JP3464658B2 - Image decoding method, image decoding device, and recording medium storing image decoding program - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image decoding method and an image decoding apparatus for decoding an encoded digital image, and a recording medium on which a program for realizing the same by software is recorded.

[0002]

2. Description of the Related Art Conventionally, as an image coding method which needs reversibility, MMR (M
odified Modified Read) is famous. However MM
Since R processes the entire input frame, I
There is a problem with compatibility with an encoding method that divides one frame adopted in TU-T H.261 or ISO / IEC MPEG into a plurality of blocks and performs processing in block units. So this
MMMR (Modified MMR), which is an improved version of MMR, is adopted as an evaluation model for MPEG4 (ISO / IECJTC / SC29 / WG11
N1277, July 1996).

In the method of coding a digital image divided into two-dimensional blocks composed of a plurality of pixels on a block-by-block basis, the presence / absence of motion compensation for each block, the presence / absence of an orthogonal transform coefficient, and the input image If is a shape image that represents the shape of the object or the ratio of synthesis, it indicates the significance of the block, etc., and is divided into coding mode information indicating the coding method of pixel value data in the block and data related to the pixel value Is encoded.

[0004]

In the method of separately coding the coding mode information of the block and the data relating to the pixel value in the block as described above, the motion information, the orthogonal transform coefficient, and the significant transform coefficient are significant in one frame. When the number of blocks having no such shape increases, the ratio of the mode information of the block to the generated coded signal relatively increases, and the coding efficiency deteriorates.

An object of the present invention is to improve the coding efficiency of mode information and reduce the code amount of one frame in such an image coding / decoding device.

[0006]

The image decoding method of the present invention is an image decoding method for receiving a coded image signal and decoding a digital image for each two-dimensional block. A step of separating and outputting a codeword relating to a coding mode and a codeword relating to block data; and a codeword corresponding to a combination of coding modes of a decoded block around a block to be decoded from the codeword relating to the coding mode A step of reproducing the coding mode of the decoding target block by switching the code word table defining the above, and based on the coding mode of the decoding target block, from the code word relating to the separated decoding target block data And reproducing the pixel data of.

Further, the image decoding apparatus of the present invention is an image decoding apparatus for inputting a coded image signal and decoding a digital image for each two-dimensional block, and a code relating to a coding mode from the coded image signal. Demultiplexing means for separating and outputting a code word relating to a word and block data, and the code word is determined corresponding to the combination of the coding mode of the decoded block around the block to be decoded from the code word relating to the coding mode. Mode information decoding means for switching the code word table to reproduce the coding mode of the decoding target block, and decoding target block data from the demultiplexing means based on the coding mode of the decoding target block Block data decoding means for reproducing the pixel data in the block from the code word.

The recording medium of the present invention is a recording medium recording an image decoding program for inputting a coded image signal and executing a procedure of decoding a digital image for each two-dimensional block. The encoding program separates and outputs a codeword relating to an encoding mode and a codeword relating to block data from an encoded image signal, and encoding of a decoded block around a block to be decoded from the codeword relating to the encoding mode. A procedure for switching a codeword table in which codewords are determined corresponding to a combination of modes and reproducing the coding mode of the decoding target block, and the separated decoding based on the coding mode of the decoding target block And a procedure for reproducing pixel data in a block from a codeword relating to target block data.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The image coding method of the present invention determines a coding method for each block when coding a digital image divided into two-dimensional blocks each having a plurality of pixels for each block. , A step of outputting the mode information, a step of encoding the data in the block according to the mode information, and a step of predicting and encoding the mode information from the mode information of surrounding already encoded blocks. To do.

With the above configuration, when encoding the mode information, the encoding mode of the encoding target block is predicted from the mode information of the already encoded peripheral block,
It is possible to improve the coding efficiency of the mode information by switching the codeword table in which the codeword is determined according to the prediction hit rate.

Further, according to the image coding method of the present invention, when a digital image divided into a two-dimensional block composed of a plurality of pixels is coded for each block, the coding method of each block is determined and the mode information is set. Is output, a step of collectively encoding the mode information for all blocks in one frame, and a step of sequentially encoding the data of each block according to the mode information. This is an image encoding method.

With the above configuration, the coding mode information of each block of the digital image divided into a plurality of blocks is collectively coded for one frame, so that the coding using the correlation between the blocks of the mode information can be performed. This can be done easily and improvement in coding efficiency can be achieved.

In the image decoding method of the present invention, a coded signal is input to reproduce an image for each two-dimensional block consisting of a plurality of pixels, and pixel values in the block are rearranged to decode a digital image. When decoding, the process of predicting and decoding the mode information of the block to be decoded from the mode information of the already decoded peripheral block, and the process of decoding the data in the block according to the decoded mode information And.

