JP2002077915A - Image decoding method and decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To receive band decode data obtained by encoding image data while dividing a luminance signal and a color difference signal thereof, respectively, into a plurality of luminance signal blocks and color difference signal blocks. SOLUTION: A luminance signal and a color difference signal constituting image data are divided, respectively, into a plurality of luminance signal blocks and color difference signal blocks, each block representing each signal is subjected to variable length encoding, and transmission blocks arranged with sequentially encoded data in units of encoded data of a specified number of luminance signal blocks less than one screen and encoded data of a specified number of color difference signal blocks at the same position as the specified number of luminance signal blocks on an image space are inputted sequentially and decoded. In such image decoding method and decoder, inputted transmission blocks are stored in a memory 29, encoded data of a luminance signal block and encoded data of a color difference signal block are read out separately from the memory 29 under control of a transmission ID detecting section 25 and an address controller 27, and decoded by corresponding decoders 35a, 35b and 35c. Decoding results are returned and recovered by inverse block circuits 39a, 39b and 39c for each signal in the order of transmission of the original signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image decoding method and apparatus for inputting and decoding encoded image data.

[0002]

2. Description of the Related Art Conventionally, when encoding image data, there are variable-length coding and fixed-length coding. In particular, in variable-length coding, coding such as predictive coding is also known.

[0003]

However, such a variable-length coding system is excellent in compression efficiency. However, if an error occurs in the compressed data on the transmission line, subsequent decoding cannot be performed at all. As a result, the image after the error has occurred in the compressed data may be disturbed, resulting in a very unsightly state.

The present invention has been made in view of the above conventional example, and divides a luminance signal and a color difference signal of image data into a plurality of luminance signal blocks and a plurality of color difference signal blocks, respectively, and encodes the encoded data. It is an object of the present invention to provide an image decoding method and apparatus for inputting and decoding.

[0005]

In order to achieve the above object, an image decoding apparatus according to the present invention has the following arrangement. That is, the luminance signal and the chrominance signal forming the image data are divided into a plurality of luminance signal blocks and a plurality of chrominance signal blocks, respectively, and each block representing each signal is subjected to variable-length coding.
The encoded data of the predetermined number of the luminance signal blocks less than one screen and the encoded data of the predetermined number of the color difference signal blocks at the same position in the image space as the predetermined number of the luminance signal blocks are used as a unit. An image decoding apparatus for sequentially inputting and decoding transmission blocks in which sequentially encoded data are arranged, wherein encoded data of the luminance signal block and encoded data of the color difference signal block are input from the input transmission block. , And decoding means for decoding the encoded data of the luminance signal block and the encoded data of the color difference signal block separated by the separating means.

In order to achieve the above object, an image decoding method according to the present invention includes the following steps. That is, the luminance signal and the chrominance signal constituting the image data are divided into a plurality of luminance signal blocks and a plurality of chrominance signal blocks, respectively, and the blocks representing the respective signals are coded in a variable length, and a predetermined number less than one screen is used. The coded data of the luminance signal block and the coded data of the predetermined number of the chrominance signal blocks at the same position in the image space as the predetermined number of the luminance signal blocks are sequentially arranged as coded data. An image decoding method for sequentially inputting and decoding transmission blocks that are present, wherein a separation step of separating encoded data of the luminance signal block and encoded data of the chrominance signal block from the input transmission block, Decoding the encoded data of the luminance signal block and the encoded data of the chrominance signal block separated in the separation step. To.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 6 is a block diagram showing a schematic configuration of an image coding apparatus according to the present embodiment.

In FIG. 6, image data input from a terminal 101 is converted from an analog signal to a digital signal in an A / D converter 102. The converted digital signal is compression-encoded in a variable length by the encoding unit 103. Then, the coded code is transmitted to the transmission path 105 by the error correction coding unit 104 added with a parity code for later error correction.
The data received from the transmission path 105 is stored in the memory 106
, And the error is corrected by the error correction unit 107. The decoding unit 108 expands and decodes the variable-length data read from the memory 106. After the decoded signal is converted from a digital signal to an analog signal by the D / A converter 109, It is output as an image signal.

