JP2013126145A - Color moving image encoding device, color moving image decoding device, color moving image encoding method, and color moving image decoding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve encoding efficiencies of a luminance signal and a color difference signal by carrying out a compression treatment in a block size suitable for a luminance signal and a color difference signal.SOLUTION: For a color difference signal as well, similarly to a luminance signal, the number of color difference maximum conversion block division hierarchies, which is the maximum number of block division hierarchies concerning a color difference signal, is set according to an input image, and a color difference signal block is hierarchically divided up to the number of color difference maximum conversion block division hierarchies at most, and a compression treatment of the color difference signal is carried out in a block unit after the division.

Description

  The present invention relates to a color moving image encoding device and a color moving image encoding method for encoding a color moving image with high efficiency, a color moving image decoding device for decoding a color moving image encoded with high efficiency, and The present invention relates to a color moving image decoding method.

For example, in the conventional color moving image encoding device described in Non-Patent Document 1 below, an input color image is divided into maximum encoding blocks of a predetermined size, and the maximum encoding block is further divided. Hierarchy is divided into fine coding blocks.
Further, the encoded block is divided into finer prediction blocks, and prediction errors are generated by performing intra prediction and motion compensation prediction on the prediction block.
In addition, the prediction error is hierarchically divided into transform blocks within the coding block, and each transform coefficient is entropy coded to achieve a high compression rate.
In a conventional color moving image encoding apparatus, when encoding a YUV 4: 2: 0 signal, the color difference signal is fixed by fixing the conversion block size of the color difference signal to a size that is half the length and width of the conversion block size of the luminance signal. This eliminates the need to encode information relating to the transform block size, thereby improving the coding efficiency of the color difference signal.

B. Bross, W.-J. Han, J.-R. Ohm, GJ Sullivan and T. Wiegand, “WD4: Working Draft 4 of High-Efficiency Video Coding”, doc. JCTVC-F803, Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11, 6th Meeting, 2011

  Since the conventional color moving image encoding apparatus is configured as described above, it is not necessary to encode information related to the conversion block size of the color difference signal and the encoding efficiency of the color difference signal is improved. The transform block size is fixed according to the transform block size of the luminance signal. However, the color difference signal in the image signal generally has a relatively flat signal change compared to the luminance signal, and the optimal conversion block size of the luminance signal and the optimal conversion block size of the color difference signal are different. For this reason, when the conversion block size of the color difference signal is fixed according to the conversion block size of the luminance signal, there is a problem that the encoding efficiency of the color difference signal may not be optimal.

The present invention has been made in order to solve the above-described problems, and is a color which can increase the coding efficiency of a luminance signal and a color difference signal by performing compression processing with a block size suitable for the luminance signal and the color difference signal. It is an object of the present invention to obtain a moving picture coding apparatus and a color moving picture coding method.
It is another object of the present invention to obtain a color moving image decoding apparatus and a color moving image decoding method capable of accurately decoding a moving image from encoded data whose encoding efficiency is improved.

  In the color moving image encoding apparatus according to the present invention, when the image compression unit compresses the difference image generated by the difference image generation unit, the maximum luminance block conversion block division hierarchy number of the luminance signal block in the difference image is increased. After the hierarchical division, the luminance signal is compressed in divided blocks, and the color difference signal block in the difference image is divided hierarchically up to the maximum number of color difference conversion block division layers. The color difference signal is compressed in units of divided blocks, and the variable-length encoding means changes the block division information, the maximum luminance conversion block division hierarchy number, and the maximum color difference conversion block division hierarchy number by the image compression means. After long encoding, the encoded data of the above division information, the maximum luminance conversion block division layer number and the maximum color difference conversion block division layer number is bit streamed. It is obtained so as to multiplex the arm.

  According to the present invention, when the image compression unit compresses the difference image generated by the difference image generation unit, the block of the luminance signal in the difference image is hierarchically divided up to the maximum luminance conversion block division hierarchy number. After that, the luminance signal is compressed in divided block units, and the color difference signal block in the difference image is hierarchically divided up to the maximum color difference conversion block division hierarchy number, and then the divided block unit The variable length coding means performs variable length coding on the block division information, the luminance maximum conversion block division hierarchy number and the color difference maximum conversion block division hierarchy number by the image compression means, The encoded data of the division information, the maximum luminance conversion block division layer number, and the color difference maximum conversion block division layer number are multiplexed into the bitstream. Since form was, been achieved is optimized block size of the compression processing for the luminance signal and the color difference signal, there is an effect that can increase the coding efficiency of the luminance signal and color difference signals.

It is a block diagram which shows the color moving image encoding device by Embodiment 1 of this invention. It is a flowchart which shows the processing content of the color moving image encoder by Embodiment 1 of this invention. It is a block diagram which shows the intra estimation part 4 of the color moving image encoder by Embodiment 1 of this invention. It is a block diagram which shows the brightness | luminance correlation utilization color difference signal prediction part 24 of the color moving image encoder by Embodiment 1 of this invention. It is a flowchart which shows the processing content of the intra estimation part 4 of the color moving image encoder by Embodiment 1 of this invention. It is a flowchart which shows the processing content of the brightness | luminance correlation utilization color difference signal prediction part 24 of the color moving image encoding device by Embodiment 1 of this invention. It is a block diagram which shows the color moving image decoding apparatus by Embodiment 1 of this invention. It is a flowchart which shows the processing content of the color moving image decoding apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows a mode that the encoding block of the largest size is divided | segmented into a some encoding block hierarchically. It is an explanatory view showing a partition _P ^{i n} that belong to the coding block ^{B n.} It is explanatory drawing which shows the distribution of the partition after a division | segmentation, and the condition where the encoding mode m ( ^Bn ) is allocated to the partition after a hierarchy division | segmentation with a quadtree graph. Is an explanatory diagram showing an example of the coding block B ⁿ belonging selectable intra prediction parameters in each partition P _i ⁿ (intra prediction mode). It is explanatory drawing which shows an example of the pixel used when producing | generating the predicted value of the pixel in partition P _i ⁿ in the case of l _i ⁿ = m _i ⁿ = 4. It is explanatory drawing which shows the example of a response | compatibility of the intra prediction parameter of a color difference signal, and a color difference intra prediction mode. It is explanatory drawing which shows the prediction block of a color difference signal, a decoded luminance signal, etc. It is an explanatory view showing a method of generating a reduced luminance reference pixel Rec _'L. It is explanatory drawing which shows the conversion block size at the time of implementing the compression process of the luminance signal and color-difference signal in the signal of 4: 2: 0 format. It is explanatory drawing which shows the conversion block size at the time of implementing the compression process of the luminance signal and color-difference signal in the signal of 4: 2: 2 format. It is explanatory drawing which shows the prediction in a flame | frame of a color difference component. Luminance maximum transform block division hierarchy number (MaxTUdepthYIpic) when the coding mode is intra coding mode, luminance maximum transformation block division hierarchy number (MaxTUdepthYPpic) when the coding mode is inter coding mode, and color difference conversion It is explanatory drawing which shows the example multiplexed on the header part of a bit stream by making a block division | segmentation hierarchy number (FixTUdepthUV) into a sequence parameter set. Maximum luminance transform block division hierarchy number (MaxTUdepthYIpic) when the encoding mode is the intra encoding mode, maximum luminance transform block division hierarchy number (MaxTUdepthYPpic) when the encoding mode is the inter encoding mode, and encoding The sequence parameter set includes the maximum number of color difference transform block division layers (MaxTUdepthUVintra) when the mode is the intra coding mode and the maximum number of color difference transform block division layers (MaxTUdepthUVinter) when the coding mode is the inter coding mode. FIG. 4 is an explanatory diagram illustrating an example of multiplexing in a header part of a bitstream. Maximum luminance transform block division hierarchy number (MaxTUdepthYIpic) when the encoding mode is the intra encoding mode, maximum luminance transform block division hierarchy number (MaxTUdepthYPpic) when the encoding mode is the inter encoding mode, and encoding The sequence parameter set includes the maximum number of color difference transform block division layers (MaxTUdepthUVIpic) when the mode is the intra coding mode and the maximum number of color difference transform block division layers (MaxTUdepthUVPpic) when the coding mode is the inter coding mode. FIG. 4 is an explanatory diagram illustrating an example of multiplexing in a header part of a bitstream.

Embodiment 1 FIG.
1 is a block diagram showing a color moving image encoding apparatus according to Embodiment 1 of the present invention.
The video signal to be processed by the color moving image encoding apparatus according to the first embodiment is an arbitrary color space such as a YUV signal composed of a luminance signal and two color difference signals, or an RGB signal output from a digital image sensor. In addition to a color video signal, the video frame is an arbitrary video signal such as a monochrome image signal or an infrared image signal, in which a video frame is composed of a horizontal / vertical two-dimensional digital sample (pixel) sequence.
The gradation of each pixel may be 8 bits, or may be gradation such as 10 bits or 12 bits.

However, in the following description, it is assumed that the input video signal is a YUV signal unless otherwise specified. In addition, it is assumed that the two color difference components U and V are subsampled 4: 2: 0 format signals with respect to the luminance component Y.
The processing data unit corresponding to each frame of the video is referred to as “picture”. In the first embodiment, “picture” is described as a signal of a video frame that has been sequentially scanned (progressive scan). However, when the video signal is an interlace signal, the “picture” may be a field image signal which is a unit constituting a video frame.

In FIG. 1, an encoding control unit 1 determines the maximum size of an encoding block that is a processing unit when intra prediction processing (intraframe prediction processing) or motion compensation prediction processing (interframe prediction processing) is performed. Then, a process of determining the upper limit number of layers when the encoding block of the maximum size is hierarchically divided is performed.
In addition, the encoding control unit 1 assigns each encoding block divided hierarchically from one or more available encoding modes (one or more intra encoding modes and one or more inter encoding modes). A process of selecting a suitable encoding mode is performed.
In addition, the encoding control unit 1 determines the quantization parameter and transform block size used when the difference image is compressed for each encoding block, and intra prediction used when the prediction process is performed. A process of determining a parameter or an inter prediction parameter is performed. The transform block division flag indicating the quantization parameter and the transform block size is included in the prediction difference coding parameter and is output to the transform / quantization unit 7, the inverse quantization / inverse transform unit 8, the variable length coding unit 13, and the like. Is done.
The encoding control unit 1 constitutes an encoding control unit.

Here, FIG. 17 is an explanatory diagram showing a conversion block size when performing compression processing (conversion processing and quantization processing) of luminance signals and color difference signals in a 4: 2: 0 format signal.
As shown in FIG. 17, the transform block size is determined by hierarchically dividing the encoded block into a quadtree.
For example, whether or not to divide the transform block so that the evaluation value is minimized based on the amount of code when the transform block is divided and when the transform block is not divided, the evaluation scale that takes into account the coding error, etc. By determining, it is possible to determine the optimal division shape of the transform block from the viewpoint of the trade-off between the code amount and the coding error.

For the luminance signal, for example, as shown in FIG. 17, when a prediction mode in which the shape of the prediction block is square is selected as the coding mode of the coding block, the coding block is converted into one or a plurality of squares. It is configured to be divided into blocks hierarchically.
On the other hand, when the prediction mode in which the shape of the prediction block is rectangular is selected as the encoding mode of the encoding block, the encoding block is configured to be hierarchically divided into one or a plurality of rectangular transform blocks. . Or after dividing | segmenting into a square conversion block, it is comprised so that it may be further divided | segmented into a rectangular conversion block in the lower hierarchy.
On the other hand, as shown in FIG. 17, the color difference signal is configured so that a transform block having the same size as the prediction block is applied when the shape of the prediction block is a square.
When the prediction block has a rectangular shape, the prediction block is configured to be divided by one layer.

As described above, the luminance signal is divided and converted into a hierarchically optimal conversion block size, and the chrominance signal is converted in a large block whose division shape is fixed. Thus, the color difference signal can be efficiently compressed without signaling information regarding the divided shape.
In addition, since the division shape of the conversion block of the color difference signal is different from the division shape of the conversion block of the luminance signal, the division shape of the conversion block most suitable for the luminance signal can be selected for the luminance signal. The signal can also be efficiently compressed.
Even if the shape of the prediction block is square, in the case of a square-size prediction block obtained by dividing the coding block into four, the color difference signal conversion block is also divided into one layer. Also good.
In this way, since the square transform block can be configured not to cross the square prediction block, generation of high frequency components can be suppressed and compression can be performed efficiently.
The division information of the transformation block of the luminance signal is output to the variable length coding unit 13 as a transformation block division flag indicating whether or not to divide for each layer.

When a color image signal indicating an input color image (current picture) is input, the block dividing unit 2 divides the input color image into encoded blocks of the maximum size determined by the encoding control unit 1, and the encoding control unit The process of dividing the encoded block hierarchically is performed until the upper limit number of hierarchies determined by 1 is reached. The block dividing unit 2 constitutes block dividing means.
If the coding mode selected by the coding control unit 1 is the intra coding mode, the changeover switch 3 outputs the coding block divided by the block dividing unit 2 to the intra prediction unit 4, and the coding control unit 1 If the coding mode selected by (2) is the inter coding mode, a process of outputting the coding block divided by the block dividing unit 2 to the motion compensation prediction unit 5 is performed.

When the intra prediction unit 4 receives the encoded block divided by the block dividing unit 2 from the changeover switch 3, the intra prediction unit 4 is adjacent to the encoded block stored in the intra prediction memory 10 with respect to the encoded block. The process which produces | generates a prediction image is implemented by implementing the intra prediction process based on the intra prediction parameter output from the encoding control part 1 using the decoded pixel which is.
That is, the intra prediction unit 4 performs intra-frame prediction of the luminance component of the encoded block divided by the block dividing unit 2 to generate a prediction image for the luminance component.
On the other hand, for the color difference component in the coding block divided by the block dividing unit 2, if the coding mode selected by the coding control unit 1 is the directional prediction mode in the intra coding mode, the block dividing unit 2 Intra-frame prediction of the color difference component in the encoded block divided by the above is performed, and a predicted image for the color difference component is generated.

