JP5725108B2 - Image decoding apparatus, image decoding method, and image decoding program, and receiving apparatus, receiving method, and receiving program - Google Patents

Description

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

As a typical moving image compression encoding method, MPEG-4 AVC / H. There are H.264 standards. MPEG-4 AVC / H. In H.264, encoding is performed in units of macro blocks obtained by dividing a picture 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 macro block includes a color difference signal, but the size of the color difference signal included in the macro block differs depending on the color difference format of the image to be encoded. 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 as X: Y: Z. MPEG-4 AVC / H. The color difference format of an image to be encoded and decoded in H.264 is 4: 2: 0, 4: 2: 2, 4: 4: 4, and monochrome.

FIG. 3 is a diagram for explaining each color difference format of an 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.
A color difference format sampled at a density of one part. In 4: 2: 0, the color difference signal may be sampled at the position shown in FIG.
4: 2: 2 shown in FIG. 3B is a color difference format in which the color difference signal is sampled with a density of 1/2 in the horizontal direction and the same density in the vertical direction with respect to the luminance signal.
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.
Monochrome shown in FIG. 3D is a color difference format having only a luminance signal without a color difference signal.

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

AVC / H. In the H.264 system, a method of predicting from already encoded / decoded blocks in an encoding / decoding target picture is used. This method is called intra prediction. In addition, motion compensation that predicts motion from a reference picture using a picture that has already been encoded / decoded as a reference picture is used. A technique for 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 H.264 intra coding will be described. 4A to 4C are diagrams for explaining a unit for switching the intra prediction mode. AVC / H. In the H.264 intra coding, “4 × 4 intra prediction”, “16 ×
Three types of “16 intra prediction” and “8 × 8 intra prediction” are prepared.

In “4 × 4 intra prediction”, a luminance signal of a macro block (luminance signal 16 × 16 pixel block, color difference signal 8 × 8 pixel block) is divided into 16 × 4 × 4 pixel blocks, and divided 4 × 4 pixel units. Then, a mode is selected from nine types of 4 × 4 intra prediction modes, and intra prediction is sequentially performed (FIG. 4A).
In “16 × 16 pixel intra prediction”, a mode is selected from four types of 16 × 16 intra prediction modes in units of 16 × 16 pixel blocks of the luminance signal, and intra prediction is performed (FIG. 4B).
In “8 × 8 pixel intra prediction”, the luminance signal of a macro block is divided into four 8 × 8 pixel blocks, and a mode is selected from nine types of 8 × 8 intra prediction modes in units of divided 8 × 8 pixels. Then, intra prediction is sequentially performed (FIG. 4C).

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

Next, AVC / H. A unit for inter prediction in H.264 inter coding will be described. FIGS. 5A to 5H are diagrams for explaining a macroblock partition and a sub-macroblock partition. To simplify the explanation here,
Only the pixel block of the luminance signal is drawn. In the MPEG series, the macroblock is defined by a square area. Generally, AVC / H. In the MPEG series including the H.264 system, 1
A block defined by 6 × 16 pixels (16 horizontal pixels and 16 vertical pixels) is called a macroblock. Furthermore, AVC / H. In the H.264 system, a block defined by 8 × 8 pixels is called a sub macroblock. The macroblock partition refers to each small block obtained by further dividing the macroblock for motion compensation prediction. The sub-macroblock partition refers to each small block obtained by further dividing the sub-macroblock for motion compensation prediction.

FIG. 5A is a diagram showing that a macroblock is composed of one macroblock partition composed of a luminance signal of 16 × 16 pixels and two corresponding color difference signals. Here, this configuration is referred to as a 16 × 16 mode macroblock type.
In FIG. 5B, the macro block is composed of two macro block partitions each composed of a luminance signal of 16 × 8 pixels (horizontal 16 pixels, vertical 8 pixels) and two corresponding color difference signals. FIG. The two macroblock partitions are arranged vertically. Here, this configuration is called a 16 × 8 mode macroblock type.
In FIG. 5 (c), 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. FIG. The two macroblock partitions are arranged side by side. Here, this configuration is referred to as an 8 × 16 mode macroblock type.
FIG. 5D is a diagram showing that a macroblock is composed of four macroblock partitions each composed of a luminance signal of 8 × 8 pixels and two corresponding color difference signals. These four macroblock partitions are arranged vertically and horizontally. This configuration is referred to as an 8 × 8 mode macroblock type.
FIG. 5E is a diagram showing that a sub macroblock is composed of one submacroblock partition composed of a luminance signal of 8 × 8 pixels and two corresponding color difference signals. Here, this configuration is referred to as an 8 × 8 mode sub-macroblock type.
In FIG. 5F, 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. FIG. These two sub-macroblock partitions are arranged vertically. This configuration is referred to as an 8 × 4 mode sub-macroblock type.
In FIG. 5G, the sub-macroblock is composed of two macroblock partitions each composed of a luminance signal of 4 × 8 pixels (horizontal 4 pixels, vertical 8 pixels) and two corresponding color difference signals. FIG. The two macroblock partitions are arranged side by side. Here, this configuration is called a 4 × 8 mode sub-macroblock type.
FIG. 5 (h) is a diagram showing that a sub macroblock is composed of four submacroblock partitions each composed of a luminance signal of 4 × 4 pixels and two corresponding color difference signals. These four sub-macroblock partitions are arranged two by two vertically and horizontally. Here, this configuration is called a 4 × 4 mode sub-macroblock type.

AVC / H. In the H.264 encoding 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 for each macroblock, one of 16 × 16, 16 × 8, 8 × 16, and 8 × 8 mode macroblock types can be selected. When the macro block type of 8 × 8 mode is selected, the motion compensation block size in units of sub macro blocks is 8 × 8.
, 8 × 4, 4 × 8, and 4 × 4 mode sub-macroblock types can be selected.

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

When encoding information about the intra prediction mode of the image signal, information about the intra prediction mode of the luminance signal and information about the intra prediction mode of the color difference signal are encoded and arranged in the encoded bit string. 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 circumstances, and an object thereof 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 corresponding to the color difference format. is there.

An image decoding apparatus that decodes information related to an intra prediction mode and performs intra prediction decoding on an image signal including a luminance signal and a color difference signal in units of blocks, and the luminance signal when performing intra prediction on an encoding block basis When the division mode for horizontally and vertically dividing is acquired and the color difference format is 4: 2: 0, the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block, the second luminance signal Same as the intra-brightness prediction mode of the prediction block, the intra-brightness prediction mode of the prediction block of the third luminance signal, the intra-brightness prediction mode of the prediction block of the fourth luminance signal, and the prediction block of the first luminance signal From the encoded sequence in which the encoding information related to the intra color difference prediction mode of the prediction block of the color difference signal at the reference position is arranged, A coded sequence decoding unit that decodes information related to the intra luminance prediction mode of the prediction block of the first to fourth luminance signals, and then decodes information related to the intra color difference prediction mode of the prediction block of the color difference signal; If set, the prediction block of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the intra luminance prediction mode for each prediction block of the decoded luminance signal A luminance signal intra prediction unit that predicts a luminance signal from a block of surrounding decoded luminance signals and the division mode are set according to each intra luminance prediction mode obtained from the information on the color difference format, and the color difference format is 4: 2. : If 0, the color difference signal prediction block is set without dividing the color difference signal of the coding block and decoded. Ntora chrominance intra chrominance obtained by the information about the prediction mode in accordance with the prediction mode, and a chrominance signal intra prediction unit for predicting a color difference signal from the block surrounding the decoded chrominance signals, the chrominance signal intra prediction unit, In the mode in which the intra color difference prediction mode is set according to the intra luminance prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block is set as the value of the color difference signal in the coding block. When the intra color difference prediction mode is set by using the value indicating the intra color difference prediction mode of the prediction block, and the intra color difference prediction mode is not set according to the intra luminance prediction mode, the intra color difference prediction of the prediction block of the color difference signal is performed. One of the set values of the mode is a vertical direction whose prediction direction is the vertical direction. Provided is an image decoding device characterized in that a value indicating direct prediction can be set.
An image decoding method for decoding information related to an intra prediction mode and performing intra prediction decoding on an image signal including a luminance signal and a color difference signal in units of blocks. When performing intra prediction of an image signal in units of encoded blocks, the luminance signal When the division mode for horizontally and vertically dividing is acquired and the color difference format is 4: 2: 0, the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block, the second luminance signal Same as the intra-brightness prediction mode of the prediction block, the intra-brightness prediction mode of the prediction block of the third luminance signal, the intra-brightness prediction mode of the prediction block of the fourth luminance signal, and the prediction block of the first luminance signal From the encoded sequence in which the encoding information related to the intra color difference prediction mode of the prediction block of the color difference signal at the reference position is arranged, A coded sequence decoding step of decoding information relating to the intra luminance prediction mode of the prediction block of the first to fourth luminance signals, and subsequently decoding information relating to the intra color difference prediction mode of the prediction block of the color difference signal; If set, the prediction block of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the intra luminance prediction mode for each prediction block of the decoded luminance signal A luminance signal intra prediction step for predicting a luminance signal from a block of surrounding decoded luminance signals and the division mode are set according to each intra luminance prediction mode obtained from the information on the color difference format, and the color difference format is 4: 2. : If 0, the color difference signal prediction block is set without dividing the color difference signal of the coding block. A color difference signal intra prediction step for predicting a color difference signal from a block of surrounding decoded color difference signals according to an intra color difference prediction mode obtained from information on the decoded intra color difference prediction mode, and the color difference signal intra In the prediction step, in the mode in which the intra color difference prediction mode is set according to the intra luminance prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block is set in the coding block. When the intra color difference prediction mode is set and the intra color difference prediction mode is not set according to the intra luminance prediction mode, the prediction block of the color difference signal is used. One of the setting values for the intra color difference prediction mode Thus, the present invention provides an image decoding method characterized in that a value indicating vertical prediction in which the prediction direction is the vertical direction can be set.
An image decoding program that decodes information related to an intra prediction mode and performs intra prediction decoding of an image signal including a luminance signal and a color difference signal in units of blocks. When performing intra prediction of an image signal in units of encoded blocks, the luminance signal When the division mode for horizontally and vertically dividing is acquired and the color difference format is 4: 2: 0, the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block, the second luminance signal Same as the intra-brightness prediction mode of the prediction block, the intra-brightness prediction mode of the prediction block of the third luminance signal, the intra-brightness prediction mode of the prediction block of the fourth luminance signal, and the prediction block of the first luminance signal Is the coded sequence in which coding information related to the intra color difference prediction mode of the prediction block of the color difference signal at the reference position is arranged? A coded sequence decoding step of decoding information related to the intra luminance prediction mode of the prediction block of the first to fourth luminance signals, and subsequently decoding information related to the intra color difference prediction mode of the prediction block of the color difference signal; When the mode is set, a prediction block of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the intra luminance for each prediction block of the decoded luminance signal In accordance with each intra luminance prediction mode obtained from information on the prediction mode, a luminance signal intra prediction step for predicting a luminance signal from a block of surrounding decoded luminance signals, the division mode, and a color difference format of 4 are set. : 2: 0, a color difference signal prediction block is set without dividing the color difference signal of the coding block. Then, the computer executes a color difference signal intra prediction step for predicting a color difference signal from a block of surrounding decoded color difference signals according to the intra color difference prediction mode obtained from the information on the decoded intra color difference prediction mode. In the color difference signal intra prediction step, in the mode for setting the intra color difference prediction mode in accordance with the intra luminance prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block, By using the value indicating the intra color difference prediction mode of the prediction block of the color difference signal in the coding block, when setting the intra color difference prediction mode and not setting the intra color difference prediction mode according to the intra luminance prediction mode, Intra color difference prediction of prediction block of color difference signal An image decoding program characterized in that a value indicating vertical prediction in which the prediction direction is the vertical direction can be set as one mode setting value.
A receiving device that decodes information related to an intra prediction mode from an encoded stream and performs intra prediction decoding on an image signal including a luminance signal and a color difference signal in units of blocks, and includes encoded data obtained by encoding a moving image. A receiving unit that receives the packet, a packet processing unit that packet-processes the encoded data to generate the encoded stream, and a horizontal luminance signal when performing intra prediction of an image signal in units of encoded blocks from the encoded stream. And when the color difference format is 4: 2: 0, the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block, and the prediction of the second luminance signal are obtained. Block intra luminance prediction mode, third luminance signal prediction block intra luminance prediction mode, fourth luminance signal prediction block The first intra-luminance prediction mode of the image and the encoded sequence in which the encoding information related to the intra-chrominance prediction mode of the prediction block of the chrominance signal at the same reference position as the prediction block of the first luminance signal is arranged. A decoding unit that decodes information related to the intra luminance prediction mode of the prediction block of the fourth luminance signal, and subsequently decodes information related to the intra color difference prediction mode of the prediction block of the color difference signal, and the division mode are set. If the prediction block of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, information on the intra luminance prediction mode for each prediction block of the decoded luminance signal Luminance to predict luminance signal from surrounding decoded luminance signal block according to each intra luminance prediction mode obtained by When the division mode is set and the color difference format is 4: 2: 0, the prediction block of the color difference signal is set without dividing the color difference signal of the coding block and decoded. A color difference signal intra prediction unit that predicts a color difference signal from a block of surrounding decoded color difference signals according to an intra color difference prediction mode obtained from information on the intra color difference prediction mode, and the color difference signal intra prediction unit includes: In the mode in which the intra color difference prediction mode is set according to the intra luminance prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block is set as the value of the color difference signal in the coding block. Intra color difference prediction mode is set by using the value indicating the intra color difference prediction mode of the prediction block. In addition, when the intra color difference prediction mode is not set according to the intra luminance prediction mode, a value indicating vertical prediction in which the prediction direction is the vertical direction is set as one of the setting values of the intra color difference prediction mode of the prediction block of the color difference signal. Provided is a receiving device that can be set.
A receiving method for decoding intra-prediction mode information from an encoded stream and intra-predicting an image signal including a luminance signal and a color difference signal in units of blocks, wherein encoded data obtained by encoding a moving image is encoded A reception step of receiving, a packet processing step of packet-processing the encoded data to generate the encoded stream, and a luminance signal when horizontally predicting an image signal in units of encoded blocks from the encoded stream. And when the color difference format is 4: 2: 0, the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block, and the prediction of the second luminance signal are obtained. Block intra luminance prediction mode, third luminance signal prediction block intra luminance prediction mode, fourth luminance signal From the coding sequence in which the coding information regarding the intra luminance prediction mode of the prediction block of the first luminance signal and the intra color difference prediction mode of the prediction block of the color difference signal at the same reference position as the prediction block of the first luminance signal are arranged, A coded sequence decoding step of decoding information relating to the intra luminance prediction mode of the prediction block of the first to fourth luminance signals, and subsequently decoding information relating to the intra color difference prediction mode of the prediction block of the color difference signal; If set, the prediction block of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the intra luminance prediction mode for each prediction block of the decoded luminance signal Luminance from a block of surrounding decoded luminance signals according to each intra luminance prediction mode obtained from information about If the division mode is set and the color difference format is 4: 2: 0, the prediction block of the color difference signal is set without dividing the color difference signal of the coding block. A color difference signal intra prediction step for predicting a color difference signal from a block of surrounding decoded color difference signals according to an intra color difference prediction mode obtained from information on the decoded intra color difference prediction mode, and the color difference In the signal intra prediction step, in the mode in which the intra color difference prediction mode is set according to the intra luminance prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block is encoded. Used as a value indicating the intra color difference prediction mode of the prediction block of the color difference signal in the block When the intra color difference prediction mode is set and the intra color difference prediction mode is not set according to the intra luminance prediction mode, the prediction direction is set as one of the setting values of the intra color difference prediction mode of the prediction block of the color difference signal. Provided is a receiving method characterized in that a value indicating vertical prediction which is a vertical direction can be set.
A reception program for decoding intra-prediction mode information from an encoded stream and performing intra-prediction decoding on an image signal including a luminance signal and a color difference signal in units of blocks, wherein encoded data obtained by encoding a moving image is encoded A reception step of receiving, a packet processing step of packet-processing the encoded data to generate the encoded stream, and a luminance signal when horizontally predicting an image signal in units of encoded blocks from the encoded stream. And when the color difference format is 4: 2: 0, the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block, and the prediction of the second luminance signal are obtained. Block intra luminance prediction mode, third luminance signal prediction block intra luminance prediction mode, fourth From the encoded sequence in which the encoding information regarding the intra luminance prediction mode of the prediction block of the degree signal and the intra color difference prediction mode of the prediction block of the color difference signal at the same reference position as the prediction block of the first luminance signal is arranged A coded sequence decoding step of decoding information related to the intra luminance prediction mode of the prediction block of the first to fourth luminance signals, and subsequently decoding information related to the intra color difference prediction mode of the prediction block of the color difference signal; When the mode is set, a prediction block of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the intra luminance for each prediction block of the decoded luminance signal Depending on each intra luminance prediction mode obtained from the information about the prediction mode, whether it is a block of surrounding decoded luminance signal A luminance signal intra prediction step for predicting a luminance signal, and when the division mode is set and the color difference format is 4: 2: 0, a prediction block of the color difference signal is set without dividing the color difference signal of the coding block Then, the computer executes a color difference signal intra prediction step for predicting a color difference signal from a block of surrounding decoded color difference signals according to the intra color difference prediction mode obtained from the information on the decoded intra color difference prediction mode. In the color difference signal intra prediction step, in the mode for setting the intra color difference prediction mode in accordance with the intra luminance prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block, Intra color difference prediction of a color difference signal prediction block in the coding block When the intra color difference prediction mode is set by using the value indicating the mode and the intra color difference prediction mode is not set according to the intra luminance prediction mode, 1 of the setting value of the intra color difference prediction mode of the prediction block of the color difference signal is set. Secondly, a receiving program is provided in which a value indicating vertical prediction in which the prediction direction is the vertical direction can be set.

