JP5839144B1 - Image encoding device, image encoding method, image encoding program, transmission device, transmission method, and transmission program - Google Patents

Abstract

When encoding information related to an intra prediction mode of a luminance signal and information related to an intra prediction mode of a color difference signal and arranging them in an encoded bit string, if the intra prediction mode is not encoded according to the color difference format, the processing efficiency is improved. May be worse. When an intra prediction unit 103 sets a division mode for dividing a luminance signal horizontally and vertically when performing intra prediction of an image signal in units of a preset minimum coding block, the intra prediction unit 103 depends on a color difference format. Intra prediction of the color difference signal is performed in units of prediction blocks for intra prediction of the color difference signal in the minimum coding block set in the above. The second encoded bit string generation unit 113 generates an encoded string of information relating to the intra luminance prediction mode of the prediction block of the luminance signal and information relating to the intra color difference prediction mode of the prediction block of the color difference signal. [Selection] Figure 1

Description

  The present invention relates to an image encoding technique, and more particularly to an intra-picture encoding 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. When the color difference format is 4: 2: 0, the color difference signal is 8 ×. When 8 pixels and the 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.
4: 2: 0 shown in FIG. 3A is a color difference format in which a color difference signal is sampled at a density of 1/2 in both horizontal and vertical directions with respect to a luminance signal. 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. In 4: 4: 4, one luminance signal and two color difference signals are independently used. There is also a mechanism for encoding and decoding as three monochromes.

  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, three types of “4 × 4 intra prediction”, “16 × 16 intra prediction”, and “8 × 8 intra prediction” are prepared as units for switching the intra prediction mode.

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. Here, in order to simplify the description, 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, a block defined by 16 × 16 pixels (16 horizontal pixels and 16 vertical pixels) is called a macro block. 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 8 × 8 mode macroblock type is selected, the motion compensation block size in units of submacroblocks is among the 8 × 8, 8 × 4, 4 × 8, and 4 × 4 mode sub macroblock types. You can select one of

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 encoding technique capable of efficiently encoding an image signal by intra prediction of a luminance signal and a color difference signal corresponding to the color difference format. There is.

