KR960013232B1 - Fixed rate video signal compressing encoding/decoding method - Google Patents

Abstract

The method is for separating an original video signal into a contast and a color difference signal, dividing them into a certain size of block and then calculating the discrete cosine transformation(DCT), and coding the DCT coefficient by quantizing. The method includes the steps of: coding DC coefficients out of the quantized multiple DCT coefficients according to the order of block; arraying AC coefficients in a certain number of pixels; and coding the AC coefficients into the positional information and data values.

Description

Image Compression Coding and Decoding for Bit Fixing

1 is a block diagram of an image compression coding apparatus for fixing bits according to the present invention.

2 is a block diagram of an image compression decoding device for fixing bits according to the present invention.

* Explanation of symbols for main parts of the drawings

10: color signal separation unit 20: sub-sampling unit

30: block division 40: DCT converter

50: quantization 60, 160: quantization matrix

70, 170: multiplier 80: DCT encoding section

90: array portion 100: AC encoding portion

110: multiplexer 120: demultiplexer

130: DC decoding unit 140: AC decoding unit

150: dequantization 180: IDCT conversion unit

190: block combination unit 200: interpolation operation unit

210: color coordinate conversion unit

The present invention relates to a video compression encoding and decoding method for fixing bits in a digital video device.

In general, various compression encoding methods are used to increase recording efficiency when recording color images on a tape or other digital recording medium.

The compression standardization method recommended by the Joint Photogrphy Expert Group (JPEG) and Moving Picture Expert Group (MPEG) by the international standardization organization uses DCT variable length coding. In such a variable coding scheme, it is important to fix the output bit amount according to the complexity of an image. In particular, in the case of a digital video cassette (DVCR), it is a decisive factor in trick play such as search.

An object of the present invention is to encode the position information and the data value of the selected pixel by arranging DCT processing for a certain coding unit in a predetermined pixel having a large absolute value among the AC coefficients of a block in order to fix the output amount of bits efficiently The present invention provides an encoding scheme and a decoding scheme for fixing bits to be transmitted.

In order to achieve the above object, the video compression encoding method and decoding method for fixing bits according to the present invention is a block order of DC coefficients among DCT coefficients quantized in a plurality of block units in a DCT encoding method for compressing a digital video signal. After coding according to the above, the AC coefficients of each block are arranged in pixels having a predetermined absolute value, and are encoded into position information and data values with respect to the selected AC coefficient, and the signals encoded by the above-described coding scheme are restored. It is characterized by decoding.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the video compression coding scheme and decoding scheme for improved bit fixing according to the present invention.

1 is a block diagram according to an embodiment of an image compression encoding apparatus for bit fixing according to the present invention.

1, the operation of the color signal separation unit 10, the quantization matrix 60, the quantization 50, and the like are described in Korean Patent Application No. 91-12412 filed by Samsung Electronics Co., Ltd. Detailed description will be omitted.

The color signal separator 10 separates Y, which is a luminance signal, and R-Y, B-Y, which are color signals, from the R, G, and B signals. In this case, the color difference signal is subsampled to 2: 1 in each of the horizontal and vertical directions by using the subsampling unit 20. When the compressed color difference signal is restored in this way, the values between the pixels are linearly interpolated to fill the original values.

The block division unit 30 inputs the luminance signal Y output from the color signal separation unit 10 and the color difference signals RY and BY output through the subsampling unit 20 to block 8 × 8 pixels. Divide. The encoding order is processed by four blocks in the Y signal and one block in each of the R-Y and B-Y signals as one unit.

In the DCT converter 40, the second DCT conversion is performed sequentially from the block division order, i.e., the block on the top left side to the block on the bottom right side. DCT is a type of change encoding that compresses data by applying two-dimensional transform to obtain statistical properties of transform coefficients and applying a quantization method suitable for the statistical properties. KT (Karhunen-- Since it has almost the same performance as Loeve Transform, it is widely used for data compression, filtering, and feature extraction.

The quantization 50 is obtained from the quantization matrix of the quantization matrix 60 and the quantization compression setting means (not shown). The quantization step size is controlled by the output of the multiplier 70 multiplied by. The above-described quantization compression setting means is described in Korean Patent No. 91-23727 filed by Samsung Electronics Co., Ltd., so detailed description thereof will be omitted. In addition, the quantization matrix 60 uses a quantization matrix proposed by ISO / CCITT.