It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect 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 corresponding 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 H.264 system. AVC / H. It is a figure explaining the unit which performs inter prediction of H.264 system. It is a figure explaining the tree block prescribed | regulated by a present Example, and an encoding block. It is a figure explaining the division mode prescribed | regulated by a present Example. It is a figure explaining the value and prediction direction of the intra prediction mode prescribed | regulated by a present Example. It is a figure of an example for demonstrating the position of the block prescribed | regulated by a present Example. It is a figure explaining an example of the definition of a syntax at the time of encoding color difference format information with the sequence parameter set used as the header which encodes the information regarding the encoding of the whole sequence prescribed | regulated by a present Example. It is a figure explaining the division | segmentation method of the color difference signal of the encoding block in the NxN division | segmentation in the case of the intra prediction prescribed | regulated in a present Example. It is a block diagram which shows the structure of the 2nd encoding bit stream production | generation part of the image coding apparatus of embodiment. It is a block diagram which shows the structure of the 2nd encoding bit stream decoding part of the image decoding apparatus of embodiment. In the conversion table for calculating 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. is there. This is a conversion table for calculating the value of the intra color difference prediction mode from 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 when the color difference format specified in this embodiment is 4: 2: 2. . The value of the syntax element related to the intra color difference prediction mode from the value of the intra color difference prediction mode used on the encoding 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 It is the conversion table which calculates. It is a figure which shows the entropy encoding or decoding order of the syntax element regarding the intra brightness | luminance prediction mode in the case of NxN division | segmentation by embodiment, and an intra color difference prediction mode. It is an example of the syntax rule for encoding and decoding of the encoding information of the prediction block prescribed | regulated by a present Example. It is an example different from FIG. 18 of the syntax rule for encoding and decoding of the encoding information of the prediction block prescribed | regulated by a present Example. It is a flowchart explaining the process sequence of the encoding process of the encoding block performed by the 2nd encoding bit stream production | generation part of embodiment, and a prediction block unit. FIG. 21 is a flowchart for describing a common encoding processing procedure used in step S1003, step S1007, step S1011, and step S1014 in FIG. 20 of the embodiment. It is a flowchart explaining the common encoding process procedure used by step S1005 of FIG. 20, step S1009, step S1013, and step S1016 of embodiment. It is a flowchart explaining the process sequence of the decoding process of the encoding block performed by the 2nd encoding bit stream decoding part of embodiment and a prediction block unit. It is a flowchart explaining the common decoding process procedure used by step S2003 of FIG. 23 of embodiment, step S2007, step S2010, and step S2013. It is a flowchart explaining the common decoding process procedure used also by step S2005 of FIG. 23, step S2009, step S2012, and step S2015 of embodiment. It is a flowchart explaining the calculation processing procedure of the value of the intra color difference prediction mode used by step S2202 of FIG. 25 of embodiment. It is a figure explaining the correspondence of the prediction direction of the luminance signal in case a color difference format is 4: 2: 2, and the intra prediction of a color difference signal. It is a figure explaining the correspondence of the prediction direction of the luminance signal in case a color difference format is 4: 2: 0, and the intra prediction of a color difference signal.

In the present embodiment, with regard to video coding, in particular, in units of blocks obtained by dividing a picture into rectangles having an arbitrary size and shape, coding has already been coded and decoded, and decoding has been decoded (hereinafter decoded). The amount of code is reduced by using intra prediction in which prediction is performed from the pixel values of the surrounding blocks and inter prediction by motion compensation from already decoded pictures.

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

(Color difference format)
The color difference format of an image to be encoded and decoded in the description of the embodiment is AVC /
H. It is assumed that monochrome, which is also a target of the H.264 system, 4: 2: 0, 4: 2: 2, 4: 4: 4, and a luminance signal and a color difference signal are encoded and decoded as a set. However, regarding the description regarding the color difference signal, the description in the case of monochrome is omitted. In the present embodiment, the method of independently encoding the luminance signal and the color difference signal at 4: 4: 4 is assumed to be monochrome.

(About tree blocks and coding blocks)
In the embodiment, as shown in FIG. 6, the inside of the screen is equally divided into square units of any same size. This unit is defined as a tree block, and is used as a basic unit of address management for specifying an encoding / decoding target block (an encoding target block in encoding and a 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 a power of 2 in accordance with the picture size and the texture in the screen. In order to optimize the encoding process according to the texture in the screen, the tree block hierarchically divides the luminance signal and chrominance signal in the tree block as necessary into four parts (two parts vertically and horizontally), The block can be made smaller in block size. Each block is defined as a coding block, and is a basic unit of processing when performing coding and decoding. Except for monochrome, the coding block is also composed of one luminance signal and two color difference signals. The maximum size of the coding block is the same as the size of the tree block. An encoded block having the minimum size of the encoded block is called a minimum encoded block, and can be freely set to a power of 2.

In FIG. 6, the encoding block A is a single encoding block without dividing the tree block. The encoding block B is an encoding block formed by dividing a tree block into four. The coding block C is a coding block obtained by further dividing the block obtained by dividing the tree block into four. The coding block D is divided into 4 tree blocks.
It is an encoded block that is obtained by further dividing the block obtained by dividing into four hierarchically twice.
It is a coding block of the minimum size.

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 coding block size is set. 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 coding block A is 64 × 64 pixels for the luminance signal and 32 × 3 for the color difference signal.
The size of the encoding block B is 32 × 32 pixels for luminance signals and 16 for color difference signals.
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.
4 pixels. When the color difference format is 4: 4: 4, the size of the luminance signal and the color difference signal of each coding block is equal. When the color difference format is 4: 2: 2, the size of the coding block A is 32 × 64 pixels for the color difference signal, the size of the coding block B is 16 × 32 pixels for the color difference signal, and the size of the coding block C is The color difference signal is 8 × 16 pixels, and the size of the coding block D, which is the smallest coding block, is 4 × 8 pixels.

(About prediction mode)
In the coding block unit, switching is performed between intra prediction in which prediction is performed from surrounding image signals that have been encoded / decoded and inter prediction in which prediction is performed from image signals of images that have been encoded / decoded.
A mode for identifying the intra prediction and the inter prediction is defined as a prediction mode (PredMode). The prediction mode (PredMode) is either intra prediction (MODE_INTRA) or inter prediction (MODE_I
NTER) as a value and can be selected and encoded.

(About split mode and prediction block)
When intra prediction and inter prediction are performed by dividing the screen into blocks, prediction is performed by dividing an encoded block as necessary in order to reduce the unit for switching the method of intra prediction and inter prediction. A mode for identifying the division method of the luminance signal and the color difference signal of the coding block is defined as a division mode (PartMode). Furthermore, this divided block is defined as a prediction block. As shown in FIG. 7, four types of partition modes (PartMode) are defined according to the method of dividing the luminance signal of the coding block. The division mode (PartMode) of the coded block luminance signal (FIG. 7A) regarded as one prediction block without being divided is 2N ×.
2N division (PART_2Nx2N), the luminance signal of the coding block is divided into two in the horizontal direction, and the division mode (PartMode) of the two prediction blocks (FIG. 7B) is set to 2N × N division (PART_2Nx
N) The luminance signal of the coding block is divided in the vertical direction, and the division mode (PartMode) of the coding block having two prediction blocks (FIG. 7C) is N × 2N division (PART_Nx2N)
Then, the division mode (PartMode) of the luminance signal of the encoded block that is divided into four prediction blocks by horizontal and vertical equal division (FIG. 7D) is defined as N × N division (PART_NxN). Except for N × N division (PART_NxN) of intra prediction (MODE_INTRA), the color difference signal is also divided for each division mode (PartMode) in the same manner as the vertical / horizontal division ratio of the luminance signal. The vertical / horizontal division ratio of the color difference signal of the N × N division (PART_NxN) coding block of intra prediction (MODE_INTRA) varies depending on the type of the color difference format, which will be described later.

In order to specify each prediction block within the coding block, a number starting from 0 is assigned to the prediction block existing inside the coding block in the coding order. This number is defined as a split index PartIdx. A number described in each prediction block of the encoded block in FIG. 7 represents a partition index PartIdx of the prediction block. FIG.
In the 2N × N division (PART_2NxN) shown in FIG. N shown in FIG.
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
ART_NxN) sets the partition index PartIdx of the upper left prediction block to 0, the partition index PartIdx of the upper right prediction block to 1, and the partition index Par of the lower left prediction block
tIdx is set to 2, and the division index PartIdx of the lower right prediction block is set to 3.

When the prediction mode (PredMode) is intra prediction (MODE_INTRA), the division mode (Part 1) is used except for the coding block D (the luminance signal is 8 × 8 pixels) which is the smallest coding block.
Mode) defines 2N × 2N partition (PART_2Nx2N), and only the coding block D, which is the smallest coding block, has a partition mode (PartMode) of 2N × 2N partition (PART_2Nx2N) and N × N partition (
PART_NxN) is defined.

When the prediction mode (PredMode) is inter prediction (MODE_INTER), the partition mode (PartMode) is 2N × 2N partition (PART_2Nx2N) except for the coding block D which is the smallest coding block.
) 2N × N partition (PART_2NxN) and N × 2N partition (PART_Nx2N) are defined, and only the coding block D, which is the smallest coding block, has a partition mode (PartMode) of 2N × 2N partition (PA).
RT_2Nx2N), 2N x N split (PART_2NxN), and N x 2N split (PART_Nx2N) plus N x
N division (PART_NxN) is defined. In addition to the smallest encoded block, N × N division (PART_N
The reason for not defining xN) is that, except for the smallest encoded block, the encoded block can be divided into four to represent a small encoded block.

(Intra prediction and intra prediction mode)
In the intra prediction, the pixel value of the processing target block is predicted from the pixel values of the decoded blocks in the same screen. In the encoding apparatus and decoding apparatus of the present embodiment, 34 intra prediction modes are selected and intra prediction is performed. FIG. 8 is an explanatory diagram of the value of the intra prediction mode and the prediction direction defined in this embodiment. The direction indicated by the solid arrow indicates the prediction direction of intra prediction, that is, the direction referred to by intra prediction, and intra prediction of the pixel at the start point of the arrow is performed with reference to the decoded pixel in the direction indicated by the arrow of the adjacent block. . The number indicates the value of the intra prediction mode. The intra prediction mode (intraPredMode) includes vertical prediction (intra prediction mode intraPredMode = 0) that predicts in the vertical direction from the above decoded block, and horizontal prediction (intra prediction mode intraPredMode) that predicts in the horizontal direction from the left decoded block. =
1) average prediction (by calculating the average value from surrounding decoded blocks)
Intra prediction mode (intraPredMode = 2), in addition to average prediction (intraPredMode = 3) that predicts at an angle of 45 degrees from surrounding decoded blocks, it also predicts diagonally at various angles from surrounding decoded blocks 30 angle prediction (intra prediction mode intraPredMod
e = 4 ... 33) is defined.

The intra prediction mode is prepared for each of the luminance signal and the color difference signal, and the intra 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 encoding and decoding of the intra luminance prediction mode, when it is determined that the encoding side can predict from the intra luminance prediction mode of the surrounding block using the correlation with the intra luminance prediction mode of the surrounding block. If it is determined that it is better to set a different value for the intra luminance prediction mode than the information for identifying the block to be referenced and predict from the intra luminance prediction mode of the neighboring blocks, the intra luminance prediction mode is further set. A mechanism for encoding or decoding the value of is used. By predicting the intra luminance prediction mode of the block to be encoded / decoded from the intra luminance prediction modes of the neighboring blocks, the amount of code to be transmitted can be reduced. On the other hand, in the coding and decoding of the intra chrominance prediction mode, the intra luminance prediction mode is used on the encoding side by utilizing the correlation with the intra luminance prediction mode of the prediction block of the luminance signal at the same position as the prediction block of the chrominance signal. From the value of the intra luminance prediction mode to predict the value of the intra color difference prediction mode,
When it is determined that it is better to set a unique value for the intra color difference prediction mode than for prediction from the intra luminance prediction mode, a mechanism for encoding or decoding the value of 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.

(Conversion block)
As in the prior art, in this embodiment, the code amount is reduced by using orthogonal transform such as DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), etc. that transforms a discrete signal into the frequency domain and its inverse transform. . Conversion or inverse conversion is performed in units of transform blocks obtained by hierarchically dividing an encoded block into four. In the embodiment, 32 × 32 pixels, 16 × 16 pixels, 8 × 8 pixels, 4 ×
Define 4 conversion sizes of 4 pixels, 32 × 32 conversion, 16 × 16 conversion, 8 × 8 conversion,
It is assumed that 4 × 4 conversion and respective inverse conversion are performed.

(Position of tree block, coding block, prediction block, transform block)
The position of each block including the tree block, the encoding block, the prediction block, and the transform block described in the present embodiment is the origin (0, 0) of the pixel position of the upper left luminance signal on the luminance signal screen. And the pixel position of the upper left luminance signal included in each block area is represented by two-dimensional coordinates (x, y). The direction of the coordinate axis is a right direction in the horizontal direction and a downward direction in the vertical direction, respectively, and the unit is one pixel unit of the luminance signal. Of course, the luminance difference and the color difference signal have the same image size (number of pixels) and the color difference format is 4: 4: 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 pixel of the luminance signal included in the block area, and the unit is one pixel of the luminance signal. In this way, not only can the position of each block of the color difference signal be specified, but also the relationship between the positions of the luminance signal block and the color difference signal block can be clarified only by comparing the coordinate values. FIG. 9 is a diagram showing an example for explaining the positions of blocks defined in this embodiment when the color difference format is 4: 2: 0. 9 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. 9 is a luminance signal block E of 8 × 8 pixels and at the same time a block F of color difference signals of 4 × 4 pixels. ▲ is the position of the pixel of the luminance signal at the top left of the block E of the luminance signal of 8 × 8 pixels indicated by the dotted line. Therefore, ▲ is the position of the luminance signal block E of 8 × 8 pixels indicated by the dotted line, and the coordinates of the luminance signal of the pixel indicated by ▲ are the coordinates of the block E of the luminance signal of 8 × 8 pixels indicated by the dotted line. Become. Similarly, ▲ is also the pixel position of the upper left luminance signal pixel included in the area of the block F of the color difference signal of 4 × 4 pixels indicated by the dotted line. Therefore, ▲ also becomes 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 coordinates of the defined luminance signal block and the x component and y component of the coordinate of the color difference signal are the same regardless of the type of the color difference format, the shape and size of the block. Only define these blocks in the same position.

FIG. 1 is a block diagram illustrating a configuration of an image encoding device according to an embodiment. The image coding apparatus according to 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, encoding method determination unit 105, residual signal generation unit 106, orthogonal transform / quantization unit 107, inverse quantization / inverse orthogonal transform unit 108, decoded image signal superimposing unit 109, decoded image memory 111 , First encoded bit string generation unit 112, second encoded bit string generation unit 1
13, a third encoded bit string generation unit 114 and an encoded bit string multiplexing unit 115 are provided.