As a color image compression method of the encoding unit 103 in FIG. 6, various methods have been proposed, and a typical one of the color image encoding methods is a method called ADCT method. The ADCT method is described in “The Still Image Coding Method” by Takahiro Saito et al. In the Journal of the Institute of Television Engineers of Japan (Vol.44, No.2 (1990)), and by Tomohiro Ochi in Preprints 14 These are described in detail in “International Standard Trends in Still Image Coding” and the like.

FIG. 7 is a diagram showing a configuration concept of the encoding unit 103 using the ADCT method.

The input image is 8-bit output from the A / D converter 102 shown in FIG.
The data is converted to colors, and the number of colors is RGB, Y
Three or four colors, such as UV, YPbPr, and YMCK. Here, the input image is immediately subjected to two-dimensional discrete cosine transform (hereinafter referred to as DCT) in units of 8 × 8 pixel sub-blocks, and then the linear quantization unit 202 performs linear quantization of the transform coefficients. At the time of this quantization, the quantization step size differs for each transform coefficient, and the quantization step size for each transform coefficient is 8 × 8 quantization considering the difference in luminosity factor for quantization noise for each transform coefficient. the matrix elements and 2 ^S multiplied value. Where S
Is 0 or a positive or negative integer and is called a scaling factor. The image quality and the amount of generated data are controlled by the value of S. Table 1 shows an example of the quantization matrix element.

[0013]

[Table 1] After the quantization, a DC conversion component (hereinafter, referred to as a DC component) is one-dimensionally predicted between neighboring sub-blocks at 203, and the prediction error is Huffman-coded at 204. Here, the quantized output of the prediction error is divided into groups, first, the identification number of the group to which the prediction error belongs is Huffman-coded, and subsequently, any value in the group is represented by an isometric code.

On the other hand, an AC conversion component other than the DC component (hereinafter, referred to as an AC component) is encoded by zigzag scanning the quantized output from a low frequency component to a high frequency component at 205 as shown in FIG. I do. That is, transform coefficients whose quantized output is not “0” (hereinafter referred to as significant coefficients) are classified into groups according to their values, and are interposed at 206 between the group identification number and the immediately preceding significant transform coefficient. The quantized output is Huffman-encoded in combination with the number of transform coefficients of “0” (hereinafter referred to as invalid coefficients). Subsequently, which value in the group is represented by an isometric code.

FIG. 1 is a block diagram showing a schematic configuration of an image coding apparatus according to the present embodiment.

The image signals Y, Pb,
Each of Pr is input from terminals 1a, 1b, 1c. Here, it is assumed that three signals of a luminance signal Y of a color image signal and color difference signals Pb and Pr are input as a plurality of signals. Each input signal is input to each of the A / D converters 3a, 3b, 3c and converted into a digital signal. In this embodiment, the luminance signal Y is sampled at twice the sampling rate of the color difference signals Pb and Pr, and the color difference signals are line-sequentialized by a line-sequencing circuit (not shown). As a result, when the data amount of each signal after the A / D conversion is compared, the ratio of the color difference signals Pb and Pr is “1” to the ratio of the luminance signal Y to “4”.

Next, each digitized data is
In each of the blocking circuits 5a, 5b, 5c, for example, each block is divided into 8 × 8 blocks. Since each data has a data amount ratio of 4: 1: 1 as described above, the size of each generated block on the screen is equal to the luminance signal Y.
The color difference signals Pb and Pr are four times as large as 1. The data thus blocked are encoded by the encoders 7a, 7a by the variable length compression method as described in the related art.
In this embodiment, the image data is divided into a plurality of regions for each signal, and the variable-length coding is closed in each of these regions. I do it. These areas are, for example, areas having a data amount of 40 forty-eight 8 × 8 blocks.

As described above, the generated code group that has been compression-coded for each signal and for each region is written to the memory 9 and is combined into one data string when read. Here, the order of reading data from the memory 9 is controlled by the address controller 11, and in the present embodiment, for each of the plurality of signals, that is, for the luminance signal Y,
For each of the color difference signals Pb and Pr, the generated generated code group is
The data is read out in a time-series manner for each region belonging to the same position on the screen or for each region belonging to a nearby position. This reading order will be described later in detail.