When the inter coding mode is selected by the coding control unit 1 as the coding mode corresponding to the coding block divided by the block dividing unit 2, the motion compensated prediction unit 5 is stored by the motion compensated prediction frame memory 12. Based on the inter prediction parameter output from the encoding control unit 1, using a reference image of one or more frames, a process for generating a predicted image is performed by performing a motion compensation prediction process for the encoded block To do.
The changeover switch 3, the intra prediction unit 4, and the motion compensation prediction unit 5 constitute a predicted image generation unit.

  The subtracting unit 6 subtracts the prediction image generated by the intra prediction unit 4 or the motion compensation prediction unit 5 from the encoded block divided by the block dividing unit 2, thereby obtaining a difference image (= encoded block−predicted image). The process to generate is performed. The subtracting unit 6 constitutes a difference image generating unit.

The transform / quantization unit 7 converts the difference image generated by the subtraction unit 6 in units of transform block size specified from the transform block division flag included in the prediction difference encoding parameter output from the encoding control unit 1. Performing transform processing (for example, DCT (discrete cosine transform), DST (discrete sine transform), orthogonal transform processing such as KL transform in which a base design is made in advance for a specific learning sequence), and the prediction differential code Using the quantization parameter included in the quantization parameter, the transform coefficient of the difference image is quantized to output the quantized transform coefficient as compressed data of the difference image.
That is, when the transform / quantization unit 7 performs transform / quantization processing (compression processing) on the luminance signal of the difference image generated by the subtraction unit 6, the coding block divided by the block division unit 2 is further hierarchized. If the luminance signal is converted and quantized in units of divided blocks and the color difference signal of the difference image generated by the subtractor 6 is converted and quantized, the block dividing unit If the shape of the coding block divided by 2 is square, color difference signal conversion / quantization processing is performed in block units of the same size as the coding block, and if the shape of the coding block is rectangular Then, the encoded block is divided by one layer, and the color difference signal conversion / quantization processing is performed in units of the divided blocks.
The transform / quantization unit 7 constitutes an image compression unit.

  The inverse quantization / inverse transform unit 8 performs inverse quantization on the compressed data output from the transform / quantization unit 7 using the quantization parameter included in the prediction difference encoding parameter output from the encoding control unit 1. And inverse transform processing of the compressed data after inverse quantization (for example, inverse DCT (Inverse Discrete Cosine Transform)) in units of transform block size specified from the transform block division flag included in the prediction difference encoding parameter By performing inverse DST (inverse discrete sine transform), inverse KL transform, or the like), a process of outputting the compressed data after the inverse transform process as a local decoded prediction difference signal is performed.

The adding unit 9 adds the local decoded prediction difference signal output from the inverse quantization / inverse transform unit 8 and the prediction signal indicating the prediction image generated by the intra prediction unit 4 or the motion compensation prediction unit 5 to thereby perform local decoding. A process of generating a locally decoded image signal indicating an image is performed.
The intra prediction memory 10 is a recording medium such as a RAM that stores a local decoded image indicated by the local decoded image signal generated by the adding unit 9 as an image used in the next intra prediction process by the intra prediction unit 4.

The loop filter unit 11 compensates for the coding distortion included in the locally decoded image signal generated by the adding unit 9, and performs motion compensation prediction using the locally decoded image indicated by the locally decoded image signal after the coding distortion compensation as a reference image. A process of outputting to the frame memory 12 is performed.
The motion compensated prediction frame memory 12 is a recording medium such as a RAM that stores a locally decoded image after the filtering process by the loop filter unit 11 as a reference image used in the next motion compensated prediction process by the motion compensated prediction unit 5.

  The variable length encoding unit 13 includes the compressed data output from the transform / quantization unit 7, the prediction differential encoding parameter including the encoding mode and the transform block division flag output from the encoding control unit 1, and the intra prediction unit. 4, the intra-prediction parameter output from 4 or the inter-prediction parameter output from the motion-compensated prediction unit 5 is variable-length encoded, and the compressed data, the encoding mode, the prediction differential encoding parameter, the intra-prediction parameter / inter-prediction parameter A process for generating a bit stream in which the encoded data is multiplexed is executed. The variable length encoding unit 13 constitutes variable length encoding means.

In FIG. 1, a coding control unit 1, a block division unit 2, a changeover switch 3, an intra prediction unit 4, a motion compensation prediction unit 5, a subtraction unit 6, a transform / quantization unit, which are components of the color moving image coding apparatus. 7, each of the inverse quantization / inverse transform unit 8, the adder unit 9, the loop filter unit 11, and the variable length coding unit 13 has dedicated hardware (for example, a semiconductor integrated circuit on which a CPU is mounted, or one chip However, when the color moving image encoding apparatus is configured by a computer or the like, the encoding control unit 1, the block division unit 2, the changeover switch 3, and the intra prediction unit 4 are assumed. Describes the processing contents of the motion compensation prediction unit 5, the subtraction unit 6, the transform / quantization unit 7, the inverse quantization / inverse transform unit 8, the adder unit 9, the loop filter unit 11 and the variable length coding unit 13. Program Or some were stored in the memory of the computer, may execute a program that the CPU of the computer is stored in the memory.
FIG. 2 is a flowchart showing the processing contents of the color moving image coding apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a block diagram showing the intra prediction unit 4 of the color moving picture coding apparatus according to Embodiment 1 of the present invention.
In FIG. 3, the luminance signal intra prediction unit 21 performs intra-frame prediction of the luminance component in the encoded block divided by the block dividing unit 2 and performs a process of generating a prediction image for the luminance component.
That is, the luminance signal intra prediction unit 21 refers to the decoded luminance reference pixel adjacent to the encoded block stored in the intra prediction memory 10 and outputs the intra prediction output from the encoding control unit 1. By performing intra-frame prediction of the luminance component based on the parameter, a process for generating a predicted image for the luminance component is performed.

  If the parameter indicating the intra coding mode of the chrominance signal indicates the directional prediction mode among the intra prediction parameters output from the coding control unit 1, the changeover switch 22 selects a reference pixel used for prediction. If the color difference signal directivity intra prediction unit 23 indicates that the parameter indicating the intra coding mode of the color difference signal is the smoothed luminance correlation use color difference signal prediction mode, the reference pixel used for prediction is used for the luminance correlation use. A process of outputting to the color difference signal prediction unit 24 is performed.

The chrominance signal directivity intra prediction unit 23 refers to the decoded chrominance reference pixel adjacent to the encoded block received from the changeover switch 22 and determines the chrominance based on the intra prediction parameter output from the encoding control unit 1. By performing intra-frame prediction of components, a process of generating a predicted image for the color difference component is performed.
The luminance correlation utilization color difference signal prediction unit 24, among the decoded pixels received from the changeover switch 22, has decoded luminance reference pixels and color difference reference pixels adjacent to the coding block, and has been decoded within the coding block. Using the luminance reference pixel, smoothing the luminance component related to a plurality of pixels adjacent in the horizontal direction and the vertical direction among the pixels constituting the coding block, A correlation parameter indicating the correlation of the color difference component is calculated, and a process of generating a predicted image for the color difference component is performed using the correlation parameter and the smoothed luminance component.
FIG. 5 is a flowchart showing the processing contents of the intra prediction unit 4 of the color moving image coding apparatus according to Embodiment 1 of the present invention.

FIG. 4 is a block diagram showing the luminance correlation utilizing color difference signal predicting unit 24 of the color moving picture coding apparatus according to Embodiment 1 of the present invention.
In FIG. 4, the smoothed luminance reference pixel reducing unit 31 is adjacent in the horizontal direction and the vertical direction among the decoded luminance reference pixels constituting the encoded block stored in the intra prediction memory 10. A reduced luminance reference pixel Rec ′ _L is generated by performing smoothing processing or the like of a plurality of luminance reference pixels.
The correlation calculation unit 32 uses the color difference reference pixels stored in the intra prediction memory 10 and the reduced luminance reference pixel Rec ′ _L generated by the smoothed luminance reference pixel reduction unit 31 to calculate the correlation between the luminance component and the color difference component. Processing for calculating the correlation parameters α and β shown in FIG.
The color difference predicted image generation unit 33 uses the correlation parameters α and β calculated by the correlation calculation unit 32 and the reduced luminance reference pixel Rec ′ _L generated by the smoothed luminance reference pixel reduction unit 31 to generate a predicted image for the color difference component. Perform the process to generate.
FIG. 6 is a flowchart showing the processing contents of the luminance correlation utilization color difference signal prediction unit 24 of the color moving image coding apparatus according to Embodiment 1 of the present invention.

FIG. 7 is a block diagram showing a color moving image decoding apparatus according to Embodiment 1 of the present invention.
In FIG. 7, the variable length decoding unit 41 is a code that is hierarchically divided from the maximum size of the coding block that is a processing unit when the intra prediction process or the motion compensation prediction process is performed, and the coding block of the maximum size. By specifying the number of hierarchized block levels, the coded data related to the largest size coded block and the hierarchically divided coded block is identified from the coded data multiplexed in the bitstream. Then, variable-length decoding is performed on each encoded data from the encoded data, the compressed data related to the encoded block, the encoding mode, the prediction differential encoding parameter including the transform block division flag, the intra prediction parameter / inter prediction parameter, and the compressed data and The prediction difference encoding parameter is output to the inverse quantization / inverse transform unit 45, and the encoding mode and And it carries out a process of outputting the prediction parameters / inter prediction parameter to the changeover switch 42. The variable length decoding unit 41 constitutes variable length decoding means.

The changeover switch 42 outputs the intra prediction parameter output from the variable length decoding unit 41 to the intra prediction unit 43 when the coding mode related to the coding block output from the variable length decoding unit 41 is the intra coding mode. When the coding mode is the inter coding mode, a process of outputting the inter prediction parameter output from the variable length decoding unit 41 to the motion compensation unit 44 is performed.
The intra prediction unit 43 uses a decoded pixel adjacent to the coding block stored in the intra prediction memory 47 and uses the decoded prediction frame output from the changeover switch 42 to generate a frame for the coding block. A process for generating a predicted image is performed by performing the intra prediction process.

The motion compensation unit 44 performs a motion compensation prediction process on the encoded block based on the inter prediction parameter output from the changeover switch 42 using one or more reference images stored in the motion compensation prediction frame memory 49. Thus, a process for generating a predicted image is performed.
The changeover switch 42, the intra prediction unit 43, and the motion compensation unit 44 constitute a predicted image generation unit.

The inverse quantization / inverse transform unit 45 uses the quantization parameter included in the prediction difference encoding parameter output from the variable length decoding unit 41 to compress the encoded block output from the variable length decoding unit 41 Inverse transform processing (for example, inverse DCT (inverse discrete cosine) of compressed data of inverse quantization in units of transform block size specified from the transform block division flag included in the prediction differential encoding parameter. Conversion), inverse DST (inverse discrete sine transform), inverse KL transformation, etc.), and the compressed data after the inverse transformation process is used as a decoded prediction difference signal (a signal indicating a difference image before compression). Perform the output process.
That is, the inverse quantization / inverse transform unit 45 converts the transform block shape of the luminance signal divided hierarchically based on the transform block partition flag included in the prediction difference encoding parameter output from the variable length decoding unit 41. Identify and perform inverse quantization and inverse transform on a transform block basis.
As for the color difference signal, as shown in FIG. 17, when the prediction block has a square shape, inverse quantization processing / inverse conversion processing is performed in units of transform blocks having the same size as the prediction block, and the prediction block has a rectangular shape. In such a case, the prediction block is divided by one layer, and inverse quantization processing / inverse transformation processing is performed in units of the divided blocks.
The inverse quantization / inverse transform unit 45 constitutes a difference image generation unit.

The addition unit 46 adds the decoded prediction difference signal output from the inverse quantization / inverse conversion unit 45 to the prediction signal indicating the prediction image generated by the intra prediction unit 43 or the motion compensation unit 44, thereby indicating a decoded image. A process of generating a decoded image signal is performed. The adding unit 46 constitutes a decoded image generating unit.
The intra prediction memory 47 is a recording medium such as a RAM that stores a decoded image indicated by the decoded image signal generated by the addition unit 46 as an image used in the next intra prediction process by the intra prediction unit 43.

The loop filter unit 48 compensates for the coding distortion included in the decoded image signal generated by the adding unit 46, and uses the decoded image indicated by the decoded image signal after the coding distortion compensation as a reference image as a motion compensated prediction frame memory 49. And a process of outputting the decoded image as a reproduced image to the outside.
The motion compensated prediction frame memory 49 is a recording medium such as a RAM that stores a decoded image after the filtering process by the loop filter unit 48 as a reference image to be used by the motion compensation unit 44 in the next motion compensation prediction process.

In FIG. 7, a variable length decoding unit 41, a changeover switch 42, an intra prediction unit 43, a motion compensation unit 44, an inverse quantization / inverse transformation unit 45, an addition unit 46, and a loop filter unit, which are components of the color moving image decoding apparatus. 48 is assumed to be configured by dedicated hardware (for example, a semiconductor integrated circuit on which a CPU is mounted, or a one-chip microcomputer), but the color moving image decoding device is a computer or the like. When configured, the processing contents of the variable length decoding unit 41, the changeover switch 42, the intra prediction unit 43, the motion compensation unit 44, the inverse quantization / inverse transformation unit 45, the addition unit 46, and the loop filter unit 48 are described. All or part of the program is stored in the memory of the computer, and the CPU of the computer executes the program stored in the memory Unishi may be.
FIG. 8 is a flowchart showing the processing contents of the color moving image decoding apparatus according to Embodiment 1 of the present invention.

The color moving image coding apparatus according to the first embodiment adapts to local changes in the spatial and temporal directions of a video signal, divides the video signal into regions of various sizes, and performs intraframe / interframe adaptive coding. The color difference signal is uniquely determined by limiting the transform block size to only two layers.
In general, video signals have the characteristic that the complexity of the signal changes locally in space and time, and when viewed spatially, comparison is made on a specific video frame, for example, sky or wall. A picture having uniform signal characteristics in a wide image area and a picture having a complicated texture pattern in a small image area may be mixed in a picture including a person or a fine texture.