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 determined by determining the color difference format from the encoded image signal supplied to the color difference format setting unit 101, or may be set from the outside. Only the luminance signal is supplied to the first encoded bit string generation unit 112 as the information of the color difference format set to 4: 2: 0, 4: 2: 2, or 4: 4: 4, and the second code Bit string generator 1
13, the encoding process based on the color difference format is performed. Although not shown, the image memory 102, the intra prediction unit 103, the inter prediction unit 104, the encoding method determination unit 105, the residual signal generation unit 106, the orthogonal transform / quantization unit 107, and the inverse quantization in FIG.・
The inverse orthogonal transform unit 108, the decoded image signal superimposing unit 109, and the third encoded bit string generating unit 114 also perform encoding processing based on the set color difference format, and the encoded information storage memory 110 and the decoded image memory 111 are processed. Then, management is performed based on the set color difference format.

The image memory 102 temporarily stores image signals to be encoded supplied in time order. The image signals to be encoded stored in the image memory 102 are rearranged in the encoding order, divided into a plurality of encoding block units in a plurality of combinations according to the setting, and further divided into prediction block units. And supplied to the intra prediction unit 103 and the inter prediction unit 104.

The intra prediction unit 103 is a prediction block unit corresponding to each division mode (PartMode) in a plurality of encoding block units, and the luminance signal of the prediction block to be encoded from the decoded image signal stored in the decoded image memory 111 Each of the color difference signals is subjected to intra prediction according to the plurality of intra luminance prediction modes and the intra color difference prediction mode to obtain an intra prediction signal. The intra color difference prediction mode is a value predicted from the intra luminance prediction mode according to the color difference format, or 0 ( vertical direction), 1 ( horizontal direction), 2 (average value), which are representative intra prediction modes, Select only 3 (45 degrees oblique). A method for predicting the intra color difference prediction mode from the intra luminance prediction mode will be described later.

A prediction residual signal is obtained by subtracting an intra prediction signal in units of prediction blocks for each pixel from a signal to be encoded supplied in units of prediction blocks. An evaluation value for evaluating the amount of code and the amount of distortion is calculated using the prediction residual signal, and the most suitable mode from the viewpoint of the amount of code and the amount of distortion among a plurality of intra prediction modes for each prediction block. And the intra prediction information corresponding to the selected intra prediction mode, the intra prediction signal, and the evaluation value of the intra prediction are supplied to the encoding method determining unit 105 as the intra prediction candidates of the prediction block. In addition,
A prediction processing unit for performing intra prediction will be described later.

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

The encoding method determination unit 105 selects an optimal code based on the intra prediction evaluation value corresponding to the intra prediction information selected for each prediction block and the inter prediction evaluation value corresponding to the inter prediction information. Block splitting method, prediction mode (
PredMode) and division mode (PartMode) are determined, and encoded information including intra prediction information or inter prediction information according to the determination is supplied to the second encoded bit string generation unit 113, and the encoded information storage memory 110 And the prediction signal subjected to intra prediction or inter prediction according to the determination is supplied to the residual signal generating unit 106 and the decoded image signal superimposing unit 109.

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

The orthogonal transform / quantization unit 107 performs orthogonal transform and quantization for transforming the supplied residual signal into a frequency domain such as DCT or DST according to a quantization parameter, and performing orthogonal transform / quantization. A signal is generated and supplied to the third encoded bit string generation unit 114 and the inverse quantization / inverse orthogonal transform unit 108.

The first encoded bit string generation unit 112 calculates the value of the syntax element related to the encoding information of the sequence, the picture, and the slice unit according to the semantic rule that defines the meaning of the syntax element and the derivation method, Entropy coding is performed on the value of the syntax element in accordance with syntax rules, such as variable length coding and arithmetic coding, to generate the first coded bit string, and the coded first coded bit string is coded. Bit string multiplexing unit 1
15 is supplied. The value of the syntax element relating to the color difference format is also calculated by the first encoded bit string generation unit 112. A syntax element relating to the color difference format is calculated from the color difference format information supplied from the color difference format setting unit 101. FIG. 10 shows an example of syntax definition when the color difference format information is encoded with a sequence parameter set which is a header for encoding information relating to the encoding of the entire sequence defined in the present embodiment. The syntax element chroma_format_idc indicates the type of color difference format. The meaning of the syntax element chroma_format_idc is 0 for monochrome, 1 for 4: 2: 0, and 2 for 4.
: 2: 2, 3 represents 4: 4: 4. Also, the syntax element separate_colour_plane_flag
Means whether the luminance and color difference signals are encoded separately, separate_colour_pl
When the value of ane_flag is 0, it indicates that the two color difference signals are associated with the luminance signal and encoded. When the value of the syntax element chroma_format_idc is 1, it represents that the luminance signal and the two color difference signals are encoded separately. Only when the value of the syntax element chroma_format_idc is 3, that is, when the color difference format is 4: 4: 4, the value of chroma_format_idc can be set to 0 or 1, and in other color difference formats, the syntax element separate_c is always set.
Encoding is performed assuming that the value of olour_plane_flag is 0.

The second encoded bit string generation unit 113 is determined by the encoding method determination unit 105 for each prediction block, in addition to the encoding information for each encoding block, according to semantic rules that define the meaning of the syntax element and the derivation method. A value of a syntax element related to the encoded information is calculated. Specifically, in addition to coding information in units of coding blocks such as a coding block division method, prediction mode (PredMode), and division mode (PartMode), values of syntax elements related to coding information in units of prediction blocks Is calculated. When the prediction mode (PredMode) is intra prediction, the value of the syntax element regarding the intra prediction mode including the intra luminance prediction mode and the intra color difference prediction mode is calculated. When the prediction mode (PredMode) is inter prediction, the inter prediction mode The value of the syntax element regarding the inter prediction information such as the information specifying the reference image and the motion vector is calculated. The value of each calculated syntax element is subjected to entropy coding by variable length coding, arithmetic coding, etc. in accordance with syntax rules to generate a second coded bit string, and the coded second coding The bit string is supplied to the encoded bit string multiplexing unit 115. Details of the syntax element calculation related to the intra luminance prediction mode and the intra color difference prediction mode performed by the second encoded bit string generation unit 113 and the details of the entropy encoding process will be described later.

The third encoded bit string generation unit 114 performs entropy encoding by variable length encoding, arithmetic encoding, etc. according to a prescribed syntax rule for the orthogonal transform and quantized residual signal,
A third encoded bit string is generated, and the third encoded bit string is converted into an encoded bit string multiplexing unit 11.
5 is supplied.

The encoded bit string multiplexing unit 115 generates a bit stream by multiplexing the first encoded bit string, the second encoded bit string, and the third encoded bit string in accordance with a prescribed syntax rule. Output a bitstream.

The inverse quantization / inverse orthogonal transform unit 108 performs inverse quantization and inverse orthogonal transform on the orthogonal transform / quantized residual signal supplied from the orthogonal transform / quantization unit 107 to calculate a residual signal, and decodes it. This is supplied to the image signal superimposing unit 109. The decoded image signal superimposing unit 109 includes a prediction signal that has been intra-predicted or inter-predicted according to the determination by the encoding method determining unit 105, and a residual that has been inversely quantized and inversely orthogonal transformed by the inverse quantization / inverse orthogonal transform unit 108. The decoded image is generated by superimposing the signal and stored in the decoded image memory 111. Note that the decoded image may be stored in the decoded image memory 111 after filtering processing that reduces block distortion or the like due to encoding.

FIG. 2 is a block diagram showing a configuration of an image decoding apparatus according to an embodiment corresponding to the image encoding apparatus of FIG. The image decoding apparatus according to the embodiment includes an encoded bit string separating unit 201, a first encoded bit string decoding unit 202, a second encoded bit string decoding unit 203, a third encoded bit string decoding unit 204, and a color difference format management unit. 205, intra prediction unit 206, inter prediction unit 2
07, an inverse quantization / inverse orthogonal transform unit 208, a decoded image signal superimposing unit 209, an encoded information storage memory 210, a decoded image memory 211, and switches 212 and 213.

The bit stream supplied to the encoded bit string separation unit 201 is separated according to a rule of a prescribed syntax, and the first encoded bit string indicating the encoded information in sequence, picture, and slice units is the first encoded bit string decoding The second encoded bit sequence that is supplied to the unit 202 and includes encoding information in units of encoded blocks is supplied to the second encoded bit sequence decoding unit 203, and includes a residual signal that is subjected to orthogonal transform and quantization. Are supplied to the third encoded bit string decoding unit 204.

The first encoded bit string decoding unit 202 entropy-decodes the supplied first encoded bit string in accordance with the syntax rule, and each value of the syntax element regarding the encoded information in units of sequences, pictures, and slices. Get. In accordance with the semantic rules that define the meaning of the syntax element and the derivation method, the sequence, the picture, and the value of the syntax element regarding the encoded information in units of slices, the sequence, the picture,
Also, encoding information for each slice is calculated. The first encoded bit string decoding unit 202 is an encoded bit string decoding unit corresponding to the first encoded bit string generation unit 112 on the encoding side, and the sequence encoded by the first encoded bit string generation unit 112, It has a function of returning to each encoded information from an encoded bit string including encoded information in units of pictures and slices. The color difference format information encoded by the first encoded bit string generation unit 112 is a syntax element related to the color difference format information obtained by entropy decoding the second encoded bit string by the first encoded bit string decoding unit 202. Calculate from the value. According to the syntax rules and semantic rules 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 value of the syntax element chroma_format_idc is 0 for monochrome, 1 for 4: 2: 0, and 2 for 4 : 2: 2, 3 becomes 4: 4: 4. Furthermore, when the value of the syntax element chroma_format_idc is 3, the syntax element separate_colour_plane_fla
g is decoded to determine whether the luminance signal and the color difference signal are encoded separately. The calculated 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 chrominance format information is supplied to the second encoded bit string decoding unit 203, and the encoding block and prediction block encoding information calculation processing based on the chrominance format information is performed. Although not explicitly shown in the figure, the third encoded bit string decoding unit 204, the intra prediction unit 206, the inter prediction unit 207, the inverse quantization / inverse orthogonal transform unit 208, and the decoded image signal superimposing unit 209 in FIG. Decoding processing based on the color difference format information is performed, and the encoding information storage memory 210 and the decoded image memory 211 are managed based on the color difference format information.

The second encoded bit string decoding unit 203 entropy-decodes the supplied first encoded bit string in accordance with the syntax rule, and each of the syntax elements related to the encoded information of the encoded block and the prediction block unit. Get the value. In accordance with the semantic rules that define the meaning of the syntax element and the derivation method, the code of the encoding block unit and the prediction block unit is calculated from the value of the syntax element related to the supplied encoding block unit and the encoding information of the prediction block unit. Calculation information is calculated. The second encoded bit string decoding unit 203 is an encoded information calculation unit corresponding to the second encoded bit string generation unit 113 on the encoding side, and is encoded by the second encoded bit string generation unit 113. It has the function to return to each encoding information from the 2nd encoding bit sequence containing the encoding information of a block and a prediction block unit. Specifically, from each syntax element obtained by decoding the second encoded bit string according to a prescribed syntax rule, a coding block division method, a prediction mode (PredMode),
In addition to the division mode (PartMode), when the prediction mode (PredMode) is intra prediction, an intra prediction mode including an intra luminance prediction mode and an intra color difference prediction mode is obtained. On the other hand, when the prediction mode (PredMode) is inter prediction, inter prediction information such as the inter prediction mode, information for specifying a reference image, and a motion vector is obtained. When the prediction mode (PredMode) is intra prediction, the intra prediction mode 206 including the intra luminance prediction mode and the intra color difference prediction mode is supplied to the intra prediction unit 206 through the switch 212, and the prediction mode (Pr
When edMode) is inter prediction, the inter prediction information such as the inter prediction mode, the information for identifying the reference image, and the motion vector is supplied to the inter prediction unit 207 through the switch 212. In addition, the entropy decoding process performed in the second encoded bit string decoding unit 203, and the intra luminance prediction mode, and the intra luminance difference prediction mode value calculation process from the syntax elements related to the intra luminance difference prediction mode, are calculated. Details of the processing will be described later.

The third encoded bit string decoding unit 204 calculates a residual signal that has been orthogonally transformed and quantized by decoding the supplied encoded bit string, and inversely quantized the residual signal that has been orthogonally transformed and quantized. This is supplied to the inverse orthogonal transform unit 208.

The intra prediction unit 206 generates a predicted image signal by intra prediction from the decoded peripheral blocks stored in the decoded image memory 211 according to the supplied intra luminance prediction mode and the intra prediction mode including the intra color difference prediction mode. Then, the predicted image signal is supplied to the decoded image signal superimposing unit 209 via the switch 213. The unit for performing intra prediction will be described later. Further, in the present embodiment, when the value of the intra color difference prediction mode is predicted from the value of the intra luminance prediction mode, the method for deriving the intra color difference prediction mode differs depending on the color difference format. In this case, intra prediction is performed using an intra prediction mode derived by a different method depending on the color difference format. A method for deriving the intra color difference prediction mode described later will be described later.

The inter prediction unit 207 uses motion compensation from the decoded reference picture stored in the decoded image memory 211 using the inter prediction mode supplied, information specifying the reference picture, and inter prediction information such as a motion vector. 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 bi-prediction, the two motion-compensated prediction image signals of L0 prediction and L1 prediction are adaptively multiplied and weighted to generate a final prediction image signal.

The inverse quantization / inverse orthogonal transform unit 208 performs inverse orthogonal transform and inverse quantization on the orthogonal transform / quantized residual signal decoded by the third coded bit string decoding unit 204 to perform inverse orthogonal transform. Obtain a dequantized residual signal.

The decoded image signal superimposing unit 209 includes a prediction image signal predicted by the intra prediction unit 206 or the inter prediction unit 207, and a residual signal that has been inversely orthogonal transformed / inversely quantized by the inverse quantization / inverse orthogonal transform unit 208. Are decoded, the decoded image signal is decoded, and the decoded image memory 211 is decoded.
To store. When stored in the decoded image memory 211, the decoded image may be stored in the decoded image memory 211 by performing a filtering process that reduces block distortion or the like due to encoding. The decoded image signals stored in the decoded image memory 211 are output in the output order.

Next, a prediction processing unit for intra prediction, which is one of the points of the embodiment, will be described in detail.

First, the minimum unit of orthogonal transformation in this embodiment will be described. In image coding, low-frequency component image quality degradation is conspicuous, but high-frequency component image quality degradation is less noticeable. Reduce the amount. However, since it is difficult to sufficiently divide the 2 × 2 conversion into frequency components, the code amount reduction effect is low. Also, if each of the intra prediction, transform, and quantization processing units is made too small, the number of corresponding processing units increases, and the processing becomes complicated. Therefore, in this embodiment, the minimum unit of orthogonal transformation is 4 × 4 pixels.

Next, the minimum unit of intra prediction in the present embodiment, that is, the minimum size of the prediction block in the case of intra prediction will be described. In the intra prediction, since the pixel value of the processing target block is predicted from the pixel values of the surrounding decoded blocks in the same screen, it is necessary to complete the decoding process before encoding and decoding the subsequent block. Specifically, using the intra-predicted prediction signal, a residual signal is calculated, and the residual signal is subjected to orthogonal transformation, quantization, and inverse quantization,
By performing inverse transformation and superimposing with the prediction signal, the decoding process is completed, and the subsequent block becomes in a state where intra prediction is possible. Therefore, intra prediction needs to be performed in units that are equal to or larger than the size of the smallest transform block. This is because if intra prediction is performed in units smaller than the minimum transform block size, then orthogonal transform cannot be performed and decoding processing cannot be performed. Therefore, in this embodiment, the minimum unit of intra prediction, that is, the minimum size of the prediction block at the time of intra prediction is also set to 4 × 4 pixels similarly to the minimum unit of orthogonal transform.

Next, the minimum size of the encoded block in the present embodiment will be described. In the minimum coding block, the prediction mode (PredMode) defines intra prediction (MODE_INTRA), and the inter prediction and partition mode (PartMode) define N × N division. N × N division is a division mode (PartMode) in which the luminance signal of an encoded block is divided into four prediction blocks by horizontal and vertical equal division.
However, in this embodiment, since the minimum unit of intra prediction is 4 × 4 pixels, the minimum size of the encoded block is 8 × 8 pixels in the luminance signal.

Next, a method of dividing the color difference signal of the encoded block by N × N division at the time of intra prediction will be described. FIG. 11 is a diagram for explaining a method of dividing a color difference signal of an encoded block by N × N division at the time of intra prediction.