That is, Q (u, v) = QM (u, v) × S

Where QM (u, v): quantization matrix

S: quantization factor

The quantization coefficient value is quantized by the following expression.

Here, the properties of the DCT conversion are classified into DC and AC components, and the farther the DC component is, the higher the frequency coefficient is. When DCT conversion of a general image, the coefficient of the low frequency component is an important factor in determining the image quality, and the magnitude of the value is much larger than the high frequency. In consideration of such factors, the quantization matrix is designed so that the low frequency components have a smaller spacing than the high frequency components. Therefore, the low frequency component near the CD component has a very high probability of being non-zero, and the probability drops significantly as the frequency goes higher.

The DC encoder 80 expresses the DC coefficient output after the DCT conversion and quantization as an 8-bit signal.

The arranging unit 90 sorts n bits, which are the values of m AC coefficients having a large absolute value (here, 5) among 63 AC coefficients excluding the DC, and sets each position information as 6 bits. The position of 64 pixels for an 8x8 block can be represented by 6 bits.

The AC encoding unit 100 encodes m large AC values output from the array unit 90.

That is, m pixels are represented by n bits + values.

Thus, the amount of bits output per block is

8 bits (DC) + m (pixels) x n bit (value).

The encoding format of the AC coefficient is

6 bit (position) + n bit (value).

If the number of non-AC coefficients is less than 5, DC is transmitted unconditionally, so the position is set to 0.

For example, when any one block is DCT converted as shown in the above table, the DC and AC coding results alternately output from the multiplexer 110 are as follows.

DC (8bit), 101 (-5), 001001 (position: 9), 100 (4), 001000 (position: 8), 011 (3), 000001 (position: 1), 001 (1), 011000 (position 24), 000 (0), 000000 (position: 0).

In this case (n = 3, m = 5), since 64 bits are fixed per DCT block, 64 bytes (bute) are compressed to 53 bits and fixed.

In the present invention, the code coded by the coded scheme may be decoded in the reverse order as shown in FIG.

That is, the demultiplexer 120 outputs the coded DC value and the AC value output from the multiplexer 110 to the DC decoding unit 130 and the AC decoding unit 140. The AC decoding unit 140 decodes m pixels selected at the time of encoding among 8 × 8 blocks and puts all ACs except 0 selected among 63 AC coefficients as 0.

The inverse quantization 150 inversely quantizes the S value used in the encoding and the quantization matrix 160.

The block combination unit 190 combines the divided blocks output through the IDCT conversion unit (Inverse DCT) 180 to position the original screen.

The interpolation operation unit 200 interpolates the color difference signals among the luminance signal Y and the color difference signals RY and BY output from the block combination unit 190 and restores the original signals to restore the original signals. Converts to G and B signals.

As described above, according to the present invention, the video compression encoding method and the decoding method for fixing bits according to the present invention provide a DC of a block in which DCT processing is performed on a predetermined coding unit in order to fix the amount of bits efficiently output in a digital video apparatus. The coefficients are encoded according to each block order, and the AC coefficients are arranged in predetermined pixels having a large absolute value, thereby encoding and transmitting position information and data values of the selected pixel, thereby improving data compression efficiency.

Claims (3)

A video compression coding method for dividing an original video signal into a luminance signal and a chrominance signal, dividing it into blocks having a predetermined size, performing discrete cosine transform (DCT), and quantizing and encoding a DCT coefficient; Encoding a DC coefficient among the plurality of DCT coefficients quantized in the divided block units according to a block order; Arranging AC coefficients of the divided blocks into predetermined pixels having a large absolute value; And encoding the AC coefficients arranged in the arrangement process into position information and data values, thereby fixing the amount of data output bits. The image compression protection method according to claim 1, wherein the position information is represented by 6 bits which can express 0 to 63 for 8 × 8 blocks. DC coefficients among a plurality of DCT coefficients quantized in divided block units are encoded according to a block order, and AC coefficients of each block are arranged in predetermined pixels having a large absolute value as position information and data values with respect to the arranged AC coefficients. An image compression decoding method for reconstructing inverse quantized coded signals, inverse discrete cosine transforming the inverse quantization coefficients, and outputting the inverse video signal; A first step of decoding a DC coefficient of each block according to the coding order of the divided block units and restoring to a first position of each block; A second step of restoring the AC coefficient to the corresponding position of each block with original data according to the predetermined position information; And a third process of restoring all AC coefficients without position information in the second process to " 0 ".