KR20000025296A - Variable encoder of block image coefficient - Google Patents

Abstract

PURPOSE: A variable encoder is provided to enable encoding in a variable length in encoding block data by zigzag-scanning input data of a raster scan and converting the zigzag scan into the raster scan. CONSTITUTION: A scan part(10) obtains a run/level with respect to block coefficients, turns coefficients which generate feedback signal into '0', and transmits a signal indicating a coefficient of each block, a signal indicating the number of '0', a signal indicating the end of each block, and a signal indicating non-'0' to a variable length encoder(20). The variable length encoder(20) receives the signals and forms code values and code lengths corresponding thereto and transmits information to scanning parts if an addition value of code lengths exceeds the number of maximum allowable bits.

Description

Variable coding device of block image coefficient

The present invention relates to the compression of image information. In particular, in the case of encoding block data, the input data of raster scan is implemented by zigzag scan, and conversely, the zigzag scan is converted to raster scan to inverse quantization stage. The present invention relates to an apparatus for transmitting a variable length, and for encoding a variable length.

When transmitting a digital image, since a lot of digital image data information is generated, compression of the image information is essential. When compressed data is transmitted after compressing an image, data is transmitted at a fixed bit rate. In the case of sending data at a fixed bit rate, there is a problem in that the data to be encoded must be limited in the process of encoding the data.

Accordingly, the present invention has been proposed to solve the above-mentioned conventional problems, and an object of the present invention is to implement input data of a raster scan as a zigzag scan and conversely to a raster scan when encoding block data. In another aspect, there is provided a variable encoding apparatus of a block image coefficient that can be sent to an inverse quantization stage and can be encoded with a variable length.

In order to achieve the above object, the variable encoding apparatus of the block image coefficient according to the present invention,

Change the order of data input from the dequantization block from raster scan to zigzag scan to obtain run / level for the changed block coefficients, make coefficients fed back from the variable-length coder to 0, and then order the coefficients. After changing from the zigzag scan to the raster scan again, the data is transmitted to the inverse quantization block.The signal indicating the coefficient values of each block, the number of zeros between the coefficients, the signal indicating the end of each block, and the coefficient value of each block A scanning unit which transmits a signal representing a non-zero value to the variable length code unit; Receives a signal indicating the count value of each block generated by the scanning unit, a signal indicating the number of zeros between coefficients, a signal indicating the end of each block and a signal indicating a non-zero value of the coefficient of each block corresponding to each Code length and code length are formed, and if the sum of the code lengths for each block exceeds the maximum possible number of bits during code formation, the code information is not generated for the corresponding run / level signal. It is characterized by the technical configuration that the variable length code is transmitted.

1 is a block diagram of a variable encoding apparatus for a block image coefficient according to the present invention;

2 is a detailed block diagram of the scanning unit of FIG. 1;

3 is a detailed block diagram of a variable length coder in FIG. 1;

4 is a view showing a zigzag scanning sequence in FIG.

5 is a change table according to the zigzag scanning sequence of FIG.

<Explanation of symbols for the main parts of the drawings>

10: scanning unit 20: variable length code portion

Hereinafter, with reference to the accompanying drawings an embodiment according to the technical idea of the variable encoding apparatus of the present invention block image coefficient as described above in detail.

First, the criterion for limiting data determines the number of data bits according to the purpose of implementation. In the case of ISO13818-2 MPEG2 standardization, the maximum number of bits per macroblock is determined according to each application purpose. Based on this value, the maximum number of bits can be determined.

In the present invention, the maximum number of bits per macroblock is determined in the process of encoding the image coefficients generated after DCT according to the variable encoding table, and this value is divided by the number of blocks to determine the maximum number of bits per block. When the number of bits generated per sugar is exceeded and the maximum value is exceeded, subsequent data coefficients are ignored, thereby generating bit data for a fixed bit rate. In an application such as a high-definition television that requires a high bit rate, data can be processed in parallel according to the present invention, and in this case, data can be generated independently in parallel when the generated data is limited in encoding image coefficients. .

Meanwhile, after motion compensation of image data, DCT (Discrete Cosine Transform, Discrete Cosine Transform) is quantized for each block, and the coefficient value is received as an input. In the case of a 4: 2: 0 system, four macroblocks and two chrominance blocks are included in each macroblock. In order to realize a high bit rate, data is received in three paths. Two paths are luminance blocks and one path is a color difference block. Therefore, a block that is simultaneously input receives three blocks as input. Each block will perform the same function.