An image encoding device that performs intra prediction encoding of an image signal including a luminance signal and a color difference signal in units of blocks and encodes information related to an intra prediction mode, and when performing intra prediction of an image signal in units of encoding blocks, When a division mode for dividing a luminance signal horizontally and vertically is set, a prediction block of first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the luminance signal For each prediction block, a luminance signal intra prediction unit that predicts a luminance signal from surrounding encoded luminance signal blocks and the division mode are set according to the intra luminance prediction mode, and the color difference format is 4: 2: If 0, intra color difference prediction is performed by setting a color difference signal prediction block without dividing the color difference signal of the coding block. A color difference signal intra prediction unit that predicts a color difference signal from surrounding blocks of color difference signals that have been encoded, and information related to a prediction mode of the encoded block. Intra-brightness prediction mode of the prediction block of the luminance signal, Intra-brightness prediction mode of the prediction block of the second luminance signal, Intra-brightness prediction mode of the prediction block of the third luminance signal, Intra of the prediction block of the fourth luminance signal Information relating to the prediction mode is encoded, then information relating to 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 encoded, and information relating to the prediction mode is arranged An encoded sequence generation unit that generates the encoded sequence, and the color difference signal intra prediction unit includes an 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 to a value of the prediction block 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 and the intra color difference prediction mode is not set according to the intra luminance prediction mode, the setting of the intra color difference prediction mode of the prediction block of the color difference signal is performed. As one of the values, there is provided an image encoding device characterized in that a value indicating vertical prediction whose prediction direction is a vertical direction can be set.
An image coding method for performing intra prediction coding on an image signal including a luminance signal and a color difference signal on a block-by-block basis and coding information on an intra-prediction mode, and for intra-predicting an image signal on a coding block basis, When a division mode for dividing a luminance signal horizontally and vertically is set, a prediction block of first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the luminance signal For each prediction block, a luminance signal intra prediction step for predicting a luminance signal from surrounding coded luminance signal blocks and the division mode are set according to the intra luminance prediction mode, and the color difference format is 4: 2: If it is 0, the color difference signal prediction block is set without dividing the color difference signal of the coding block, and the intra color According to the prediction mode, a chrominance signal intra prediction step for predicting a chrominance signal from surrounding coded chrominance signal blocks, information on the prediction mode of the coding block is encoded, and the first in the coding block is encoded. Intra-brightness prediction mode of the prediction block of the luminance signal, Intra-brightness prediction mode of the prediction block of the second luminance signal, Intra-brightness prediction mode of the prediction block of the third luminance signal, Intra of the prediction block of the fourth luminance signal Information relating to the prediction mode is encoded, then information relating to 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 encoded, and information relating to the prediction mode is arranged An encoded sequence generation step for generating the encoded sequence, and the color difference signal intra prediction step. In the mode for setting the intra color difference prediction mode 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 color difference 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 of the signal and the intra color difference prediction mode is not set according to the intra luminance prediction mode, the intra of the prediction block of the color difference signal is set. As one of the setting values of the color difference prediction mode, an image encoding method characterized in that a value indicating vertical prediction whose prediction direction is the vertical direction can be set.
An image encoding program for intra prediction encoding 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, and when performing intra prediction of an image signal in units of encoding blocks, When a division mode for dividing a luminance signal horizontally and vertically is set, a prediction block of first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically is set, and the luminance signal For each prediction block, a luminance signal intra prediction step for predicting a luminance signal from surrounding coded luminance signal blocks and the division mode are set according to the intra luminance prediction mode, and the color difference format is 4: 2: If it is 0, the prediction block of the color difference signal is set without dividing the color difference signal of the coding block, and In accordance with the color difference prediction mode, a color difference signal intra prediction step for predicting a color difference signal from surrounding coded color difference signal blocks, and information on the prediction mode of the coding block are encoded, Intra luminance prediction mode of the prediction block of the first luminance 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, Prediction block of the fourth luminance signal The information related to the intra luminance prediction mode of the first luminance signal, and then the information related to 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. A coded sequence generation step of generating a coded sequence in which the colors are arranged, and the color The signal intra prediction step sets a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block in the mode in which the intra color difference prediction mode is set according to the intra luminance prediction mode. When the intra color difference prediction mode is set by using the value indicating the intra color difference prediction mode of the prediction block of the color difference signal in the block, and the intra color difference prediction mode is not set according to the intra luminance prediction mode, the color difference signal Provided is an image coding program characterized in that a value indicating vertical prediction in which a prediction direction is a vertical direction can be set as one of set values of an intra color difference prediction mode of a prediction block.
Encoded data is obtained by packetizing an encoded stream encoded by an image encoding method that encodes information related to an intra prediction mode while encoding an image signal including a luminance signal and a color difference signal in units of blocks. A packet processing unit; and a transmission unit that transmits the packetized encoded data. The image encoding method divides a luminance signal horizontally and vertically when intra-predicting an image signal in units of encoded blocks. When the division mode to be set is set, prediction blocks of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically are set, and intra luminance prediction is performed for each prediction block of the luminance signal. A luminance signal intra prediction step that predicts a luminance signal from a block of surrounding encoded luminance signals, depending on the mode; When the color division format is set and the 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 surroundings are set according to the intra color difference prediction mode. A chrominance signal intra prediction step for predicting a chrominance signal from the encoded chrominance signal block, encoding information on a prediction mode of the encoding block, and a prediction block of a first luminance signal in the encoding block. Codes information regarding the intra luminance prediction mode, 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 intra luminance prediction mode of the prediction block of the fourth luminance signal. Subsequently, the prediction of the prediction block of the color difference signal at the same reference position as the prediction block of the first luminance signal is performed. A coding sequence generation step of encoding information related to the intra color difference prediction mode and generating an encoded sequence in which the information related to the prediction mode is arranged, and the color difference signal intra prediction step includes an intra color difference according to the intra luminance prediction mode. In the mode for setting the prediction mode, the value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block indicates the intra color difference prediction mode of the prediction block of the color difference signal in the coding block. By using the value, when setting the intra color difference prediction mode and not setting the intra color difference prediction mode according to the intra luminance prediction mode, as one of the setting values of the intra color difference prediction mode of the prediction block of the color difference signal, It is possible to set a value indicating vertical prediction where the prediction direction is vertical. A characteristic transmission apparatus is provided.
Encoded data is obtained by packetizing an encoded stream encoded by an image encoding method that encodes information related to an intra prediction mode while encoding an image signal including a luminance signal and a color difference signal in units of blocks. A packet processing step; and a transmission step of transmitting the packetized encoded data. The image encoding method divides a luminance signal horizontally and vertically when intra-predicting an image signal in units of encoded blocks. When the division mode to be set is set, prediction blocks of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically are set, and intra luminance prediction is performed for each prediction block of the luminance signal. Luminance signal intra prediction that predicts the luminance signal from a block of surrounding encoded luminance signals, depending on the mode If the division mode is set and the 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 is set. A chrominance signal intra prediction step for predicting a chrominance signal from surrounding blocks of the encoded chrominance signal, and information on a prediction mode of the encoding block, and encoding a first luminance signal in the encoding block. The present invention relates to an intra luminance prediction mode of a prediction block, an intra luminance prediction mode of a prediction block of a second luminance signal, an intra luminance prediction mode of a prediction block of a third luminance signal, and an intra luminance prediction mode of a prediction block of a fourth luminance signal. Encoding information, followed by prediction of the chrominance signal at the same reference position as the prediction block of the first luminance signal A coding sequence generation step of encoding information related to the lock intra color difference prediction mode and generating a coded sequence in which the information related to the prediction mode is arranged, wherein the color difference signal intra prediction step corresponds to the intra luminance prediction mode. In the mode for setting the intra color difference prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block is used as the intra color difference prediction mode of the prediction block of the color difference signal 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, one of the setting values of the intra color difference prediction mode of the prediction block of the color difference signal is used. Can be set to a value indicating vertical prediction where the prediction direction is vertical A transmission method characterized by the above is provided.
Encoded data is obtained by packetizing an encoded stream encoded by an image encoding method that encodes information related to an intra prediction mode while encoding an image signal including a luminance signal and a color difference signal in units of blocks. A packet processing step and a transmission step for transmitting the packetized encoded data are executed by a computer, and the image encoding method is configured to horizontally and luminance-brightness signals when intra-predicting an image signal in units of encoding blocks. When a division mode for dividing vertically is set, prediction blocks of the first to fourth luminance signals obtained by dividing the luminance signal of the coding block horizontally and vertically are set, and each prediction block of the luminance signal is set. Brightness that predicts a luminance signal from a block of surrounding encoded luminance signals, depending on the intra luminance prediction mode When the signal intra prediction step and the division mode are 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 the intra color difference prediction is performed. According to the mode, a chrominance signal intra prediction step for predicting a chrominance signal from a block of surrounding chrominance signal that has been encoded, and information on a prediction mode of the encoding block are encoded, and a first in the encoding block is encoded. Intra luminance prediction mode of the prediction block of the luminance 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 of the prediction block of the fourth luminance signal Encode information about the prediction mode, then place it in the same reference position as the prediction block of the first luminance signal A coding sequence generating step of encoding information relating to the intra color difference prediction mode of the prediction block of the color difference signal to generate an encoded sequence in which information relating to the prediction mode is arranged, and the color difference signal intra prediction step includes intra luminance In the mode for setting the intra color difference prediction mode according to the prediction mode, a value indicating the intra luminance prediction mode of the prediction block of the first luminance signal in the coding block is used as a prediction block of the color difference signal 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 intra color difference prediction mode of the prediction block of the color difference signal is used. One of the set values is vertical prediction where the prediction direction is the vertical direction It is possible to provide a transmission program characterized in that a value indicating 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 encoded 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)
In the description of the embodiment, the color difference format of an image to be encoded and decoded 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 a coding block obtained by further dividing the block obtained by dividing the tree block into four parts and further dividing the block into four twice hierarchically, and 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 × 32 pixels for the color difference signal, and the size of the coding block B is 32 × 32 pixels for the luminance signal and 16 × 16 pixels for the color difference signal. Thus, 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 × 4 pixels for the color difference signal. . 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) has intra prediction (MODE_INTRA) or inter prediction (MODE_INTER) 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 coding block luminance signal that is regarded as one prediction block without being divided (FIG. 7 (a)) is 2N × 2N division (PART_2Nx2N), and the luminance signal of the coding block is in the horizontal direction. Dividing into two prediction blocks (FIG. 7B) (PartMode) is divided into 2N × N (PART_2NxN), the luminance signal of the encoded block is divided in the vertical direction, and the encoded block is The division mode (PartMode) of the two prediction blocks (FIG. 7 (c)) is N × 2N division (PART_Nx2N), and the luminance signal of the encoded block is divided into four prediction blocks by horizontal and vertical equal divisions. The division mode (PartMode) in FIG. 7D is defined as N × N division (PART_NxN), respectively. 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. In the 2N × N division (PART_2NxN) shown in FIG. 7B, the division index PartIdx of the upper prediction block is set to 0, and the division index PartIdx of the lower prediction block is set to 1. In the N × 2N division (PART_Nx2N) shown in FIG. 7C, 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. In the N × N partition (PART_NxN) shown in FIG. 7D, the partition index PartIdx of the upper left prediction block is 0, the partition index PartIdx of the upper right prediction block is 1, and the partition index PartIdx of the lower left prediction block is 2. And the division index PartIdx of the prediction block at the lower right is set to 3.