Even in terms of time, the sky and the wall have small changes in the local pattern in the time direction, but moving people and objects have temporal and rigid movements, so the time changes. Is big.
The encoding process generates a prediction difference signal with low signal power and entropy by temporal and spatial prediction, and performs a process of reducing the overall code amount. However, the prediction parameter used for the prediction process is as large as possible. If it can be applied uniformly to the region, the code amount of the prediction parameter can be reduced.
On the other hand, if the same prediction parameter is applied to a large image region with respect to an image signal pattern having a large temporal and spatial change, a prediction error increases, and therefore the code amount of the prediction difference signal cannot be reduced. .
Therefore, it is desirable to reduce the power / entropy of the prediction difference signal even if the prediction target area is reduced and the data amount of the prediction parameter used for the prediction process is increased in an area where the temporal and spatial changes are large. .
In order to perform encoding processing adapted to the general characteristics of such a video signal, the color moving image encoding apparatus according to the first embodiment hierarchically divides the video signal area from a predetermined maximum block size. A configuration is adopted in which the image is divided and the prediction process and the prediction difference encoding process are adapted for each divided region.

Next, the operation will be described.
First, the processing contents of the color moving image encoding apparatus in FIG. 1 will be described.
First, the encoding control unit 1 determines the maximum size of an encoding block that is a processing unit when intra prediction processing (intraframe prediction processing) or motion compensation prediction processing (interframe prediction processing) is performed, The upper limit number of layers when the coding block of the maximum size is divided hierarchically is determined (step ST1 in FIG. 2).

As a method of determining the maximum size of the encoded block, for example, a method of determining a size corresponding to the resolution of the input image for all the pictures can be considered.
Also, the difference in the complexity of the local motion of the input color image is quantified as a parameter, and the maximum size is determined to be a small value for pictures with intense motion, and the maximum size is determined to be a large value for pictures with little motion. Possible methods.
The upper limit of the number of hierarchies is set so that, for example, the more intense the input color image moves, the deeper the number of hierarchies, so that more detailed movement can be detected. The method of setting to can be considered.

In addition, the encoding control unit 1 includes each encoding block divided hierarchically from one or more available encoding modes (M types of intra encoding modes and N types of inter encoding modes). Is selected (step ST2). The M types of intra coding modes prepared in advance will be described later.
However, when each coding block hierarchically divided by the block division unit 2 described later is further divided into partitions, it is possible to select a coding mode corresponding to each partition.
In the following description of the first embodiment, each encoded block is further divided into partitions.
Since the encoding mode selection method by the encoding control unit 1 is a known technique, a detailed description thereof will be omitted. For example, an encoding process for an encoding block is performed using any available encoding mode. There is a method in which coding efficiency is verified by performing and a coding mode having the best coding efficiency is selected from among a plurality of available coding modes.

Further, the encoding control unit 1 determines a quantization parameter and a transform block size used when the difference image is compressed for each partition included in each encoding block, and a prediction process is performed. Intra prediction parameters or inter prediction parameters used in the determination are determined.
The encoding control unit 1 outputs the prediction difference encoding parameter including the quantization parameter and the transform block size to the transform / quantization unit 7, the inverse quantization / inverse transform unit 8, and the variable length encoding unit 13. Moreover, a prediction difference encoding parameter is output to the intra estimation part 4 as needed.

When a video signal indicating an input color image is input, the block dividing unit 2 divides the input color image into encoded blocks of the maximum size determined by the encoding control unit 1 and is determined by the encoding control unit 1. The encoded block is divided hierarchically until the upper limit number of layers is reached. Further, the encoded block is divided into partitions (step ST3).
Here, FIG. 9 is an explanatory diagram showing a state in which a maximum-size encoded block is hierarchically divided into a plurality of encoded blocks.
In the example of FIG. 9, the coding block of the maximum size is the coding block B ⁰ of the 0th layer, and has a size of (L ⁰ , M ⁰ ) as a luminance component.
In the example of FIG. 9, the encoding block B ⁿ is obtained by performing hierarchical division to a predetermined depth determined separately in a quadtree structure with the maximum size encoding block B ⁰ as a starting point. Yes.

At the depth n, the coding block B ⁿ is an image area of size (L ⁿ , M ⁿ ).
However, L ⁿ and M ⁿ may be the same or different, but the example of FIG. 9 shows a case of L ⁿ = M ⁿ .
Later, the size of the encoded block ^{B n} is defined as the size of the luminance component of the encoded block ^{B n (L n, M n} ).

Since the block division unit 2 performs quadtree division, (L ^{n + 1} , M ^{n + 1} ) = (L ⁿ / 2, M ⁿ / 2) always holds.
However, in a color video signal (4: 4: 4 format) in which all color components have the same number of samples, such as RGB signals, the size of all color components is (L ⁿ , M ⁿ ). When the 4: 2: 0 format is handled, the size of the corresponding color difference component coding block is (L ⁿ / 2, M ⁿ / 2).
Hereinafter, an encoding mode that can be selected in the encoding block B ⁿ in the n-th layer is denoted as m (B ⁿ ).

In the case of a color video signal composed of a plurality of color components, the encoding mode m (B ⁿ ) may be configured to use an individual mode for each color component, but hereinafter, unless otherwise specified, YUV The description will be made on the assumption that it indicates the coding mode for the luminance component of the coding block of the signal 4: 2: 0 format.
The coding mode m (B ⁿ ) includes one or more intra coding modes (collectively “INTRA”), one or more inter coding modes (collectively “INTER”), As described above, the encoding control unit 1 selects an encoding mode having the highest encoding efficiency for the encoding block B ⁿ from all the encoding modes available for the picture or a subset thereof. .

As shown in FIG. 9, the encoded block ^Bn is further divided into one or more prediction processing units (partitions).
Hereinafter, the partition belonging to the coding block B ⁿ is ^denoted as P _i ⁿ (i: the partition number in the nth layer). FIG. 10 is an explanatory diagram showing partitions P _i ⁿ belonging to the coding block B ⁿ .
How the partition P _i ⁿ belonging to the coding block B ⁿ is divided is included as information in the coding mode m (B ⁿ ).
All partitions P _i ⁿ are subjected to prediction processing according to the coding mode m (B ⁿ ), but individual prediction parameters can be selected for each partition P _i ⁿ .

For example, the encoding control unit 1 generates a block division state as illustrated in FIG. 11 for the encoding block of the maximum size, and specifies the encoding block ^Bn .
11A shows the distribution of the partitions after the division, and FIG. 11B shows a situation where the encoding mode m (B ⁿ ) is assigned to the partition after the hierarchical division in a quadtree graph. Show.
In FIG. 11B, nodes surrounded by squares indicate nodes (encoded blocks B ⁿ ) to which the encoding mode m (B ⁿ ) is assigned.
Also, the encoding control unit 1 determines the division shape of the transform block as described above for the divided partition.

When the coding control unit 1 selects the intra coding mode (m (B ⁿ ) εINTRA), the changeover switch 3 performs intra prediction on the partition P _i ⁿ belonging to the coding block B ⁿ divided by the block dividing unit 2. When the coding control unit 1 selects the inter coding mode (m (B ⁿ ) εINTER), the partition P _i ⁿ belonging to the coding block B ⁿ is output to the motion compensation prediction unit 5. .

When the intra prediction unit 4 receives the partition P _i ⁿ belonging to the coding block B ⁿ from the changeover switch 3 (step ST4), the specific processing contents will be described later, but the intra prediction determined by the coding control unit 1 is performed. Based on the parameters, intra prediction processing (P _i ⁿ ) is generated by performing intra prediction processing for each partition P _i ⁿ (step ST5).
Hereinafter, in this specification, P _i ⁿ indicates a partition, and (P _i ⁿ ) indicates a predicted image of the partition P _i ⁿ .

Since the intra prediction parameters used to generate the intra-prediction image (P i ^_n) is also a color video decoding apparatus side, it is necessary to generate exactly the same intra prediction image (P i ^_n), the variable length coding unit 13 Is multiplexed into the bitstream.
Note that the number of intra prediction directions that can be selected as the intra prediction parameter may be configured to differ depending on the size of the block to be processed.
Since the efficiency of intra prediction decreases in a large size partition, the number of intra prediction directions that can be selected can be reduced, and the number of intra prediction directions that can be selected in a small size partition can be increased.
For example, a 4 × 4 pixel partition or an 8 × 8 pixel partition may be configured in 34 directions, a 16 × 16 pixel partition in 17 directions, a 32 × 32 pixel partition in 9 directions, or the like.

When the motion compensated prediction unit 5 receives the partition P _i ⁿ belonging to the coding block B ⁿ from the changeover switch 3 (step ST4), each of the partitions P _i is based on the inter prediction parameter determined by the coding control unit 1. ^The inter prediction image (P _i ⁿ ) is generated by performing the inter prediction process for ⁿ (step ST6).
That is, the motion compensated prediction unit 5 uses the reference image of one or more frames stored in the motion compensated prediction frame memory 12, and based on the inter prediction parameter output from the coding control unit 1, the coding block By performing the motion compensated prediction process for the inter prediction image (P _i ⁿ ),
For inter prediction parameters to be used in generating the inter prediction image (P i ^_n) is also a color video decoding apparatus side, it is necessary to generate exactly the same inter-prediction image (P i ^_n), the variable length coding unit 13 Is multiplexed into the bitstream.

When the subtraction unit 6 receives the predicted image (P _i ⁿ ) from the intra prediction unit 4 or the motion compensation prediction unit 5, the subtraction unit 6 performs prediction from the partition P _i ⁿ belonging to the encoded block B ⁿ divided by the block division unit 2. By subtracting the image (P _i ⁿ ), a prediction difference signal e _i ⁿ indicating the difference image is generated (step ST7).

Transform and quantization unit 7, the subtraction unit 6 generates a prediction difference signal e _i ^n, the transformation block size determined by the coding control unit 1, the conversion processing for the prediction difference signal e _i ⁿ (e.g., DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), and orthogonal transform processing such as KL transform in which a base design is made in advance for a specific learning sequence) are included in the prediction differential encoding parameters. By quantizing the transform coefficient of the prediction difference signal e _i ⁿ using the quantized parameter, the compressed image of the differential image, which is the transform coefficient after quantization, is converted into the inverse quantization / inverse transform unit 8 and the variable It outputs to the long encoding part 13 (step ST8).
That is, when the subtraction unit 6 generates the prediction difference signal e _i ⁿ , the transform / quantization unit 7 performs division / quantization processing on the luminance signal of the prediction difference signal e _i ⁿ by the block division unit 2. The encoded block is further divided hierarchically, luminance signal conversion / quantization processing is performed in units of the divided blocks, and conversion / quantization processing is performed on the color difference signal of the prediction difference signal e _i ^n. In this case, if the shape of the coding block divided by the block dividing unit 2 is square, the color difference signal is converted and quantized in units of blocks having the same size as the coding block, and the shape of the coding block Is a rectangle, the encoded block is divided by one layer, and the color difference signal is converted and quantized in units of divided blocks.
Even if the shape of the prediction block is square, in the case of a square-size prediction block obtained by dividing the coding block into four, the color difference signal conversion block is also divided into one layer. Also good.
In this way, since the square transform block can be configured not to cross the square prediction block, the bit stream output from the coding apparatus configured in this way can be suitably decoded.

  When receiving the compressed data from the transform / quantization unit 7, the inverse quantization / inverse transform unit 8 uses the quantization parameter included in the prediction difference coding parameter output from the coding control unit 1 to The compressed data is inversely quantized, and inverse transform processing (for example, inverse DCT (inverse discrete) of the quantized compressed data is performed in transform block size units specified from the transform block division flag included in the prediction differential encoding parameter. By performing (cosine transform), inverse DST (discrete sine transform), inverse KL transform, etc.), the compressed data after the inverse transform is output to the adder 9 as a local decoded prediction difference signal (step ST9). ).

Upon receiving the local decoded prediction difference signal from the inverse quantization / inverse transform unit 8, the adder 9 receives the local decoded prediction difference signal and the predicted image (P _i ) generated by the intra prediction unit 4 or the motion compensated prediction unit 5. ⁿ ) to generate a locally decoded image signal indicating a locally decoded partition image or a locally decoded block image (hereinafter referred to as “locally decoded image”) as a collection thereof. The locally decoded image signal is output to the loop filter unit 11 (step ST10).
The intra prediction memory 10 stores the local decoded image for use in intra prediction.

When the loop filter unit 11 receives the local decoded image signal from the adder unit 9, the loop filter unit 11 compensates for the encoding distortion included in the local decoded image signal, and the local decoded image indicated by the local decoded image signal after the encoding distortion compensation Is stored in the motion compensated prediction frame memory 12 as a reference image (step ST11).
Here, since the coding distortion occurs along the transform block boundary, the coding distortion is compensated for the transform block boundary. For small transform blocks, coding distortion at the transform block boundary is inconspicuous. Therefore, the minimum loop filter application block size is signaled in the header, and the coding distortion is only applied to blocks whose transform block size is larger than the minimum loop filter application block size. You may comprise so that compensation may be applied.
In this way, unnecessary coding distortion compensation can be omitted, and the amount of calculation can be reduced while maintaining image quality. In addition, since the division shape of the transform block is different between the luminance signal and the color difference signal, the coding distortion compensation is configured to specify and process the division shape of the conversion block using the luminance signal and the color difference signal, respectively.
Note that the filtering process by the loop filter unit 11 may be performed in units of the maximum encoded block or individual encoded blocks of the input local decoded image signal, or a local decoded image signal corresponding to a macroblock for one screen. It may be performed for one screen after the input.

Processing in step ST4~ST10 is repeatedly performed until the processing for the partitions _P ^{i n} that belong to all the coding blocks ^{B n} divided by the block dividing unit 2 is completed (step ST12).
The variable length encoding unit 13 includes the compressed data output from the transform / quantization unit 7, the prediction differential encoding parameter including the encoding mode and the transform block division flag output from the encoding control unit 1, and intra prediction. The intra-prediction parameter output from the unit 4 or the inter-prediction parameter output from the motion compensated prediction unit 5 is variable-length encoded, and the compressed data, the encoding mode, the prediction differential encoding parameter, the intra-prediction parameter / inter prediction A bit stream in which encoded data of parameters is multiplexed is generated (step ST13).

Next, the processing content of the intra estimation part 4 is demonstrated concretely.
FIG. 12 is an explanatory diagram showing an example of intra prediction parameters (intra prediction mode) that can be selected in each partition P _i ⁿ belonging to the coding block B ⁿ .
In the example of FIG. 12, the prediction direction vector corresponding to the intra prediction mode is shown, and the relative angle between the prediction direction vectors is designed to decrease as the number of selectable intra prediction modes increases.