With the above configuration, when the mode information is decoded, the coding mode of the block to be decoded is predicted from the mode information of the peripheral block that has already been decoded, and the prediction mode is determined according to the prediction hit rate. The mode information can be correctly decoded by switching the codeword table defining the codeword.

Further, according to the image decoding method of the present invention, a coded signal is input, an image is reproduced for each two-dimensional block consisting of a plurality of pixels, and pixel values in the block are rearranged to reproduce a digital image. In this case, the process includes a step of decoding the mode information of all blocks in one frame and outputting the mode information, and a step of sequentially decoding the data of each block according to the decoded mode information.

With the above configuration, by collectively decoding the code words relating to the mode information for one frame, the decoding can be easily performed by utilizing the correlation between the blocks of the mode information, and the mode information can be correctly decoded.

Further, the image coding apparatus of the present invention is a coding mode for deciding a coding method of each block when coding a digital image divided into two-dimensional blocks composed of a plurality of pixels for each block. Deciding means, block data coding means for coding data in a block according to the mode information decided by the coding mode deciding means, and mode information decided by the coding mode deciding means for the surrounding codes. A mode information coding unit for predicting and coding from the mode information of the converted block is provided.

With the above configuration, when encoding the mode information, the encoding mode of the encoding target block is predicted from the mode information of the already encoded peripheral blocks,
It is possible to improve the coding efficiency of the mode information by switching the codeword table in which the codeword is determined according to the prediction hit rate.

Further, the image coding apparatus of the present invention is a coding mode for determining a coding method of each block when coding a digital image divided into a two-dimensional block composed of a plurality of pixels for each block. Determining means, mode information encoding means for collectively encoding the mode information determined by the encoding mode determining means for all blocks in one frame, and sequentially encoding data of each block according to the mode information. And block data encoding means.

With the above configuration, the coding mode information of each block of the digital image divided into a plurality of blocks is coded together for one frame, and coding using the correlation between the blocks of the mode information is performed. This can be done easily and improvement in coding efficiency can be achieved.

Further, the image decoding apparatus of the present invention reproduces an image for each two-dimensional block consisting of a plurality of pixels by inputting a coded signal, and reproduces a digital image by rearranging pixel values in the block. In doing so, the mode information decoding means for predicting and decoding the mode information of the decoding target block from the mode information of the already decoded peripheral block, and the block according to the mode information reproduced by the mode information decoding means Block data decoding means for decoding the data in the block.

With the above configuration, when the mode information is decoded, the coding mode of the block to be decoded is predicted from the mode information of the peripheral block that has already been decoded, and the prediction mode is determined according to the prediction hit rate. The mode information can be correctly decoded by switching the codeword table defining the codeword.

Further, the image decoding apparatus of the present invention reproduces a digital image by reproducing an image for each two-dimensional block consisting of a plurality of pixels by inputting a coded signal and rearranging pixel values in the block. In this case, a mode information decoding unit that decodes the mode information of all blocks in one frame and outputs the mode information, and a data decoding unit that sequentially decodes the data of each block based on the mode information are provided. To do.

With the above configuration, by collectively decoding the code words relating to the mode information for one frame, the decoding using the correlation between the blocks of the mode information can be easily performed, and the mode information can be correctly decoded.

The image encoding apparatus of the present invention is an apparatus for encoding, for each block, a digital image divided into a two-dimensional block consisting of a plurality of pixels by a programmed computer, and encoding each block. A coding mode determining means for determining a method, a block data encoding means for encoding data in a block according to the mode information determined by the encoding mode determining means, and a determination for the encoding mode determining means. A mode information coding means for predicting and coding the mode information from the mode information of the surrounding already coded blocks is provided.

With the above configuration, when the digital image divided into the two-dimensional block composed of a plurality of pixels by the programmed computer is encoded for each block, the encoding is already performed when the mode information is encoded. The coding efficiency of the mode information is improved by predicting the coding mode of the target block to be coded from the mode information of the neighboring blocks that have been coded and switching the codeword table that defines the codeword according to the prediction accuracy. Can be achieved.

The image decoding apparatus of the present invention receives an encoded signal as an input by a programmed computer, reproduces an image for each two-dimensional block composed of a plurality of pixels, and rearranges pixel values in the block. A device for reproducing a digital image by means of a mode information decoding means for predicting and decoding the mode information of a decoding target block from the mode information of the already decoded peripheral block, and reproducing by the mode information decoding means. Block data decoding means for decoding the data in the block according to the mode information.

With the above configuration, a coded signal is input by a programmed computer, an image is reproduced for each two-dimensional block consisting of a plurality of pixels, and pixel values in the block are rearranged to reproduce a digital image. At this time, by collectively encoding the mode information for encoding each block of the digital image divided into a plurality of blocks, one frame can be easily encoded using the correlation between the blocks of the mode information, An improvement in coding efficiency can be achieved.