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

  When the prediction mode (PredMode) is inter prediction (MODE_INTER), except for the coding block D which is the smallest coding block, the partition mode (PartMode) is 2N × 2N partition (PART_2Nx2N), 2N × N partition (PART_2NxN), and N × 2N partition (PART_Nx2N) is defined, and only the coding block D which is the smallest coding block, the partition mode (PartMode) is 2N × 2N partition (PART_2Nx2N), 2N × N partition (PART_2NxN), and N × 2N In addition to the division (PART_Nx2N), N × N division (PART_NxN) is defined. The reason why N × N division (PART_NxN) is not defined other than the smallest coding block is that, except for the smallest coding block, the coding block can be divided into four to represent a small coding 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 value prediction predicted by calculating an average value from surrounding decoded blocks (intra prediction mode intraPredMode = 2), average value prediction predicted at an angle of 45 degrees diagonally from surrounding decoded blocks In addition to (intraPredMode = 3), 30 angle predictions (intra prediction mode intraPredMode = 4... 33) for predicting diagonally at various angles from surrounding decoded blocks are 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 It is better to predict the value of the intra color difference prediction mode from the value of the intra luminance prediction mode and to set a unique value for the intra color difference prediction mode than to predict from the intra luminance prediction mode. When it is determined, 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, four conversion sizes of 32 × 32 pixels, 16 × 16 pixels, 8 × 8 pixels, and 4 × 4 pixels are defined, and 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 signal and the color difference signal have the same image size (number of pixels) and the color difference format is 4: 4: 4. Of course, the luminance signal and the color difference signal have a different color size format of 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, ▲ is also the position of the color difference signal block F of 4 × 4 pixels indicated by the dotted line, and the coordinates of the luminance signal of the pixel indicated by ▲ are the coordinates of the block F of the color difference signal of 4 × 4 pixels indicated by the dotted line. It becomes. 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 encoding apparatus according to the embodiment includes a color difference format setting unit 101, an image memory 102, an intra prediction unit 103, an inter prediction unit 104, an encoding method determination unit 105, a residual signal generation unit 106, and an 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 generating unit 112, second encoded bit string generating unit 113, and third encoded bit string A 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 The encoded bit string generation unit 113 supplies the encoded bit string to the encoding process based on the color difference format. 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, the decoded image memory In 111, 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 (horizontal direction), 1 (vertical 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. A prediction processing unit for performing intra prediction will be described later.

  The inter prediction unit 104 uses a plurality of inter prediction modes (from a decoded image signal stored in the decoded image memory 111 in units corresponding to respective partition modes (PartMode) in a plurality of encoded block units, that is, in prediction block units). (L0 prediction, L1 prediction, bi-prediction) and inter prediction according to the reference image are 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. A block coding method, a prediction mode (PredMode), and a partition 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 At the same time, the prediction signal stored in the encoded information storage memory 110 and 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. This is supplied to the bit string multiplexing unit 115. 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, 2 for 4: 2: 2, and 3 for 4: 4: 4. The meaning of the syntax element separate_colour_plane_flag indicates whether the luminance signal and the color difference signal are encoded separately. When the value of the separate_colour_plane_flag is 0, the luminance signal is encoded in association with the two color difference signals. Represents that. 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, 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 value of the syntax element separate_colour_plane_flag is always set Is encoded as 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 coded bit string generation unit 114 performs entropy coding by variable length coding, arithmetic coding, and the like on the orthogonally transformed and quantized residual signal according to a specified syntax rule, and the third coded bit string And the third encoded bit string is supplied to the encoded bit string multiplexing unit 115.

  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 for reducing block distortion or the like due to encoding is performed.

  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, an intra prediction unit 206, an inter prediction unit 207, 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. The encoding information for each sequence, picture, and slice is calculated from the value of the syntax element for the decoded sequence, picture, and coding information for each slice according to the semantic rules that define the meaning of the syntax element and the derivation method. To do. 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. Further, when the value of the syntax element chroma_format_idc is 3, the syntax element separate_colour_plane_flag 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, in addition to the encoding block division method, prediction mode (PredMode), and division mode (PartMode), each syntax element obtained by decoding the second encoded bit string in accordance with a prescribed syntax rule. 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 via the switch 212. When the prediction mode (PredMode) is inter prediction, The inter prediction information such as the inter prediction mode, the information specifying 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, and performs 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 orthogonally transformed / inversely quantized by the inverse quantization / inverse orthogonal transformation unit 208. Is decoded, and the decoded image signal is decoded and stored in the decoded image memory 211. When stored in the decoded image memory 211, the decoded image may be stored in the decoded image memory 211 after filtering processing that reduces block distortion or the like due to encoding is performed on the decoded image. 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 the present 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, by calculating the residual signal using the intra-predicted prediction signal, performing orthogonal transformation, quantization, inverse quantization, and inverse transformation on the residual signal, and superimposing it on the prediction signal The decoding process is completed, and the subsequent block is 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. In this embodiment, the minimum unit of intra prediction is 4 × 4 pixels. Therefore, the minimum size of the encoding 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, 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 × 4 pixels in the color difference signal, and further division is possible. Can not. Therefore, in the present embodiment, when the color difference format is 4: 2: 0, 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, but in the color difference signal, the encoded block is divided as shown in FIG. Instead, intra prediction is performed in units of 4 × 4 pixels in the same manner as the size of the prediction block of the luminance signal as one prediction block. 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, intra-prediction is performed in units of 4 × 4 pixels as four prediction blocks by equally dividing the encoded block horizontally and vertically, but in the chrominance signal, the encoded block is horizontally converted as shown in FIG. Intra-prediction is performed in the same 4 × 4 pixel unit as two prediction blocks without equally dividing only into and dividing vertically. 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. The reference position of the prediction block of the chrominance signal and the prediction block of the luminance signal is the coordinate position of the pixel at the upper left corner of the prediction block. 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. Intra prediction is performed in units of 4 × 4 pixels as four prediction blocks by vertical equal division. Similar to the luminance signal, the division index PartIdx of the prediction block of the color difference signal is also set to 0, 1, 2, 3 in the encoding order (upper left, upper right, lower left, lower right).