First, the luminance signal intra prediction unit 21 of the intra prediction unit 4 performs intra-frame prediction of the luminance component in the encoded block divided by the block dividing unit 2, and generates a prediction image for the luminance component (FIG. 5). Step ST21).
Hereinafter, the processing content of the luminance signal intra prediction unit 21 will be specifically described.
Here, the luminance signal intra prediction unit 21 of the intra prediction unit 4, based on the intra prediction parameters (intra prediction mode) for the luminance signal partitions P _i ^n, the intra processing for generating an intra prediction signal of the luminance signal described To do.
For convenience of explanation, the size of the partition _P ^{i n} a _l ^{i n} × _m ^{i n} pixels.

FIG. 13 is an explanatory diagram illustrating an example of pixels used when generating predicted values of pixels in the partition P _i ⁿ when l _i ⁿ = m _i ⁿ = 4.
In the example of FIG. 13, the partition _P ^{i n} in the pixel on the partition already coded that is adjacent to ^{_{((2 × l i n +1}} ) pixels), the left partition pixel ((2 × _m ⁱ n) Number of pixels) is used as a reference pixel for prediction, but the number of pixels used for prediction may be more or less than that shown in FIG.
Further, in the example of FIG. 13, pixels for one row or one column adjacent to each other are used for prediction. However, pixels for two rows or two columns or more may be used for prediction. .

ただし、ｋは正のスカラ値である。 Luminance signal intra prediction unit 21, for example, the partition P _i if the index value of the intra prediction mode for ⁿ is 2 (average prediction), the average value of neighboring pixels of the adjacent pixel and the left partition of the upper partition partition P _i ^A predicted image is generated as a predicted value of the pixels in ⁿ .
If the index value of the intra prediction mode is other than 2 (average prediction), the prediction direction vector index value indicates v _{p =} (dx, dy) on the basis of, generating a prediction value of the pixel in the partition P _i ⁿ To do.
Partitioning P _i ⁿ in the relative coordinates of the pixels for generating the prediction value (prediction target pixel) a (an origin at the upper left pixel of the partition) as (x, y), the position of the reference pixels used for prediction, the following This is the intersection of L and adjacent pixels.

However, k is a positive scalar value.

When the reference pixel is at the integer pixel position, the integer pixel is set as the prediction value of the prediction target pixel. When the reference pixel is not located at the integer pixel position, an interpolation pixel generated from the integer pixel adjacent to the reference pixel is set as the predicted value.
In the example of FIG. 13, since the reference pixel is not located at the integer pixel position, the average value of two pixels adjacent to the reference pixel is used as the predicted value.
Note that an interpolation pixel may be generated not only from two adjacent pixels but also from two or more adjacent pixels, and used as a predicted value.

The luminance signal intra prediction unit 21 generates prediction pixels for all the pixels of the luminance signal in the partition P _i ⁿ in the same procedure, and outputs the generated intra prediction image (P _i ⁿ ).
As described above, the intra-prediction parameters used for generating the intra-predicted image (P _i ⁿ ) are output to the variable-length encoding unit 13 for multiplexing into the bitstream.

The changeover switch 22 of the intra prediction unit 4 determines whether the parameter indicating the intra coding mode of the color difference signal among the intra prediction parameters output from the coding control unit 1 is the directionality prediction mode, or uses smoothed luminance correlation. It is determined whether the color difference signal prediction mode is set (step ST22).
If the parameter indicating the intra coding mode of the chrominance signal indicates that it is the directional prediction mode, the changeover switch 22 gives the reference pixel used for prediction to the chrominance signal directional intra prediction unit 23, and If the parameter indicating the intra coding mode indicates that it is the smoothed luminance correlation utilization color difference signal prediction mode, the reference pixel used for the prediction is given to the luminance correlation utilization color difference signal prediction unit 24.

Here, FIG. 14 is an explanatory diagram showing a correspondence example between the intra prediction parameters of the color difference signal and the color difference intra prediction modes.
In the example of FIG. 14, when the color difference signal intra prediction parameter is “34”, a reference pixel used for prediction is given to the luminance correlation utilization color difference signal prediction unit 24, and the color difference signal intra prediction parameter is other than “34”. In some cases, reference pixels used for prediction are given to the color difference signal directional intra prediction unit 23.

Color difference signal directional intra-prediction unit 23 receives the reference pixels used for prediction from the changeover switch 22, with reference to the decoded chrominance reference pixels adjacent to the partition P _i ^n, output from the coding controller 1 By performing intra-frame prediction of the color difference component based on the intra prediction parameter thus generated, a predicted image for the color difference component is generated (step ST23).
The intra prediction target in the chrominance signal directional intra prediction unit 23 is a color difference signal, and the intra prediction target is different from the luminance signal intra prediction unit 21 which is a luminance signal. 21. Therefore, by performing directional prediction, horizontal prediction, vertical prediction, DC prediction, etc., an intra prediction image of a color difference signal is generated.

Brightness correlation utilizing the color difference signal prediction section 24 receives the reference pixels used for prediction from the changeover switch 22, the decoded luminance reference pixel and the chrominance reference pixels adjacent to the partition P _i ⁿ is a coding block, partition decoded brightness reference pixels in P _i ⁿ (brightness reference pixels in the local decoded in an image obtained from the intra prediction image of the partition P _i ⁿ previously generated by the luminance signal intra prediction unit 21 (P i ^_n)) Are used to smooth the luminance component of a plurality of pixels adjacent in the horizontal direction and the vertical direction among the pixels constituting the coding block, and the smoothed luminance component and color difference component A correlation parameter indicating the correlation is calculated, and a predicted image for the color difference component is generated using the correlation parameter and the smoothed luminance component (step ST24).
Hereinafter, the processing content of the luminance correlation utilization color difference signal prediction unit 24 will be specifically described.

Smoothing luminance correlation utilizing the color difference signal prediction section 24 brightness reference pixel reducing unit 31, partition P _i ⁿ structure to have decoded luminance reference pixels stored by the intra prediction memory 10 (the luminance signal intra prediction unit 21, among the luminance reference pixels in the local decoded image obtained from the intra-predicted image (P _i ⁿ ) of the partition P _i ⁿ previously generated by the image 21, in the horizontal direction and the vertical direction. By performing pixel smoothing processing and the like, a reduced luminance reference pixel Rec ′ _L is generated (step ST31 in FIG. 6).
That is, the smoothed luminance reference pixel reducing unit 31, as shown in FIG. 15, (in the figure, the block on the left side of N × N) prediction block of the color difference signals in the partition P _i ⁿ in the block (drawing corresponding to, A reduced luminance reference pixel using a decoded luminance signal which is a decoded pixel value in the right 2N × 2N block) and a decoded luminance signal adjacent to the upper end and the left end of the decoded luminance signal. Rec ′ _L is generated.
Here, as shown in FIG. 16, the reduced luminance reference pixel Rec ′ _L is arranged in the horizontal direction with respect to the luminance reference pixel Rec _L so that the YUV 4: 2: 0 signal has the same phase as the color difference signal pixel. After a 1: 2: 1 low-pass filter and a 1: 1 low-pass filter are applied in the vertical direction, only an even column is sub-sampled in the vertical and horizontal directions.

式（１），（２）において、Ｉは処理対象となる色差信号の予測ブロックの１辺の画
素数の２倍の値である。 When the smoothed luminance reference pixel reducing unit 31 generates the reduced luminance reference pixel Rec ′ _L , the correlation calculating unit 32 of the luminance correlation using color difference signal predicting unit 24 and the reduced luminance reference pixel Rec ′ _L and the prediction block of the color difference signal Using the color difference reference pixel Rec _C , which is a decoded pixel value of the color difference signal adjacent to the upper end and the left end of the image, as shown in the following formulas (1) and (2), α and β are calculated (step ST32).

In equations (1) and (2), I is a value twice the number of pixels on one side of the prediction block of the color difference signal to be processed.

When the correlation calculation unit 32 calculates the correlation parameters α and β, the color difference predicted image generation unit 33 uses the correlation parameters α and β and the reduced luminance reference pixel Rec ′ _L as shown in the following equation (3). Then, the color difference prediction image Pred _C is generated (step ST33).

Intra prediction is a means for predicting an unknown area in the screen from a known area, but the texture of the luminance signal and the color difference signal are correlated, and in the spatial direction, neighboring pixels change pixel values. Predictive efficiency by calculating the correlation parameter between the luminance signal and the color difference signal using the decoded luminance signal and the color difference signal adjacent to the prediction block and predicting the color difference signal from the luminance signal and the correlation parameter. Can be improved.
In this case, since the resolution of the luminance signal and the color difference signal is different for the YUV 4: 2: 0 signal, it is necessary to subsample the luminance signal. Can be improved.

  As described above, the variable length coding unit 13 performs variable length coding on the intra prediction parameter output from the intra prediction unit 4 and multiplexes the codeword of the intra prediction parameter into the bitstream. Is encoded, a representative prediction direction vector (prediction direction representative vector) is selected from prediction direction vectors of a plurality of directional predictions, and an intra prediction parameter is used as an index of the prediction direction representative vector (prediction direction representative). Index) and an index (prediction direction difference index) representing the difference from the prediction direction representative vector, and by performing Huffman coding such as arithmetic coding according to the probability model for each index, the code amount is You may comprise so that it may reduce and encode.

Next, processing contents of the color moving image decoding apparatus in FIG. 7 will be described.
When the variable length decoding unit 41 receives the bit stream generated by the color moving image encoding apparatus in FIG. 1, the variable length decoding unit 41 performs variable length decoding processing on the bit stream (step ST41 in FIG. 8), and performs one or more frames. The frame size is decoded in units of sequences composed of pictures or in units of pictures.
When the variable length decoding unit 41 decodes the frame size, it becomes the maximum encoded block size determined by the color moving image encoding apparatus in FIG. 1 (a processing unit when intra prediction processing or motion compensation prediction processing is performed). The maximum size of the encoding block) and the upper limit of the number of division layers (the number of layers of the encoding block divided hierarchically from the encoding block of the maximum size) are determined by the same procedure as that of the color moving image encoding apparatus. (Step ST42).

For example, when the maximum size of the encoding block is determined to be the size corresponding to the resolution of the input color image for all the pictures, the maximum size of the encoding block is determined based on the previously decoded frame size in FIG. The maximum size of the encoded block is determined by the same procedure as that of the color moving image encoding apparatus.
When the maximum size of the encoded block and the number of layers of the encoded block are multiplexed in the bit stream by the color moving image encoding device, the maximum size of the encoded block and the layer of the encoded block are encoded from the bit stream. Decode the number.

The variable length decoding unit 41 determines the maximum size of the encoded block and the number of layers of the encoded block, and grasps the hierarchical division state of each encoded block from the maximum encoded block as a starting point. Among the encoded data multiplexed in the bit stream, the encoded data related to each encoded block is specified, and the encoding mode assigned to each encoded block is decoded from the encoded data.
Then, the variable length decoding unit 41 refers to the partition information of the partition P _i ⁿ belonging to the coding block B ⁿ included in the coding mode, and encodes the encoded data that is multiplexed in the bit stream. in, it identifies the coded data according to each partition _P ^{i n} (step ST43).
Variable-length decoding unit 41, compressed data, predictive differential coding parameters including transform block division flag, an intra prediction parameter / inter prediction parameters by variable length decoding the coded data according to each partition P _i ^n, the compressed data The prediction differential encoding parameter is output to the inverse quantization / inverse transform unit 45, and the encoding mode and the intra prediction parameter / inter prediction parameter are output to the changeover switch 42 (step ST44).

For example, when the prediction direction representative index and the prediction direction difference index are multiplexed in the bitstream, the prediction direction representative index and the prediction direction difference index are entropy decoded by arithmetic decoding or the like according to each probability model, An intra prediction parameter is specified from the prediction direction representative index and the prediction direction difference index.
Thereby, even when the code amount of the intra prediction parameter is reduced on the color moving image encoding device side, the intra prediction parameter can be correctly decoded.

When the coding mode of the partition P _i ⁿ belonging to the coding block B ⁿ output from the variable length decoding unit 41 is the intra coding mode, the changeover switch 42 outputs the intra prediction parameter output from the variable length decoding unit 41. Is output to the intra prediction unit 43, and when the encoding mode is the inter encoding mode, the inter prediction parameter output from the variable length decoding unit 41 is output to the motion compensation unit 44.

The intra prediction unit 43 receives the intra prediction parameter from the variable length decoding unit 41 (step ST45), like the intra prediction unit 4 in FIG. 1, on the basis of the intra prediction parameters, intra prediction for each partition P _i ⁿ By performing the process, an intra-predicted image (P _i ⁿ ) is generated (step ST46).
That is, the intra prediction unit 43 receives the intra prediction parameter from the variable length decoding unit 41, similarly to the luminance signal intra prediction unit 21 of the color video encoding apparatus, for example, an index of an intra prediction mode for the partition P _i ⁿ If the value is 2 (average prediction), and generates a prediction image the mean value of neighboring pixels of the adjacent pixel and the left partition of the upper partition as the predicted value of the pixel in the partition P _i ^n.
If the index value of the intra prediction mode is other than 2 (average prediction), the prediction direction vector index value indicates v _{p =} (dx, dy) on the basis of, generating a prediction value of the pixel in the partition P _i ⁿ To do.
The intra prediction unit 43 generates prediction pixels for all the pixels of the luminance signal in the partition P _i ⁿ in the same procedure, and outputs the generated intra prediction image (P _i ⁿ ).

Motion compensation unit 44 receives the inter prediction parameters from the changeover switch 42, similarly to the motion compensation prediction unit 5 of the color video encoding apparatus, based on the inter prediction parameters, inter-prediction processing for each partition P _i ⁿ To generate an inter predicted image (P _i ⁿ ) (step ST47).
That is, motion compensation unit 44, using one or more frames of reference images stored by the motion compensated prediction frame memory 49, by performing the motion compensation prediction processing on partition P _i ⁿ based on the inter prediction parameters, An inter prediction image (P _i ⁿ ) is generated.