When the color difference format is 4: 2: 0, the minimum size of the coding block is 8 × for the luminance signal.
If the number of pixels is 8, the minimum size of the encoded block is 4 × 4 pixels in the color difference signal, and no further division is possible. Therefore, in this embodiment, the color difference format is 4
In the case of 2: 0, when the prediction mode is intra prediction and the partition mode (PartMode) is N × N partition, as shown in FIG. Intra-prediction is performed in units of 4 × 4 pixels as four prediction blocks by division, but the luminance signal is predicted as one prediction block without dividing the encoded block in the chrominance signal as shown in FIG. 11B. Similar to the block size, intra prediction is performed in units of 4 × 4 pixels. Note that the division index PartIdx of the prediction block of the color difference signal is set to 0.

When the color difference format is 4: 2: 2, if the minimum size of the encoded block is 8 × 8 pixels in the luminance signal, the minimum size of the encoded block is 4 × 8 pixels in the color difference signal. Although it can be divided equally, it cannot be divided vertically. Therefore, in the present embodiment, when the color difference format is 4: 2: 2, when the prediction mode is intra prediction and the division mode (PartMode) is N × N division, as shown in FIG. In the luminance signal, the encoded block is divided into 4 prediction blocks by dividing horizontally and vertically into four prediction blocks.
Intra prediction is performed in units of four pixels. As shown in FIG. 11C, in the color difference signal, the encoded block is equally divided only horizontally and is not divided vertically. Intra prediction is performed in units of four pixels. Note that the division index PartIdx of the prediction block of the color difference signal is set to 0 and 2 in the encoding order (from top to bottom). The reason why the division index PartIdx of the lower block is set to 2 is that the prediction block below the color difference signal is at the same position as the prediction block of the luminance signal division index PartIdx.

The prediction block of the chrominance signal and the prediction block of the luminance signal are in the same position when the coordinates of the pixel at the upper left corner of the prediction block are used as the reference position Say the same.

When the color difference format is 4: 4: 4, if the minimum size of the encoded block is 8 × 8 pixels in the luminance signal, the minimum size of the encoded block is 8 × 8 pixels in the color difference signal. Similarly to the above, four prediction blocks can be obtained by horizontal and vertical equal division. Therefore, in the present embodiment, when the color difference format is 4: 4: 4, when the prediction mode is intra prediction and the division mode (PartMode) is N × N division, as shown in FIG. In the luminance signal, intra-prediction is performed in units of 4 × 4 pixels as four prediction blocks by equally dividing the encoded block horizontally and vertically, and the encoded block is also horizontally converted from the color difference signal as shown in FIG. 4 × as 4 prediction blocks by vertical equal division
Intra prediction is performed in units of four pixels. Similar to the luminance signal, the partition index PartIdx of the prediction block of the color difference signal is also in the encoding order (upper left, upper right, lower left, lower right), 0, 1
2 and 3.

In the embodiment, regardless of the type of the chrominance format, when the values of the division index PartIdx of the prediction block of the luminance signal and the division index PartIdx of the prediction block of the chrominance signal are the same, the position of the prediction block of the luminance signal is indicated. Since the coordinates (the coordinates of the pixel at the top left of the prediction block) and the coordinates indicating the position of the prediction block of the color difference signal (the coordinates of the pixel at the top left of the prediction block) are also the same, they are assumed to be at the same position. .

Next, when the chrominance format is 4: 2: 0, the encoded block is divided into four luminance signals and chrominance signals by N × N division of inter prediction, and the luminance signal is 4 × 4 pixels, and the chrominance signal is 2 × 2. Consider the case of a pixel prediction block. In inter prediction, inter prediction by motion compensation is performed using common encoding information for both the luminance signal and the color difference signal. However, in the motion compensation of the color difference signal with the color difference format of 4: 2: 0, the luminance signal uses a value obtained by scaling the magnitude of the value of the reference motion vector by half in both the horizontal and vertical components. Unlike intra prediction, inter prediction does not use decoded signals of neighboring blocks in the same image, and therefore it is possible to use an inter prediction processing unit smaller than the orthogonal transform processing unit. For this reason, orthogonal transformation can be performed in units larger than the prediction block, so even if the coding block is divided into four by color difference signals and inter prediction is performed in units of 2 × 2 pixels, it is not necessarily in units of 2 × 2 pixels. There is no need to perform orthogonal transformation, and after performing inter prediction of the four prediction blocks,
By combining the four prediction blocks, a residual signal in units of 4 × 4 pixels can be calculated, and orthogonal transformation can be performed in units of 4 × 4 pixels.

Next, when the color difference format is 4: 2: 2, the encoded block is divided into four luminance signals and chrominance signals by N × N division of inter prediction, the luminance signal is 4 × 4 pixels, and the chrominance signal is 2 × 4. Consider the case of a pixel prediction block. In inter prediction, inter prediction by motion compensation is performed using common encoding information for both the luminance signal and the color difference signal. However, in motion compensation of 4: 2: 2 color difference signals with the color difference format, the luminance signal uses the value of the standard motion vector as it is for the vertical component, and the value obtained by scaling the horizontal component by half. Use. Similarly to the case where the color difference format is 4: 2: 0, orthogonal transformation can be performed in units larger than the prediction block. Therefore, even in the color difference signal, the coding block is divided into four and inter prediction is performed in units of 2 × 4 pixels. Even if it is performed, it is not always necessary to perform orthogonal transform in units of 2 × 2 pixels, and after performing inter prediction of four prediction blocks, two prediction blocks arranged in the horizontal direction are respectively combined to obtain two 4 × A residual signal in units of 4 pixels can be calculated, and orthogonal transformation can be performed in units of 4 × 4 pixels.

Therefore, in the N × N division of the inter prediction, it is assumed that the luminance signal and the color difference signal are equally divided both horizontally and vertically regardless of the type of the color difference format to form four prediction blocks.

Next, points relating to the intra prediction mode, which is a feature of the embodiment, regarding the encoding processing of the encoding block and the encoding information in units of prediction blocks performed by the second encoded bit string generation unit 113 in FIG. The explanation is centered. FIG. 12 is a block diagram showing the configuration of the second encoded bit string generation unit 113 of FIG.

As shown in FIG. 12, the second encoded bit string generation unit 113 in FIG. 1 includes a syntax element calculation unit 121 related to encoding information in units of encoded blocks, a syntax element calculation unit 122 related to an intra luminance prediction mode, an intra It comprises a syntax element calculation unit 123 related to the color difference prediction mode, a syntax element calculation unit 124 related to inter prediction information, an intra prediction mode encoding control unit 125, and an entropy encoding unit 126. In each unit constituting the second encoded bit string generation unit 113, processing corresponding to the color difference format information supplied from the color difference format setting unit 101 is performed, and a prediction mode and a division mode (PartMode) in units of encoded blocks are performed. Etc., processing corresponding to the encoded information is performed.

The syntax element calculation unit 121 related to the coding information for each coding block calculates the value of the syntax element related to the coding information for each coding block, and sends the calculated value of each syntax element to the entropy coding unit 126. Supply. Intra prediction of coded block (
MODE_INTRA) or prediction mode (PredMode) to determine inter prediction (MODE_INTER),
And the value of the syntax element regarding the partition mode (PartMode) for determining the shape of the prediction block is calculated by the syntax element calculation unit 121 of the encoding information in units of the encoding block.

The syntax element calculation unit 122 related to the intra luminance prediction mode, when the prediction mode (PredMode) of the encoded block is intra prediction (MODE_INTRA), sets the value of the syntax element related to the intra luminance prediction mode of the prediction block of the luminance signal. The calculated value of each syntax element is supplied to the entropy encoding unit 126. The syntax element related to the intra luminance prediction mode is a flag indicating whether or not prediction can be performed from the intra luminance prediction mode of the surrounding blocks. Syntax element prev_intra_luma_pred_flag [x0] [y0
], A syntax element mpm_idx [x0] that is an index that points to the prediction block of the prediction source
[y0] and a syntax element rem_in indicating an intra luminance prediction mode in units of prediction blocks
tra_luma_pred_mode [x0] [y0]. Note that x0, and y0 are coordinates indicating the position of the prediction block. In calculating the value of the syntax element related to the intra luminance prediction mode,
This is a flag indicating that the value is used when prediction is possible from the intra-brightness prediction mode of the surrounding block using the correlation with the intra-brightness prediction mode of the surrounding block stored in the encoded information storage memory 110. Syntax element prev_intra_luma_pred_flag [x0
] [y0] is set to 1 (true), and a value specifying the reference destination is set in the syntax element mpm_idx [x0] [y0], which is an index indicating the prediction block of the prediction source. , Prev_intra_luma_pred_flag [x0] [y0] is set to 0 (false), and a value specifying the intra luminance prediction mode is set to the syntax element rem_intra_luma_pred_mode [x0] [y0] indicating the intra luminance prediction mode to be encoded.

In addition, when the number of intra luminance prediction modes of the prediction block in the coding block differs depending on the division block, and the division mode (PartMode) is 2N × 2N division, the intra luminance of one set of prediction blocks for each coding block. The value of the syntax element regarding the prediction mode is calculated. When the division mode is N × N division, the value of the syntax element regarding the intra luminance prediction mode of four sets of prediction blocks is calculated for each coding block.

The syntax element calculation unit 123 related to the intra color difference prediction mode, when the prediction mode (PredMode) of the encoded block is intra prediction (MODE INTRA), the syntax element related to the intra color difference prediction mode of the prediction block of the color difference signal. The value of mode [x0] [y0] is calculated, and the value of the calculated syntax element intra chroma pred mode [x0] [y0] is supplied to the entropy encoding unit 126. In calculating the value of the syntax element related to the intra chrominance prediction mode, the correlation between the prediction block of the luminance signal at the same position as the prediction block of the chrominance signal and the intra luminance prediction mode of the prediction block of the chrominance signal is used. When prediction is possible from the intra luminance prediction mode of the prediction block of the luminance signal at the same position as the prediction block, the value of the intra color difference prediction mode is predicted from the value of the intra luminance prediction mode, and the intra color difference prediction mode cannot be predicted from the intra luminance prediction mode In such a case, a mechanism for setting any one of 0 ( vertical direction), 1 (horizontal direction), 2 (average value), and 3 (diagonal 45 degrees), which is a representative intra prediction mode, to the intra color difference prediction mode. By using it, the code amount is reduced.

Here, a method for predicting 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 on the decoding side will be described.
FIG. 14 shows a syntax element intra_ch related to the intra color difference prediction mode defined in this embodiment.
It is a conversion table that calculates the value of the intra color difference prediction mode from the value of roma_pred_mode [x0] [y0] 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, and using this conversion table, On the decoding side, the value of the intra color difference prediction mode is calculated.
When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0, the value of the intra color difference prediction mode is predicted from 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 according to the color difference format. Is done.

The color difference format is 4: 2: 0 or 4: 4: 4 and the syntax element intra_chroma_pre
When the value of d_mode [x0] [y0] is 0, 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 becomes the value of the intra color difference prediction mode as it is.

The color difference format is 4: 2: 2 and the syntax element intra_chroma_pred_mode [x0] [y0
] Is 0, the intra color difference prediction mode value is calculated according to the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal, using the conversion table shown in FIG. FIG. 15 is a diagram for predicting the value of the intra color difference prediction mode from 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 when the color difference format specified in this embodiment is 4: 2: 2. It is a conversion table.

When the color difference format is 4: 2: 2, when the value of the intra color difference prediction mode is predicted from the value of the intra luminance prediction mode, the value is left as it is as 4: 2: 0 or 4: 4: 4. First, the reason for calculating using the conversion table of FIG. 15 will be described. The color difference format is 4
: 2: 2 shows that the color difference signal is half of the luminance signal in the horizontal direction as shown in FIG.
Is a color difference format sampled at the same density in the vertical direction. Therefore, when intra prediction of a color difference signal is performed in a prediction direction scaled by a factor of two in the horizontal direction with respect to each prediction direction of the intra luminance prediction mode, or a prediction direction in the vicinity thereof, a color difference signal prediction block Is equivalent to or close to equivalent to the intra prediction of the luminance signal of the prediction block at the same position.

This will be described in more detail with reference to FIG. In FIG. 27, the color difference format is 4: 2.
: Is a figure explaining the correspondence of the prediction direction of the intra prediction of the luminance signal in the case of 2, and a color difference signal. In FIG. 27, x indicates the pixel position of the luminance signal, and ◯ indicates the pixel position of the color difference signal. In 4: 2: 2, the color difference signal is sampled (sampled) in half in the horizontal direction with respect to the luminance signal. FIG. 27A shows the sampled pixel positions of the 4: 2: 2 luminance signal and the color difference signal. The code P1 is a pixel that is intra-predicted, and the code P2 is a pixel that is referred to during intra-prediction (actually, since it is filtered, the adjacent pixel is also referred to). Reference 27
An arrow from the pixel P1 to the pixel P2 shown in 01 indicates the intra prediction direction of the pixel P1 of the luminance signal and also indicates the intra prediction direction of the pixel P1 of the color difference signal.

FIG. 27B shows an array of pixels of the color difference signal sampled by 1/2 in the horizontal direction. Here, in the case of performing the intra prediction of the color difference signal, if the half scaling is not performed in the horizontal direction, the intra prediction direction of the pixel P1 of the color difference signal becomes the arrow direction indicated by reference numeral 2702, and the color difference signal In this pixel arrangement, the pixel P3 is erroneously referred to. However, the correct reference destination is the pixel P2. Therefore, the intra prediction direction of the luminance signal is scaled by a factor of 1/2 in the horizontal direction to obtain the intra prediction direction of the color difference signal, thereby calculating the correct intra prediction direction in the arrangement of the color difference signals as indicated by reference numeral 2703. Then, the pixel adjacent to the upper side, which is the correct reference destination in the intra prediction direction (actually, since it is filtered, the adjacent pixel is also referred to) is acquired.

In FIGS. 27A and 27B, the case where the pixel adjacent to the upper side of the prediction block is referred to has been described, but the same applies to the case where the pixel adjacent to the left side is referred to. In the case of the pixel adjacent to the left side, the intra prediction direction of the luminance signal is scaled twice in the vertical direction (this is equivalent in terms of obtaining the intra prediction direction by scaling to 1/2 times in the vertical direction). ) To calculate the correct intra prediction direction in the chrominance signal array, and obtain the pixels adjacent to the left side (including pixels adjacent to the upper part), which is the correct reference destination in the intra prediction direction. To do.

Therefore, in the conversion table of FIG. 15, as indicated by the dotted arrows in FIG. 8, the values of the intra luminance prediction modes in which the reference destinations are arranged in the horizontal direction (on the horizontal axis) are 3, 18, 10, 19,
4, 20, 11, 21, 0, 22, 12, 23, 5, 24, 13, 25, 6 in the prediction direction calculated by scaling those values by a factor of 2 in the horizontal direction The value of the intra color difference prediction mode in the nearest prediction direction is selected, and the values of the intra color difference prediction mode are set to 19, 4, 20, 20, 11, 11, 21, 0, 0, 0, 22, 12, 12, 23
, 23, 5 and 24. Scaling the prediction direction of intra prediction by a factor of two in the horizontal direction is equivalent to scaling by a factor of two in the vertical direction. Therefore, when intra prediction of a color difference signal is performed in a prediction direction scaled twice in the vertical direction with respect to each prediction direction of the intra luminance prediction mode or a prediction direction in the vicinity thereof, the same position as the prediction block of the color difference signal It is equivalent to or close to the intra prediction of the luminance signal of the prediction block. Therefore, in the conversion table of FIG. 15, as shown in FIG. 8, the values of the intra luminance prediction modes in which the reference destinations are arranged in the vertical direction (on the vertical axis) are 26, 14, 27, 7,
In the case of 28, 15, 29, 1, 30, 16, 31, 8, 32, 17, 33, 9, the intra color difference prediction mode of the prediction direction closest to the prediction direction calculated by scaling twice in the vertical direction And the intra color difference prediction mode values are 10, 18, 3, 26, 27.
, 28, 15, 1, 16, 31, 32, 33, 9, 9, 9, 9.