  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, inter prediction of four prediction blocks is performed, and then the four prediction blocks are combined to calculate a residual signal in units of 4 × 4 pixels, and orthogonal transformation is performed in units of 4 × 4 pixels. It can be performed.

  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. The values of syntax elements relating to the prediction mode (PredMode) for determining intra prediction (MODE_INTRA) or inter prediction (MODE_INTER) of the coding block and the partition mode (PartMode) for determining the shape of the prediction block are the coding block. It is calculated by the syntax element calculation unit 121 of the encoded information of the unit.

  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 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 An element mpm_idx [x0] [y0] and a syntax element rem_intra_luma_pred_mode [x0] [y0] indicating an intra luminance prediction mode in units of prediction blocks. Note that x0, and y0 are coordinates indicating the position of the prediction block. In the calculation of the value of the syntax element related to the intra luminance prediction mode, the correlation with the intra luminance prediction mode of the surrounding block stored in the encoded information storage memory 110 is used, and the intra luminance prediction mode of the surrounding block is used. The syntax element prev_intra_luma_pred_flag [x0] [y0], which is a flag indicating that the value is used when prediction is possible, is set to 1 (true) and the syntax element mpm_idx [ If a value that identifies the reference destination is set in x0] [y0] and cannot be predicted, prev_intra_luma_pred_flag [x0] [y0] is set to 0 (false) to indicate the intra luminance prediction mode to be encoded. A value specifying the intra luminance prediction mode is set in the element rem_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 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 intra_chroma_pred_mode [x0] The value of [y0] is calculated, and the calculated value of the 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 (horizontal 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 the intra color difference prediction mode based on the value of the syntax element intra_chroma_pred_mode [x0] [y0] related to the intra color difference prediction mode defined in this embodiment and the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal. The conversion table is used to calculate the value of the intra color difference prediction mode on the decoding side using this conversion table.
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.

  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.

  When the color difference format is 4: 2: 2 and the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0, the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal is converted according to the conversion table shown in FIG. The value of the intra color difference prediction mode is calculated according to the value of. 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. When the color difference format is 4: 2: 2, as shown in FIG. 3B, the color difference signal is sampled at a density of half the horizontal direction and the same density in the vertical direction with respect to the luminance signal. is there. 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. FIG. 27 is a diagram illustrating the 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: 2. 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). An arrow from the pixel P1 to the pixel P2 indicated by reference numeral 2701 indicates the intra prediction direction of the pixel P1 of the luminance signal and 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 half in the horizontal direction. The value of the intra color difference prediction mode in the near 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, respectively. , 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, 28, 15, 29. When 1, 30, 16, 31, 8, 32, 17, 33, 9 is selected, the value of the intra color difference prediction mode in the prediction direction closest to the prediction direction calculated by scaling twice in the vertical direction is selected. 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. 28 is a diagram for explaining the 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. FIG. 28A shows the arrangement of the luminance signal and the color difference signal when the color difference format is 4: 2: 0, and the color difference signal is sampled at 1/2 both horizontally and vertically with respect to the luminance signal ( Sampling). An arrow indicated by reference numeral 2704 from the pixel P4 to the pixel P5 indicates the intra prediction direction of the pixel P4 of the luminance signal. An arrow indicated by reference numeral 2705 from the pixel P1 to the pixel P2 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 color difference signal array 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 reference destination of the pixel P1 of the color difference signal Can be correctly referred to.

  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. When the color difference format is 4: 2: 2 and the value of the intra color difference prediction mode is predicted, 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, according to the conversion table illustrated in FIG. 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 1 to 4, the decoding side uses the conversion table in FIG. 14 to predict the value of the syntax element intra_chroma_pred_mode [x0] [y0] and the color difference signal prediction block The value of the intra color difference prediction mode is calculated in combination with the value of the intra luminance prediction mode of the prediction block at the same position.

  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. This is a conversion table to be calculated. The conversion table in FIG. 16 corresponds to the conversion table in FIG. Using the conversion table shown in FIG. 16, the encoding side calculates the value of the syntax element intra_chroma_pred_mode [x0] [y0].

  When the value of the intra color difference prediction mode is 0, the value of the syntax element intra_chroma_pred_mode [x0] [y0] 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 intra chrominance prediction mode is 1, the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0, 1 or according to the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the chrominance signal. Takes a value of 2.

  When the value of the intra color difference prediction mode is 2, the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0, 2 or 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 A value of 3 is taken.

  When the value of the intra chrominance prediction mode is 3, the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0, 3 or according to the value of the intra luminance prediction mode of the prediction block at the same position as the prediction block of the chrominance signal. A value of 4 is taken.

  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 103 uses the conversion table shown in FIG. 15 to determine the intra luminance of the prediction block at the same position as the prediction block of the color difference signal. Since the value of the intra color difference prediction mode is calculated according to the value of the prediction mode, the values of the intra color difference prediction mode are 4, 5, 9, 10, 11, 12, 15, 16, 18, 19, 20, Only one of the values 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.

  When the prediction mode (PredMode) of the coding block is inter prediction (MODE_INTER), the syntax element calculation unit 124 of the inter prediction information calculates and calculates the value of the syntax element related to the inter prediction information in units of prediction blocks. The 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 indicate that the luminance signal division index PartIdx is a syntax element related to the intra luminance prediction modes 0, 1, 2, and 3, respectively, and C0, C1, C2, and C3 indicate color difference signals. This indicates that the division index PartIdx is a syntax element related to the intra color difference prediction modes of prediction blocks 0, 1, 2, and 3, respectively.

  When the color difference format is 4: 2: 0, C0 is encoded after L0, L1, L2, and L3 are 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 is a block diagram showing a configuration of the second encoded bit string decoding unit 203 of 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. The calculation unit 224 includes an intra color difference prediction mode calculation unit 225 and an inter prediction information calculation unit 226. In each unit constituting the second encoded bit string decoding unit 203, processing corresponding to the color difference format information supplied from the color difference format management unit 205 is performed, and encoding such as a prediction mode and a division mode in units of encoded blocks is performed. Processing according to the conversion information is performed.