  When the inverse quantization / inverse transform unit 45 receives the prediction difference encoding parameter including the transform block division flag from the variable length decoding unit 41, the inverse quantization / inverse transform unit 45 performs transform using the quantization parameter included in the prediction difference encoding parameter. For each transform block size determined according to the block partition flag, the compressed data related to the coding block output from the variable length decoding unit 41 is inversely quantized, and the transform block partition flag included in the prediction differential coding parameter is used. Inverse transform processing of compressed data after inverse quantization (for example, inverse DCT (Inverse Discrete Cosine Transform), inverse DST (Inverse Discrete Sine Transform), inverse KL transform, etc.) As a result, the compressed data after the inverse transform process is output to the adder 46 as a decoded prediction difference signal (a signal indicating a difference image before compression). (Step ST48).

The addition unit 46 adds the decoded prediction difference signal output from the inverse quantization / inverse conversion unit 45 and the prediction signal indicating the prediction image (P _i ⁿ ) generated by the intra prediction unit 43 or the motion compensation unit 44. Thus, a decoded image signal indicating a decoded partition image or a decoded image as a collection thereof is generated, and the decoded image signal is output to the loop filter unit 48 (step ST49).
The intra prediction memory 47 stores the decoded image for use in intra prediction.

When the loop filter unit 48 receives the decoded image signal from the adder unit 46, the loop filter unit 48 compensates for the encoding distortion included in the decoded image signal, and uses the decoded image indicated by the decoded image signal after the encoding distortion compensation as a reference image. While storing in the motion compensation prediction frame memory 49, the decoded image is output as a reproduced image (step ST50).
Here, since the coding distortion occurs along the transform block boundary, the coding distortion is compensated for the transform block boundary. For small transform blocks, coding distortion at the transform block boundary is inconspicuous. Therefore, the minimum loop filter application block size is signaled in the header, and the coding distortion is only applied to blocks whose transform block size is larger than the minimum loop filter application block size. You may comprise so that compensation may be applied.
In this way, unnecessary coding distortion compensation can be omitted, so that the amount of calculation can be reduced while maintaining image quality. In addition, since the division shape of the transform block is different between the luminance signal and the color difference signal, the coding distortion compensation is configured to specify and process the division shape of the transformation block based on the luminance signal and the color difference signal, respectively.
Note that the filtering processing by the loop filter unit 48 may be performed for the maximum encoded block of the input decoded image signal or for each individual encoded block, or a decoded image signal corresponding to a macroblock for one screen is input. After being done, it may be performed for one screen at a time.
The processes in steps ST43 to ST49 are repeatedly performed until the processes for the partitions P _i ⁿ belonging to all the coding blocks B ⁿ are completed (step ST51).

  As apparent from the above, according to the first embodiment, when the transform / quantization unit 7 performs the transform / quantization processing on the luminance signal of the difference image generated by the subtraction unit 6, the block division unit The coding block divided by 2 is further divided hierarchically, luminance signal conversion / quantization processing is performed in units of the divided blocks, and the difference image generated by the subtracting unit 6 is converted to color difference signals. When the quantization process is performed, if the shape of the encoded block divided by the block dividing unit 2 is square, the conversion / quantization process of the color difference signal is performed in block units having the same size as the encoded block, If the shape of the coding block is rectangular, the coding block is divided by one layer, and the color difference signal conversion / quantization processing is performed in units of the divided blocks. Since an effect that can be achieved is optimized block size of the transform and quantization processes for the luminance signal and color difference signals, enhancing the coding efficiency of the luminance signal and color difference signals.

That is, since the division shape of the conversion block in the color difference signal of the color moving image encoding device is uniquely determined in a division state having a small number of layers according to the encoding block and the prediction mode, the division of the conversion block of the color difference signal is performed. Since the color difference signal is converted with a block size relatively larger than the conversion block size of the luminance signal without signaling information about the shape, the color difference signal can be efficiently compressed. .
Also, since the division shape of the transform block in the color difference signal of the color moving image decoding apparatus is uniquely determined according to the encoding block and the prediction mode, the bit stream generated by the color moving image encoding apparatus is preferably decoded. be able to.
Similarly, the division shape of the transform block in the color difference signal may be configured to be the same size as the division shape of the prediction block.
With this configuration, the divided shape of the color difference signal conversion block is uniquely determined, and the color difference signal is converted with a relatively large block size, so that the same effect can be obtained.

Embodiment 2. FIG.
In the first embodiment, the example in which the video signal is in the YUV 4: 2: 0 format has been described. In the second embodiment, the case in which the video signal is in the YUV 4: 2: 2 format will be described.
In the YUV 4: 2: 2 format, the number of color difference components in the vertical direction is the same as that of the luminance signal, and the number of sampling in the horizontal direction is half that of the luminance signal. Accordingly, since only the processing of the color difference component is different from the encoding / decoding processing of the YUV 4: 2: 0 format, the processing of the color difference component will be mainly described here.

As in the first embodiment, the coding control unit 1 in the color moving image coding apparatus according to the second embodiment performs intra prediction processing (intraframe prediction processing) or motion compensation prediction processing (interframe prediction processing). In addition to determining the maximum size of a coding block that is a processing unit when implemented, processing for determining the upper limit number of layers when the coding block of the maximum size is hierarchically divided is performed.
In addition, the encoding control unit 1 assigns each encoding block divided hierarchically from one or more available encoding modes (one or more intra encoding modes and one or more inter encoding modes). A process of selecting a suitable encoding mode is performed.
In addition, the encoding control unit 1 determines the quantization parameter and transform block size used when the difference image is compressed for each encoding block, and intra prediction used when the prediction process is performed. A process of determining a parameter or an inter prediction parameter is performed. The transform block division flag indicating the quantization parameter and the transform block size is included in the prediction difference coding parameter and is output to the transform / quantization unit 7, the inverse quantization / inverse transform unit 8, the variable length coding unit 13, and the like. Is done.

FIG. 18 is an explanatory diagram showing a conversion block size when performing a compression process of a luminance signal and a color difference signal in a 4: 2: 2 format signal.
As shown in FIG. 18, the transform block size is determined by hierarchically dividing the encoded block into a quadtree.
For example, whether or not to divide the transform block so that the evaluation value is minimized based on the amount of code when the transform block is divided and when the transform block is not divided, the evaluation scale that takes into account the coding error, etc. By determining, it is possible to determine the optimal division shape of the transform block from the viewpoint of the trade-off between the code amount and the coding error.

For the luminance signal, for example, as shown in FIG. 18, when a prediction mode in which the shape of the prediction block is a square is selected as the encoding mode of the encoding block, the encoding block is converted into one or a plurality of squares. It is configured to be divided into blocks hierarchically.
On the other hand, when the prediction mode in which the shape of the prediction block is rectangular is selected as the encoding mode of the encoding block, the encoding block is configured to be hierarchically divided into one or a plurality of rectangular transform blocks. . Or after dividing | segmenting into a square conversion block, it is comprised so that it may be further divided | segmented into a rectangular conversion block in the lower hierarchy.
On the other hand, the color difference signal is configured such that a transform block having the same size as the prediction block is applied when the prediction block has a square shape.
When the prediction block has a rectangular shape, as shown in FIG. 18, the prediction block is configured to be divided by one layer.

As described above, the luminance signal is divided and converted into a hierarchically optimal conversion block size, and the chrominance signal is converted in a large block whose division shape is fixed. Thus, the color difference signal can be efficiently compressed without signaling information regarding the divided shape.
In addition, since the division shape of the conversion block of the color difference signal is different from the division shape of the conversion block of the luminance signal, the division shape of the conversion block most suitable for the luminance signal can be selected for the luminance signal. The signal can also be efficiently compressed.
The division information of the transformation block of the luminance signal is output to the variable length coding unit 13 as a transformation block division flag indicating whether or not to divide for each layer.

When the intra prediction unit 4 receives the encoded block divided by the block dividing unit 2 from the changeover switch 3, the intra prediction unit 4 stores the encoded block in the intra prediction memory 10 as in the first embodiment. A process for generating a prediction image is performed by performing an intra-frame prediction process based on an intra prediction parameter output from the encoding control unit 1 using a decoded pixel adjacent to the encoded block. .
That is, the intra prediction unit 4 performs intra-frame prediction of the luminance component of the encoded block divided by the block dividing unit 2 to generate a prediction image for the luminance component.
On the other hand, for the color difference component in the coding block divided by the block dividing unit 2, if the coding mode selected by the coding control unit 1 is the directional prediction mode in the intra coding mode, the block dividing unit 2 Intra-frame prediction of the color difference component in the encoded block divided by the above is performed, and a predicted image for the color difference component is generated.

Here, the intra-frame prediction of the color difference component is applied to a vertically long block as shown in FIG.
In the case of directionality prediction, as shown in FIG. 19, a predicted image is obtained by linearly repeating adjacent local decoded images.
In the case of average value prediction, the average value of the pixel adjacent on the upper side and the pixel adjacent on the left is used as the predicted value. Alternatively, the left average predicted value that is the average value of the pixels adjacent to the left and the upper average predicted value that is the average value of the pixels adjacent to the upper are calculated separately, and the left average predicted value and the upper average predicted The average value may be used as the average predicted value.
In this way, the arithmetic circuit can perform processing by shift operation without using division, so that the circuit scale can be reduced.
Further, it may be configured to add 3 times the left average value predicted value and the upper average value predicted value and shift right by 2 bits.
By doing so, since the shape of the prediction block is vertically long, it is possible to obtain a prediction value obtained by adding a weight to the pixel value on the left side, which is a longer side, and can be realized by a shift operation. Efficient prediction can be performed on a circuit scale.

When the inter coding mode is selected by the coding control unit 1 as the coding mode corresponding to the coding block divided by the block dividing unit 2, the motion compensated prediction unit 5 is stored by the motion compensated prediction frame memory 12. Based on the inter prediction parameter output from the encoding control unit 1, using a reference image of one or more frames, a process for generating a predicted image is performed by performing a motion compensation prediction process for the encoded block To do.
For the color difference component, the motion compensation prediction process is performed by applying a value obtained by halving only the horizontal motion vector component to the motion vector of the luminance component.

Next, the operation will be described.
First, the processing contents of the color moving image encoding apparatus in FIG. 1 will be described.
First, the encoding control unit 1 determines the maximum size of an encoding block that is a processing unit when intra prediction processing (intraframe prediction processing) or motion compensation prediction processing (interframe prediction processing) is performed, The upper limit number of layers when the coding block of the maximum size is divided hierarchically is determined (step ST1 in FIG. 2).

As a method of determining the maximum size of the encoded block, for example, a method of determining a size corresponding to the resolution of the input color image for all the pictures can be considered.
Also, the difference in the complexity of the local motion of the input color image is quantified as a parameter, and the maximum size is determined to be a small value for pictures with intense motion, and the maximum size is determined to be a large value for pictures with little motion. Possible methods.
The upper limit of the number of hierarchies is set so that, for example, the more intense the input color image moves, the deeper the number of hierarchies, so that more detailed movement can be detected. The method of setting to can be considered.

In addition, the encoding control unit 1 includes each encoding block divided hierarchically from one or more available encoding modes (M types of intra encoding modes and N types of inter encoding modes). Is selected (step ST2).
However, when each coding block hierarchically divided by the block division unit 2 described later is further divided into partitions, it is possible to select a coding mode corresponding to each partition.
In the following, the second embodiment will be described assuming that each encoded block is further divided into partitions.
Since the encoding mode selection method by the encoding control unit 1 is a known technique, a detailed description thereof will be omitted. For example, an encoding process for an encoding block is performed using any available encoding mode. There is a method in which coding efficiency is verified by performing and a coding mode having the best coding efficiency is selected from among a plurality of available coding modes.

Further, the encoding control unit 1 determines a quantization parameter and a transform block size used when the difference image is compressed for each partition included in each encoding block, and a prediction process is performed. Intra prediction parameters or inter prediction parameters used in the determination are determined.
The encoding control unit 1 sends the prediction difference encoding parameter including the conversion block division flag indicating the quantization parameter and the conversion block size to the conversion / quantization unit 7, the inverse quantization / inverse conversion unit 8, and the variable length encoding unit 13. Output. Moreover, a prediction difference encoding parameter is output to the intra estimation part 4 as needed.

When the video signal indicating the input color image is input, the block dividing unit 2 divides the input color image into encoded blocks of the maximum size determined by the encoding control unit 1 as in the first embodiment. The encoded block is hierarchically divided until the upper limit number of layers determined by the encoding control unit 1 is reached. Further, the encoded block is divided into partitions (step ST3).
In the example of FIG. 9, the coding block of the maximum size is the coding block B ⁰ of the 0th layer, and has a size of (L ⁰ , M ⁰ ) as a luminance component.
In the example of FIG. 9, the encoding block B ⁿ is obtained by performing hierarchical division to a predetermined depth determined separately in a quadtree structure with the maximum size encoding block B ⁰ as a starting point. Yes.

For example, the encoding control unit 1 generates a block division state as illustrated in FIG. 11 for the encoding block of the maximum size, and specifies the encoding block ^Bn .
11A shows the distribution of the partitions after the division, and FIG. 11B shows a situation where the encoding mode m (B ⁿ ) is assigned to the partition after the hierarchical division in a quadtree graph. Show.
In FIG. 11B, nodes surrounded by squares indicate nodes (encoded blocks B ⁿ ) to which the encoding mode m (B ⁿ ) is assigned.
Also, the encoding control unit 1 determines the division shape of the transform block as described above for the divided partition.

When the coding control unit 1 selects the intra coding mode (m (B ⁿ ) εINTRA), the changeover switch 3 is the coded block B ⁿ divided by the block dividing unit 2 as in the first embodiment. outputs partition _P ^{i n} that belongs to the intra prediction unit 4, the encoding control unit 1 selects the inter coding mode ^{(m (B n) ∈INTER)} , the partition _P ^{i n} that belong to the coding block ^{B n} Is output to the motion compensation prediction unit 5.

Intra prediction unit 4 receives the partition P _i ⁿ belonging from the changeover switch 3 to the coding block B ⁿ (step ST4), as in the first embodiment, the intra prediction parameters determined by the coding control unit 1 Based on the above, intra prediction processing (P _i ⁿ ) is generated by performing intra prediction processing for each partition P _i ⁿ (step ST5).
However, intra-frame prediction of chrominance components is applied to a vertically long block as shown in FIG.
Since the intra prediction parameters used to generate the intra-prediction image (P i ^_n) is also a color video decoding apparatus side, it is necessary to generate exactly the same intra prediction image (P i ^_n), the variable length coding unit 13 Is multiplexed into the bitstream.