The image coding method of the present invention is a method of coding a digital image divided into two-dimensional blocks consisting of a plurality of pixels by a programmed computer for each block, and coding each block. Determining the method, outputting the mode information, and the step of encoding the data in the block according to the mode information,
And a step of predicting and encoding the mode information from the mode information of surrounding already encoded blocks.

With the above configuration, when the digital image divided into the two-dimensional block consisting of a plurality of pixels by the programmed computer is encoded for each block, the encoding is already performed when the mode information is encoded. The coding efficiency of the mode information is improved by predicting the coding mode of the target block to be coded from the mode information of the neighboring blocks that have been coded and switching the codeword table that defines the codeword according to the prediction accuracy. Can be achieved.

In the image decoding method of the present invention, a coded signal is input by a programmed computer to reproduce an image for each two-dimensional block consisting of a plurality of pixels, and the pixel values in the block are rearranged. A method of reproducing a digital image by the method, the step of predicting and decoding the mode information of the decoding target block from the mode information of the already decoded peripheral block, and the step of And the step of decrypting the data.

With the above configuration, a coded signal is input by a programmed computer, an image is reproduced for each two-dimensional block consisting of a plurality of pixels, and pixel values in the block are rearranged to reproduce a digital image. At this time, when decoding the mode information, the coding mode of the decoding target block is predicted from the mode information of the peripheral blocks that have already been decoded, and the code word is determined according to the prediction hit rate. Mode information can be correctly decoded by switching the code word table.

The recording medium recording the image encoding program of the present invention records an image encoding program for encoding a digital image divided into two-dimensional blocks composed of a plurality of pixels by a computer for each block. In the medium, the image coding program determines a coding method of each block to a computer, outputs mode information, codes data in the block according to the mode information, The image coding program is characterized by predicting from the mode information of the already coded block and coding.

With the above-mentioned structure, the computer is a recording medium, and by transferring this recording medium, a digital image divided into a two-dimensional block composed of a plurality of pixels is encoded for each block in another independent computer. By executing the image coding program that performs the above, highly efficient coding can be performed.

In the recording medium recording the image decoding program of the present invention, the image is reproduced for each two-dimensional block composed of a plurality of pixels by inputting the encoded signal by the computer, and the pixel values in the block are rearranged. A recording medium recording an image decoding program for decoding a digital image by predicting the mode information of a decoding target block from the mode information of peripheral blocks already decoded by a computer. And an image decoding program for decoding the data in the block according to the decoded mode information.

With the above-mentioned structure, it is a recording medium of a computer, and by transferring this recording medium, an image is reproduced for each two-dimensional block consisting of a plurality of pixels by inputting a coded signal in another independent computer. , Run an image decoding program that decodes the digital image by rearranging the pixel values in that block,
Accurate reproduction is possible.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 16.

(Embodiment 1) FIG. 1 is a block diagram of an image coding apparatus according to Embodiment 1 of the present invention. In the figure, reference numeral 1 is a coding mode determining means for determining a coding mode of a block, and 2 is mode information for generating a code word relating to the coding mode information from the coding mode information of the block determined by the coding mode determining means 1. Encoding means 3, block data encoding means for encoding pixel values in the block according to the encoding mode information of the block determined by the encoding mode determination means 1 to generate a code word, 4 is mode information encoding means 2 Is a multiplexing means for generating a coded image signal by multiplexing the code word relating to the coding mode information outputted by the block data and the code word relating to the pixel value data outputted by the block data coding means 3. In addition, 11 is a pixel value signal of a block of a digital input image divided by a block dividing unit (not shown), 12 is coding mode information of the block, 13 is a code word relating to the coding mode information, 1
Reference numeral 4 is a code word related to block data, and 15 is a coded image signal of a block-divided digital input image.

The operation of the image coding apparatus of Embodiment 1 configured as above will be described below.

First, as shown in FIG. 2, the digital input image is a normal color signal in which one frame is composed of horizontal M pixels and vertical N lines, or shape information representing the shape of an object or the ratio of composition. The input pixel value signal 11 is divided into a plurality of blocks composed of horizontal m pixels and vertical n lines by a block dividing means (not shown). The input pixel value signal 11 of the divided block is input to the coding mode determination means 1 and the block data coding means 3.

In the coding mode determination means 1, the position (i, j)
The coding mode of the block is determined from the pixel value data of the block (hereinafter referred to as POS (i, j)). In the case of a normal color signal, the presence / absence of motion compensation and the presence / absence of an orthogonal transform coefficient are determined. (POS (i, j)
The coding mode of the block is described as MODE (i, j) below. The coding mode determination means 1 outputs the determined MODE (i, j) to the mode information coding means 2 and the block data coding means 3, respectively.

