JPS6221389A - Block encoder - Google Patents

Abstract

PURPOSE:To attain a highly efficient encoding small in distortion for any picture with respect to correlation in a time base direction and large in compressibility by having K types of second block means dividing into small blocks. CONSTITUTION:A sampled value of 8 bits for one sample inputted from an input part is divided into large blocks by the first block part 2 and divided into small blocks by a two-dimentional small block part 3 and a three- dimensional small block part 4. Two two-dimensional small blocks obtained by the two dimensional small block part 3 are converted into coding words of 32 bits respectively by a cross converting encoding part 5 and at least one of head two bits among the coding words of a total of 64 bits is encoded so as to take a value except '0'. Similarly, two three-dimensional small blocks obtained by the three dimensional small block part 4 are converted into coding words of 31 bits by a orthogonal converting encoding part 6 and '0' of two bits is added to a head of the coding words of a total of 62 bits. During decod ing, when either one of the first two bits of the coding words of 64 bits is '0', it indicates the three dimensional small blocking, and when it is not '0', it indicates the two dimensional small blocking, so that the decoding can be directly performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a block encoding device used for highly efficient encoding of images and the like.

Conventional technology Coding that removes redundancy of image information, etc. and improves transmission efficiency is called high-efficiency coding. As a high-efficiency encoding method, there is a block encoding method in which a specific number of image samples are collected into blocks, and compression is performed within the blocks. This method includes an orthogonal transformation method that orthogonally transforms sample values within a block and quantizes them.

There is a vector doji conversion method that directly quantizes each block. In either method, compression is performed by utilizing the strong correlation between adjacent samples of an image, so it is preferable that the samples within a block are as close as possible.

Here, a method of dividing one block into blocks each consisting of eight samples will be explained.

Figure 6 (?L) shows one-dimensional blocking, and the distance between the samples at both ends is quite large. In contrast, Fig. 6 (
b) shows two-dimensional blocking, in which the distance between the samples at both ends is considerably shortened by taking advantage of the two-dimensional continuous nature of the image. Furthermore, for images that have continuity in the time axis direction, such as the Tv multiplied signal, 3
By applying dimensional blocking, the distance between the samples at both ends is further reduced.

By block encoding image information two-dimensionally or three-dimensionally in this way, greater compression than one-dimensional block encoding is possible.

Problems to be Solved by the Invention As mentioned above, two-dimensional or three-dimensional encoding is generally used for highly efficient encoding of image information.

However, in two-dimensional blocking, if the image changes significantly within a block, the correlation between samples becomes small, resulting in large distortions.

On the other hand, in three-dimensional blocking, if the image does not change in the time axis direction, the correlation in the time axis direction is extremely high.
Great compression is possible for two-dimensional blocks. However, in images with large movements in the time axis direction, there is almost no correlation in the time axis direction, resulting in a problem of large distortion.

In view of this point, it is an object of the present invention to provide a block encoding device that improves the above-mentioned drawbacks.

Means for Solving the Problems The present invention divides sample points of an image that are continuous in three dimensions including the time axis direction in a three-dimensional space to form large blocks each consisting of N sample points. and a second blocking means for further dividing the large block into small blocks, each of K types of second blocking means.
block encoding means for respectively block encoding sets of X types of small blocks obtained by the blocking means to generate sets of X types of block code words, and block codes of X types obtained by the block encoding means; a receiver comprising selection means for selecting one set of block codewords from a set of words, further transmitting the set of block codewords selected by the selection means, and receiving the transmitted set of block codewords; and identification means for informing a user of a set of block code words generated from which second blocking means has been selected.

According to the above-described configuration, the present invention selects a small block that is long in the time axis direction for large blocks that have a large correlation in the time axis direction, and selects a small block that is short in the time axis direction for large blocks that have a small correlation in the time axis direction. This makes it possible to encode any image with high quality and high efficiency with a high compression ratio.

Embodiment First, as a first embodiment, an apparatus will be described that compresses images that are correlated in the temporal direction as well by dividing them into blocks and performing orthogonal transform encoding.

FIG. 1 (2L) shows a large block generated by the first blocking of the first embodiment, and this block has a total of 16 blocks, 2 in the vertical direction, 4 in the horizontal direction, and 2 in the time axis direction.
This is a block consisting of (=N) samples. Further, FIGS. 1(b) and 1(C) show how the large block shown in FIG. 1(a) is converted into a second block. Figure 1 ('
In b), a large block is divided into 2-dimensional blocks (small blocks) consisting of 8 samples, and in Figure 1 (C), a large block is divided into 3-dimensional blocks (small blocks) consisting of 8 samples. It expresses the state of being ~.