Note that the number of intra prediction directions that can be selected as the intra prediction parameter may be configured to differ depending on the size of the block to be processed.
Since the efficiency of intra prediction decreases in a large size partition, the number of intra prediction directions that can be selected can be reduced, and the number of intra prediction directions that can be selected in a small size partition can be increased.
For example, a 4 × 4 pixel partition or an 8 × 8 pixel partition may be configured in 34 directions, a 16 × 16 pixel partition in 17 directions, a 32 × 32 pixel partition in 9 directions, or the like.

When the motion compensation prediction unit 5 receives the partition P _i ⁿ belonging to the coding block B ⁿ from the changeover switch 3 (step ST4), the inter prediction determined by the coding control unit 1 is performed as in the first embodiment. Based on the parameters, an inter prediction image (P _i ⁿ ) is generated by performing an inter prediction process on each partition P _i ⁿ (step ST6).
That is, the motion compensated prediction unit 5 uses the reference image of one or more frames stored in the motion compensated prediction frame memory 12, and based on the inter prediction parameter output from the coding control unit 1, the coding block By performing the motion compensated prediction process for the inter prediction image (P _i ⁿ ),
For inter prediction parameters to be used in generating the inter prediction image (P i ^_n) is also a color video decoding apparatus side, it is necessary to generate exactly the same inter-prediction image (P i ^_n), the variable length coding unit 13 Is multiplexed into the bitstream.

When receiving the prediction image (P _i ⁿ ) from the intra prediction unit 4 or the motion compensation prediction unit 5, the subtraction unit 6 converts the encoded block B ⁿ divided by the block division unit 2 as in the first embodiment. By subtracting the prediction image (P _i ⁿ ) from the partition P _i ⁿ to which it belongs, a prediction difference signal e _i ⁿ indicating the difference image is generated (step ST7).

When the subtraction unit 6 generates the prediction difference signal e _i ⁿ , the transform / quantization unit 7 generates the prediction difference signal in units of the transform block size determined by the encoding control unit 1 as in the first embodiment. The transformation processing for e _i ⁿ is performed, and the quantization coefficient included in the prediction difference encoding parameter is used to quantize the transformation coefficient of the prediction difference signal e _i ⁿ , so that The compressed data of the difference image that is the transform coefficient is output to the inverse quantization / inverse transform unit 8 and the variable length coding unit 13 (step ST8).
That is, when the subtraction unit 6 generates the prediction difference signal e _i ⁿ , the transform / quantization unit 7 performs division / quantization processing on the luminance signal of the prediction difference signal e _i ⁿ by the block division unit 2. The encoded block is further divided hierarchically, luminance signal conversion / quantization processing is performed in units of the divided blocks, and conversion / quantization processing is performed on the color difference signal of the prediction difference signal e _i ^n. In this case, if the shape of the coding block divided by the block dividing unit 2 is square, the color difference signal is converted and quantized in units of blocks having the same size as the coding block, and the shape of the coding block Is a rectangle, the encoded block is divided by one layer, and the color difference signal is converted and quantized in units of divided blocks.

  When receiving the compressed data from the transform / quantization unit 7, the inverse quantization / inverse transform unit 8 is included in the prediction difference encoding parameter output from the encoding control unit 1 as in the first embodiment. The inverse quantization of the compressed data of the inverse quantization is performed in the unit of the transform block size specified by the transform block division flag included in the prediction differential encoding parameter. By performing processing (for example, inverse transform processing such as inverse DCT (inverse discrete cosine transform), inverse DST (discrete sine transform), inverse KL transform), the compressed data after the inverse transform processing is used as a local decoded prediction difference signal. It outputs to the addition part 9 (step ST9).

When receiving the local decoded prediction difference signal from the inverse quantization / inverse transform unit 8, the adding unit 9 receives the local decoded prediction difference signal and the intra prediction unit 4 or the motion compensation prediction unit 5, as in the first embodiment. By adding the prediction signal indicating the prediction image (P _i ⁿ ) generated by the above, a locally decoded partition image or a locally decoded coded block image (hereinafter referred to as “local decoded image”) as a collection thereof is shown. A local decoded image signal is generated, and the local decoded image signal is output to the loop filter unit 11 (step ST10).
The intra prediction memory 10 stores the local decoded image for use in intra prediction.

When receiving the locally decoded image signal from the adder 9, the loop filter unit 11 compensates for the coding distortion included in the locally decoded image signal as in the first embodiment, and after the coding distortion compensation The local decoded image indicated by the local decoded image signal is stored in the motion compensated prediction frame memory 12 as a reference image (step ST11).
Note that the filtering process by the loop filter unit 11 may be performed in units of the maximum encoded block or individual encoded blocks of the input local decoded image signal, or a local decoded image signal corresponding to a macroblock for one screen. It may be performed for one screen after the input.

Processing in step ST4~ST10 is repeatedly performed until the processing for the partitions _P ^{i n} that belong to all the coding blocks ^{B n} divided by the block dividing unit 2 is completed (step ST12).
As with the first embodiment, the variable length encoding unit 13 converts the compressed data output from the conversion / quantization unit 7 and the encoding mode and conversion block size output from the encoding control unit 1. Variable length coding of the prediction differential coding parameter including the block division flag and the intra prediction parameter output from the intra prediction unit 4 or the inter prediction parameter output from the motion compensated prediction unit 5, and the compressed data, the coding mode Then, a bit stream in which encoded data of the prediction differential encoding parameter and the intra prediction parameter / inter prediction parameter is multiplexed is generated (step ST13).
For the color difference signal, the transform block has a vertically long shape of 1: 2, so when scanning a two-dimensional transform coefficient into a one-dimensional series, the coefficient is diagonally at a ratio of one horizontal to two vertical. A raster scan or an oblique zigzag scan is performed, and the obtained one-dimensional sequence is entropy-encoded.

Next, processing contents of the color moving image decoding apparatus in FIG. 7 will be described.
When the variable length decoding unit 41 receives the bit stream generated by the color moving image encoding apparatus in FIG. 1, the variable length decoding unit 41 performs variable length decoding processing on the bit stream as in the first embodiment (FIG. 8). Step ST41) The frame size is decoded in sequence units or picture units composed of pictures of one frame or more.
When the variable length decoding unit 41 decodes the frame size, it becomes the maximum encoded block size determined by the color moving image encoding apparatus in FIG. 1 (a processing unit when intra prediction processing or motion compensation prediction processing is performed). The maximum size of the encoding block) and the upper limit of the number of division layers (the number of layers of the encoding block divided hierarchically from the encoding block of the maximum size) are determined by the same procedure as that of the color moving image encoding apparatus. (Step ST42).

For example, when the maximum size of the encoding block is determined to be the size corresponding to the resolution of the input color image for all the pictures, the maximum size of the encoding block is determined based on the previously decoded frame size in FIG. The maximum size of the encoded block is determined by the same procedure as that of the color moving image encoding apparatus.
When the maximum size of the encoded block and the number of layers of the encoded block are multiplexed in the bit stream by the color moving image encoding device, the maximum size of the encoded block and the layer of the encoded block are encoded from the bit stream. Decode the number.

The variable length decoding unit 41 determines the maximum size of the encoded block and the number of layers of the encoded block, and grasps the hierarchical division state of each encoded block from the maximum encoded block as a starting point. Among the encoded data multiplexed in the bit stream, the encoded data related to each encoded block is specified, and the encoding mode assigned to each encoded block is decoded from the encoded data.
Then, the variable length decoding unit 41 refers to the partition information of the partition P _i ⁿ belonging to the coding block B ⁿ included in the coding mode, and encodes the encoded data that is multiplexed in the bit stream. in, it identifies the coded data according to each partition _P ^{i n} (step ST43).
Variable-length decoding unit 41, the compressed data from the encoded data according to each partition P _i ^n, predictive differential coding parameters including transform block division flag indicating a transform block size, the intra prediction parameter / inter prediction parameter variable length decoding Then, the compressed data and the prediction difference encoding parameter are output to the inverse quantization / inverse transform unit 45, and the encoding mode and the intra prediction parameter / inter prediction parameter are output to the changeover switch 42 (step ST44).
For the color difference signal, since the transform block has a vertically long shape of 1: 2, when a decoded transform coefficient that is a one-dimensional series is reverse-scanned to a two-dimensional series, the coefficients are divided into two longitudinal parts. An oblique raster scan or an oblique zigzag scan is performed at a ratio of one horizontal, and the obtained two-dimensional sequence is used as a coefficient of a transform block.

For example, when the prediction direction representative index and the prediction direction difference index are multiplexed in the bitstream, the prediction direction representative index and the prediction direction difference index are entropy decoded by arithmetic decoding or the like according to each probability model, An intra prediction parameter is specified from the prediction direction representative index and the prediction direction difference index.
Thereby, even when the code amount of the intra prediction parameter is reduced on the color moving image encoding device side, the intra prediction parameter can be correctly decoded.

Similarly to the first embodiment, the changeover switch 42 performs variable length decoding when the coding mode of the partition P _i ⁿ belonging to the coding block B ⁿ output from the variable length decoding unit 41 is the intra coding mode. The intra prediction parameter output from the unit 41 is output to the intra prediction unit 43. When the encoding mode is the inter encoding mode, the inter prediction parameter output from the variable length decoding unit 41 is output to the motion compensation unit 44. To do.

The intra prediction unit 43 receives the intra prediction parameter from the variable length decoding unit 41 (step ST45), like the intra prediction unit 4 in FIG. 1, on the basis of the intra prediction parameters, intra prediction for each partition P _i ⁿ By performing the process, an intra-predicted image (P _i ⁿ ) is generated (step ST46).
That is, the intra prediction unit 43 receives the intra prediction parameter from the variable length decoding unit 41, similarly to the luminance signal intra prediction unit 21 of the color video encoding apparatus, for example, an index of an intra prediction mode for the partition P _i ⁿ If the value is 2 (average prediction), and generates a prediction image the mean value of neighboring pixels of the adjacent pixel and the left partition of the upper partition as the predicted value of the pixel in the partition P _i ^n.
Alternatively, the left average predicted value that is the average value of the pixels adjacent to the left and the upper average predicted value that is the average value of the pixels adjacent to the upper are calculated separately, and the left average predicted value and the upper average predicted The average value may be used as the average predicted value.
In this way, the arithmetic circuit can perform processing by shift operation without using division, so that the circuit scale can be reduced.
Further, it may be configured to add 3 times the left average value predicted value and the upper average value predicted value and shift right by 2 bits.
By doing so, since the shape of the prediction block is vertically long, it is possible to obtain a prediction value obtained by adding a weight to the pixel value on the left side, which is a longer side, and can be realized by a shift operation. Efficient prediction can be performed on a circuit scale.
If the index value of the intra prediction mode is other than 2 (average prediction), the prediction direction vector index value indicates v _{p =} (dx, dy) on the basis of, generating a prediction value of the pixel in the partition P _i ⁿ To do.
The intra prediction unit 43 generates prediction pixels for all the pixels of the luminance signal in the partition P _i ⁿ in the same procedure, and outputs the generated intra prediction image (P _i ⁿ ).

Motion compensation unit 44 receives the inter prediction parameters from the changeover switch 42, similarly to the motion compensation prediction unit 5 of the color video encoding apparatus, based on the inter prediction parameters, inter-prediction processing for each partition P _i ⁿ To generate an inter predicted image (P _i ⁿ ) (step ST47).
That is, motion compensation unit 44, using one or more frames of reference images stored by the motion compensated prediction frame memory 49, by performing the motion compensation prediction processing on partition P _i ⁿ based on the inter prediction parameters, An inter prediction image (P _i ⁿ ) is generated.

  When the inverse quantization / inverse transform unit 45 receives the prediction difference encoding parameter including the transform block division flag indicating the transform block size from the variable length decoding unit 41, the quantization parameter included in the prediction difference encoding parameter Is used to inverse-quantize the compressed data related to the coding block output from the variable-length decoding unit 41 for each transform block size determined according to the transform block division flag, and is included in the prediction difference coding parameter. Inverse transform processing of compressed data after inverse quantization (for example, inverse DCT (inverse discrete cosine transform), inverse DST (inverse discrete sine transform), inverse KL transform, etc.) in the transform block size unit specified by the transform block division flag Inverse transform processing), the compressed data after the inverse transform processing is decoded into a decoded prediction difference signal (a signal indicating a difference image before compression). And it outputs the result to adding section 46 as a (step ST48).

Similarly to the first embodiment, the adder 46 outputs the decoded prediction difference signal output from the inverse quantization / inverse transform unit 45 and the prediction image (P _i ) generated by the intra prediction unit 43 or the motion compensation unit 44. ⁿ ) is added to the prediction signal to generate a decoded image signal indicating a decoded partition image or a decoded image as a collection thereof, and the decoded image signal is output to the loop filter unit 48 (step ST49).
The intra prediction memory 47 stores the decoded image for use in intra prediction.

When receiving the decoded image signal from the adding unit 46, the loop filter unit 48 compensates for the encoding distortion included in the decoded image signal, and decodes the encoded image after the encoding distortion compensation, as in the first embodiment. The decoded image indicated by the signal is stored as a reference image in the motion compensated prediction frame memory 49, and the decoded image is output as a reproduced image (step ST50).
Note that the filtering processing by the loop filter unit 48 may be performed for the maximum encoded block of the input decoded image signal or for each individual encoded block, or a decoded image signal corresponding to a macroblock for one screen is input. After being done, it may be performed for one screen at a time.
The processes in steps ST43 to ST49 are repeatedly performed until the processes for the partitions P _i ⁿ belonging to all the coding blocks B ⁿ are completed (step ST51).

As is apparent from the above, according to the second embodiment, even if the video signal is in the YUV 4: 2: 2 format, the conversion in the color difference signal of the color moving image coding apparatus is performed as in the first embodiment. Since the block division shape is uniquely determined as a division state having a small number of hierarchies according to the encoded block and the prediction mode, the color difference signal can be efficiently compressed.
Further, since the division shape of the transform block in the color difference signal of the color moving image decoding apparatus is uniquely determined according to the encoding block and the prediction mode, the bit stream generated by the color moving image encoding apparatus is preferably decoded. can do.