The coding mode determination means 1 will be described in detail with reference to FIG. FIG. 3B shows a digital input image divided into 4 × 4 blocks for convenience of explanation.
In each block of the digital input image shown in FIG. 3B, the coding mode determination means 1 is A when the pixels in the block are all “0” as shown in FIG. When "0" and "1" are present, the coding mode is added as B, and when all the pixels in the block are "1" as C, the coding mode is added. As a result of adding three types of coding modes to the digital input image of FIG.
(C).

Next, the mode information coding means 2 codes the coding mode assigned to each block by the coding mode determination means 1 from the code word table shown in FIG. 4 to a code corresponding to MODE (i, j). A word is selected and output as a code word related to the encoding mode.

When the coding mode of the block to be coded is MODE (i, j), the mode information coding means 2 shows the already coded coding modes MODE (i-1, j) around the periphery shown in FIG.
It is possible to predict MODE (i, j) from j), MODE (i-1, j-1), and MODE (i, j-1). That is, the encoding mode is A,
In case of 3 modes of B and C, MODE (i-1, j), MOD
If E (i-1, j-1) and MODE (i, j-1) are all A, MODE (i, j)
Also, based on the statistical property that there is a high probability that A is also A, a code word with a small amount of information (for example, “0”:
(1 bit) is generated, and the codeword table is adaptively switched by using the codeword table as shown in FIG. 4, whereby the improvement of the coding efficiency in the coding mode can be achieved.

Specifically, when the coding mode of the peripheral block is biased to A, the code word of the coding mode A is 0.
(Codeword length = 1 bit), codeword in coding mode B is 1
0 (codeword length = 2 bits) and the codeword of the coding mode C are set to 11 (codeword length = 2 bits). Even when the encoding mode of the peripheral block includes a large amount of B and when the encoding mode of the peripheral block includes a large amount of C, the code word length of the dominant encoding mode is similarly shortened. . In this case, the codewords are selected from the three types of codeword sets according to the peripheral codewords.
However, as shown in FIG. 3C, for the peripheral blocks, for example, if the encoding mode of the peripheral blocks is “A”,
The encoding mode of each peripheral block is encoded.

Next, regarding the mode information encoding means 2,
A detailed block diagram is shown in FIG. 6 and will be described.

The mode information encoding means 2 encodes the encoding mode sent from the encoding mode determining means 1 in order to easily obtain the information on the encoding mode of the peripheral block of the encoding target block. Conversion mode storage unit 10
Save to 1. The coding mode of a block is stored in a position associated with the block position of the block in one frame.

When the block position POS (i, j) of the coding target block is input, the coding mode reading unit 102 receives the block position POS (i-1, j) of the peripheral block of the coding target block.
j-1), POS (i, j-1), POS (i-1, j) coding mode MODE (i-1,
j), MODE (i-1, j-1), and MODE (i, j-1) are read from the coding mode storage unit 101 and given to the codeword table selection unit 104.

The code word table selection unit 104 encodes the coding modes MODE (i-1, j), MODE (i-1, j-1) and MODE (i, j- of the peripheral blocks.
The codeword table set in association with the combination that matches the combination of 1) is selected from the codeword table 103.
For example, the coding modes of the peripheral blocks are (A, A,
A), (A, A, B), (A, A, C), (B, A,
A), (C, A, A), (A, B, A), (A, C,
In the case of A), the code word table of (A = 0, B = 10, C = 11) is selected. The above example is the case where the coding mode A of the peripheral block is dominant. When the coding mode B of the peripheral block is dominant, (A = 10, B = 0, C =
When the code word table of 11) is selected and the coding mode C of the peripheral block is dominant, (A = 10, B = 11, C =
The code word table of 0) is selected. The codeword table selected according to the mode state of the peripheral block is provided to the encoding unit 105.

As described above, in the first embodiment, the codeword table used for coding the mode information is adaptively switched according to the coding mode state of the peripheral blocks.

Encoding section 105 encodes the encoding mode of the encoding target block based on the selected code word table. If the coding mode input from the coding mode determination means 1 is A and the code word table input from the code word table selecting unit 104 is (A = 0, B = 10, C = 11), the code word is = 0 will be output. The result of encoding the encoding mode of FIG.3 (c) is shown in FIG.3 (d).

Therefore, when the dominant block is included in the peripheral block of the block to be coded and the mode of the block to be coded matches the dominant mode, a code word having a short code word length is generated.

On the other hand, the block data coding means 3 receives the pixel value code of the coding target block when A or C is inputted from the coding mode determination means 1 as the coding mode for the block of POS (i, j). Stop conversion. This is because, in the case of the coding modes A and C, all the pixels in the block are black or white, so that the block can be decoded only in the coding mode. In the case of the coding mode C, the pixel value of the block to be coded is coded to output the code word relating to the block data.