In the data sequence read from the memory 9, a sync code is inserted at a predetermined position in a sync code adding unit 13, and a transmission ID is added in a transmission ID adding unit 15.
Is inserted. Reference numeral 17 denotes a boundary information adding unit that inserts information of a generated code delimiter for the divided area into the data string in the form of, for example, a marker code. As a result, the receiving side can detect the break of each generated code, and can reliably decode the variable-length code for each of the divided areas.

Further, the error-correction coding circuit 19 performs error correction coding on the compression-coded generated code, and inserts parity bits of the error detection / correction code into predetermined positions of the data sequence. Transmitted.

Reference numeral 21 denotes a transmission line, which is a transmission medium such as a terrestrial radio wave such as an optical fiber, a satellite, or a microwave for an immediate transmission, an optical space, and a digital VTR or D for a storage transmission.
The storage medium is a medium on a tape such as an AT, a disk-shaped medium such as a floppy (registered trademark) disk or an optical disk, or a solid medium such as a semiconductor memory. The transmission rate is determined by the information amount of the original image, the compression ratio, and the required transmission time, and varies from several tens of kilobits / second to several tens of megabits / second.

Next, the operation of the receiving side will be described with reference to FIG.

The data received from the transmission line 21 is first synchronously detected by the sync code detection unit 23, and the transmission ID
The detection unit 25 detects the attribute of the data based on the ID, and temporarily stores the data in the memory 29 under the control of the address controller 27 based on the information. The data in the memory 29 is subjected to data error detection and correction in an error detection / correction unit 31, and errors added during transmission are removed as much as possible. If there is an error that cannot be corrected, a flag is set for the data group, and the interpolation circuits 37a, 37b, 37
Interpolation processing is performed at c.

Then, the boundary information detecting section 33 detects the boundary of the compression code section of the divided area, and based on the information, controls the read address from the memory 29 by the address controller 27 to transfer the data. A plurality of signals, that is, a luminance signal Y, a color difference signal Pb,
The data is read out from the memory 29 by being divided for each Pr and for each divided area. The data thus divided and read from the memory 29 is supplied to the decoders 35a and 35a.
b, 35c, respectively, are decompressed and decoded, and interpolation circuits 37a, 37b, 37c perform an interpolation process on a data group including an error that cannot be completely corrected in units of divided areas. As a specific method of the interpolation processing, there is interpolation using the previous frame data and the like. Further, after the interpolation processing, the data is supplied to the inverse block circuits 39a, 39b,
At 39c, each signal is returned to the original signal transmission order, and the color signal P
With respect to b and Pr, line-sequentialized data is restored by a synchronization circuit (not shown).

Each signal is supplied to a D / A conversion circuit 41a,
The data is converted into analog data at 41b and 41c and
3a, 43b and 43c output image signals of a luminance signal Y and color difference signals Pb and Pr, respectively. Here, when the decoders 35a, 35b, and 35c decompress and decode the variable-length code, if an encoded region is not divided as in the related art, once an error occurs, the subsequent decoding processing is performed. Will not be performed at all. However, in this embodiment, as described above, since the area of the image data is divided at the time of encoding and the boundary information is added and transmitted, it is possible to quickly return from the decoding processing. it can.

Next, the present embodiment will be described in more detail with reference to FIGS. 2, 3, 4, and 5. FIG.

FIGS. 2A and 2B are diagrams showing an example of image data to be transmitted. FIG. 2A shows a luminance signal Y of one image, which is composed of 1280 pixels horizontally, 1088 pixels vertically, and each pixel. Is an 8-bit A / D-converted image. In this case, the data capacity of one luminance signal Y is 1,280 × 1,088 × 8 (bits) = 11,14
1,120 bits.

On the other hand, as described above, each of the color difference signals Pb and Pr is sampled at a sampling rate of に 対 し て with respect to the luminance signal Y, and is further subjected to color difference line sequential processing. As shown in FIG. 2B, 640 × 544 × 8 (bits) = 2,785,280
Bit.

