicating horizontal prediction, and the first intra color difference When the mode number of the prediction mode is a mode number indicating vertical prediction, the mode number of the second intra-color difference prediction mode is also a mode number indicating vertical prediction. The moving image receives the encoded stream, decodes the information about the intra prediction mode in the predicted block unit contained in the received coded stream, and includes the luminance signal and the color difference signal in the converted block unit. A receiving program that decodes an image signal using intra-prediction.
Decoding the syntax element related to the intra-prediction mode of the luminance signal from the encoded stream in which the information about the intra-luminance prediction mode indicating the intra-prediction method of the prediction block of the luminance signal is encoded to derive the intra-prediction mode of the luminance signal. Intra-brightness prediction mode decoding step and
Decode the syntax element related to the intra color difference prediction mode of the color difference signal from the encoded stream in which the information about the intra color difference prediction mode indicating the intra prediction method of the color difference signal prediction block is encoded, and also refer to the intra brightness prediction mode. Then, the intra-color difference prediction mode decoding step for deriving the first intra-color difference prediction mode, and
A luminance signal intra-prediction step for predicting the luminance signal of the luminance signal conversion block from the luminance signals around the luminance signal conversion block according to the intra-luminance prediction mode specified for each luminance signal prediction block.
A computer performs a color difference signal intra prediction step of predicting the color difference signal of the color difference signal conversion block from the color difference signal around the color difference signal conversion block according to the intra color difference prediction mode specified for each color difference signal prediction block. To execute,
The intra-color difference prediction mode decoding step converts the mode number of the first intra-color difference prediction mode to be used when the aspect ratios of the pixels of the brightness signal and the color difference signal are different and the aspect ratios are the same. The second intra color difference prediction mode is derived based on the conversion table set as the intra prediction mode of the second color difference signal used when the aspect ratios are different.
In the conversion table, when the mode number of the first intra color difference prediction mode is a mode number indicating horizontal prediction, the mode number of the second intra color difference prediction mode is also a mode number indicating horizontal prediction, and the first intra color difference When the mode number of the prediction mode is a mode number indicating vertical prediction, the mode number of the second intra-color difference prediction mode is also a mode number indicating vertical prediction.

Images