Finally, the multiplexing means 4 multiplexes the code word relating to the coding mode and the code word relating to the block data and outputs the coded image signal. FIG. 7 shows an example of a bit stream for multiplexing. When all the pixels in the block are “0” or “1”, only the code word 701 in the encoding mode is set and “0” is set for the pixel in the block. "When"
The codeword 701 of the encoding mode and the codeword 702 of the block data are output only when 1 ″ exists.

As described above, in the present embodiment, a plurality of code word tables for converting each coding mode into a code word are prepared in association with the coding mode states of the peripheral blocks, and are included in many peripheral blocks. A codeword with a short codeword length is assigned to the dominant mode, and the codeword table is adaptively switched according to the state of the coding mode of the peripheral blocks.

Note that the contents of the codeword table selected by the codeword table selection unit 104 are not passed to the encoding unit 105, but only the number of the selected codeword table is notified to the encoding unit 105.
The encoding unit 105 may take in the contents of the code word table designated by the number from the code word table table 103.

(Second Embodiment) FIG. 8 is a block diagram of an image decoding apparatus according to the second embodiment of the present invention. In the figure, the same means and signals as those of the first embodiment shown in FIG.

In the figure, 21 is a demultiplexing means for separating and outputting a codeword relating to the coding mode and a codeword relating to block data from the coded image signal, and 22 is relating to the coding mode outputted by the demultiplexing means 21. The mode information decoding means for reproducing the coding mode of the block from the code word, 23 is based on the coding mode of the block output by the mode information decoding means 22, and based on the code word relating to the block data output by the demultiplexing means 21 Block data decoding means 31 for reproducing the pixel value in the block, 31 represents the reproduced digital pixel value signal in the block.

The operation of the image decoding apparatus of the second embodiment having the above configuration will be described below.

First, the demultiplexing means 21 receives a coded image signal, separates it into a codeword 13 relating to a coding mode and a codeword 14 relating to block data, and outputs it.

The mode information decoding means 22 receives the code word 13 relating to the coding mode and reproduces and outputs the coding mode information 12 of the corresponding block from the code word table table.

If the object to be decoded by the mode information decoding means 22 is a POS (i, j) block, the MO shown in FIG.
DE (i-1, j), MODE (i-1, j-1), MODE (i, j-1) have already been played, and MODE (i, j) is MODE (i-1, j) , MODE (i-1, j-
1), decoding from the codeword relating to the coding mode coded according to the first embodiment by switching the codeword table table based on FIG. 4 from the state of the coding mode of MODE (i, j-1) The coding mode of the target block can be reproduced correctly.

Next, a detailed block diagram of the mode information decoding means 22 is shown in FIG. 9 and will be described.

When the decoding unit 110 decodes the code word of the coding mode, the decoded coding mode is written in the pixel block position of the coding mode storage unit 111.

The position information of the block to be decoded within one frame is input to the coding mode reading section 112.
The coding mode reading unit 112 sets the coding modes of the decoded blocks around the decoding target block based on the position information of the decoding target block.
Read out from and input to the code word table selection unit 114.

The codeword table selection unit 114 extracts the same codeword table as the codeword table at the time of encoding from the codeword table prediction table 113 based on the state of the coding mode of the peripheral blocks of the block to be decoded. The code word table extracted from the code word table table 113 is passed to the decoding unit 110.

The decoding unit 110 has a codeword table selecting unit 114.
The codeword relating to the coding mode of the block to be decoded is decoded using the codeword table passed from.

The decoded coding mode is input to the block data decoding means 23 while being stored in the coding mode storage unit 111.

The block data decoding means 23 receives the code word 14 relating to the block data and performs a decoding process corresponding to the coding mode indicated in the coding mode information 12 to obtain the digital pixel value signal 31 in the block. Play and output.

Although the coding modes of the three peripheral blocks are used for predicting the coding mode of the coding target block in the first and second embodiments, it is possible to further increase the number of reference blocks. It is possible.

Further, although the above embodiment describes the case where there are three kinds of encoding modes (A, B, C), the same processing can be performed even if the number of states is further increased.

Further, in the above embodiment, the code word table shown in FIG. 4 is used for coding the coding mode information, but the arithmetic coding method is used to predict the coding mode information of the current block. It is possible to switch the probabilistic model used for arithmetic coding depending on the value.

By combining the image coding apparatus according to the first embodiment and the image decoding apparatus according to the second embodiment,
It is possible to realize an encoding / decoding device. (Embodiment 3) FIG. 10 is a block diagram of an image coding apparatus according to Embodiment 3 of the present invention. In the figure,
The same means and signals as those in the first embodiment shown in FIG.