1 is a block diagram of a variable encoding apparatus for a block image coefficient according to the present invention;

As shown in this figure, the data order input from the inverse quantization block is changed from raster scan to zigzag scan to obtain run / level for the changed block coefficients, and a feedback signal is generated from the variable length coder 20. After making the coefficients to be 0, the order of these coefficients is changed from the zigzag scan to the raster scan, and then transmitted to the dequantization block.The signal indicating the coefficient values of each block, the signal indicating the number of zeros between the coefficients, and each block A scanning unit 10 for transmitting a signal indicating the end of the signal and a signal indicating a non-zero value of each block to the variable length code unit 20; Receives a signal indicating the count value of each block generated by the scanning unit 10, a signal indicating the number of zeros between the coefficients, a signal indicating the end of each block and a signal indicating a non-zero count value of each block Code lengths and code lengths are formed for each code, and if the sum of the code lengths for each block exceeds the maximum possible number of bits during code formation, the code is not created for the corresponding run / level signals. It consists of a variable length code unit 20 which is transmitted to the scanning unit.

FIG. 2 is a detailed block diagram of the scanning unit in FIG. 1.

As shown therein, the write control unit 11 controls the count values coming into the input to be sequentially written to the first memory; A first memory (12) for storing coefficient values under control of the write control unit (11); A scan converter (13) for performing zigzag scanning by reading data stored in the first memory (12) in a zigzag order; A run counting unit (14) for counting the number of nonzero coefficients and zeros between the coefficients for the coefficients converted in the zigzag scanning order by the Scan converter (13); A coefficient mask unit 15 for delaying data input from the run count unit 14 and making run / level information having no code value inputted from the variable length code unit 20 to 0; An IScan converter (16) for converting the data of the coefficient mask section (15) into raster scanning order and writing it to the second memory (17); A second memory (17) for storing data of the IScan converter (16); And a read control unit 18 which controls to read the data of the second memory 17 in the raster scanning order.

FIG. 3 is a detailed block diagram of a variable length coder in FIG. 1.

As shown therein, a variable length table coder 21 for generating a code value and a code length by referring to a table of variable encoding by receiving a level / run signal; When the sum of the codes output from the variable length table coder 21 is exceeded and the maximum number of bits is exceeded, a code value for the run / level signal is generated without generating a code value to the scan unit 10. It consists of the counting mask generator 22 which transmits.

Thus, the scanning unit 10 converts the data (DCM []) order from the raster scan to the zigzag scan, obtains the run / level for the changed block coefficients, and feeds back the fed back coefmask from the variable length code unit 20. Coefmask is generated by referring to the signal as 0, then the order of these coefficients is changed from zigzag scan to raster scan order, and DCMPND [] signal is sent to the dequantization block. The signal level [] represents the coefficient values of each block and the signal run [] represents the number of zeros between the coefficients. The signal eob is a signal indicating the end of each block, and the signal stb indicates a value of level [] that is not zero.

4 illustrates a raster scan and a zigzag scan of the scan unit 10. Thus, each block is composed of 8x8 coefficients, and the raster scan reads the coefficient values in order as shown in Fig. 5A. The zigzag scan reads the data at the upper left first and reads the data at the lower right later as shown in FIG. 5B. The reason for changing the order by zigzag scanning for variable coding is that low frequency components of DCT coefficients are concentrated on the upper left side and high frequency components are collected on the lower right side. If the coefficients are encoded first and the maximum number of code bits is exceeded, this is to discard the high frequency part which has relatively little effect on the image quality.

Accordingly, the write control unit 11, the first memory 12, the scan conversion unit 13, and the run count unit 14 perform a scan function, and the coefficient mask unit 15 and the IScan conversion unit 16 are performed. ), The second memory 17 and the read control unit 18 perform an inverse scan function. Scan and iscan are performed by changing the address to be written and the address to be written to the first and second memories 12 and 17 using DPSRAM (Dual Port SRAM). The write control unit 11 sequentially writes count values coming into the input into the first memory 12 of the DPSRAM. The scan converting section 13 reads the reading order in a zigzag order so that a zigzag scan is performed. The run count unit 14 counts the number of nonzero coefficients and zeros between the coefficients for the coefficients converted in the zigzag scanning order.