The entropy decoding unit 222 performs entropy decoding on the encoded block including the encoded block supplied from the encoded bit sequence separation unit and the encoded information in units of prediction blocks according to a predetermined syntax rule, and Value of the syntax element related to the conversion information, the value of the syntax element related to the intra luminance prediction mode of the prediction block of the luminance signal,
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 supplied to the intra luminance prediction mode calculation unit 224, and the value of the syntax element related to the intra color difference prediction mode of the prediction block of the color difference signal is supplied to the intra color difference prediction mode calculation unit 225, and the value related to the inter prediction information for each prediction block. The value of the tax element is supplied to the inter prediction information calculation 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, and performs intra prediction via the switch 212. To the unit 206 or the inter prediction unit 207.

  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. The values related to the prediction mode (PredMode) for determining intra prediction (MODE_INTRA) or inter prediction (MODE_INTER) of the coding block and the partition mode (PartMode) for determining the shape of the prediction block are coded in units of this coding block. Calculated by the information calculation unit 223.

  The intra luminance prediction mode calculation unit 224 predicts a luminance 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 intra luminance prediction mode of the prediction block of the luminance signal is calculated from the value of the syntax element relating to the intra luminance prediction mode of the block, and is supplied to the intra color difference prediction mode calculation unit 225 and also supplied to the intra prediction unit 206 via the switch 212. To do. The intra luminance prediction mode calculation unit 224 is an encoding information calculation unit corresponding to the syntax element calculation unit 122 regarding the intra luminance prediction mode on the encoding side, and calculates according to the same semantic rule. 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 An element mpm_idx [x0] [y0] and a syntax element rem_intra_luma_pred_mode [x0] [y0] indicating an intra luminance prediction mode in units of prediction blocks. In the calculation of the intra luminance prediction mode, the correlation with the intra luminance prediction mode of the surrounding block stored in the encoded information storage memory 210 is used, and if the prediction can be made from the intra luminance prediction mode of the surrounding block, The syntax element prev_intra_luma_pred_flag [x0] [y0], which is a flag indicating that a value is used, is 1 (true), and the syntax element mpm_idx [x0] [y0] is an index indicating the prediction block of the prediction source The intra luminance prediction mode of the indicated prediction block in the vicinity is set as the intra luminance prediction mode of the prediction mode. When the syntax element prev_intra_luma_pred_flag [x0] [y0] is 0 (false), the syntax element rem_intra_luma_pred_mode [x0 indicating the decoded intra luminance prediction mode is used instead of predicting the intra luminance prediction mode from the surrounding prediction blocks. ] Intra luminance prediction mode is calculated from the value of [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 predicts the supplied color difference signal 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] related to the block intra color difference prediction mode and the value of the intra luminance prediction mode supplied from the intra luminance prediction mode calculation unit. To the intra prediction unit 206. 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, the value of the intra color difference prediction mode is predicted from the value of the intra luminance prediction mode, and 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 (horizontal 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 described on the encoding side, when the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0, 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 The value of the intra color difference prediction mode is predicted from the value of. 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. When the color difference format is 4: 2: 2 and the value of the syntax element intra_chroma_pred_mode [x0] [y0] is 0, the intra luminance prediction mode of the prediction block at the same position as the prediction block of the color difference signal is converted according to the conversion table shown in FIG. From this value, the value of the intra color difference prediction mode is calculated. 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 is a prediction block unit, and when the prediction mode (PredMode) is intra prediction (MODE_INTRA) and the IntraChroma flag is 0 (false), the entropy code of the syntax element regarding the intra luminance prediction mode in one set of prediction blocks Or performing entropy decoding. The IntraChroma flag is 1 (true) when information related to the intra color difference prediction mode is encoded in intra prediction, and is 0 (false) in other cases. When the prediction mode (PredMode) is intra prediction (MODE_INTRA) and the IntraChroma flag is 0 (false), prev_intra_luma_pred_flag [x0] [y0] is entropy encoded or entropy decoded, and the syntax element prev_intra_luma_pred_flag [x0] When [y0] is 1 (true), entropy coding or entropy decoding of the syntax element mpm_idx [x0] [y0] is performed, and when the syntax element prev_intra_luma_pred_flag [x0] [y0] is 0 (false), Entropy encoding or entropy decoding of the syntax element rem_intra_luma_pred_mode [x0] [y0] is performed. When the division mode is 2N × 2N division, when the syntax element for one set of intra luminance prediction modes is entropy-encoded or entropy-decoded for each coding block, the IntraChroma flag becomes 0 (false), and this syntax Rules apply. When the division mode is N × N division, the IntraChroma flag becomes 0 (false) 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. The rules of this syntax apply.

  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] regarding the intra color difference prediction mode is performed. . When the division mode is 2N × 2N division, the IntraChroma flag is set to 1 (true) when entropy encoding or entropy decoding is performed on syntax elements related to a set of intra color difference prediction modes for each coding block, and this syntax Rules apply. 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 is an example different from FIG. 18 of the 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. 19, x0, and y0 are coordinates indicating the position of the prediction block in the luminance signal. FIG. 19 shows that when the prediction mode (PredMode) is intra prediction (MODE_INTRA), the syntax element entropy coding or entropy decoding is performed on the intra-brightness prediction mode of one set of prediction blocks. Show. When the prediction mode (PredMode) is intra prediction (MODE_INTRA), prev_intra_luma_pred_flag [x0] [y0] is entropy encoded or entropy decoded, and the syntax element prev_intra_luma_pred_flag [x0] [y0] is 1 (true) The entropy coding or entropy decoding of the syntax element mpm_idx [x0] [y0]. If the syntax element prev_intra_luma_pred_flag [x0] [y0] is 0 (false), the syntax element rem_intra_luma_pred_mode [x0] [y0 ] Entropy coding or entropy decoding. 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. .

  In addition, when the prediction mode (PredMode) is intra prediction (MODE_INTRA), syntax elements related to 0 to 4 intra color difference prediction modes depending on the partition mode (PartMode), the color difference format (ChromaArrayType), and the partition index (PartIdx). Entropy coding or entropy decoding 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 indicates 4: 2: 0, 2 indicates 4: 2: 2, and 3 indicates 4: 4: 4.

  When the prediction mode (PredMode) is intra prediction (MODE_INTRA), the partition mode (PartMode) is 2N × 2N partition (PART_2Nx2N), and the color difference format (ChromaArrayType) is not monochrome (0), the intra color difference prediction mode for each prediction block Indicates that entropy coding or entropy decoding of the syntax element intra_chroma_pred_mode [x0] [y0] is performed. When the division mode is 2N × 2N division, syntax elements related to a set of intra luminance prediction modes per encoded block after entropy coding or entropy decoding of syntax elements related to a set of intra luminance prediction modes per encoded block are performed. The rules of this syntax are applied when entropy encoding or entropy decoding an element.