In FIG. 10, reference numeral 41 is a memory for holding the coding mode information for each block output from the coding mode determination means 1 and collectively outputting one frame, and 42 is one frame output from the memory 41. Mode information coding means for collectively coding the coding mode information of 4 to create a code word, and 43 holds the code words relating to the block data for each block created in the block data coding means 3 and collectively outputs one frame. The memory 44 is a multiplexing unit that multiplexes a code word relating to one frame of mode information output from the memory 43 and a code word relating to one frame of block data output from the memory 43 to generate a coded image signal. In addition, 51 is coding mode information for 12 frames, 52 is a code word for mode information for 1 frame, 53 is a code word for block data for 1 frame, and 54 is a coded image signal of a digital input image. Is.

The operation of the image coding apparatus of the third embodiment having the above configuration will be described below.

First, the digital input image signal 11 is output to the PO mode by the coding mode determination means 1 as in the first embodiment.
The coding mode MODE (i, j) of the block of S (i, j) is determined. The determined MODE (i, j) is held in the memory 41 and all the encoding modes for one frame MODE (1,1), MODE
(1,2), ... MODE (2,1), .. MODE (X, Y) is input to the mode information encoding means 42.

Next, in the mode information encoding means 42, 1
The mode information for the frame is encoded and the code word 52 is output. As for the pixel data in the block, the code word relating to the block data encoded by the block data encoding means 3 is held in the memory 43 as in the case of the first embodiment, and is combined into the code word 53 relating to all the block data for one frame. . The encoding operation of the mode information encoding means 42 will be specifically described.

Mode Information Encoding means 42 has a code word table (Table 1) for encoding the encoding modes of a plurality of blocks at once. In this codeword table, unique codewords are assigned to all combinations of two combinations of three types of encoding modes (A, B, C).
In particular, combinations of identical coding modes (A, A), (B,
For B) and (C, C), the code word length is relatively shorter than other combinations.

[0079]

[Table 1]

Now, it is assumed that the coding mode for one frame having the contents shown in FIG. 11A has been transferred to the mode information coding means 42 as the coding mode for one frame.

The coding mode is cut out every two blocks in order from the beginning of the line. In the case shown in FIG. 11A, in the order of (A, B) (B, B) (A, A), two consecutive encoding modes in the horizontal direction are set as one unit and are to be encoded. Becomes

FIG. 1 shows the result of encoding the encoding mode for one frame shown in FIG. 11A with the codeword table of (Table 1).
1 (b). It can be seen that the region where the same mode continues has a short codeword length.

On the other hand, the pixel data of the pixel block is coded by the block data coding means 3 as in the first embodiment, and the code word relating to the block data is stored in the memory 4.
3 is stored in the code word 53 for all the block data for one frame.

Then, the multiplexing means 44 multiplexes the code word 52 relating to the coding mode and the code word 53 relating to all the block data for one frame to obtain the coded image signal 5
4 is output.

As described above, in the third embodiment, the coding modes of the pixel block for one frame are accumulated in the memory, and then the plural coding modes are coded at once. In a codeword table for encoding a plurality of encoding modes at once, a codeword having a shorter codeword length is assigned to a combination of the same encoding modes.

(Embodiment 4) FIG. 12 is a block diagram of an image decoding apparatus according to Embodiment 4 of the present invention. In the figure, the same signals as those in the second embodiment shown in FIG. 8 are designated by the same reference numerals, and description thereof will be omitted.

In the figure, reference numeral 61 is a demultiplexing means for separating a codeword string related to the coding mode and a codeword string related to block data from the coded signal, and 62 is related to the coding mode output by the demultiplexing means 61. Mode information decoding means for obtaining mode information from the code word string, 63 is a memory for holding the mode information of all blocks for one frame output by the mode information decoding means 62, and 23 is a memory 63.
Is a block data decoding unit that reproduces a pixel value from a codeword string relating to the corresponding block data output by the demultiplexing unit 61 according to the block encoding mode output by the. The numeral 31 indicates a reproduced digital image signal.

The operation of the image decoding apparatus according to the fourth embodiment having the above configuration will be described below.

First, in the demultiplexing means 61, the encoded signal 5
4 is received and separated into a codeword string relating to the coding mode of all blocks for one frame and a codeword string relating to the block data of each block, and output.

Next, in the mode information decoding means 62, the code word table (Table 1) is processed in the reverse order of the encoding in the third embodiment.
Is used to decode the coding modes of all the blocks in one frame from the codeword string 52 related to the coding mode of one frame. Then, the memory 63 holds the coding modes of all the blocks in one frame, and POS is performed in accordance with the request from the block data decoding means 23.
Outputs the coding mode MODE (i, j) of the block at the (i, j) position.

