JPH05268588A - Coder - Google Patents

Abstract

PURPOSE:To attain highly efficient coding through the use of a characteristic of a quantization transformation coefficient string of each block by setting an end code representing end of coding to each partial coefficient string and using only a final end code among consecutive end codes when the end codes appear consecutively. CONSTITUTION:The coder consists of an orthogonal transformation device 1 applying orthogonal transformation to blocked television signals, a quantization device 2 applying quantization to a transformation coefficient of each block obtained by the orthogonal transformation device 1 and a coder 3 coding the quantization transformation coefficient string of each block obtained by the quantization device 2. The coder 3 uses a division means to divide a quantization transformation coefficient string of each block into M sets of partial coefficient strings when the quantization transformation coefficient string is subject to variable length coding and the variable length coder applies variable length coding to each partial coefficient string. In this case, an end code representing the end of coding is set to each partial coefficient and when end codes appear consecutively, only a final end code among the consecutive end codes is used for the coding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal coding apparatus.

[0002]

2. Description of the Related Art Generally, in a coding device for compressing a video signal, an input image is first divided into small blocks of N × N pixels, each block is subjected to orthogonal transform, and the resulting transform coefficient string is quantized. Encoding is being done.

As a coding method, a quantized transform coefficient string of a one-dimensional array is coded in order from the beginning. A quantized transform coefficient whose quantized output is not 0 (hereinafter referred to as a significant transform coefficient) is as follows. Is encoded as follows. First, the number of quantized transform coefficients (hereinafter referred to as insignificant transform coefficients) having a quantized output of 0 sandwiched between the significant transform coefficient to be coded and the already-signed significant transform coefficient immediately before it are calculated. The run length L is obtained. When the run length L is 0, the significant conversion coefficient is encoded using an encoding table (hereinafter referred to as encoding table 1). When the run length L is 1 or more, first, the coding table 1 is used to code a symbol for identifying the coding mode of the run length (hereinafter referred to as RL), and then the run length L is set to the coding table 1. Encodes using another encoding table (hereinafter referred to as encoding table 2), and finally encodes the quantized output using encoding table 1. When the encoding of all significant transform coefficients in the small block is completed, the encoding table 1 is used to encode a symbol indicating the end of encoding (hereinafter referred to as EOB). Such an encoding method is described, for example, on page 203 to page 204 of image information compression (edited by the Television Society).

[0004]

However, in the above-mentioned conventional coding apparatus, since the coding table 1 is set by the occurrence probability of the significant transform coefficient in the small block, the occurrence probability of the significant transform coefficient is, for example, There is a problem that the encoding table 1 does not necessarily correspond appropriately depending on the characteristics of the quantization conversion coefficient sequence, such as the difference between the low frequency band part and the high frequency band part of the frequency band of the quantized conversion coefficient sequence. Was there.

The present invention solves the above-mentioned drawbacks of the conventional coding apparatus, and an object of the present invention is to provide a video signal coding apparatus having higher efficiency than the conventional one.

[0006]

In order to achieve this object, an encoding apparatus according to the present invention comprises an orthogonal transformer for dividing a television signal into blocks and performing orthogonal transformation, and each block obtained by the orthogonal transformer. A quantizer for quantizing the transform sequence number of, and an encoder for coding the quantized transform coefficient sequence of each block obtained by the quantizer. When variable length encoding the quantized transform coefficient sequence of a block, the quantized transform coefficient sequence of each block is divided into M partial coefficient sequences, each partial coefficient sequence is variable length encoded, and each partial coefficient is encoded. An end code indicating the end of encoding is set for each column, and when the end codes appear consecutively, only the trailing end code of the continuous end codes is used.

[0007]

With this configuration, the coding apparatus of the present invention can perform highly efficient coding by utilizing the characteristics of the quantized transform coefficient string of each block.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the basic configuration of the present invention. In FIG. 1, reference numeral 1 is an orthogonal transformer for dividing a television signal into blocks to perform orthogonal transformation, 2 is a quantizer for quantizing the transformation sequence of each block obtained by the orthogonal transformer 1, 3 Is an encoder that encodes the quantized transform coefficient sequence of each block obtained by the quantizer 2.

When variable length coding the quantized transform coefficient sequence of each block, the encoder 3 first divides the quantized transform coefficient sequence of each block into M partial coefficient sequences by the dividing means 4. To divide. Next, each partial coefficient sequence is variable-length coded by the variable-length encoder 5. At this time, an end code indicating the end of encoding is set for each partial coefficient sequence, but when the end codes appear consecutively, only the end code located behind the continuous end codes is encoded.