  On the other hand, when the prediction mode (PredMode) is intra prediction (MODE_INTRA), the partition mode (PartMode) is N × N partition (PART_NxN), and the partition index (PartIdx) is 3, the syntax rules described below apply Is done. 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 division index PartIdx is 1 when the color difference format (ChromaArrayType) is 4: 4: 4 (3). Entropy coding or entropy decoding of the syntax element intra_chroma_pred_mode [x0] [y1] regarding the intra color difference prediction mode of the current color, and then the color difference format (ChromaArrayType) is 4: 2: 2 (2) or 4: 4: In the case of 4 (3), the syntax element in for the intra color difference prediction mode whose partition index PartIdx is 2 Performs entropy coding or entropy decoding of tra_chroma_pred_mode [x1] [y0], and then, if the color difference format (ChromaArrayType) is 4: 4: 4 (3), the intra color difference prediction mode with the division index PartIdx of 3 Indicates that entropy coding or entropy decoding of the syntax element intra_chroma_pred_mode [x0] [y0] 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. 17 is entropy-encoded or entropy-decoded, and then corresponds to the color difference format. The rules of this syntax are applied when entropy encoding or entropy decoding is performed on the syntax elements C0, C1, C2, and C3 related to the number of intra color difference prediction modes.

  Next, the processing procedure of the encoding process of the encoded block and the encoded information performed in the second encoded bit string generation unit 113 in FIG. 1 is changed to the intra prediction mode that is the feature of the embodiment. 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. The unit 126 performs entropy encoding (S1001). Subsequently, when the prediction mode (PredMode) of the encoded block is not intra prediction (MODE_INTRA) (NO in S1002), the process proceeds to step S1017, and the syntax element calculation unit 124 regarding the inter prediction information determines each prediction block according to the division mode. Then, the value of the syntax element related to the inter information is calculated and entropy-encoded by the entropy encoding unit 126 (S1017), and the encoding process ends. When the prediction mode (PredMode) of the encoded block is intra prediction (MODE_INTRA) (YES in S1002), the process proceeds to the encoding process in the intra prediction mode after step S1003.

  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 122 regarding the intra luminance prediction mode calculates the value of each syntax element regarding the intra luminance prediction mode of the prediction block of the luminance signal (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. 21 is a common encoding processing 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), there is only a prediction block whose division index PartIdx is 0. Since there is no intra prediction mode for the prediction block of the luminance signal to be encoded any more, the processing of steps S1005 to S1007 is skipped, and the process proceeds to the encoding processing of 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, 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 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 (YES in S1008), the color difference is calculated by the syntax element calculation unit 123 and the entropy encoding unit 126 regarding the intra color difference prediction mode. An intra color difference prediction mode encoding process is performed for a prediction block whose signal division index PartIdx 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 123 related to the intra color difference prediction mode calculates the value of each syntax element related to the intra color difference prediction mode of the prediction block of the color difference signal (S1201). At this time, the syntax element intra_chroma_pred_mode [x0 for 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 [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 in FIG. 22 is a common encoding processing procedure that is used in step S1012, step S1014, and step S1016 in addition to step S1009 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 S1010), there is only a prediction block whose division index PartIdx is 0. Since there is no intra prediction mode for the prediction block of the color difference signal to be encoded any more, the processing after step S1011 is skipped, and the present 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 S013), the intra color difference prediction mode of the prediction block of the color difference signal division index PartIdx is 2 in the encoding processing procedure of FIG. Encoding processing 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, when the color difference format is 4: 2: 0 or 4: 2: 2 (NO in S1015), there is a prediction block having a color difference signal division index PartIdx of 3 Therefore, 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. 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.

  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 222 and the intra luminance prediction mode calculation unit 224 perform decoding processing of the intra luminance prediction mode of the prediction block whose luminance signal division index PartIdx is 0. This 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). ). At this time, when the value of the syntax element prev_intra_luma_pred_flag [x0] [y0] is 1 (true), it is indicated by the syntax element mpm_idx [x0] [y0] that is an index indicating the prediction block of the prediction source The intra luminance prediction mode of the surrounding prediction block is set as the intra luminance prediction mode of the prediction mode. When the value of the syntax element prev_intra_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 is performed. The process ends. Note that the decoding processing procedure in FIG. 24 is a common decoding processing procedure used in step S2005, step S2006, and step S2007 in addition to step S2003 in FIG.

  Returning to FIG. 23 again, when the coding block division mode is not N × N division, that is, when the division mode is 2N × 2N (NO in S2004), there is only a prediction block whose division index PartIdx is 0. Since there is no further intra prediction mode to be decoded, the processing from step S2005 to S2007 is skipped, and the process proceeds to the decoding processing 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. 24 (S2007).

  Subsequently, when the chrominance format is 4: 2: 0, 4: 2: 2 or 4: 4: 4 (YES in S2008), the entropy decoding unit 222 and the intra chrominance prediction mode calculation unit 225 use the chrominance signal division index PartIdx. The decoding process of the intra color difference prediction mode of the prediction block of 0 is performed (S2009). If the color difference format is not 4: 2: 0, 4: 2: 2 or 4: 4: 4, that is, if the color difference format is monochrome (NO in S2008), there is no color difference signal prediction block, so the step Step S2009 and 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 calculation process procedure of the intra color difference prediction mode of the prediction block of the color difference signal performed by the intra color difference prediction mode calculation unit 225 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, it is determined whether 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 is 0 (S2301). If the value is 0 (YES in S2301), the process proceeds to step S2302. . When the color difference format is 4: 2: 0 or 4: 4: 4 (YES in S2302), 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 directly used as the value of the intra color difference prediction mode. (Step S2303), the calculation process is terminated. On the other hand, when the color difference format is 4: 2: 0 or 4: 4: 4, that is, 4: 2: 2 (NO in S2302), it is the same as the prediction block of the color difference signal using the conversion table shown in FIG. The value of the intra color difference prediction mode is calculated from the value of the intra luminance prediction mode of the position prediction block (step S2304), and this calculation process ends. On the other hand, if the value of intra_chroma_pred_mode [x0] [y0] is other than 0 (NO in S2301), the intra luminance prediction mode value is converted to the intra color difference prediction mode value using the conversion table of FIG. In step S2305), the 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 coding block division mode is not N × N division, that is, when the division mode is 2N × 2N (NO in S2010), there is only a prediction block whose division index PartIdx is 0. Since there is no intra prediction mode for the prediction block of the chrominance signal to be decoded any more, the processing after step S2011 is skipped, and this decoding processing ends.