Finally, the block data decoding means 23 is separated by the demultiplexing means 61 and output POS (i, j).
Codeword string 14 regarding the block data of the block at the position
And the coding mode MO of the block output from the memory 63
It receives DE (i, j), reproduces and outputs the pixel value in the block according to MODE (i, j).

Further, the output pixel values for each block are rearranged in the scanning order by an appropriate rearranging means not shown in the figure to reproduce the digital image signal.

In the embodiment described above, the coding modes of all the blocks in one frame decoded by the mode information decoding means 62 are held in the memory 63, and the block data decoding means 23 requests them. Therefore, the coding mode MODE (i,
By obtaining j), the coded image signal coded by the image coding apparatus shown in the third embodiment can be correctly reproduced.

In the third and fourth embodiments, the coding modes of two consecutive pixel blocks are collectively coded, but the coding modes of more pixel blocks are collectively coded. It is also possible. Further, although a plurality of pixel blocks continuous in the horizontal direction are targeted for encoding, a plurality of pixel blocks continuous in the vertical direction or pixel blocks continuous in a two-dimensional direction may be collectively targeted for encoding. it can. in this case,
A codeword table corresponding to a combination of blocks to be collectively encoded is required.

Further, in the above embodiment, the code word table of (Table 1) showing the coding of the mode information is used, but it is also possible to use another coding method such as an arithmetic coding method. The decoding device according to the fourth embodiment is combined with the encoding device according to the third embodiment to perform encoding / decoding.
It is possible to realize a decoding device.

(Embodiment 5) The present invention is based on Embodiment 1,
To realize easily by another independent computer system by realizing the configuration shown in 2, 3, 4 as a software by a program, recording it on a recording medium such as a floppy (R) disk and transferring it. You can

FIG. 14 shows a block diagram of a computer system, which will be described below. 120 is a TV signal, V
A moving image input device for reproducing and inputting moving images from TRs, DVDs, etc., 121 is a memory, 122 is a CPU (central processing unit) for performing image encoding processing or image decoding processing by a program, and 123 is an instruction to the CPU 122. Give keyboard and display and FD (floppy (R)
Disk), IC card, CD-ROM, and other input / output devices configured to read a storage medium storing a program, 124 is a display for displaying the results processed by the CPU 122, and 125 is an external memory for storing the results processed by the CPU 122. It is a device.

First, prior to the processing, an image encoding program or an image decoding program is installed in the CPU 122 in advance by an instruction of the input / output device 123 through a device that reads a recording medium such as an FD or a CD-ROM. It is assumed that the image encoding program or the image decoding program is activated by the input / output device 123.

In the computer system configured as described above, an image coding apparatus for coding a digital image divided into two-dimensional blocks consisting of a plurality of pixels by the programmed computer for each block is shown in FIG. A description will be given along the processing flow.

In step 200, an image signal is sent from the moving image input device 120 to the CPU 1 according to an instruction from the input / output device 123.
It is recorded in the memory 121 via 22. The image signal is
It may be one frame unit or a plurality of frame units.

In step 201, the image signal of one frame in the memory 121 is divided into a plurality of blocks, and a block P
The pixel value of (i, j) is taken out.

In step 202, from the pixel values in the block, the coding modes A (all "0" in the block), B ("0" and "1" exist in the block), C (all "1" in the block) are selected. ) Is determined. Step 203 converts the block data from the memory 121 into a code word only when the coding mode is "B". In step 204, the coding mode of the target block is converted into a code word from the surrounding coding modes according to the code word table table.

In step 205, the code word of the coding mode and the code word of the block data are multiplexed. Step 20
6 moves to the next block position. Step 208
Determines whether or not the processing is completed. If NO, repeats steps 201 to 206. Yes
In the case of, the process proceeds to step 208 and the coded image signal formed by multiplexing is recorded in the external storage device 125.
It should be noted that there is no problem even if the image is recorded in the external storage device 125 in block units.

Next, a coded image signal is input by the programmed computer to a plurality of pixels 2
An image decoding apparatus that reproduces an image for each dimensional block and rearranges pixel values in the block to reproduce a digital image will be described with reference to the processing flow of FIG.

In step 220, the moving image input device 120 is used.
The encoded image signal from the memory 12 via the CPU 122.
Enter 1.

In step 221, the multiplexed encoded image signal is read in block units, and the target block P (i,
For j), the code word of the coding mode and the code word of the block data are separated. In step 222, the coding mode of the target block is reproduced based on the coding modes of the surrounding decoded blocks and the coding table table. Step 223 decodes the block data according to the reproduced coding mode. Step 224 stores the block data of the target block in the memory 121.

Step 225 moves to the next block position. In step 226, it is determined whether or not the processing is completed. If NO, the processing from step 221 to step 226 is repeated. If YES, the process proceeds to step 227, and the decoded digital image signal is recorded in the external storage device 125 or output to the display 124.