Accordingly, the luminance signal Y and the color difference signals Pb, Pr
Are 16,711,680 (= 11,141,120 + 2,78
One image is composed of (5,280 × 2) bits.

Here, (horizontal 8 pixels) × (vertical 8 pixels)
Is a DCT sub-block, and as shown in FIG. 2, one image to be transmitted is divided into 40 DCT sub-blocks for each signal.
It is divided as a resync block (320 horizontal pixels × 8 vertical pixels). This is set as a divided region in the present embodiment, and variable length coding closed in each divided region is performed. Note that such a divided area is not limited to the present embodiment, and may be another divided method.

In this case, with respect to the luminance signal Y, data for one screen is four horizontal pixels and 136 vertical pixels by a resync block.
Are divided into a total of 544 areas. On the other hand, the color difference signals Pb and Pr are each divided into a total of 136 areas of horizontal 2 and vertical 68. Here, the data capacity per resync block is 40 × 8 × 8 × 8 =
The size of one resync block on the screen is (luminance signal resync block) :( color difference signal block) = 20,480 (bits), as shown in FIG.
1: 4.

FIG. 3 is a diagram showing an example of a transmission format according to the present embodiment.

The coded data coded as described above is added with the boundary information (marker code) of the present embodiment so that it can be distinguished in units of resync blocks. And a case where a marker code is inserted at the boundary between the resync block and the resync block. It is necessary to assign a bit pattern that cannot occur in the encoded data as the marker code.

The coded data to which the boundary information has been added in this manner is further subjected to error detection / correction coding. In this case, data of 128 symbols (hereinafter, 1 symbol = 8 bits) is used for 4 bits. It is assumed that the parity bit of the symbol is added. The data obtained by adding two symbols of the sync code and two symbols of the transmission ID to this data is a transmission unit.

Here, since the coded data is variable-length coded, the length of the coded data sequence for each resync block is not constant, and each data length varies. Data may span a plurality of error detection / correction blocks. Conversely, one error detection / correction code block may be composed of data of a number of resync blocks, and the number is not constant. When one error detection / correction code block is composed of a plurality of resync blocks, when an error in the error detection / correction block becomes uncorrectable, the effect extends to a plurality of resync blocks. That is, the plurality of resync blocks are subjected to the interpolation processing as described above.

In the present embodiment, the transmission order of the encoded data is defined so that even if an uncorrectable error occurs as described above, the effect is reduced.

Assuming that resync blocks are numbered for each signal as shown in FIGS. 4-1 and 4-2,
In consideration of the data amount of each signal, the color difference signals Pb and Pr are transmitted by one resync block for each of the four resync blocks of the luminance signal Y. For example, Y (0,0),
Y (0,1), Pb (0,0), Y (0,2), Y
(0,3), Pr (0,0), Y (1,0), Y (1,
3), Pb (0, 1), Y (1, 2), Y (1, 3),
Assuming that Pr (0,1),... Is transmitted,
If (0,2), Y (0,3), and Pr (0,0) are included in the same error detection / correction block and the error detection / correction block cannot be corrected, The interpolation area will be dispersed.

Therefore, in the present embodiment, as shown in FIG. 5, for example, Y (0,0), Y (0,1), Pb
(0,0), Y (1,0), Y (1,1), Pr (0,
0), Y (0,2), Y (0,3), Pb (0,1),
Y (1,2), Y (1,3), Pr (0,1),... Or Y (0,0), Y (0,1), Y (1,0), Y
(1,1), Pb (0,0), Pr (0,0), Y
(0,2), Y (0,3), Y (1,2), Y (1,
3), the address controller 11 is controlled so as to collectively transmit resync blocks at the same position or near positions on the screen, such as Pr (0,1), Pr (0,1),. .

Thus, even if the error detection / correction block becomes uncorrectable, the probability that the interpolation area on the screen is divided as described above is reduced.

In this embodiment, a plurality of types of signals constituting the image data are a luminance signal Y and a color difference signal P.
b, Pr, but not limited to, for example, RGB,
It may be composed of signals such as YUV, YMCK and the like. Further, a method of configuring an area for dividing image data is also described as follows.
The present invention is not limited to the division method described in the present embodiment.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus.