  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). Note that if the color difference format is not 4: 4: 4, that is, if the color difference format is 4: 2: 0 or 4: 2: 2 (NO in S2011), there is no prediction block with the division index PartIdx of 1 for the color difference signal. Therefore, step S2012 is skipped and the process proceeds to next step S2013.

  Subsequently, when the chrominance format is 4: 2: 2 or 4: 4: 4 (YES in S2013), the decoding process of the intra chrominance prediction mode of the prediction block of the chrominance signal division index PartIdx is 2 in the processing procedure of FIG. (S2014). 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 S2013), there is a prediction block having a color difference signal division index PartIdx of 2. Therefore, skip S2014 and go 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. In this case, the value of the intra luminance prediction mode is set as the value of the intra color difference prediction mode.

  When the color difference format is 4: 2: 2 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 intra luminance prediction mode An image coding apparatus characterized by using an intra prediction direction obtained by scaling the intra prediction direction of ½ in the horizontal direction or double in the vertical direction for intra prediction of a color difference signal.

  When the color difference format is 4: 2: 2 when predicting 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 coded sequence generation unit (113) Intra prediction mode corresponding to an intra prediction direction corresponding to an intra prediction direction corresponding to the intra prediction direction obtained by scaling the intra prediction direction of the prediction mode to 1/2 times in the horizontal direction or twice in the vertical direction. An image coding apparatus characterized in that the value of is used as a value of an intra color difference prediction mode.

  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 case where the color difference format is 4: 2: 0 or 4: 4: 4 when predicting 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 coded sequence generation step An image encoding method, wherein 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, and the color difference format is 4: 2: 2, the intra prediction of the intra luminance prediction mode is performed. An image coding method characterized by using an intra prediction direction in which a direction is scaled to 1/2 times in a horizontal direction or twice in a vertical direction for intra prediction of a color difference signal.

  When the color difference format is 4: 2: 2 when predicting 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 coded sequence generation step is performed in the intra luminance prediction mode. A value of an intra prediction mode corresponding to an intra prediction direction corresponding to an intra prediction direction obtained by scaling the intra prediction direction by ½ times in the horizontal direction or twice in the vertical direction, or an intra prediction mode value corresponding to an intra prediction direction close to the intra prediction direction. An image coding method characterized in that the value is an intra color difference prediction mode value.

  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 an intra luminance prediction mode acquired for each prediction block of the luminance signal;
And a color difference signal intra prediction unit (206) for predicting a color difference signal from surrounding decoded color difference signal blocks according to an intra color difference prediction mode acquired for each prediction block of the color difference signal. Image 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: 0 or 4: 4: 4. In this case, the image decoding apparatus is characterized in that the value of the intra luminance prediction mode is set as the value of the intra color difference prediction mode.

  The color difference signal intra prediction unit (206) predicts the intra luminance prediction when the color difference format is 4: 2: 2 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. An image decoding apparatus characterized in that an intra prediction direction obtained by scaling a mode intra prediction direction by a factor of ½ in the horizontal direction or by a factor of two in the vertical direction is used for intra prediction of a color difference signal.

  When the color difference format is 4: 2: 2, the encoded 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. Intra prediction mode corresponding to an intra prediction direction corresponding to an intra prediction direction corresponding to the intra prediction direction obtained by scaling the intra prediction direction of the prediction mode to 1/2 times in the horizontal direction or twice in the vertical direction. An image decoding apparatus characterized in that the value of is used as a value of an intra color difference prediction mode.

  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 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: 0 or 4: 4: 4. An image decoding method, wherein the value of the intra luminance prediction mode is set as the value of the intra color difference prediction mode.

  When the color difference format is 4: 2: 2 when predicting 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 signal intra prediction step is performed in the intra luminance prediction mode. An image decoding method, wherein an intra prediction direction obtained by scaling a prediction direction by a factor of 1/2 in a horizontal direction or by a factor of 2 in a vertical direction is used for intra prediction of a color difference signal.

  When the color difference format is 4: 2: 2 when predicting 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 coded sequence decoding step is performed in the intra luminance prediction mode. A value of an intra prediction mode corresponding to an intra prediction direction corresponding to an intra prediction direction obtained by scaling the intra prediction direction by ½ times in the horizontal direction or twice in the vertical direction, or an intra prediction mode value corresponding to an intra prediction direction close to the intra prediction direction. An image decoding method, wherein the value is an intra color difference prediction mode value.

  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 superposition unit, 110 encoded information storage memory, 111 decoded image memory, 112 first encoded bit string generation unit, 113 second encoded bit string generation unit, 114 third encoded bit string generation unit 115 Coding bit stream multiplexing unit, 121 Coding information syntax element calculation unit of coding block unit, 122 Intra luminance prediction mode syntax element calculation unit, 123 Intra color difference prediction mode syntax element calculation unit, 124 Inter prediction information syntax element calculation , 125 intra prediction mode coding control unit, 126 entropy coding unit, 201 coded bit string separation unit, 202 first coded bit string decoding unit, 203 second coded 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, 209 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 encoding information calculation unit for each coding block, 224 intra luminance prediction mode calculation unit, 225 intra color difference prediction mode calculation unit, 226 inter prediction information Calculation unit.

Claims (6)