On the other hand, when the color difference format is 4: 2: 0 or 4: 4: 4, when predicting the value of the intra color difference prediction mode from the value of the intra luminance prediction mode, the intra prediction direction of the luminance signal and the intra of the color difference signal are calculated. Since the prediction directions match, it is not necessary to convert the value of the intra luminance prediction mode to the value of the intra color difference prediction mode. This will be described with reference to FIG. FIG.
8 is a diagram for explaining a correspondence relationship between the prediction direction of the luminance signal and the intra prediction of the color difference signal when the color difference format is 4: 2: 0. In FIG. 28A, the color difference format is 4: 2: 0.
In this case, the arrangement of the luminance signal and the color difference signal is shown, and the color difference signal is sampled (sampled) in both horizontal and vertical directions with respect to the luminance signal. Pixel P4 indicated by reference numeral 2704
The arrow from to the pixel P5 indicates the intra prediction direction of the pixel P4 of the luminance signal. Reference numeral 2705
An arrow from the pixel P1 to the pixel P2 shown in FIG. 4 indicates the intra prediction direction of the pixel P1 of the color difference signal. The arrow from pixel P4 to pixel P5 indicated by reference numeral 2704 and the arrow from pixel P1 to pixel P2 indicated by reference numeral 2705 are directed in the same direction, and the intra prediction direction is the same. in this case,
Also in the arrangement of color difference signals shown in FIG. 28B, the intra prediction direction of the luminance signal is the same as the intra prediction direction of the color difference signal as indicated by reference numeral 2706, and the pixel P1 of the color difference signal
Can be referred to correctly.

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 luminance 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. To predict the value of the intra color difference prediction mode. That is, when the color difference format is 4: 2: 0 or 4: 4: 4 and the value of the intra color difference prediction mode is predicted, the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal is used as it is. The color difference prediction mode value is used. Color difference format is 4: 2:
15, when the intra color difference prediction mode value is predicted, the intra color difference prediction mode value is set according to the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal, using the conversion table shown in FIG. calculate.

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 1 to 4, FIG.
On the decoding side, the syntax element intra_chroma_pred_mode [x0]
The value of the intra color difference prediction mode is calculated by combining the value of [y0] 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.

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 1, the value of the intra color difference prediction mode is 0 or 1 depending on 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. Takes a value.

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 2, the value of the intra color difference prediction mode is 1 or 2 depending on 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. Takes a value.

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 3, the value of the intra color difference prediction mode is 2 or 3, depending on 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. Takes a value.

When the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 4, the value of the intra color difference prediction mode takes a value of 3.

FIG. 16 shows the value of the syntax element intra_chroma_pred_mode [x0] [y0] regarding the intra color difference prediction mode from the value of the intra color difference prediction mode 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. A conversion table to calculate,
The conversion table in FIG. 16 corresponds to the conversion table in FIG. Using the conversion table shown in FIG. 16, on the encoding side, the syntax element intra_chroma_pred_mode [x0] [y0]
Is calculated.

When the value of the intra color difference prediction mode is 0, the syntax element intra_chroma_pred_mo is used according to 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 value of de [x0] [y0] is 0 or 1.

When the value of the intra color difference prediction mode is 1, the syntax element intra_chroma_pred_mo is used according to 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 value of de [x0] [y0] is 0, 1 or 2.

When the value of the intra color difference prediction mode is 2, the syntax element intra_chroma_pred_mo is used according to 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 value of de [x0] [y0] is 0, 2 or 3.

When the value of the intra color difference prediction mode is 3, the syntax element intra_chroma_pred_mo is used according to 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 value of de [x0] [y0] is 0, 3 or 4.

When the value of the intra color difference prediction mode is from 4 to 33, this indicates that the intra color difference prediction mode is predicted from the value of the intra luminance prediction mode of the prediction block at the same position, and the syntax element intra_chroma_pred_mode [x0] [y0] The value is 0. 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 10
3, the intra color difference prediction mode value is calculated according to 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 using the conversion table shown in FIG. Values of 4, 5, 9, 10, 11, 12, 15, 16,
Only one of the values 18, 19, 20, 21, 22, 23, 24, 26, 27, 28, 31, 32, and 33 can be taken.

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, You may specify by referring the coordinate which shows a position.

Note that 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 calculated for each coding block regardless of the type of the 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 luminance prediction mode of one prediction block is calculated for each coding block. When the division mode is N × N division and the color difference format is 4: 2: 2, the value of the syntax element related to the intra luminance prediction mode of two prediction blocks is calculated for each coding block. When the division mode is N × N division and the color difference format is 4: 4: 4, the value of the syntax element regarding the intra luminance prediction mode of four prediction blocks is calculated for each coding block.

The syntax element calculation unit 124 of the inter prediction information uses a prediction mode (
When PredMode) is inter prediction (MODE_INTER), a value of a syntax element related to inter prediction information in units of prediction blocks is calculated, and the calculated value of each syntax element is supplied to the entropy encoding unit 126. The inter prediction information in units of prediction blocks includes information such as an inter prediction mode (L0 prediction, L1 prediction, bi-prediction), an index for specifying a plurality of reference images, and a motion vector.

The entropy encoding unit 126
A value of a syntax element related to encoding information in units of encoding blocks supplied from the syntax element calculation unit 121 related to encoding information in units of encoding blocks;
A value of a syntax element related to the intra luminance prediction mode of the prediction block of the luminance signal supplied from the syntax element calculation unit 122 related to the intra luminance prediction mode;
Prediction block unit supplied from the syntax element calculation unit 124 of the inter prediction information and 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 calculation unit 123 related to the intra color difference prediction mode The value of the syntax element related to the inter prediction information is entropy-encoded according to a predetermined syntax rule. At this time, the intra prediction mode encoding control unit 125 controls the order of the entropy encoding of the intra luminance prediction mode and the intra color difference prediction mode according to the division mode and the color difference format, and the entropy encoding unit 126 performs the intra prediction mode. Entropy encoding processing of the intra luminance prediction mode and the intra color difference prediction mode is performed in the order instructed by the encoding control unit 125.

The order of entropy encoding in the intra luminance prediction mode and the intra color difference prediction mode in the N × N division in the entropy encoding unit 126 controlled by the intra prediction mode encoding control unit 125 will be described. FIG. 17 is a diagram illustrating entropy encoding or decoding order of syntax elements related to the intra luminance prediction mode and the intra color difference prediction mode in the case of N × N division according to the embodiment. FIGS. 17 (a), 17 (b), and 17 (c) show entropy encoding and decoding orders when the color difference format is 4: 2: 0, 4: 2: 2, and 4: 4: 4, respectively. . L0, L1, L2, and L3 are luminance signal division indexes PartId.
x indicates a syntax element related to the intra luminance prediction modes of 0, 1, 2, and 3 respectively, and C0, C1, C2, and C3 indicate predictions of color difference signal division indexes PartIdx of 0, 1, 2, and 3, respectively. It shows that the syntax element is related to the intra color difference prediction mode of the block.

When the color difference format is 4: 2: 0, after L0, L1, L2, and L3 are encoded,
C0 is encoded. (C1, C2, and C3 do not exist and are not encoded.)

When the color difference format is 4: 2: 2, L0, L1, L2, and L3 are encoded, and then C0 and C2 are encoded. (C1 and C3 do not exist and are not encoded.)

When the color difference format is 4: 4: 4, L0, L1, L2, and L3 are encoded, and subsequently encoded in the order of C0, C1, C2, and C3.

That is, after the inter luminance prediction modes included in the same encoded block are continuously encoded, the intra color difference prediction modes are continuously encoded.

Next, with regard to the decoding process of the encoded information in units of the encoded block and the prediction block performed by the second encoded bit string decoding unit 203 in FIG. 2, the points related to the intra prediction mode, which is a feature of the embodiment, are mainly described. Explained. FIG. 13 shows the second encoded bit string decoding unit 2 in FIG.
3 is a block diagram showing the configuration of 03. FIG.

As illustrated in FIG. 13, the second coded bit string decoding unit 203 in FIG. 2 includes an intra prediction mode decoding control unit 221, an entropy decoding unit 222, a coding information calculation unit 223 for each coding block, an intra luminance prediction mode. Calculation unit 224, intra color difference prediction mode calculation unit 225
The inter prediction information calculation unit 226 is configured. Second encoded bit string decoding unit 20
3, processing corresponding to the color difference format information supplied from the color difference format management unit 205 is performed, and processing corresponding to encoding information such as a prediction mode and a division mode for each encoding block is performed. Is called.

The entropy decoding unit 222 is a coding block supplied from the coding bit string separation unit,
And entropy decoding of a coded bit string including coding information in units of prediction blocks according to a predetermined syntax rule, values of syntax elements relating to coding information in units of coding blocks, and intra luminance prediction modes of prediction blocks of luminance signals The value of the syntax element for the
The value of the syntax element regarding the intra color difference prediction mode of the prediction block of the color difference signal and the value of the syntax element regarding the inter prediction information in units of prediction blocks are obtained. At that time, the intra prediction mode decoding control unit 221 controls the order of the entropy decoding of the intra luminance 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 process of the intra luminance prediction mode and the intra color difference prediction mode is performed in the order instructed 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 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 that is the same as the encoding 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 a decoding unit corresponding to the encoding-side entropy encoding unit 126, and performs entropy decoding processing according to the same rules as the syntax rules used in the entropy encoding unit 126. That is, the intra prediction mode decoding process is performed in the same order as the encoding order shown in FIG. That is, after the inter luminance prediction modes belonging to the same coding block are successively decoded, the intra color difference prediction modes are successively decoded.

The value of the syntax element relating to the coding information in units of coding blocks obtained by decoding is supplied to the coding information calculation unit 223 in units of coding blocks, and the syntax elements relating to the intra luminance prediction mode of the prediction block of the luminance signal The value is an intra luminance prediction mode calculation unit 224.
The value of the syntax element related to the intra color difference prediction mode calculation unit 225 of the prediction block of the color difference signal is supplied to the intra color difference prediction mode calculation unit 225, and the value of the syntax element related to the inter prediction information for each prediction block is calculated as the inter prediction information. To the unit 226.

The coding information calculation unit 223 for each coding block calculates coding information for each coding block from the value of the syntax element related to the supplied coding information for each coding block,
This is supplied to the intra prediction unit 206 or the inter prediction unit 207 via the switch 212.

The coding information calculation unit 223 for each coding block is a coding information calculation unit corresponding to the syntax element calculation unit 121 related to coding information for each coding block on the coding side, and calculates according to the same semantic rule. Intra prediction of coded block (MODE_INTRA)
Alternatively, a value related to the prediction mode (PredMode) for determining the inter prediction (MODE_INTER) and the partition mode (PartMode) for determining the shape of the prediction block are calculated by the encoding information calculation unit 223 for each encoding block.

The intra luminance prediction mode calculation unit 224 is a coding information calculation unit 22 for each coding block.
The prediction mode (PredMode) of the coding block calculated in step 3 is intra prediction (MODE_INTRA)
In this case, the intra luminance prediction mode of the prediction block of the luminance signal is calculated from the value of the syntax element related to the intra luminance prediction mode of the prediction block of the supplied luminance signal, and is supplied to the intra color difference prediction mode calculation unit 225. This is supplied to the intra prediction unit 206 via the switch 212. The intra luminance prediction mode calculation unit 224 is an encoding information calculation unit corresponding to the syntax element calculation unit 122 related to the intra luminance prediction mode on the encoding side,
Calculate according to the same semantic rules. The syntax element related to the intra luminance prediction mode is a syntax element prev_intra_luma_pred_flag [x0] [y0], which is a flag indicating whether prediction is possible from the intra luminance prediction mode of surrounding blocks, and a syntax that is an index indicating the prediction block of the prediction source Element mpm_idx [x0] [y0] and a syntax element rem_intra_luma_pred_mode indicating an intra luminance prediction mode in units of prediction blocks
[x0] [y0]. In the calculation of the intra luminance prediction mode, using the correlation with the intra luminance prediction mode of the surrounding blocks stored in the encoded information storage memory 210,
The syntax element prev_intra_luma_pred_flag [x0] [y0], which is a flag indicating that the value is used when prediction is possible from the intra-brightness prediction mode of the surrounding block, is 1 (true), and indicates the prediction block of the prediction source The syntax element mpm_ that is the index
The intra luminance prediction mode of the surrounding prediction block indicated by idx [x0] [y0] is set as the intra luminance prediction mode of the prediction mode. Syntax element prev_intra_luma_pred
When _flag [x0] [y0] is 0 (false), the syntax element re indicating the decoded intra luminance prediction mode is used instead of predicting the intra luminance prediction mode from the surrounding prediction blocks.
The intra luminance prediction mode is calculated from the value of m_intra_luma_pred_mode [x0] [y0].

In addition, when the number of intra luminance prediction modes of the prediction block in the coding block differs according to the division mode, and the division mode is 2N × 2N division, the intra luminance prediction mode of one set of prediction blocks for each coding block. When the division mode is N × N division, the value of the intra luminance prediction mode of four sets of prediction blocks is calculated for each coding block.

The intra color difference prediction mode calculation unit 225 outputs the color difference signal to be supplied when the prediction mode (PredMode) of the coding block calculated by the coding information calculation unit 223 for each coding block is intra prediction (MODE INTRA). The value of the intra color difference prediction mode is calculated from the value of the syntax element intra chroma pred mode [x0] [y0] and the value of the intra luminance prediction mode supplied from the intra luminance prediction mode calculation unit regarding the intra color difference prediction mode of the prediction block. , And supplied to the intra prediction unit 206 via the switch 212. The intra color difference prediction mode calculation unit 225 is an encoding information calculation unit corresponding to the syntax element calculation unit 123 related to the intra color difference prediction mode on the encoding side, and calculates according to the same semantic rule. In the calculation of the value of the intra color difference prediction mode, the correlation between the prediction block of the luminance signal at the same position as the prediction block of the color difference signal and the intra luminance prediction mode of the prediction block is used. When it is determined that the prediction can be made from the intra luminance prediction mode of the prediction block of the luminance signal at the same position as the prediction block of the current image, the value of the intra color difference prediction mode is predicted from the value of the intra luminance prediction mode, and the prediction is performed from the intra luminance prediction mode. If it is determined that it is better to set a unique value for the intra color difference prediction mode than 0 ( vertical direction), 1 (horizontal direction), 2 ( The code amount is reduced by using a mechanism for setting any one of (average value) and 3 (45 degrees oblique).

FIG. 14 is a conversion table for calculating the value of the intra color difference prediction mode from the value of the syntax element intra_chroma_pred_mode [x0] [y0] 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. The intra color difference prediction mode value is calculated using the conversion table. Also, as explained on the encoding side, the syntax element intra_ch
When the value of roma_pred_mode [x0] [y0] is 0, the value of the intra color difference prediction mode is predicted from 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 according to the color difference format. When the color difference format is 4: 2: 0 or 4: 4: 4 and the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0, 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 the value of the intra color difference prediction mode. The color difference format is 4: 2: 2 and the syntax element intra_chroma_pre
When the value of d_mode [x0] [y0] is 0, the value of the intra color difference prediction mode is calculated from 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 by the conversion table shown in FIG. To do. FIG. 15 is a diagram for predicting the value of the intra color difference prediction mode from 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 when the color difference format specified in this embodiment is 4: 2: 2. It is a conversion table.

When the prediction mode (PredMode) of the coding block is inter prediction (MODE_INTER), the inter prediction information calculation unit 226 calculates inter prediction information from the value of the syntax element related to the inter prediction information in units of prediction blocks, and calculates The value of the inter prediction information is supplied to the inter prediction unit 207 via the switch 212. The inter prediction information calculation unit 226 is a coding information calculation unit corresponding to the syntax element calculation unit 124 of the inter prediction information on the coding side, and calculates according to the same semantic rule. The calculated inter prediction information for each prediction block includes information such as an inter prediction mode (L0 prediction, L1 prediction, bi-prediction), an index for specifying a plurality of reference images, and a motion vector.

Next, syntax rules used in the present embodiment will be described focusing on points related to the intra prediction mode that is a feature of the embodiment. FIG. 18 is an example of a syntax rule for encoding and decoding the encoding information of the prediction block used in the entropy encoding unit 126 on the encoding side and the entropy decoding unit 222 on the decoding side. In FIG. 18, x0 and y0 are coordinates indicating the position of the prediction block in the luminance signal. FIG. 18 shows the prediction mode (Pr) for each prediction block.
edMode) is intra prediction (MODE_INTRA) and the IntraChroma flag is 0 (false)
It shows that entropy encoding or entropy decoding of syntax elements related to an intra luminance prediction mode in a set of prediction blocks is performed. The IntraChroma flag is set to 1 (true) when information about the intra color difference prediction mode is encoded in intra prediction.
Otherwise, it is 0 (false). The prediction mode (PredMode) is intra prediction (MODE_INTRA
) And the IntraChroma flag is 0 (false), prev_intra_luma_pred_flag [x0] [
Entropy encoding or entropy decoding of y0], and syntax element prev_in
If tra_luma_pred_flag [x0] [y0] is 1 (true), the syntax element mpm_idx [x0] [y
0] entropy encoding or entropy decoding and syntax element prev_int
If ra_luma_pred_flag [x0] [y0] is 0 (false), the syntax element rem_intra_luma_pr
Entropy encoding or entropy decoding of ed_mode [x0] [y0] is performed. When the division mode is 2N × 2N division, the IntraChr is used when entropy encoding or entropy decoding is performed on syntax elements related to a set of intra luminance prediction modes for each encoded block.
The oma flag becomes 0 (false), and the rules of this syntax are applied. Split mode is NxN
In the case of division, syntax elements P0 and P1 related to the intra luminance prediction mode shown in FIG.
, P2 and P3 each time entropy coding or entropy decoding
The oma flag becomes 0 (false), and the rules of this syntax are applied.