Next, FIG. 2 shows a block diagram of the apparatus of the first embodiment. In FIG. 2, 1 is an input part of this device, 2 is a first blocking part, 3 is a two-dimensional small block part, 4 is a three-dimensional small block part, 5 and 6 are orthogonal transform coding parts,
7 and 8 are distortion measuring parts, 9 is an output selection part, and 10 is an output part of this device.

First, B per sample input from input part 1 in Figure 2
The sample values of bits are converted into large blocks in the first blocking section 2, and large blocks as shown in FIG. 1 (self) are generated. Next, the generated large block is input to a two-dimensional small block forming section 3 and a three-dimensional small block forming section 4, and is divided into small blocks as shown in FIGS. 1(b) and 1(c), respectively.

The two two-dimensional small blocks obtained in the two-dimensional small block conversion section are each orthogonally transformed encoded in the orthogonal transform encoding section 5, and each is converted into a 32-bit code word, resulting in a total of 64 bits code word. can get. However, at least one of the first 2 bits of these 64 bits is encoded to take a value other than Q.

Similarly, the two three-dimensional small blocks obtained in the three-dimensional small block conversion section are also orthogonally transformed encoded in the orthogonal transform encoding section 6, and each is converted into a code word of 31b1tS. Then, O of 2B and TS is added to the beginning of the code word of 62 bits in total obtained thereby to form a code word of 64 bits. Two 64 bis obtained by the above
For the code word ts, the magnitude of distortion due to orthogonal transform encoding is calculated by distortion measuring sections 7 and 8, respectively. The magnitude of the two distortions obtained by this is the output selection part 9
The codeword with the smaller distortion is selected and output to the output section 10.

In this way, 128bitS (sbits Xl
The image information of 6 samples) is highly efficiently encoded into 64 bitB. Also, when decoding, if the first 2 bits of a 64-bit code word are both O, it indicates that it has been made into a 3-dimensional small block, and if not, it can be seen that it has been made into a 2-dimensional small block. can be decrypted automatically.

With this device, three-dimensional block encoding is applied to images with high correlation in the time axis direction, such as still images, and conversely, two-dimensional block encoding is applied to images with small correlation in the temporal axis direction, such as videos. Therefore, it is possible to perform highly efficient encoding with small distortion and high compression ratio for images with any correlation in the time axis direction. Furthermore, in this embodiment, since there is no need to separately transmit information regarding which block code has been selected, the compression rate does not deteriorate due to the transmission of selection information.

Next, a second embodiment using vector quantization will be described.

FIG. 3(1) shows a large block of this embodiment, and this block is a block consisting of a total of 64 sample points, each consisting of 4 samples in both the vertical direction, the horizontal direction, and the time axis direction.

Also, each sample is expressed in B bits, so one large block consists of 512 bits.

Next, the four types of small blocks obtained by forming the four types of second blocks are shown in Figures 2(b), (C),
(d).

It is shown in (15). (b) is a small block with length 1 in the time axis direction.

(C) and (d) are divided into small blocks of length 2 in the time axis direction, (6) are divided into small blocks of length 4 in the time axis direction, and each is divided into (b) type small blocks, ( This is called C) type small block formation, (d) type small block formation, and (θ) type small block formation. In addition, these small blocks are vector quantized into small blocks, and as a result, each large block (b
) is 4obits X4=160bitg, (C)
E, t and (d) are 32 bitS X4 = 128 bitS
, (6) is 24 bits x 4 = 96 bits
compressed into s. In this embodiment, one code word is selected from the four small block results and transmitted together with selection information indicating which code has been selected.

FIG. 4 is a block diagram of the apparatus of this embodiment.

In Fig. 4, 11 is a large block input part, 12 to 15 are small block parts from type ('b) to type (6), respectively.
16 to 19 are vector quantizers, 20 to 23 are distortion measurement parts, 24 is output selection part, 25.26 is improvement level 1 and 2 measurement part, 27 to 29 are buffers, 30 is output selection part, 31 is output The switching portion 32 indicates the output portion of the code word.

8 bitsX input from large block input section 11
The sample values of 64=512 bits are respectively input to four small block forming parts from (b) type small block forming part 12 to (0) type small block forming part 15, and the resulting small blocks are vector quantized. The signals are encoded by the encoders 16-19. As a result, the code word obtained from the (b) type small block is 160 bitg, (c) type and ((1
) type is 128 bits, (6) type is 96 bits
It becomes s.

Next, the distortion measurement parts 20 to 23 calculate the magnitude of distortion caused by each encoding, and from the results, the output selection part 24 calculates the code word obtained from the (0) type or (+1) type small block formation. The one with smaller distortion is selected. At the same time, the improvement level 1 measurement section 25 selects the distortion measurement section 2 based on the magnitude of distortion due to the code word selected by the output selection section 24.
The result of subtracting the magnitude of distortion determined by o is output. Similarly, the improvement level 2 measurement part 26 also includes the output selection part 2.
The magnitude of distortion determined by the distortion measuring section 23 is subtracted from the magnitude of distortion due to the code word selected in step 4, and the result is output.