FIG. 13 shows a floppy (R) disk as an example of the recording medium.

Although a floppy (R) disk is shown as a recording medium in this embodiment, the same operation can be performed as long as a program such as an IC card, a CD-ROM, or a magnetic tape can be recorded. it can.

The present invention is not limited to the above-described embodiments, but various modifications can be made without departing from the gist of the present invention, which are included in the scope of the present invention.

[0111]

As described above, the effects of the present invention are as follows.
In an image decoding apparatus / method for dividing a digital image into blocks, and decoding the encoded data by dividing each block into a block encoding mode and block data, it is possible to improve the encoding efficiency of codewords related to the encoding mode. As a result, it is possible to obtain a remarkable effect that encoding can be performed with a smaller number of bits.

[Brief description of drawings]

FIG. 1 is a block diagram of an image encoding device according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing block division of a digital input image according to the first embodiment.

FIG. 3 is a diagram for explaining a coding mode determination means according to the first embodiment.

FIG. 4 is a diagram showing a code word table table of the image coding apparatus according to the first embodiment.

FIG. 5 is a conceptual diagram showing a target block and peripheral blocks according to the first embodiment.

FIG. 6 is a detailed block diagram of mode information coding means of the image coding apparatus according to the first embodiment.

FIG. 7 is a diagram illustrating a bitstream of the image coding apparatus according to the first embodiment.

FIG. 8 is a block connection diagram of an image decoding device according to a second embodiment of the present invention.

FIG. 9 is a detailed block diagram of mode information decoding means of the image decoding apparatus according to the second embodiment.

FIG. 10 is a block diagram of an image coding apparatus according to Embodiment 3 of the present invention.

FIG. 11 is an example in which adjacent blocks are combined in encoding in the encoding mode according to the third embodiment.

FIG. 12 is a block diagram of an image decoding apparatus according to Embodiment 4 of the present invention.

FIG. 13 is a plan view of a floppy (R) disk as an example of a recording medium according to a fifth embodiment of the present invention.

FIG. 14 is a block diagram of a computer system according to the fifth embodiment.

FIG. 15 is an operation flowchart of the image encoding device by the computer in the fifth embodiment.

FIG. 16 is an operation flowchart of the image decoding device by the computer in the fifth embodiment.

[Explanation of symbols]

1 Encoding mode determination means 2,42 Mode information coding means 3 block data encoding means 4,44 Multiplexing means 21, 61 Demultiplexing means 22, 62 Mode information decoding means 23 block data decoding means 41, 43, 63 memory 101 encoding mode storage unit 102 encoding mode reading unit 103 codeword table table 104 codeword table selection unit 105 encoder 110 Decoding unit 111 encoding mode storage unit 112 Encoding Mode Reading Unit 113 codeword table 114 codeword table selection unit 120 Video input device 121 memory 122 CPU 123 I / O device 124 display 125 external storage device 701 encoding mode codeword 702 Block data codeword

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 1/413 H03M 7/36 H04N 7/24

Claims (3)

(57) [Claims] 1. An image decoding method for inputting a coded image signal and decoding a digital image for each two-dimensional block, wherein a codeword relating to a coding mode and a codeword relating to block data are generated from the coded image signal. A step of separating and outputting, and switching the codeword table defining the codeword corresponding to the combination of the coding modes of the decoded blocks around the decoding target block from the codeword related to the coding mode of the decoding target block Reproducing a coding mode; and reproducing pixel data in a block from a codeword relating to the separated decoding target block data based on the coding mode of the decoding target block. An image decoding method characterized by: 2. An image decoding apparatus for inputting a coded image signal and decoding a digital image for each two-dimensional block, wherein a codeword relating to a coding mode and a codeword relating to block data are generated from the coded image signal. Demultiplexing means for separating and outputting, and switching and decoding a codeword table in which codewords are determined corresponding to a combination of coding modes of decoded blocks around a decoding target block from the codewords related to the coding mode Mode information decoding means for reproducing the coding mode of the target block, and pixel data in the block from the code word relating to the decoding target block data from the demultiplexing means based on the coding mode of the decoding target block And a block data decoding means for reproducing the image. 3. A recording medium recording an image decoding program for receiving a coded image signal and executing a procedure of decoding a digital image for each two-dimensional block, wherein the image decoding program is Corresponding to a procedure of separating and outputting a code word related to the coding mode and a code word related to the block data from the image signal, and a combination of the coding mode of the decoded block around the decoding target block And a procedure for reproducing the coding mode of the decoding target block by switching the codeword table defining the codeword, and a codeword relating to the separated decoding target block data based on the coding mode of the decoding target block. And a procedure for reproducing pixel data in a block from a machine-readable recording medium.