On the other hand, when intra prediction (MODE_INTRA) and the IntraChroma flag is 1 (true), it indicates that entropy coding or entropy decoding of the syntax element intra_chroma_pred_mode [x0] [y0] related to the intra color difference prediction mode is performed. . Split mode is 2
In the case of N × 2N division, when the syntax elements related to one set of intra color difference prediction modes are entropy-encoded or entropy-decoded per encoding block, the IntraChroma flag is set to 1 (true), and the rules of this syntax are applied. Is done. When the division mode is N × N division, the IntraChroma flag is set every time the syntax elements C0, C1, C2, and C3 related to the intra color difference prediction mode shown in FIG. 17 are entropy encoded or entropy decoded according to the color difference format. 1 (true) and the rules of this syntax apply.

Next, an example of syntax rules different from the syntax rules shown in FIG. 18 will be described. FIG. 19 shows the entropy encoding unit 126 on the encoding side and the entropy decoding unit 2 on the decoding side.
18 is another example of the syntax rule for encoding and decoding the encoding information of the prediction block used in FIG. In FIG. 19, x0, and y0 are coordinates indicating the position of the prediction block in the luminance signal. FIG. 19 is a prediction block unit, and the prediction mode (PredMode) is intra prediction (MO
DE_INTRA) indicates that entropy coding or entropy decoding of syntax elements related to an intra luminance prediction mode in a set of prediction blocks is performed. If the prediction mode (PredMode) is intra prediction (MODE_INTRA), prev_intra_luma_pred
Entropy coding or entropy decoding of _flag [x0] [y0] is performed, and when the syntax element prev_intra_luma_pred_flag [x0] [y0] is 1 (true), the syntax element mpm
Entropy coding or entropy decoding of _idx [x0] [y0] is performed, and when the syntax element prev_intra_luma_pred_flag [x0] [y0] is 0 (false), the syntax element rem
Entropy encoding or entropy decoding of _intra_luma_pred_mode [x0] [y0] is performed. When the division mode is 2N × 2N division, the rules of this syntax are applied when entropy encoding or entropy decoding is performed on syntax elements related to one set of intra luminance prediction modes for each encoded block. When the division mode is N × N division, the syntax rules are applied every time the syntax elements P0, P1, P2, and P3 related to the intra luminance prediction mode shown in FIG. 17 are entropy-encoded or entropy-decoded. .

Furthermore, if the prediction mode (PredMode) is intra prediction (MODE_INTRA), split mode (
PartMode), the color difference format (ChromaArrayType), and the division index (PartIdx) indicate that entropy encoding or entropy decoding of syntax elements regarding 0 to 4 intra color difference prediction modes is performed. ChromaArrayType is a variable indicating a color difference format, and 0 is monochrome (originally includes 4: 4: 4 and includes a mode in which a luminance signal and a color difference signal are independently encoded, but in this case, it is regarded as monochrome). 1 is 4
: 2: 0, 2 indicates 4: 2: 2, and 3 indicates 4: 4: 4.

The prediction mode (PredMode) is intra prediction (MODE_INTRA), the partition mode (PartMode) is 2N x 2N partition (PART_2Nx2N), and the color difference format (ChromaArrayType) is monochrome (
If not 0), entropy coding or entropy decoding of the syntax element intra_chroma_pred_mode [x0] [y0] regarding the intra color difference prediction mode in units of prediction blocks is performed. When the split mode is 2N × 2N split, 1 per coding block
This syntax is used when entropy coding or entropy decoding is performed on syntax elements related to a set of intra luminance prediction modes, and then entropy coding or entropy decoding is performed on syntax elements related to a set of intra luminance prediction modes per coding block. The following rules apply.

On the other hand, the prediction mode (PredMode) is intra prediction (MODE_INTRA) and the split mode (PartMo
When de) is N × N division (PART_NxN) and the division index (PartIdx) is 3, the syntax rules described below are applied. First, when the color difference format (ChromaArrayType) is not monochrome (0), that is, when the color difference format is 4: 2: 0, 4: 2: 2, or 4: 4: 4, the intra color difference whose division index PartIdx is 0 Entropy coding or entropy decoding of the syntax element intra_chroma_pred_mode [x1] [y1] regarding the prediction mode is performed, and then the color difference format (ChromaArrayType) is 4: 4: 4.
In the case of (3), entropy encoding or entropy decoding of the syntax element intra_chroma_pred_mode [x0] [y1] regarding the intra color difference prediction mode with the division index PartIdx of 1 is performed, and then the color difference format (ChromaArrayType) is 4: 2: 2 (2)
Or 4: 4: 4 (3), entropy coding or entropy decoding of the syntax element intra_chroma_pred_mode [x1] [y0] regarding the intra color difference prediction mode with the division index PartIdx of 2, and then performing the color difference Format (ChromaArrayType)
Or 4: 4: 4 (3) indicates that entropy encoding or entropy decoding of the syntax element intra_chroma_pred_mode [x0] [y0] regarding the intra color difference prediction mode with the division index PartIdx of 3 is performed. . When the division mode is N × N division, the syntax element P3 related to the intra luminance prediction mode of the prediction block having a division index (PartIdx) of 3 shown in FIG. Syntax element C for number of intra color difference prediction modes
The rules of this syntax are applied when entropy coding or entropy decoding of 0, C1, C2, and C3, respectively.

Next, the processing procedure of the encoding process of the encoding block and the encoding information performed in units of prediction blocks performed in the second encoded bit string generation unit 113 in FIG. The explanation will focus on the points involved. FIG. 20 is a flowchart for explaining a processing procedure of coding processing in units of prediction blocks and prediction blocks performed by the second encoded bit string generation unit 113 in FIG.

First, on the encoding side, a syntax element calculation unit 121 for encoding information in units of encoding blocks calculates values of syntax elements related to encoding information including a prediction mode and a division mode of the encoding block, and entropy encoding is performed. Entropy coding is performed by the unit 126 (S
1001). Subsequently, the prediction mode (PredMode) of the coded block is set to intra prediction (MODE_I
If it is not (NTRA) (NO in S1002), the process proceeds to step S1017, where the syntax element calculation unit 124 for inter prediction information calculates the value of the syntax element for inter prediction for each prediction block according to the division mode, and performs entropy coding. Entropy encoding is performed by the unit 126 (S1017), and this encoding process is terminated. Prediction mode of coding block (
If PredMode) is intra prediction (MODE_INTRA) (YES in S1002), step S1
It progresses to the encoding process of intra prediction mode after 003.

Subsequently, when the prediction mode of the coding block is intra prediction, the syntax element calculation unit 122 and the entropy coding unit 126 regarding the intra luminance prediction mode perform intra luminance prediction of a prediction block whose luminance signal division index PartIdx is 0 A mode encoding process is performed (S1003).

Here, the encoding process procedure of the intra luminance prediction mode of the prediction block of the luminance signal performed by the syntax element calculation unit 122 and the entropy encoding unit 126 regarding the intra luminance prediction mode will be described with reference to the flowchart of FIG. FIG. 21 is a flowchart illustrating the coding process procedure of the intra luminance prediction mode of the prediction block of the luminance signal performed by the syntax element calculation unit 122 and the entropy coding unit 126 regarding the intra luminance prediction mode. First, the syntax element calculation unit 12 related to the intra luminance prediction mode.
2, the value of each syntax element relating to the intra luminance prediction mode of the prediction block of the luminance signal is calculated (S1101). At this time, the value of the intra luminance prediction mode is compared with the intra luminance prediction mode of the surrounding blocks, and when there is a prediction block having the same value, the value of the syntax element prev_intra_luma_pred_flag [x0] [y0] is 1 (true) If the value specifying the reference destination is set in the syntax element mpm_idx [x0] [y0] that is an index that points to the prediction block of the prediction source, and there is no prediction block with the same value, the syntax element The value of prev_intra_luma_pred_flag [x0] [y0] is set to 0 (false), and the value specifying the intra luminance prediction mode is set to the syntax element rem_intra_luma_pred_mode [x0] [y0] indicating the intra luminance prediction mode. Subsequently, the entropy encoding unit 126 performs entropy encoding on the value of each syntax element related to the intra luminance prediction mode of the prediction block of the luminance signal (S1102), and the present encoding process ends. In addition, the encoding process procedure of FIG.
This is a common encoding process procedure used in step S1005, step S1006, and step S1007 in addition to step S1003 in FIG.

Returning to FIG. 20 again, when the coding block division mode is not N × N division, that is, when the division mode is 2N × 2N (NO in S1004), the division index PartIdx
Since there is only a prediction block of 0 and there is no intra prediction mode of the prediction block of the luminance signal to be encoded any more, the processing of steps S1005 to S1007 is skipped,
The process proceeds to the encoding process in the intra prediction mode of the prediction block of the color difference signal after step S1008.

On the other hand, when the division mode of the encoded block is N × N division (YES in S1004), the process proceeds to the intra prediction mode encoding process of the prediction block of the luminance signal whose division index PartIdx is greater than zero. First, the luminance signal division index PartIdx in the encoding processing procedure of FIG.
The intra-brightness prediction mode encoding process of the prediction block of 1 is performed (S1005). Subsequently, in the encoding process procedure of FIG. 21, the encoding process of the intra luminance prediction mode of the prediction block whose luminance signal division index PartIdx is 2 is performed (S1006). Subsequently, in the encoding process procedure of FIG. 21, the encoding process of the intra luminance prediction mode of the prediction block whose luminance signal division index PartIdx is 3 is performed (S1007).

Subsequently, when the color difference format is 4: 2: 0, 4: 2: 2 or 4: 4: 4 (S100).
8), the syntax element calculation unit 123 related to the intra color difference prediction mode and the entropy coding unit 126 perform the coding process of the intra color difference prediction mode of the prediction block whose division index PartIdx of the color difference signal is 0 (S1009). If the color difference format is neither 4: 2: 0, 4: 2: 2 or 4: 4: 4, that is, if the color difference format is monochrome (NO in S1008), there is no prediction block for the color difference signal, so the step S1009 and subsequent steps are skipped, and the present encoding process is terminated.

Here, the encoding process procedure of the intra color difference prediction mode of the prediction block of the color difference signal performed by the syntax element calculation unit 123 and the entropy encoding unit 126 regarding the intra color difference prediction mode will be described with reference to the flowchart of FIG. FIG. 22 is a flowchart illustrating the coding process procedure of the intra color difference prediction mode of the prediction block of the color difference signal performed by the syntax element calculation unit 123 and the entropy coding unit 126 regarding the intra color difference prediction mode. First, the syntax element calculation unit 12 related to the intra color difference prediction mode.
3, the value of each syntax element relating to the intra color difference prediction mode of the prediction block of the color difference signal is calculated (S1201). At this time, the syntax element intra_chroma_pred_mo regarding the intra color difference prediction mode is calculated using the conversion table shown in FIG. 16 from the value of the intra color difference prediction mode 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.
Calculate the value of de [x0] [y0]. Subsequently, the entropy encoding unit 126 performs entropy encoding on the value of each syntax element related to the intra color difference prediction mode of the prediction block of the color difference signal (S1202), and the present encoding process ends. Note that the encoding processing procedure of FIG.
This is a common encoding processing procedure used in step S1012, step S1014, and step S1016 in addition to 0 step S1009.

Returning to FIG. 20 again, when the coding block division mode is not N × N division, that is, when the division mode is 2N × 2N (NO in S1010), the division index PartIdx
Since there is only a prediction block of 0 and there is no intra prediction mode of the prediction block of the chrominance signal to be encoded any more, the processing after step S1011 is skipped and the encoding processing is terminated.

Subsequently, when the color difference format is 4: 4: 4 (YES in S1011), the encoding process procedure of FIG. 22 performs the encoding process of the intra color difference prediction mode of the prediction block having the division index PartIdx of the color difference signal of 1 ( S1012). When the color difference format is not 4: 4: 4, that is, when the color difference format is 4: 2: 0 or 4: 2: 2 (NO in S1011), there is no prediction block having the color difference signal division index PartIdx of 1. Therefore, step S1012 is skipped and the process proceeds to next step S1013.

Subsequently, when the color difference format is 4: 2: 2 or 4: 4: 4 (YES in S 1 013), intra color difference prediction of a prediction block having a color difference signal division index PartIdx of 2 in the encoding processing procedure of FIG. A mode encoding process is performed (S1014). When the color difference format is neither 4: 2: 2 nor 4: 4: 4, that is, when the color difference format is 4: 2: 0 (NO in S1013), there is a prediction block having a color difference signal division index PartIdx of 2. Therefore, step S1014 is skipped and the process proceeds to next step S1015.

Subsequently, when the color difference format is 4: 4: 4 (YES in S1015), the encoding process procedure of FIG. 22 performs the encoding process of the intra color difference prediction mode of the prediction block having the color difference signal division index PartIdx of 3 ( S1016), the present encoding process is terminated. When the color difference format is other than 4: 4: 4, that is, the color difference format is 4: 2: 0 or 4: 2.
: 2 (NO in S1015), there is no prediction block having a color difference signal division index PartIdx of 3, so step S1016 is skipped and the present encoding process is terminated.

According to the present encoding process, the intra color difference prediction mode is continuously encoded after the intra luminance prediction modes belonging to the same encoded block are sequentially encoded in the order shown in FIG. 17, and the intra color difference is encoded on the decoding side. Since the calculation process is performed by referring to 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 when calculating the prediction mode, the intra color difference mode of the intra luminance difference mode is referred to by referring to the intra luminance prediction mode. Encoding efficiency can be increased. Furthermore, according to the present encoding process, when the value of the intra color difference prediction mode is predicted from the value of the intra luminance prediction mode, the method for deriving the intra color difference prediction mode is changed according to the color difference format, so that the color difference format can be changed. Furthermore, since intra prediction can be performed in an appropriate prediction direction, encoding efficiency can be improved. Specifically, when the color difference format is 4: 2: 0 or 4: 4: 4, the value of the intra luminance prediction mode is set as the value of the intra color difference prediction mode, and the color difference format is 4: 2: 2. Figure 1
By converting the value of the intra luminance prediction mode into the value of the intra color difference prediction mode using the conversion table of 5, and performing the intra prediction according to the value of these intra color difference prediction modes,
Since intra prediction can be performed in an appropriate prediction direction, the coding efficiency related to the residual signal is improved, and the overall coding efficiency can be improved.

Next, the processing procedure of decoding processing of encoded information in units of prediction blocks and prediction blocks performed in the second encoded bit string decoding unit 203 in FIG. 2 relates to the intra prediction mode that is a feature of the embodiment. The explanation will focus on the points. FIG. 23 is a flowchart for explaining a processing procedure of decoding processing in units of encoded blocks and prediction blocks performed by the second encoded bit string decoding unit 203 in FIG. 2.

First, on the decoding side, the entropy decoding unit 222 performs entropy decoding on the encoded bit string to obtain values of syntax elements related to the encoded information including the prediction mode and the division mode of the encoded block, and encoding in units of encoded blocks From the value of each syntax element decoded by the information calculation unit 223, the value of the encoded information including the prediction mode and the division mode of the encoded block is calculated (S2001). Subsequently, when the prediction mode (PredMode) of the encoded block is not intra prediction (MODE_INTRA) (NO in S2002), the process proceeds to step S2017, where entropy decoding is performed by the entropy decoding unit 222 and the prediction block is interpolated for each prediction block. A value of a syntax element related to information is obtained, and the inter prediction information calculation unit 226 calculates the value of inter information for each prediction block according to the division mode (S2017), and the decoding process is terminated. When the prediction mode (PredMode) of the encoded block is intra prediction (MODE_INTRA) (YES in S2002), the process proceeds to decoding processing in intra prediction mode in step S2003 and subsequent steps.

Subsequently, when the prediction mode of the encoded block is intra prediction, the entropy decoding unit 2
22 and the luminance index division index PartIdx in the intra luminance prediction mode calculation unit 224
The decoding process of the intra-brightness prediction mode of the prediction block with 0 is performed (S2003).