Now, the three types of codewords obtained in the following steps are stored in buffers 27 to 29, respectively. In this example, 360
It is assumed that codewords corresponding to large blocks are stored. Further, in the output selection section 30, the outputs of the improvement degree 1 measurement section 25 and the improvement degree 2 measurement section 26 are arranged in ascending order as shown in FIG. 6(1).

Here, the fact that the improvement level 1 or 2 is positive means that the distortion of the code word obtained from the (b) type and (6) type small block formation is smaller than the result of the output selection part 24. means. Also, improvement levels 1 and 2 obtained from the same block
If both are positive, keep the larger improvement degree and exclude the smaller one from the table.

Next, as shown in Figure 5 (1) and (2), if the number of positive improvement degrees 2 is equal to or greater than the number of positive improvement degrees 1, then the positive value improvement degree 1 Select the code word obtained from the (b) type small block for the block that takes
A code word obtained from an (el) type small block is selected for a block that takes . In addition, if the number of positive improvement degrees 1 is larger than the number of positive improvement degrees 1, as shown in Figure 5 (Yu), the (b) type and (6) type Select each codeword obtained from the block. For blocks other than these, the result of the output selection part 24 is obtained (C)
The codeword obtained from the type or (d) type block shall be selected. With the above output selection, the number of (8) type blocks (code length - 96 bits) selected is ('b)
The type block (code length - 160 bitg) is equal to or greater than the selected number. Since the codewords selected from the (C) type and (d) type blocks are still 128 bitg, the overall average code length is 128 bitg or less.

The outputs of the buffers 27 to 29 are switched as described above by the output switching section 31, and the output selection information (2b2b1t is outputted to the output section 32 since four types can be selected).

This embodiment is a device that compresses rs 12 bits to 130 bits, approximately A, and can efficiently compress both moving images and still images.

Detailed Description of the Invention As described above, the present invention is applicable to both images with a high correlation in the time axis direction and images with a small correlation in the time axis direction3.
This is a dimensional block encoding device that performs high-quality, high-compression, and high-efficiency encoding for both moving images and still images.

[Brief explanation of the drawing]

Fig. 1 is a sample value block diagram for explaining the first embodiment of the present invention, Fig. 2 is a block diagram of the same embodiment, and Fig. 3 is a sample value block diagram for explaining the second embodiment. block diagram,
FIG. 4 is a block diagram of the same embodiment, FIG. 5 is an explanatory diagram of block selection in the same embodiment, and FIG. 6 is an explanatory diagram of blocking. 2... First block formation, 3, 4... Second block formation, 5, 6... Orthogonal transform coding, 7
, 8... Distortion measurement, 9... Output selection, 1
6-19...Vector quantization, 25.26...
...Measurement of improvement, 27-29--+---) Z Sofa 0 Agent's name: Patent attorney Toshi Nakao, male, and 1 other person
Figure 5 (C door type small Glock side)

Claims (8)

[Claims] (1) It has a first block forming means that divides sample points of an image having continuity in three dimensions including the time axis direction in a three-dimensional space to construct a large block consisting of N sample points each. Further, K types of second blocking means are provided for further dividing the large block into small blocks, and a set of K types of small blocks obtained by each of the K types of second blocking means is block encoded. A block encoding means for generating a set of K types of block codewords, and a selection means for selecting one set of block codewords from the set of K types of block codewords obtained by the block encoding means. Further, the set of block code words selected by the selection means is transmitted, and the set of block code words generated from which second blocking means is selected to the recipient who receives the transmitted set of block code words. A block encoding device characterized in that it has an identification means for notifying. (2) When K=2, one second blocking means divides a large block into small blocks in a two-dimensional space, and another
2. The block encoding device according to claim 1, wherein the second blocking means divides a large block into small blocks in a three-dimensional space. (3) Claim 1 characterized in that the selection means selects a set of block code words that minimizes distortion from the original sample value after decoding from K types of block code word sets. Or the block encoding device according to item 2. (4) When there are K types of block codes with different code lengths, the selection means selects a set of block code words so that the amount of transmission is always constant within a certain range. A block encoding device according to claim 1, 2, or 3. (5) The block according to claim 1, 2, 3, or 4, wherein the identification means enables identification by transmitting an identification signal separately from the block code word. Encoding device. (6) When the block encoding means has a feature that the K types of block codes do not have the same code word, the identifying means uniquely identifies the block code word by examining the transmitted block code word. Claim 1
4. The block encoding device according to item 1, 2, 3, or 4. (7) Block encoding according to claim 1, 2, 3, 4, 5, or 6, characterized in that the block encoding means is orthogonal transform encoding. Device. (8) The block encoding device according to claim 1, 2, 3, 4, 5, or 6, characterized in that the block encoding means is vector quantization. .