Embodiment 3 FIG.
In the third embodiment, the color moving image coding device and the color moving image decoding device share the division of the color difference signal conversion block with the divided shape of the luminance signal conversion block for the YUV 4: 2: 2 signal. It is characterized by doing. Other configurations and processes are the same as those in the second embodiment.

In the YUV 4: 2: 2 image, the number of pixels of the color difference component is the same as that of the luminance component in the vertical direction, and thus there is a characteristic that the ratio of the high frequency component is higher than the color difference component of the YUV 4: 2: 0 signal. Therefore, for a YUV 4: 2: 2 image, encoding efficiency may not decrease even if the divided shape of the transform block is shared by the luminance component and the color difference component.
Therefore, in the third embodiment, in order to share the divided shape of the color difference component conversion block in the YUV 4: 2: 2 image with the luminance component, the size of the luminance component block is made half the size only in the horizontal direction. Apply transform block.

That is, for example, when the luminance component conversion block size is 32 × 32 pixels, the chrominance component conversion block size is 32 × 16 pixels and the luminance component conversion block size is 16 × 16 pixels. In this case, when the color difference component conversion block size is 16 × 8 horizontal pixels and the luminance component conversion block size is 8 × 8 horizontal pixels, the color difference component conversion block size is 8 × 4 horizontal pixels. To do.
For example, when the minimum value of the conversion block size of the luminance component is 4 pixels, if the conversion block size of the luminance component is 4 × 4 pixels horizontally, 4 pixels are combined and 8 pixels × 8 pixels horizontally A conversion block size of 8 × 4 pixels is applied to the color difference component corresponding to the region.
With this configuration, it is possible to efficiently encode the YUV 4: 2: 2 image without encoding the information on the block division shape of the color difference component.

Embodiment 4 FIG.
In Embodiment 1 described above, when the transform / quantization process is performed on the color difference signal of the prediction difference signal e _i ⁿ , the coding block is further divided into hierarchies, and the transform block that is the coded block after the division is divided. The conversion / quantization processing is performed.
Since the color difference signal has fewer high-frequency components than the luminance signal, applying a relatively large transform block compared to the luminance signal reduces the overhead for each transform block and improves the encoding performance.

However, since the waveform characteristics of the residual signal differ depending on the image, it is not always desirable that the number of hierarchical divisions of the color difference signal conversion block is small. Therefore, there are cases where the coding efficiency can be further improved by switching the number of layers of the color-division signal conversion block according to the image.
Therefore, in the fourth embodiment, the maximum luminance conversion block division hierarchy number which is the maximum number of block division hierarchies related to the luminance signal is set according to the input image, and the luminance signal block is the maximum luminance conversion block at maximum. Dividing up to the number of division layers and dividing the blocks of the color difference signals to a fixed number of layers, and the color difference signals also for the color difference signal, the maximum number of block division layers related to the color difference signals, depending on the input image An embodiment will be described in which the number of conversion block division layers is set, the color difference signal block is hierarchically divided up to the maximum number of color difference conversion block division layers, and then the color difference signal compression processing is performed in units of divided blocks. .

  First, in accordance with the input image, a maximum luminance conversion block division hierarchy number, which is the maximum number of block division hierarchies related to the luminance signal, is set, and the luminance signal block is hierarchical up to the maximum luminance conversion block division hierarchy number. A mode in which the color difference signal block is divided into a fixed number of layers will be described.

The encoding control unit 1 of the color moving image encoding device converts the input image into an image in the frequency domain by performing, for example, FFT (Fast Fourier Transform) on the input image, and the high-frequency signal included in the luminance signal. Calculate the ratio of frequency components.
Then, the encoding control unit 1 sets a larger value as the maximum luminance transform block division hierarchy number (MaxTUdepthY) as the ratio of the high frequency components included in the luminance signal is higher.
Also, the color difference conversion block division layer number (FixTUdepthUV), which is the number of layer divisions of the color difference signal conversion block, is set.

Here, although the encoding control part 1 showed what sets the luminance maximum conversion block division | segmentation hierarchy number (MaxTUdepthY) according to the content rate of a high frequency component, this is only an example and is other methods. The maximum luminance conversion block division hierarchy number (MaxTUdepthY) may be set.
For example, the user may check the input image and manually set the maximum luminance conversion block division hierarchy number (MaxTUdepthY).
Note that the color difference conversion block division hierarchy number (FixTUdepthUV) is a fixed hierarchy number, and may be a preset value. However, the user confirms the input image and manually checks the color difference conversion block division hierarchy number. (FixTUdepthUV) may be set.

When the maximum luminance conversion block division layer number (MaxTUdepthY) is set, the encoding control unit 1 converts the maximum luminance conversion block division layer number (MaxTUdepthY) and the chrominance conversion block division layer number (FixTUdepthUV) into the conversion / quantization unit 7 and The data is output to the variable length coding unit 13.
Note that the encoding control unit 1 determines that the luminance signal conversion block has the maximum luminance conversion block division hierarchy number (MaxTUdepthY) so that the balance between the coding amount and the encoding error is optimal for each encoding block of the luminance signal. ) A transform block quantization flag (block partition information) indicating an instruction to hierarchically divide into quadtrees up to the number of layers not exceeding) and the shape of the transform block partition, and the variable length code To the conversion unit 13.

When the transform / quantization unit 7 receives the luminance maximum transform block division hierarchy number (MaxTUdepthY), the color difference transformation block division hierarchy number (FixTUdepthUV), and the transform block division flag from the encoding control unit 1, the transform / quantization unit 7 obtains the maximum luminance transform block division. Based on the number of hierarchies (MaxTUdepthY) and the transform block division flag, the luminance signal transform blocks are divided into four in a range of hierarchies where the number of transform blocks of the brightness signal does not exceed the maximum brightness transform block partition hierarchy number (MaxTUdepthY). The data is divided into trees, transform / quantization processing is performed on each transform block, and compressed data that is the processing result is output to the inverse quantization / inverse transform unit 8 and the variable length coding unit 13.
Further, the transform / quantization unit 7 divides the chrominance signal conversion block into a quadtree until the number of chrominance signal conversion blocks matches the number of chrominance conversion block division tiers (FixTUdepthUV). The block is subjected to transform / quantization processing, and the compressed data that is the processing result is output to the inverse quantization / inverse transform unit 8 and the variable length coding unit 13.

  The variable length coding unit 13 adds the maximum luminance transform block division hierarchy number (MaxTUdepthY) and the color difference transformation block division hierarchy output from the coding control unit 1 in addition to the information subjected to variable length coding in the first embodiment. Number (FixTUdepthUV) and transform block partitioning flag are variable-length encoded using, for example, Golomb code, etc., and encoded data of the transform block partitioning flag, maximum luminance transform block partitioning layer number (MaxTUdepthY), and color difference transform block partitioning layer number (FixTUdepthUV) Is multiplexed with the header of the bitstream and output.

Here, even if the coding mode is an intra coding mode (coding mode for intra-frame prediction) or an inter coding mode (coding mode for inter-frame prediction), the number of luminance maximum transform block division layers (MaxTUdepthY) shows the same value, but when the coding mode is the intra coding mode, the value of the maximum luminance transform block division layer number (MaxTUdepthY) and the coding mode is the inter coding mode. In some cases, the value of the maximum luminance conversion block division hierarchy number (MaxTUdepthY) may be different.
FIG. 20 shows the maximum luminance transform block division hierarchy number (MaxTUdepthYIpic) when the encoding mode is the intra encoding mode, and the maximum luminance transform block division hierarchy number (MaxTUdepthYPpic) when the encoding mode is the inter encoding mode. FIG. 10 is an explanatory diagram illustrating an example of multiplexing the color difference conversion block division layer number (FixTUdepthUV) as a sequence parameter set in a header portion of a bitstream.
In this case, when the picture type or slice type is an intra type, the maximum luminance conversion block division hierarchy number is MaxTUdepthYIpic, and when the picture type or slice type is an inter type, the maximum luminance conversion block division hierarchy number is MaxTUdepthYPpic.

The variable length decoding unit 41 of the color moving image decoding apparatus adds the maximum luminance conversion block division layer number (MaxTUdepthY) and the color difference conversion block division layer number from the bitstream in addition to the information subjected to variable length decoding in the first embodiment. Variable length decoding is performed on (FixTUdepthUV) and the transform block division flag.
The inverse quantization / inverse transform unit 45 determines the number of transform blocks of the brightness signal based on the brightness maximum transform block partition hierarchy number (MaxTUdepthY) and transform block partition flag variable length decoded by the variable length decoder 41. The luminance signal transform block is divided into quadrants within the range of the number of hierarchies that does not exceed the maximum transform block division hierarchy number (MaxTUdepthY), and compression is performed by performing inverse quantization and inverse transform processing for each divided block. Is released.
Also, the chrominance signal conversion block is divided into quadtrees until the number of chrominance signal conversion block layers matches the chrominance conversion block division layer number (FixTUdepthUV). Perform the conversion process to release the compression.

  As a result, the number of transform block division hierarchies of the color difference component can be appropriately determined according to the characteristics of the image, and the coding efficiency can be improved. Moreover, the bit stream obtained in this way can be suitably decoded.

Since the characteristics of the residual signal of the chrominance component differ between the intra prediction block and the motion compensated prediction block (inter prediction block), the conversion block size of the chrominance component is also optimal for the intra prediction block and the motion compensated prediction block. By using a small size, compression with higher encoding efficiency can be performed.
Therefore, the number of transform block hierarchies of the color difference component may be set to a different value for each of the intra prediction block and the motion compensation prediction block.
Specifically, when the coding mode is the intra coding mode, the chrominance conversion block division hierarchy number (FixTUdepthUV) is set as the chrominance conversion block division hierarchy number for intra prediction (FixTUdepthUVintra). When the coding mode is the inter coding mode, the color difference conversion block division layer number (FixTUdepthUV) is set as the color difference conversion block division layer number for inter-frame prediction, and the color difference component inter conversion block layer number (FixTUdepthUVinter) is set. Set.

  In this case, the variable-length encoding unit 13 adds the maximum luminance transform block division hierarchy number (MaxTUdepthY) output from the encoding control unit 1 and the color difference in addition to the information subjected to variable-length encoding in the first embodiment. The component intra transform block hierarchy number (FixTUdepthUVintra), the chrominance component inter transform block hierarchy number (FixTUdepthUVinter), and the transform block division flag are variable-length coded by, for example, Golomb code, and the maximum luminance transform block division hierarchy number (MaxTUdepthY) The chrominance component intra-transform block hierarchy number (FixTUdepthUVintra), the chrominance component inter-transform block hierarchy number (FixTUdepthUVinter), and the coded data of the transform block division flag are multiplexed and output in the header part of the bitstream.

The variable length decoding unit 41 of the color moving image decoding apparatus, in addition to the information subjected to variable length decoding in the first embodiment, adds the maximum luminance conversion block division hierarchy number (MaxTUdepthY), the color difference component intra conversion block hierarchy from the bitstream. The variable length decoding is performed on the number (FixTUdepthUVintra), the chrominance component inter conversion block hierarchy number (FixTUdepthUVinter), and the conversion block division flag.
The inverse quantization / inverse transform unit 45, if the coding mode variable length decoded by the variable length decoding unit 41 is the intra coding mode, the number of layers of the color difference signal transform block is the number of color difference component intra transform block layers ( The conversion block of the color difference signal is divided into quadtrees until it matches (FixTUdepthUVintra), and compression is released by performing inverse quantization / inverse conversion processing for each divided block.
On the other hand, if the encoding mode variable-length decoded by the variable-length decoding unit 41 is the inter-encoding mode, the color difference is maintained until the number of layers of the color difference signal conversion block matches the number of color difference component inter conversion block layers (FixTUdepthUVinter). The signal transform block is divided into quadtrees, and compression is released by performing inverse quantization / inverse transform processing for each divided block.

  As a result, the number of layers of the color difference component conversion block can be set to an optimum value for each of the intra prediction block and the motion compensation prediction block, and higher compression performance can be realized. In addition, the bitstream generated in this way can be suitably decoded.

Next, for the chrominance signal, the maximum chrominance conversion block division layer number, which is the maximum number of block division tiers related to the chrominance signal, is set according to the input image, and the maximum chrominance signal conversion block division layer is set for the chrominance signal block. A description will be given of an embodiment in which color difference signal compression processing is performed in units of blocks after division after being divided hierarchically into numbers.
When the encoding control unit 1 sets the maximum luminance conversion block division layer number (MaxTUdepthY), the lower the ratio of the high frequency components included in the color difference component, the smaller the maximum color difference conversion block division layer number (MaxTUdepthUV). Set to a value.
When the maximum color difference transform block division layer number (MaxTUdepthUV) is set to a small value, encoding processing is performed with a transform block that is relatively larger than the luminance component, so that higher compression performance can be realized.

When the transform / quantization unit 7 receives the maximum luminance conversion block division hierarchy number (MaxTUdepthY), the maximum color difference transformation block division hierarchy number (MaxTUdepthUV), and the transformation block division flag from the encoding control unit 1, the transformation maximum quantization block Based on the number of division layers (MaxTUdepthY) and the transformation block division flag, the luminance signal conversion blocks are divided into four within the range of the number of hierarchies of the luminance signal conversion block that does not exceed the maximum luminance conversion block division hierarchy number (MaxTUdepthY). The data is divided into trees, transform / quantization processing is performed on each transform block, and compressed data that is the processing result is output to the inverse quantization / inverse transform unit 8 and the variable length coding unit 13.
Further, the transform / quantization unit 7 determines the maximum number of color difference conversion block division layers (MaxTUdepthUV) based on the maximum number of color difference conversion block division layers (MaxTUdepthUV) and the conversion block division flag. Divide the chrominance signal conversion block into quadtrees within the range of the number of hierarchies that do not exceed, perform conversion / quantization processing on each conversion block, and dequantize the compressed data that is the processing result Output to the inverse transform unit 8 and the variable length coding unit 13.