Here, the decoding process procedure of the intra luminance prediction mode of the prediction block of the luminance signal performed by the entropy decoding unit 222 and the intra luminance prediction mode calculation unit 224 will be described with reference to the flowchart of FIG. FIG. 24 is a flowchart illustrating the decoding process procedure of the intra luminance prediction mode of the prediction block of the luminance signal performed by the entropy decoding unit 222 and the intra luminance prediction mode calculation unit 224. First, the entropy decoding unit 222 performs entropy decoding on the encoded bit string, and obtains the value of each syntax element related to the intra luminance prediction mode of the prediction block of the luminance signal (S2101). Subsequently, the intra luminance prediction mode calculation unit 224 of the intra luminance prediction mode calculates the value of the intra luminance prediction mode of the prediction block of the luminance signal from the value of each syntax element decoded in step S2101 (S2102). ). In this case, the syntax element prev_intra_luma_pred_flag [x0] [y0
] Is 1 (true), the intra luminance prediction mode of the surrounding prediction block indicated by the syntax element mpm_idx [x0] [y0], which is an index indicating the prediction block of the prediction source, is predicted. The mode is the intra luminance prediction mode. Syntax element prev_i
When the value of ntra_luma_pred_flag [x0] [y0] is 0 (false), the intra luminance prediction mode is calculated from the value of the syntax element rem_intra_luma_pred_mode [x0] [y0] indicating the intra luminance prediction mode, and this decoding process is terminated. To do. Note that the decoding processing procedure in FIG. 24 includes steps S2005, S2006, and S200 in addition to step S2003 in FIG.
7 is a common decryption processing procedure used in FIG.

Returning to FIG. 23 again, when the division mode of the encoded block is not N × N division, that is, when the division mode is 2N × 2N (NO in S2004), the division index PartIdx
Since there is only a prediction block with 0, there is no intra prediction mode to decode any more,
The process from step S2005 to S2007 is skipped, and the process proceeds to the decoding process in the intra prediction mode of the prediction block of the color difference signal after step S2008.

On the other hand, when the division mode of the encoded block is N × N division (YES in S2004), the process proceeds to the decoding process in the intra prediction mode of the prediction block in which the division index PartIdx is greater than zero. First, the decoding process procedure of FIG. 24 performs the decoding process of the intra luminance prediction mode of the prediction block whose luminance signal division index PartIdx is 1 (S2005). Subsequently, the decoding process of the intra luminance prediction mode of the prediction block whose luminance signal division index PartIdx is 2 is performed in the processing procedure of FIG. 24 (S2006). Subsequently, the decoding process of the intra luminance prediction mode of the prediction block having the luminance signal division index PartIdx of 3 is performed in the processing procedure of FIG.
07).

Subsequently, when the color difference format is 4: 2: 0, 4: 2: 2 or 4: 4: 4 (S200).
8), the entropy decoding unit 222 and the intra chrominance prediction mode calculation unit 225 perform the decoding process of the intra chrominance prediction mode of the prediction block whose division index PartIdx of the chrominance signal is 0 (S2009). When the color difference format is not 4: 2: 0, 4: 2: 2 or 4: 4: 4, that is, when the color difference format is monochrome (N in S2008)
O) Since there is no color difference signal prediction block, step S2009 and the subsequent steps are skipped, and the present decoding process is terminated.

Here, the decoding process procedure of the intra color difference prediction mode of the prediction block of the color difference signal performed by the entropy decoding unit 222 and the intra color difference prediction mode calculation unit 225 will be described with reference to the flowchart of FIG. FIG. 25 is a flowchart illustrating the decoding process procedure of the intra color difference prediction mode of the prediction block of the color difference signal performed by the entropy decoding unit 222 and the intra color difference prediction mode calculation unit 225. First, the entropy decoding unit 222 performs entropy decoding on the encoded bit string to obtain the value of the syntax element intra_chroma_pred_mode [x0] [y0] regarding the intra color difference prediction mode of the prediction block of the color difference signal (S2201).
Subsequently, the intra color difference prediction mode calculation unit 225 calculates the value of the intra color difference prediction mode of the prediction block of the color difference signal (S2202). Here, the intra color difference prediction mode calculation unit 2
The calculation process procedure of the intra color difference prediction mode of the prediction block of the color difference signal performed in 25 will be described with reference to the flowchart of FIG. FIG. 26 is a flowchart showing the calculation processing procedure of the intra color difference prediction mode performed in step S2202 of FIG. First, the syntax element intra_chroma_p for the intra color difference prediction mode of the prediction block of the color difference signal
It is determined whether the value of red_mode [x0] [y0] is 0 (S2301). If the value is 0 (S230)
1 YES), the process proceeds to step S2302. Color difference format is 4: 2: 0 or 4: 4
: 4 (YES in S2302), the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal is used as it is as the value of the intra color difference prediction mode (step S2303), and this calculation process is terminated. On the other hand, the color difference format is 4: 2: 0 or 4
: 4: 4, that is, 4: 2: 2 (NO in S2302), using the conversion table shown in FIG. 15, the intra luminance prediction mode value of the prediction block at the same position as the prediction block of the color difference signal Then, the value of the intra color difference prediction mode is calculated (step S2304), and this calculation process ends. On the other hand, if the value of intra_chroma_pred_mode [x0] [y0] is non-zero,
14 (NO in S2301), the conversion table of FIG. 14 is used to convert the value of the intra luminance prediction mode into the value of the intra color difference prediction mode (step S2305), and this calculation process ends.
At this time, the value of the syntax element intra_chroma_pred_mode [x0] [y0] related to the intra color difference prediction mode decoded in step S2201 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 are shown in FIG. Using the conversion table, the value of the syntax element is calculated, and this calculation process ends. Note that the decoding processing procedure in FIG. 25 is a common decoding processing procedure used in step S2012, step S2014, and step S2016 in addition to step S2009 in FIG.

Returning to FIG. 23 again, when the division mode of the encoded block is not N × N division, that is, when the division mode is 2N × 2N (NO in S2010), the division index PartIdx
Since there is only a prediction block of 0 and there is no intra prediction mode of the prediction block of the color difference signal to be decoded any more, the processing after step S2011 is skipped and the decoding processing is terminated.

Subsequently, when the color difference format is 4: 4: 4 (YES in S2011), the decoding process of the intra color difference prediction mode of the prediction block having the division index PartIdx of 1 for the color difference signal is performed by the processing procedure of FIG. 25 (S2012). If the color difference format is not 4: 4: 4,
That is, when the color difference format is 4: 2: 0 or 4: 2: 2 (NO in S2011),
Since there is no prediction block having a division index PartIdx of 1 for the color difference signal, step S
2012 is skipped and the process proceeds to the next step S2013.

Subsequently, when the color difference format is 4: 2: 2 or 4: 4: 4 (YES in S2013).
25) In the processing procedure of FIG. 25, the decoding process of the intra color difference prediction mode of the prediction block whose color difference signal division index PartIdx is 2 is performed (S2014). The color difference format is 4: 2.
: 2 or 4: 4: 4, that is, if the color difference format is 4: 2: 0 (S2
013), since there is no prediction block having the color difference signal division index PartIdx of 2, skip S2014 and proceed to the next step S2015.

Subsequently, when the color difference format is 4: 4: 4 (YES in S2015), the decoding process of the intra color difference prediction mode of the prediction block having the color difference signal division index PartIdx of 3 is performed by the processing procedure of FIG. 25 (S2016). The decryption process ends. When the color difference format is other than 4: 4: 4, that is, when the color difference format is 4: 2: 0 or 4: 2: 2 (NO in S2015), there is a prediction block whose color difference signal division index PartIdx is 3. Therefore, step S2016 is skipped, and the present decoding process is terminated.

According to the present decoding process, intra color difference prediction modes are successively decoded after intra luminance prediction modes belonging to the same coding block are sequentially encoded in the order shown in FIG. 17, and the intra color difference prediction modes are calculated. Since the calculation process is performed by referring to 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 coding efficiency of the intra color difference mode is improved by referring to the intra luminance prediction mode. be able to. Furthermore, according to the present decoding process, when predicting the value of the intra color difference prediction mode from the value of the intra luminance prediction mode, the method for deriving the intra color difference prediction mode is changed according to the color difference format, so that Since intra prediction can be performed in an appropriate prediction direction, coding efficiency can be improved. Specifically, when the color difference format is 4: 2: 0 or 4: 4: 4, the value of the intra luminance prediction mode is set as the value of the intra color difference prediction mode, and the color difference format is 4: 2: 2. 15 converts an intra luminance prediction mode value into an intra color difference prediction mode value using the conversion table of FIG. 15 and performs intra prediction according to the values of the intra color difference prediction mode, so that the intra prediction is performed in an appropriate prediction direction. Since the prediction can be performed, the coding efficiency regarding the residual signal is improved, and the overall coding efficiency can be improved.

  As another aspect of the image coding apparatus of the present invention, there are the following.

An image coding apparatus that performs intra prediction coding on an image signal including a luminance signal and a color difference signal in units of blocks and encodes information on an intra prediction mode,
When performing intra prediction of an image signal in units of prediction blocks, a luminance signal prediction block is set, and luminance signal intra prediction that predicts a luminance signal from surrounding encoded luminance signal blocks according to the intra luminance prediction mode Part (103),
A color difference signal intra prediction unit (103) for setting a color difference signal prediction block and predicting a color difference signal from surrounding encoded color difference signal blocks according to an intra color difference prediction mode;
When encoding the information about the intra color difference prediction mode of the prediction block of the color difference signal, the value of the intra color difference prediction mode is predicted from 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. An encoded sequence generation unit that generates an encoded sequence by encoding the syntax element related to the intra luminance prediction mode and the syntax element related to the intra color difference prediction mode. 113).

When the encoded sequence generation unit (113) predicts the intra color difference prediction mode from the intra luminance prediction mode at the same position as the prediction block of the color difference signal, the color difference format is 4: 2.
: 0 or 4: 4: 4, the image coding apparatus characterized by setting the value of the intra luminance prediction mode as the value of the intra color difference prediction mode.

When the intra prediction unit (103) predicts the intra color difference prediction mode from the intra luminance prediction mode at the same position as the prediction block of the color difference signal, the color difference format is 4: 2.
: In the case of 2, the intra prediction direction obtained by scaling the intra prediction direction of the intra luminance prediction mode to 1/2 times in the horizontal direction or twice in the vertical direction is used for intra prediction of the color difference signal. apparatus.

When the encoded sequence generation unit (113) predicts the intra color difference prediction mode from the intra luminance prediction mode at the same position as the prediction block of the color difference signal, the color difference format is 4: 2.
: In the case of 2, the intra prediction mode value corresponding to the intra prediction direction obtained by scaling the intra prediction direction of the intra luminance prediction mode by 1/2 times in the horizontal direction or twice in the vertical direction, or an intra close to the intra prediction direction. An image encoding apparatus, wherein an intra prediction mode value corresponding to a prediction direction is set as an intra color difference prediction mode value.

  Still another aspect of the image encoding method of the present invention is as follows.

An image coding method for coding an image signal including a luminance signal and a color difference signal in units of blocks and encoding information related to an intra prediction mode,
When performing intra prediction of an image signal in units of prediction blocks, a luminance signal prediction block is set, and luminance signal intra prediction that predicts a luminance signal from surrounding encoded luminance signal blocks according to the intra luminance prediction mode Steps,
A color difference signal intra prediction step for setting a color difference signal prediction block and predicting a color difference signal from surrounding encoded color difference signal blocks according to an intra color difference prediction mode;
When encoding the information about the intra color difference prediction mode of the prediction block of the color difference signal, the value of the intra color difference prediction mode is predicted from 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. A coding sequence generating step for generating a coded sequence by encoding the syntax element related to the intra luminance prediction mode and the syntax element related to the intra color difference prediction mode; An image encoding method comprising:

In the encoded sequence generation step, when the intra color difference prediction mode is predicted from the intra luminance prediction mode at the same position as the prediction block of the color difference signal, the color difference format is 4: 2: 0.
Alternatively, in the case of 4: 4: 4, the value of the intra luminance prediction mode is set as the value of the intra color difference prediction mode.

In the intra prediction step, when the intra color difference prediction mode is predicted from the intra luminance prediction mode at the same position as the prediction block of the color difference signal, the color difference format is 4: 2: 2.
In this case, the intra prediction direction obtained by scaling the intra prediction direction of the intra luminance prediction mode by ½ times in the horizontal direction or twice in the vertical direction is used for intra prediction of the color difference signal.

In the encoded sequence generation step, when the intra color difference prediction mode is predicted from the intra luminance prediction mode at the same position as the prediction block of the color difference signal, the color difference format is 4: 2: 2.
The intra prediction direction value corresponding to the intra prediction direction obtained by scaling the intra prediction direction of the intra luminance prediction mode by ½ times in the horizontal direction or twice in the vertical direction, or an intra prediction direction close to the intra prediction direction. An image coding method characterized in that the value of the intra prediction mode corresponding to is used as the value of the intra color difference prediction mode.

  Still another aspect of the image decoding apparatus of the present invention is as follows.

An image decoding apparatus that decodes information related to an intra prediction mode and performs intra prediction decoding of an image signal including a luminance signal and a color difference signal in units of blocks,
When the image signal is intra-predicted in units of prediction blocks, intra luminance is obtained from an encoded sequence in which information on the intra luminance prediction mode of the prediction block of the luminance signal and information on the intra color difference prediction mode of the prediction block of the color difference signal are encoded. The syntax element regarding the prediction mode and the intra color difference prediction mode of the prediction block of the color difference signal is decoded, the value of the intra luminance prediction mode of the prediction block of the luminance signal is calculated, and the luminance signal of the same position as the prediction block of the color difference signal is calculated. A coded sequence decoding unit (203) that obtains the value of the intra color difference prediction mode from the value of the intra luminance prediction mode of the prediction block;
A luminance signal intra prediction unit (206) that predicts a luminance signal from surrounding decoded luminance signal blocks according to the intra luminance prediction mode acquired for each prediction block of the luminance signal.
)When,
A color difference signal intra prediction unit (206) that predicts a color difference signal from surrounding decoded color difference signal blocks according to the intra color difference prediction mode acquired for each prediction block of the color difference signal.
An image decoding apparatus comprising:

When the coded sequence decoding unit (203) predicts the intra color difference prediction mode from the intra luminance prediction mode at the same position as the prediction block of the color difference signal, the color difference format is 4: 2.
: 0 or 4: 4: 4, the image decoding apparatus characterized by setting the value of the intra luminance prediction mode as the value of the intra color difference prediction mode.

The chrominance signal intra prediction unit (206) has a chrominance format of 4 when predicting the intra chrominance prediction mode from the intra luminance prediction mode at the same position as the prediction block of the chrominance signal.
When the ratio is 2: 2, the intra prediction direction obtained by scaling the intra prediction direction of the intra luminance prediction mode by 1/2 in the horizontal direction or double in the vertical direction is used for intra prediction of the color difference signal. Decoding device.

When the coded sequence decoding unit (203) predicts the intra color difference prediction mode from the intra luminance prediction mode at the same position as the prediction block of the color difference signal, the color difference format is 4: 2.
: In the case of 2, the intra prediction mode value corresponding to the intra prediction direction obtained by scaling the intra prediction direction of the intra luminance prediction mode by 1/2 times in the horizontal direction or twice in the vertical direction, or an intra close to the intra prediction direction. An image decoding apparatus, wherein an intra prediction mode value corresponding to a prediction direction is set as an intra color difference prediction mode value.

  Still another aspect of the image decoding method of the present invention is as follows.

An image decoding method for decoding information on an intra prediction mode and performing intra prediction decoding on an image signal including a luminance signal and a color difference signal in units of blocks,
When the image signal is intra-predicted in units of prediction blocks, intra luminance is obtained from an encoded sequence in which information on the intra luminance prediction mode of the prediction block of the luminance signal and information on the intra color difference prediction mode of the prediction block of the color difference signal are encoded. The syntax element regarding the prediction mode and the intra color difference prediction mode of the prediction block of the color difference signal is decoded, the value of the intra luminance prediction mode of the prediction block of the luminance signal is calculated, and the luminance signal of the same position as the prediction block of the color difference signal is calculated. An encoded sequence decoding step to obtain by predicting the value of the intra color difference prediction mode from the value of the intra luminance prediction mode of the prediction block;
A luminance signal intra prediction step for predicting a luminance signal from a surrounding decoded luminance signal block according to an intra luminance prediction mode acquired for each prediction block of the luminance signal;
An image decoding method comprising: a color difference signal intra prediction step for predicting a color difference signal from a surrounding decoded color difference signal block according to an intra color difference prediction mode acquired for each prediction block of the color difference signal .