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 the image signal is intra-predicted in units of coding blocks, when a division mode for dividing the luminance signal horizontally and vertically is set, the first to fourth divisions in which the luminance signal of the coding block is divided horizontally and vertically are set. A luminance signal intra prediction unit that sets a prediction block of a luminance signal and predicts a luminance signal from a surrounding encoded luminance signal block according to an intra luminance prediction mode for each prediction block of the luminance signal;
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 the surroundings are set according to the intra color difference prediction mode. A color difference signal intra prediction unit that predicts a color difference signal from a block of encoded color difference signals of
Encoding information related to the prediction mode of the encoded block; intra luminance prediction mode of a prediction block of the first luminance signal in the encoded block; intra luminance prediction mode of a prediction block of the second luminance signal; Information on the intra luminance prediction mode of the prediction block of the luminance signal and the information on the intra luminance prediction mode of the prediction block of the fourth luminance signal are encoded, and then the color difference signal at the same reference position as the prediction block of the first luminance signal An encoded sequence generation unit that encodes information related to the intra color difference prediction mode of the prediction block and generates an encoded sequence in which information about the prediction mode is arranged,
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. An image encoding device characterized by the above. 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 the image signal is intra-predicted in units of coding blocks, when a division mode for dividing the luminance signal horizontally and vertically is set, the first to fourth divisions in which the luminance signal of the coding block is divided horizontally and vertically are set. A luminance signal intra prediction step for setting a luminance signal prediction block and predicting a luminance signal from a surrounding encoded luminance signal block according to an intra luminance prediction mode for each prediction block of the luminance signal;
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 the surroundings are set according to the intra color difference prediction mode. A color difference signal intra prediction step for predicting a color difference signal from a block of encoded color difference signals of
Encoding information related to the prediction mode of the encoded block; intra luminance prediction mode of a prediction block of the first luminance signal in the encoded block; intra luminance prediction mode of a prediction block of the second luminance signal; Information on the intra luminance prediction mode of the prediction block of the luminance signal and the information on the intra luminance prediction mode of the prediction block of the fourth luminance signal are encoded, and then the color difference signal at the same reference position as the prediction block of the first luminance signal An encoded sequence generation step of encoding information related to the intra color difference prediction mode of the prediction block and generating an encoded sequence in which the information related to the prediction mode is arranged,
The color difference signal intra prediction step 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. An image encoding method characterized by the above. An image encoding program for intra-predicting an image signal including a luminance signal and a color difference signal in units of blocks and encoding information on an intra-prediction mode,
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 set, the first to fourth divisions in which the luminance signal of the coding block is divided horizontally and vertically are set. A luminance signal intra prediction step for setting a luminance signal prediction block and predicting a luminance signal from a surrounding encoded luminance signal block according to an intra luminance prediction mode for each prediction block of the luminance signal;
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 the surroundings are set according to the intra color difference prediction mode. A color difference signal intra prediction step for predicting a color difference signal from a block of encoded color difference signals of
Encoding information related to the prediction mode of the encoded block; intra luminance prediction mode of a prediction block of the first luminance signal in the encoded block; intra luminance prediction mode of a prediction block of the second luminance signal; Information on the intra luminance prediction mode of the prediction block of the luminance signal and the information on the intra luminance prediction mode of the prediction block of the fourth luminance signal are encoded, and then the color difference signal at the same reference position as the prediction block of the first luminance signal Encoding information related to the intra color difference prediction mode of the prediction block of the encoding block, generating a coded sequence in which the information related to the prediction mode is arranged, and causing the computer to execute,
The color difference signal intra prediction step 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. An image encoding program characterized by the above. Encoded data is obtained by packetizing an encoded stream encoded by an image encoding method that encodes information related to an intra prediction mode while encoding an image signal including a luminance signal and a color difference signal in units of blocks. A packet processing unit;
A transmission unit for transmitting the packetized encoded data,
The image encoding method includes:
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 set, the first to fourth divisions in which the luminance signal of the coding block is divided horizontally and vertically are set. A luminance signal intra prediction step for setting a luminance signal prediction block and predicting a luminance signal from a surrounding encoded luminance signal block according to an intra luminance prediction mode for each prediction block of the luminance signal;
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 the surroundings are set according to the intra color difference prediction mode. A color difference signal intra prediction step for predicting a color difference signal from a block of encoded color difference signals of
Encoding information related to the prediction mode of the encoded block; intra luminance prediction mode of a prediction block of the first luminance signal in the encoded block; intra luminance prediction mode of a prediction block of the second luminance signal; Information on the intra luminance prediction mode of the prediction block of the luminance signal and the information on the intra luminance prediction mode of the prediction block of the fourth luminance signal are encoded, and then the color difference signal at the same reference position as the prediction block of the first luminance signal An encoded sequence generation step of encoding information related to the intra color difference prediction mode of the prediction block and generating an encoded sequence in which the information related to the prediction mode is arranged,
The color difference signal intra prediction step 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. A transmitter characterized by the above. Encoded data is obtained by packetizing an encoded stream encoded by an image encoding method that encodes information related to an intra prediction mode while encoding an image signal including a luminance signal and a color difference signal in units of blocks. A packet processing step;
Transmitting the packetized encoded data, and
The image encoding method includes:
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 set, the first to fourth divisions in which the luminance signal of the coding block is divided horizontally and vertically are set. A luminance signal intra prediction step for setting a luminance signal prediction block and predicting a luminance signal from a surrounding encoded luminance signal block according to an intra luminance prediction mode for each prediction block of the luminance signal;
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 the surroundings are set according to the intra color difference prediction mode. A color difference signal intra prediction step for predicting a color difference signal from a block of encoded color difference signals of
Encoding information related to the prediction mode of the encoded block; intra luminance prediction mode of a prediction block of the first luminance signal in the encoded block; intra luminance prediction mode of a prediction block of the second luminance signal; Information on the intra luminance prediction mode of the prediction block of the luminance signal and the information on the intra luminance prediction mode of the prediction block of the fourth luminance signal are encoded, and then the color difference signal at the same reference position as the prediction block of the first luminance signal An encoded sequence generation step of encoding information related to the intra color difference prediction mode of the prediction block and generating an encoded sequence in which the information related to the prediction mode is arranged,
The color difference signal intra prediction step 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. A transmission method characterized by that. Encoded data is obtained by packetizing an encoded stream encoded by an image encoding method that encodes information related to an intra prediction mode while encoding an image signal including a luminance signal and a color difference signal in units of blocks. A packet processing step;
Transmitting the packetized encoded data to the computer, and
The image encoding method includes:
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 set, the first to fourth divisions in which the luminance signal of the coding block is divided horizontally and vertically are set. A luminance signal intra prediction step for setting a luminance signal prediction block and predicting a luminance signal from a surrounding encoded luminance signal block according to an intra luminance prediction mode for each prediction block of the luminance signal;
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 the surroundings are set according to the intra color difference prediction mode. A color difference signal intra prediction step for predicting a color difference signal from a block of encoded color difference signals of
Encoding information related to the prediction mode of the encoded block; intra luminance prediction mode of a prediction block of the first luminance signal in the encoded block; intra luminance prediction mode of a prediction block of the second luminance signal; Information on the intra luminance prediction mode of the prediction block of the luminance signal and the information on the intra luminance prediction mode of the prediction block of the fourth luminance signal are encoded, and then the color difference signal at the same reference position as the prediction block of the first luminance signal An encoded sequence generation step of encoding information related to the intra color difference prediction mode of the prediction block and generating an encoded sequence in which the information related to the prediction mode is arranged,
The color difference signal intra prediction step 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. The transmission program characterized by being.

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