As described above, according to the present embodiment, the error mixed in the transmission path can be corrected by the error detection / correction code without deteriorating the characteristics of the variable length coding method which is excellent in compression efficiency. Even if it is not possible, the effect can be minimized.

That is, an error occurs in the data on the transmission path,
Even if the error cannot be corrected on the receiving side, the effect can be converged for each resync block.

Further, as for the interpolation processing performed when the error cannot be corrected, the resync blocks to be subjected to the interpolation processing can be grouped at the same position or in a nearby position without being dispersed on the screen. Further, it is possible to minimize the deterioration of the image data, and it is possible to provide an image coding apparatus capable of reproducing an extremely good image without any noticeable deterioration in human eyes.

[0045]

As described above, according to the present invention, encoded data obtained by dividing a luminance signal and a color difference signal of image data into a plurality of luminance signal blocks and a plurality of color difference signal blocks, respectively, and inputting them is input. By decoding the image data, even if an error occurs in the encoded image data, the image data can be reproduced with less disturbance of the image.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an image encoding device according to the present embodiment.

FIG. 1-2 is a block diagram illustrating a schematic configuration of an image encoding device according to the present embodiment.

FIG. 2 is a diagram showing a configuration of image data encoded in the present embodiment.

FIG. 3 is a diagram illustrating an example of a transmission format according to the present embodiment.

FIG. 4-1 is a diagram illustrating an example of a number configuration of a resync block of a luminance signal Y according to the present embodiment.

FIG. 4-2 is a diagram illustrating an example of a number configuration of a resync block of a color difference signal according to the present embodiment.

FIG. 5 is a diagram showing a transmission order of resync blocks in the present embodiment.

FIG. 6 is a block diagram illustrating a schematic configuration of an image encoding device according to the present embodiment.

FIG. 7 is a diagram for explaining the variable-length coding system of FIG.

FIG. 8 is a diagram for explaining the variable-length coding system of FIG.

[Explanation of symbols]

 3a, 3b, 3c A / D converter 5a, 5b, 5c Blocking unit 7a, 7b, 7c Encoding unit 9, 29 Memory 11, 27 Address controller 13 Sync code adding unit 15 Transmission ID adding unit 17 Boundary information adding unit 19 Error correction encoding 21 Transmission path 35a, 35b, 35c Decoder 37a, 37b, 37c Interpolator 39a, 39b, 39c Deblocker 41a, 41b, 41c D / A converter

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) BC02 BC06 BC07 BC16 BD01

Claims (2)

[Claims] 1. A luminance signal and a chrominance signal constituting image data are divided into a plurality of luminance signal blocks and a plurality of chrominance signal blocks, respectively, and each block representing each of the signals is subjected to variable-length coding to fill one screen. The encoded data of the predetermined number of the luminance signal blocks and the encoded data of the predetermined number of the color difference signal blocks at the same position in the image space as the predetermined number of the luminance signal blocks are sequentially encoded data. An image decoding apparatus for sequentially inputting and decoding arranged transmission blocks, comprising: separating means for separating encoded data of the luminance signal block and encoded data of the color difference signal block from the input transmission block. And decoding means for decoding the encoded data of the luminance signal block and the encoded data of the chrominance signal block separated by the separating means. Image decoding apparatus according to claim and. 2. A luminance signal and a chrominance signal constituting image data are divided into a plurality of luminance signal blocks and a plurality of chrominance signal blocks, respectively, and each block representing each signal is subjected to variable-length coding to fill one screen. The encoded data of the predetermined number of the luminance signal blocks and the encoded data of the predetermined number of the color difference signal blocks at the same position in the image space as the predetermined number of the luminance signal blocks are sequentially encoded data. What is claimed is: 1. An image decoding method for sequentially inputting and decoding arranged transmission blocks, comprising: separating encoded data of the luminance signal block and encoded data of the chrominance signal block from the input transmission block. And a decoding step of decoding the encoded data of the luminance signal block and the encoded data of the chrominance signal block separated in the separation step. Image decoding method comprising.