Thus, level [], run [], eob [], and stb, which are input data of the coefficient mask unit 15, vary the level [], run [], eob [], and stb signals that are the outputs of the run count unit 14. Data delayed by the clock at which the coefmask signal of the length code unit 20 is generated. By delaying, it is possible to synchronize the coefmask signals with level [], run [], eob [], stb which are input data of the coefficient mask unit 15. Therefore, the coefficient mask unit 15 receives the coefmask signal from the variable length coder 20 and serves to make the level [] value generated by the coefmask high to zero. In addition, the IScan conversion unit 16 converts the address used when writing the coefficient value received as an input to the second memory 17 of the DPSRAM. The read control unit 18 converts the read address of the second memory 17 of the DPSRAM into the raster scan order in the raster scan order. In the case of scan, the change table according to the zigzag scan order of FIG. 5 is used when reading to the DSPRAM, and the change table by the zigzag scan order of FIG. 5 is used when writing to the DPSRAM in the case of iscan. Make it possible.

The variable length coder 20 receives the level [], run [], eob, and stb signals generated by the scan unit 10, and creates a code value and a code length corresponding to each level [], run []. Serve In the process of generating the code, if the length of the code exceeds the maximum possible number of bits for each block, the signal coefmask is raised to high and used by the scanning unit 10 without creating a code value for the input level and run.

Therefore, the variable length table coder 21 receives the level [] and run [] signals and generates codes [] and size [] by referring to the table of variable encoding, and the coefficient mask generator 22 adds the sum of the codes. If the maximum number of bits is exceeded, the coefmask signal is generated high.

As described above, when the block data is encoded, the input data of the raster scan is implemented by the zigzag scan, and conversely, the zigzag scan can be converted to the raster scan and sent to the inverse quantization stage, and the variable length is encoded.

Although the preferred embodiment of the present invention has been described above, the present invention may use various changes, modifications, and equivalents. It is clear that the present invention can be applied in the same manner by appropriately modifying the above embodiments. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

As described above, in the case of encoding block data, the variable encoding apparatus of the block image coefficient according to the present invention implements input data of raster scan into zigzag scan, and conversely, converts zigzag scan into raster scan and sends it to the dequantization stage. It is possible to have a variable length at the time of encoding.

Claims (3)

Change the order of data input from the dequantization block from raster scan to zigzag scan to obtain run / level for the changed block coefficients, make coefficients fed back from the variable-length coder to 0, and then order the coefficients. After changing from the zigzag scan to the raster scan again, the data is transmitted to the inverse quantization block.The signal indicating the coefficient values of each block, the number of zeros between the coefficients, the signal indicating the end of each block, and the coefficient value of each block A scanning unit which transmits a signal representing a non-zero value to the variable length code unit; Receives a signal indicating the count value of each block generated by the scanning unit, a signal indicating the number of zeros between coefficients, a signal indicating the end of each block and a signal indicating a non-zero value of the coefficient of each block corresponding to each Code length and code length are formed, and if the sum of the code lengths for each block exceeds the maximum possible number of bits during code formation, the code information is not generated for the corresponding run / level signal. And a variable length coder for transmitting the block image coefficient. The method of claim 1, wherein the scanning unit, A write control unit controlling the count values coming into the input to be sequentially written to the first memory; A first memory for storing coefficient values under control of the write control unit; A scan converter configured to read data stored in the first memory in a zigzag order and perform a zigzag scan; A run count unit for counting the number of nonzero coefficients and zeros between the coefficients with respect to the coefficients converted in the zigzag scanning order by the Scan converter; A coefficient mask unit for delaying data input from the run count unit and making run / level information with no code value inputted from the variable length code unit 0; An IScan converting unit converting data of the counting mask unit into raster scanning order and writing the data to a second memory; A second memory for storing data of the IScan converter; And a read control unit configured to control reading of data of the second memory in raster scanning order. The method of claim 1, wherein the variable length code unit, a variable length table encoder for generating a code value and a code length by receiving a level / run signal and referring to a table of variable encoding; If the sum of the codes output from the variable-length table coder is exceeded and the maximum number of bits is exceeded, the coefficient mask generator generates high signal for the run / level signal and transmits it to the scan unit without generating a code value. A variable encoding device of a block image coefficient, characterized in that.