In the coded sequence decoding step, when the intra color difference prediction mode is predicted from the intra luminance prediction mode at the same position as the prediction block of the color difference signal, the color difference format is 4: 2: 0.
Alternatively, in the case of 4: 4: 4, the value of the intra luminance prediction mode is set as the value of the intra color difference prediction mode.

In the color difference signal intra prediction step, when the intra color difference prediction mode is predicted from the intra luminance prediction mode at the same position as the prediction block of the color difference signal, the color difference format is 4: 2.
: In the case of 2, the intra prediction direction in which the intra prediction direction of the intra luminance prediction mode is scaled to 1/2 times in the horizontal direction or twice in the vertical direction is used for intra prediction of the color difference signal. .

In the encoding sequence decoding step, when the intra color difference prediction mode is predicted from the intra luminance prediction mode at the same position as the prediction block of the color difference signal, the color difference format is 4: 2: 2.
The intra prediction direction value corresponding to the intra prediction direction obtained by scaling the intra prediction direction of the intra luminance prediction mode by ½ times in the horizontal direction or twice in the vertical direction, or an intra prediction direction close to the intra prediction direction. An image decoding method characterized in that the value of the intra prediction mode corresponding to is used as the value of the intra color difference prediction mode.

The moving image encoded stream output from the image encoding apparatus according to the embodiment described above has a specific data format so that it can be decoded according to the encoding method used in the embodiment. Thus, an image decoding apparatus corresponding to the image encoding apparatus can decode the encoded stream of this specific data format.

When a wired or wireless network is used to exchange an encoded stream between an image encoding device and an image decoding device, the encoded stream is converted into a data format suitable for the transmission form of the communication path and transmitted. May be. In that case, an image transmission apparatus that converts the encoded stream output from the image encoding apparatus into encoded data in a data format suitable for the transmission form of the communication path and transmits the encoded data to the network, and receives the encoded data from the network There is provided an image receiving apparatus that restores the encoded stream and supplies the encoded stream to the image decoding apparatus.

An image transmission device includes a memory that buffers an encoded stream output from the image encoding device, a packet processing unit that packetizes the encoded stream, and a transmission unit that transmits packetized encoded data via a network. including. The image reception device receives a packetized encoded data via a network, a memory for buffering the received encoded data, packetizes the encoded data to generate an encoded stream, And a packet processing unit provided to the image decoding device.

The above processing relating to encoding and decoding can be realized as a transmission, storage, and reception 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 can be recorded on a computer-readable recording medium, provided from a server through a wired or wireless network, or provided as a data broadcast of terrestrial or satellite digital broadcasting Is also possible.

The present invention has been described based on the embodiments. The embodiments are exemplifications, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are 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 transform / quantization unit, 108 inverse quantization / inverse orthogonal transform , 109 decoded image signal superimposing unit, 110 encoded information storage memory, 111 decoded image memory, 11
2 1st encoding bit stream production | generation part, 113 2nd encoding bit stream production | generation part, 114
A third encoded bit sequence generation unit; 115 an encoded bit sequence multiplexing unit; 121 a syntax element calculation unit of encoding information in units of encoded blocks; 122 an intra luminance prediction mode syntax element calculation unit; and 123 intra color difference prediction mode Syntax element calculation unit, 124 inter prediction information syntax element calculation unit, 125 intra prediction mode coding control unit, 126 entropy coding unit, 201 coded bit string separating unit, 202 first coded bit string decoding unit, 203 second encoded bit string decoding unit,
204 third coded bit string decoding unit, 205 color difference format management unit, 206
Intra prediction unit, 207 Inter prediction unit, 208 Inverse quantization / inverse orthogonal transform unit, 2
09 decoded image signal superimposing 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, 223 encoded information calculation unit for each encoded block, 224 Intra brightness prediction mode calculation part, 225 Intra color difference prediction mode calculation part, 226 Inter prediction information calculation part.

Claims (6)

An image decoding apparatus that decodes information related to an intra prediction mode and performs intra prediction decoding of an image signal including a luminance signal and a color difference signal in units of blocks,
When the image signal is intra-predicted in units of coding blocks, when a division mode for dividing the luminance signal horizontally and vertically is acquired and the color difference format is 4: 2: 0, the first luminance in the coding block Intra luminance prediction mode of the prediction block of the signal, Intra luminance prediction mode of the prediction block of the second luminance signal, Intra luminance prediction mode of the prediction block of the third luminance signal, Intra luminance prediction of the prediction block of the fourth luminance signal From the coding sequence in which coding information regarding the mode and the intra color difference prediction mode of the prediction block of the color difference signal at the same reference position as the prediction block of the first luminance signal is arranged, the first to fourth luminances Decodes information about the intra luminance prediction mode of the prediction block of the signal, followed by the intra color difference prediction mode of the prediction block of the color difference signal A coding sequence decoding unit for decoding the information about,
When the division mode is set, the prediction block of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the decoded luminance signal for each prediction block is set. A luminance signal intra prediction unit that predicts a luminance signal from a block of surrounding decoded luminance signals according to each intra luminance prediction mode obtained from information on the intra luminance prediction mode;
When the division mode is set and the color difference format is 4: 2: 0, the prediction block of the color difference signal is set without dividing the color difference signal of the coding block, and information on the decoded intra color difference prediction mode A color difference signal intra prediction unit that predicts a color difference signal from a block of surrounding decoded color difference signals according to the intra color difference prediction mode obtained by
The color difference signal intra prediction unit includes:
In the mode in which the intra color difference prediction mode is set according to the intra luminance prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block is set as the value of the color difference signal in the coding block. By using the value indicating the intra color difference prediction mode of the prediction block, the intra color difference prediction mode is set,
When the intra color difference prediction mode is not set according to the intra luminance prediction mode, a value indicating vertical prediction in which the prediction direction is the vertical direction can be set as one of the setting values of the intra color difference prediction mode of the prediction block of the color difference signal. Is,
An image decoding apparatus characterized by that. An image decoding method for decoding information on an intra prediction mode and performing intra prediction decoding on an image signal including a luminance signal and a color difference signal in units of blocks,
When the image signal is intra-predicted in units of coding blocks, when a division mode for dividing the luminance signal horizontally and vertically is acquired and the color difference format is 4: 2: 0, the first luminance in the coding block Intra luminance prediction mode of the prediction block of the signal, Intra luminance prediction mode of the prediction block of the second luminance signal, Intra luminance prediction mode of the prediction block of the third luminance signal, Intra luminance prediction of the prediction block of the fourth luminance signal From the coding sequence in which coding information regarding the mode and the intra color difference prediction mode of the prediction block of the color difference signal at the same reference position as the prediction block of the first luminance signal is arranged, the first to fourth luminances Decodes information about the intra luminance prediction mode of the prediction block of the signal, followed by the intra color difference prediction mode of the prediction block of the color difference signal A coding sequence decoding step of decoding information about,
When the division mode is set, the prediction block of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the decoded luminance signal for each prediction block is set. A luminance signal intra prediction step for predicting a luminance signal from a block of surrounding decoded luminance signals according to each intra luminance prediction mode obtained by information on the intra luminance prediction mode;
When the division mode is set and the color difference format is 4: 2: 0, the prediction block of the color difference signal is set without dividing the color difference signal of the coding block, and information on the decoded intra color difference prediction mode A color difference signal intra prediction step for predicting a color difference signal from a block of surrounding decoded color difference signals according to the intra color difference prediction mode obtained by
In the color difference signal intra prediction step,
In the mode in which the intra color difference prediction mode is set according to the intra luminance prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block is set as the value of the color difference signal in the coding block. By using the value indicating the intra color difference prediction mode of the prediction block, the intra color difference prediction mode is set,
When the intra color difference prediction mode is not set according to the intra luminance prediction mode, a value indicating vertical prediction in which the prediction direction is the vertical direction can be set as one of the setting values of the intra color difference prediction mode of the prediction block of the color difference signal. Is,
An image decoding method characterized by the above. An image decoding program that decodes information related to an intra prediction mode and performs intra prediction decoding of an image signal including a luminance signal and a color difference signal in units of blocks,
When the image signal is intra-predicted in units of coding blocks, when a division mode for dividing the luminance signal horizontally and vertically is acquired and the color difference format is 4: 2: 0, the first luminance in the coding block Intra luminance prediction mode of the prediction block of the signal, Intra luminance prediction mode of the prediction block of the second luminance signal, Intra luminance prediction mode of the prediction block of the third luminance signal, Intra luminance prediction of the prediction block of the fourth luminance signal From the coding sequence in which coding information regarding the mode and the intra color difference prediction mode of the prediction block of the color difference signal at the same reference position as the prediction block of the first luminance signal is arranged, the first to fourth luminances Decodes information about the intra luminance prediction mode of the prediction block of the signal, followed by the intra color difference prediction mode of the prediction block of the color difference signal A coding sequence decoding step of decoding information about,
When the division mode is set, the prediction block of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the decoded luminance signal for each prediction block is set. A luminance signal intra prediction step for predicting a luminance signal from a block of surrounding decoded luminance signals according to each intra luminance prediction mode obtained by information on the intra luminance prediction mode;
When the division mode is set and the color difference format is 4: 2: 0, the prediction block of the color difference signal is set without dividing the color difference signal of the coding block, and information on the decoded intra color difference prediction mode According to the intra color difference prediction mode obtained by the above, the computer executes a color difference signal intra prediction step for predicting a color difference signal from a block of surrounding decoded color difference signals, and
In the color difference signal intra prediction step,
In the mode in which the intra color difference prediction mode is set according to the intra luminance prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block is set as the value of the color difference signal in the coding block. By using the value indicating the intra color difference prediction mode of the prediction block, the intra color difference prediction mode is set,
When the intra color difference prediction mode is not set according to the intra luminance prediction mode, a value indicating vertical prediction in which the prediction direction is the vertical direction can be set as one of the setting values of the intra color difference prediction mode of the prediction block of the color difference signal. Is,
An image decoding program characterized by the above. A reception device that decodes information related to an intra prediction mode from an encoded stream and performs intra prediction decoding of an image signal including a luminance signal and a color difference signal in units of blocks,
A receiving unit that receives encoded data in which a moving image is encoded;
A packet processing unit that packet-processes the encoded data to generate the encoded stream;
When an image signal is intra-predicted from the encoded stream in units of encoded blocks, a division mode for dividing the luminance signal horizontally and vertically is acquired, and the color difference format is 4: 2: 0. Of the prediction blocks of the first luminance signal, the intra luminance prediction mode of the prediction block of the second luminance signal, the intra luminance prediction mode of the prediction block of the third luminance signal, and the fourth luminance signal From the coded sequence in which coding information related to the intra luminance prediction mode of the prediction block and the intra color difference prediction mode of the prediction block of the color difference signal at the same reference position as the prediction block of the first luminance signal is arranged. The information on the intra luminance prediction modes of the first to fourth luminance signal prediction blocks is decoded, and then the prediction block of the color difference signal is decoded. A coding sequence decoding unit for decoding the information about the intra chrominance prediction mode,
When the division mode is set, the prediction block of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the decoded luminance signal for each prediction block is set. A luminance signal intra prediction unit that predicts a luminance signal from a block of surrounding decoded luminance signals according to each intra luminance prediction mode obtained from information on the intra luminance prediction mode;
When the division mode is set and the color difference format is 4: 2: 0, the prediction block of the color difference signal is set without dividing the color difference signal of the coding block, and information on the decoded intra color difference prediction mode A color difference signal intra prediction unit that predicts a color difference signal from a block of surrounding decoded color difference signals according to the intra color difference prediction mode obtained by
The color difference signal intra prediction unit includes:
In the mode in which the intra color difference prediction mode is set according to the intra luminance prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block is set as the value of the color difference signal in the coding block. By using the value indicating the intra color difference prediction mode of the prediction block, the intra color difference prediction mode is set,
When the intra color difference prediction mode is not set according to the intra luminance prediction mode, a value indicating vertical prediction in which the prediction direction is the vertical direction can be set as one of the setting values of the intra color difference prediction mode of the prediction block of the color difference signal. Is,
A receiving apparatus. A reception method for decoding intra-prediction mode information from an encoded stream and intra-prediction decoding an image signal including a luminance signal and a color difference signal in units of blocks,
A reception step of receiving encoded data in which a moving image is encoded;
A packet processing step of packet-processing the encoded data to generate the encoded stream;
When an image signal is intra-predicted from the encoded stream in units of encoded blocks, a division mode for dividing the luminance signal horizontally and vertically is acquired, and the color difference format is 4: 2: 0. Of the prediction blocks of the first luminance signal, the intra luminance prediction mode of the prediction block of the second luminance signal, the intra luminance prediction mode of the prediction block of the third luminance signal, and the fourth luminance signal From the coded sequence in which coding information related to the intra luminance prediction mode of the prediction block and the intra color difference prediction mode of the prediction block of the color difference signal at the same reference position as the prediction block of the first luminance signal is arranged. The information on the intra luminance prediction modes of the first to fourth luminance signal prediction blocks is decoded, and then the prediction block of the color difference signal is decoded. A coding sequence decoding step of decoding information about the intra chrominance prediction mode,
When the division mode is set, the prediction block of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the decoded luminance signal for each prediction block is set. A luminance signal intra prediction step for predicting a luminance signal from a block of surrounding decoded luminance signals according to each intra luminance prediction mode obtained from information on the intra luminance prediction mode, and the division mode are set, and a color difference format Is 4: 2: 0, the color difference signal prediction block is set without dividing the color difference signal of the coding block, and the intra color difference prediction mode obtained by the information on the decoded intra color difference prediction mode is set. And a color difference signal intra prediction step for predicting a color difference signal from a block of the surrounding decoded color difference signals. Have
In the color difference signal intra prediction step,
In the mode in which the intra color difference prediction mode is set according to the intra luminance prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block is set as the value of the color difference signal in the coding block. By using the value indicating the intra color difference prediction mode of the prediction block, the intra color difference prediction mode is set,
When the intra color difference prediction mode is not set according to the intra luminance prediction mode, a value indicating vertical prediction in which the prediction direction is the vertical direction can be set as one of the setting values of the intra color difference prediction mode of the prediction block of the color difference signal. Is,
A receiving method. A reception program that decodes information about an intra prediction mode from an encoded stream and performs intra prediction decoding of an image signal including a luminance signal and a color difference signal in units of blocks,
A reception step of receiving encoded data in which a moving image is encoded;
A packet processing step of packet-processing the encoded data to generate the encoded stream;
When an image signal is intra-predicted from the encoded stream in units of encoded blocks, a division mode for dividing the luminance signal horizontally and vertically is acquired, and the color difference format is 4: 2: 0. Of the prediction blocks of the first luminance signal, the intra luminance prediction mode of the prediction block of the second luminance signal, the intra luminance prediction mode of the prediction block of the third luminance signal, and the fourth luminance signal From the coded sequence in which coding information related to the intra luminance prediction mode of the prediction block and the intra color difference prediction mode of the prediction block of the color difference signal at the same reference position as the prediction block of the first luminance signal is arranged. The information on the intra luminance prediction modes of the first to fourth luminance signal prediction blocks is decoded, and then the prediction block of the color difference signal is decoded. A coding sequence decoding step of decoding information about the intra chrominance prediction mode,
When the division mode is set, the prediction block of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the decoded luminance signal for each prediction block is set. A luminance signal intra prediction step for predicting a luminance signal from a block of surrounding decoded luminance signals according to each intra luminance prediction mode obtained from information on the intra luminance prediction mode, and the division mode are set, and a color difference format Is 4: 2: 0, the color difference signal prediction block is set without dividing the color difference signal of the coding block, and the intra color difference prediction mode obtained by the information on the decoded intra color difference prediction mode is set. And a color difference signal intra prediction step for predicting a color difference signal from a block of the surrounding decoded color difference signals. Let the computer run,
In the color difference signal intra prediction step,
In the mode in which the intra color difference prediction mode is set according to the intra luminance prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block is set as the value of the color difference signal in the coding block. By using the value indicating the intra color difference prediction mode of the prediction block, the intra color difference prediction mode is set,
When the intra color difference prediction mode is not set according to the intra luminance prediction mode, a value indicating vertical prediction in which the vertical direction is the vertical direction can be set as one of the setting values of the intra color difference prediction mode of the prediction block of the color difference signal. Is,
A receiving program characterized by the above.

Images