  The variable length coding unit 13 adds the maximum luminance conversion block division layer number (MaxTUdepthY) and the maximum color difference transformation block division output from the coding control unit 1 in addition to the information subjected to variable length coding in the first embodiment. The number of hierarchies (MaxTUdepthUV) and the transform block division flag are variable-length coded using, for example, Golomb code, and the codes of the transform block division flag, the maximum luminance conversion block division hierarchy number (MaxTUdepthY), and the maximum chrominance transformation block division hierarchy number (MaxTUdepthUV) The multiplexed data is multiplexed with the header part of the bit stream and output.

The variable length decoding unit 41 of the color moving image decoding apparatus adds the maximum luminance conversion block division layer number (MaxTUdepthY) and the maximum color difference conversion block division layer from the bitstream in addition to the information subjected to variable length decoding in the first embodiment. Variable length decoding of the number (MaxTUdepthUV) and the transform block division flag.
The inverse quantization / inverse transform unit 45 determines the number of transform blocks of the brightness signal based on the brightness maximum transform block partition hierarchy number (MaxTUdepthY) and transform block partition flag variable length decoded by the variable length decoder 41. The luminance signal transform block is divided into quadrants within the range of the number of hierarchies that does not exceed the maximum transform block division hierarchy number (MaxTUdepthY), and compression is performed by performing inverse quantization and inverse transform processing for each divided block. Is released.
Also, the chrominance signal conversion block is divided into quadrants within the range of the number of chrominance signal conversion block layers that does not exceed the maximum chrominance conversion block division layer number (MaxTUdepthUV). Perform inverse quantization / inverse transform processing to release compression.

Here, although the coding mode of the coding block is the intra coding mode or the inter coding mode, the value of the maximum color difference transform block division layer number (MaxTUdepthUV) is shown. The color difference signal has a limited intra prediction mode, and in the case of the intra coding mode, the residual component energy tends to be large, so the maximum color difference when the coding mode of the coding block is the intra coding mode. If the value of the transform block division layer number (MaxTUdepthUV) and the value of the color difference maximum transform block division layer number (MaxTUdepthUV) when the coding mode of the coding block is the inter coding mode are configured to be different, further compression is performed. Efficiency can be improved.
FIG. 21 shows the maximum luminance transform block division hierarchy number (MaxTUdepthYIpic) when the picture type or slice type is an intra-coded picture, and the maximum luminance conversion block division hierarchy number when the picture type or slice type is an inter coding mode. (MaxTUdepthYPpic), color difference maximum transform block division layer number (MaxTUdepthUVintra) when the coding mode of the coding block is the intra coding mode, and color difference when the coding mode of the coding block is the inter coding mode It is explanatory drawing which shows the example multiplexed with the maximum conversion block division | segmentation hierarchy number (MaxTUdepthUVinter) as a sequence parameter set in the header part of a bit stream.
In this case, when the picture type or slice type is an intra type, the maximum luminance conversion block division hierarchy number is MaxTUdepthYIpic, and when the picture type or slice type is an inter type, the maximum luminance conversion block division hierarchy number is MaxTUdepthYPpic. In addition, when the coding block in the picture or slice is in the intra coding mode, the maximum color difference conversion block division layer number is MaxTUdepthUVintra, and the maximum color difference conversion is performed when the coding block in the picture or slice is in the inter coding mode. The number of block division layers is MaxTUdepthUVinter.

Note that the maximum color difference transform block division layer number (MaxTUdepthUVintra) when the coding mode is the intra coding mode, and the maximum color difference transform block division layer number (MaxTUdepthUVinter) when the coding mode is the inter coding mode, Variable length coding may be used as the Tintra and Tinter obtained from the difference value from the maximum luminance conversion block division hierarchy number (MaxTUdepthY).
Tintra = MaxTUdepthY-MaxTUdepthUVintra
Tinter = MaxTUdepthY-MaxTUdepthUVinter

On the decoding side, the maximum color difference when the coding mode of the coding block is the intra coding mode, the maximum number of color difference transform block division layers (MaxTUdepthUVintra), and the coding mode of the coding block is the inter coding mode. The number of transform block division layers (MaxTUdepthUVinter) is obtained by the following equation.
MaxTUdepthUVintra = max (0, MaxTUdepthY-Tintra)
MaxTUdepthUVinter = max (0, MaxTUdepthY-Tinter)

Also, for example, as shown in FIG. 22, the coding mode is set to intra coding by setting the maximum number of color difference transform block division layers and the maximum luminance conversion block division layer number to different values for an intra-coded picture and an inter-coded picture. The chrominance maximum transform block division layer number (MaxTUdepthUVIpic) in the mode and the chrominance maximum conversion block division layer number (MaxTUdepthUVPpic) when the encoding mode is the inter coding mode are multiplexed in the header. Also good.
In this case, when the picture type or slice type is an intra type, the maximum color difference conversion block division hierarchy number is MaxTUdepthUVIpic, and when the picture type or slice type is an inter type, the maximum color difference conversion block division hierarchy number is MaxTUdepthUVPpic.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  DESCRIPTION OF SYMBOLS 1 Coding control part (coding control means), 2 block division part (block division means), 3 changeover switch (prediction image generation means), 4 intra prediction part (prediction image generation means), 5 motion compensation prediction part (prediction) Image generation means), 6 subtraction section (difference image generation means), 7 transform / quantization section (image compression means), 8 inverse quantization / inverse transform section, 9 addition section, 10 intra prediction memory, 11 loop filter section , 12 motion compensation prediction frame memory, 13 variable length coding unit (variable length coding means), 21 luminance signal intra prediction unit, 22 changeover switch, 23 color difference signal directional intra prediction unit, 24 luminance correlation use color difference signal prediction unit 31 smoothing luminance reference pixel reduction unit, 32 correlation calculation unit, 33 color difference prediction image generation unit, 41 variable length decoding unit (variable length decoding means), 42 changeover switch ( Measurement image generation means), 43 Intra prediction section (prediction image generation means), 44 Motion compensation section (prediction image generation means), 45 Inverse quantization / inverse transform section (difference image generation means), 46 Addition section (decoded image generation) Means), 47 intra prediction memory, 48 loop filter section, 49 motion compensated prediction frame memory.

Claims (6)

Corresponding to a block dividing unit that divides an input color image into maximum coding blocks of a predetermined size and hierarchically divides the maximum coding block into coding blocks, and a coding block divided by the block dividing unit. A prediction image corresponding to the encoding mode selected by the encoding control unit is applied to the encoding control unit that selects the encoding mode, and the encoding block divided by the block dividing unit. Prediction image generation means for generating the difference image generation means for generating a difference image between the encoded block divided by the block division means and the prediction image generated by the prediction image generation means, and the difference image generation means An image compression unit that compresses the difference image generated by the output and outputs compressed data of the difference image; and Variable length code for variable length coding the output compressed data and the coding mode selected by the coding control means to generate a bit stream in which the compressed data and the coded data of the coding mode are multiplexed Comprising
The image compression means includes a luminance maximum conversion block division hierarchy number that is the maximum number of block division layers related to the luminance signal and a color difference maximum conversion block division hierarchy number that is the maximum block division hierarchy number related to the color difference signal. When the difference image generated by the difference image generation means is set and compressed, the luminance signal block in the difference image is divided hierarchically up to the maximum luminance conversion block division hierarchy number, and then divided. The luminance signal compression process is performed in units of subsequent blocks, and the color difference signal block in the difference image is hierarchically divided up to the maximum number of color difference conversion block division layers, and then the color difference signal in units of the divided blocks The compression process of
The variable length coding means performs variable length coding on the block division information by the image compression means, the maximum luminance conversion block division hierarchy number and the maximum color difference conversion block division hierarchy number, and the division information and the maximum luminance conversion. A color moving image encoding apparatus, wherein encoded data of the number of block division layers and the maximum number of color difference conversion block division layers is multiplexed into the bit stream. When the color difference maximum conversion block division hierarchy number for the intra-frame prediction process and the color difference maximum conversion block division hierarchy number for the inter-frame prediction process are set as the color difference maximum conversion block division hierarchy number, If the coding mode selected by the conversion control means is a mode in which intra-frame prediction is performed, the color difference signal block in the difference image is hierarchically divided up to the maximum number of color difference conversion block division layers for the intra-frame prediction processing. If the coding mode is a mode in which inter-frame prediction is performed, the block of the color difference signal in the difference image is hierarchically divided up to the maximum number of color difference transform block division layers for the inter-frame prediction process,
The variable length coding means includes block division information by the image compression means, the maximum luminance conversion block division hierarchy number, the maximum color difference conversion block division hierarchy number for the intra-frame prediction process, and the color difference for the inter-frame prediction process. The maximum number of transform block division layers is variable-length encoded, and the division information, the maximum luminance conversion block division layer number, the maximum color difference conversion block division layer number for the intra-frame prediction process, and the maximum color difference for the inter-frame prediction process. The color moving image encoding apparatus according to claim 1, wherein encoded data of the number of transform block division layers is multiplexed into the bit stream. Variable length decoding means for variable length decoding compressed data and coding modes related to each coding block hierarchically divided from the encoded data multiplexed into the bitstream, and variable length decoding by the variable length decoding means A prediction image generation unit that performs a prediction process corresponding to the encoding mode related to the decoded encoding block and generates a prediction image for the encoding block, and an encoding variable-length decoded by the variable-length decoding unit A difference image generation unit that generates a pre-compression difference image from the compressed data related to the block, a difference image generated by the difference image generation unit, and a prediction image generated by the prediction image generation unit are added to obtain a decoded image And a decoded image generating means for generating
The variable length decoding means variable length decodes block division information, luminance maximum conversion block division hierarchy number and color difference maximum conversion block division hierarchy number from the encoded data multiplexed in the bitstream,
The difference image generation means specifies a block of a compression processing unit for the luminance signal in the difference image from the division information of the block variable-length decoded by the variable-length decoding means and the maximum luminance conversion block division hierarchy number, and for each block The luminance signal in the difference image before compression is decoded by performing compression release processing on the luminance signal, and the difference is obtained from the division information of the block variable-length decoded by the variable-length decoding unit and the maximum number of color difference conversion block division layers. A color moving image decoding characterized by identifying a block of a compression processing unit for a color difference signal in an image, performing a decompression process on the color difference signal for each block, and decoding a color difference signal in a difference image before compression apparatus. The variable length decoding means variably encodes the encoded data of the maximum color difference conversion block division layer number for intra-frame prediction processing and the maximum difference of color difference conversion block division layer for inter-frame prediction processing from the encoded data multiplexed in the bitstream. Long decoding,
If the encoding mode that has been variable-length decoded by the variable-length decoding unit is a mode that performs intra-frame prediction, the difference image generation unit is for the division information and the intra-frame prediction process that are variable-length decoded by the variable-length decoding unit. The block of the compression processing unit for the color difference signal in the difference image is identified from the maximum number of color difference conversion block division layers, and if the encoding mode is a mode for performing inter-frame prediction, the division information and the inter-frame prediction processing are used. The color moving image decoding apparatus according to claim 3, wherein a block of a compression processing unit for a color difference signal in a difference image is specified from the number of color difference maximum conversion block division layers. A block dividing unit that divides the input color image into maximum encoded blocks of a predetermined size and hierarchically divides the maximum encoded block into encoded blocks; and an encoding control unit includes the block A coding control processing step for selecting a coding mode corresponding to the coding block divided in the division processing step, and a prediction image generation means for the coding block divided in the block division processing step for the code A prediction image generation processing step for generating a prediction image by performing prediction processing corresponding to the encoding mode selected in the conversion control processing step, and a coding block in which the difference image generation means is divided in the block division processing step And a difference image generation processing step for generating a difference image between the prediction image generated in the prediction image generation processing step. And an image compression means for compressing the difference image generated in the difference image generation processing step and outputting compressed data of the difference image; and a variable length encoding means for the image compression processing. The compressed data output in the step and the encoding mode selected in the encoding control processing step are variable length encoded to generate a bit stream in which the compressed data and the encoded data in the encoding mode are multiplexed. Variable length encoding processing step,
In the image compression processing step, the luminance maximum conversion block division hierarchy number that is the maximum block division hierarchy number related to the luminance signal, and the color difference maximum conversion block division hierarchy number that is the maximum block division hierarchy number related to the color difference signal, Is set, and when the difference image generated in the difference image generation processing step is compressed, the luminance signal block in the difference image is hierarchically divided up to the maximum luminance conversion block division hierarchy number. , The luminance signal compression processing is performed in units of the divided blocks, and the blocks of the color difference signals in the difference image are hierarchically divided up to the maximum number of color difference conversion block division layers, and then in units of blocks after the division Performs color difference signal compression processing,
In the variable length coding processing step, the block division information in the image compression processing step, the luminance maximum conversion block division layer number and the color difference maximum conversion block division layer number are variable length encoded, and the division information, A color moving image encoding method comprising: multiplexing encoded data of the maximum luminance conversion block division hierarchy number and the maximum color difference conversion block division hierarchy number into the bitstream. A variable-length decoding means for variable-length decoding the compressed data and the coding mode associated with each coding block hierarchically divided from the coded data multiplexed in the bitstream; Prediction image generation processing step in which the image generation means performs a prediction process corresponding to the encoding mode related to the encoded block subjected to variable length decoding in the variable length decoding processing step, and generates a predicted image for the encoded block The difference image generation means generates a difference image before compression from the compressed data related to the encoded block variable length decoded in the variable length decoding processing step, and the decoded image generation means The difference image generated in the difference image generation processing step is added to the prediction image generated in the prediction image generation processing step to obtain a decoded image And a decoded image generation processing step of generating a,
The variable length decoding means variable length decodes block division information, luminance maximum conversion block division hierarchy number and color difference maximum conversion block division hierarchy number from the encoded data multiplexed in the bitstream,
In the difference image generation processing step, the block of the compression processing unit for the luminance signal in the difference image is specified from the division information of the block variable-length decoded in the variable-length decoding processing step and the luminance maximum transform block division hierarchy number, and the block The decoding process for the luminance signal is performed every time, the luminance signal in the difference image before compression is decoded, and the division information of the block variable-length decoded in the variable-length decoding processing step and the color difference maximum conversion block division hierarchy A block that identifies a block of a compression processing unit for a color difference signal in a difference image from the number, performs a decompression process on the color difference signal for each block, and decodes the color difference signal in the difference image before compression Video decoding method.

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