Next, this embodiment will be described in detail based on (FIG. 2) to (FIG. 5). (Fig. 2) shows 4x4 input image
The transformation coefficient string of a two-dimensional array obtained by dividing the pixel into small blocks and performing orthogonal transformation is shown, and the numbers in the figure show transformation coefficients. FIG. 3 shows the order of scanning the transform coefficient sequence of the two-dimensional array of FIG. 2 into a one-dimensional array (hereinafter referred to as the scan order). The scan order of FIG. A one-dimensional array of transform coefficient sequences is shown in FIG. (FIG. 5) is a quantized transform coefficient sequence obtained by performing quantization on the transform coefficient sequence of (FIG. 4), and the numbers in the figure represent quantized transform coefficients. 1, 2, 3, 4, 5, 12 are significant conversion coefficients. The quantization error is constant because there is one quantizer table.

At this time (FIG. 5), the scan order 1 to 5 (FIG. 3) corresponding to the quantized transform coefficient is set to the first partial coefficient sequence,
Same order 6 to 9 as second partial coefficient sequence, same order 10 to 14
Is the third partial coefficient sequence, the same order 15 and 16 is the fourth partial coefficient sequence, EOB of the first partial coefficient sequence is EOB1, EOB of the second partial coefficient sequence is EOB2, and EOB of the third partial coefficient sequence is EOB.
OB3 and the EOB of the fourth partial coefficient sequence are EOB4. Further, the significant conversion coefficients in (FIG. 5) are coded by using the coding table provided for each partial coefficient sequence, and are 12c, 5c, 4c, 3c, 2c for the first partial coefficient sequence, and The two partial coefficient sequences are 1d and 2d, the third partial coefficient sequence is 1e, the encoded RL is a, and when the run length L is 0, 2, 4 the run length L is encoded table 2. The codes encoded by using are defined as 0b, 2b, and 4b. That is, the partial coefficient sequence is composed of two partial coefficient sequences of low band and high band in the two-dimensional frequency band.

The code obtained when the quantized transform coefficient (FIG. 5) is coded under the above conditions will be described.

The code obtained under the above conditions is (Equation 1). Here, there is no significant conversion coefficient between EOB3 and EOB4 of (Equation 1). In such a case EOB3 and EO
The insignificant conversion coefficient between B4 is omitted and set to (Equation 2). At this time, EOB3 and EOB4 appear consecutively, so E
OB3 is omitted and is set to (Equation 3).

[0015]

[Equation 1]

[0016]

[Equation 2]

[0017]

[Equation 3]

As described above, according to the present embodiment, it is possible to perform highly efficient coding by utilizing the characteristics of the quantized transform coefficient string of each block.

Although not shown in the above embodiment, the significant conversion coefficient between EOB2 and EOB4 is 1 as shown in (Equation 3).
To improve coding efficiency when there are only
There is also a method of converting the code (Equation 4) between EOB2 and EOB4 into (Equation 5) and omitting EOB2 for encoding. However, when converting (Equation 4) into (Equation 5), 0 and 1 are converted into the second
The codes obtained by encoding with the encoding table used for the partial transform coefficient sequence are 0d and 1d. The code obtained by the method is (Equation 6).

[0020]

[Equation 4]

[0021]

[Equation 5]

[0022]

[Equation 6]

Although the input image is a television signal in this embodiment, the input image may be an image obtained by subjecting the television signal to pre-processing such as subband division. In the present embodiment, the setting of the division of the input image into small blocks, the transform coefficient sequence obtained by orthogonal transformation, the scan order, the code, and the quantization in the quantizer are as described above. Division, the transform coefficient sequence obtained by orthogonal transformation, the scan order, the code, and the quantization in the quantizer may be set arbitrarily. For example, the orthogonal transform of the orthogonal transformer may be a three-dimensional orthogonal transform, and the partial coefficient sequence may be composed of two partial coefficient sequences of a low band and a high band in a three-dimensional frequency band.

[0024]

As described above, the coding apparatus according to the present invention has an orthogonal transformer for dividing a television signal into blocks and performing orthogonal transformation, and a transformation sequence of each block obtained by the orthogonal transformer. A quantizer for performing quantization; and an encoder for performing encoding on the quantized transform coefficient sequence of each block obtained by the quantizer, wherein the encoder is for quantizing each block. When variable-length coding a transform coefficient string, the quantized transform coefficient string of each block is divided into M partial coefficient strings, each partial coefficient string is variable-length coded, and each partial coefficient string is coded. When the end code indicating the end is set, and when the end codes appear consecutively, the characteristics of the quantized transform coefficient string of each block are encoded by performing the encoding only on the trailing end code of the continuous end codes. Can be used for highly efficient encoding. Excellent encoding device can be realized that.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic configuration of the present invention.

FIG. 2 is a diagram showing a transform coefficient sequence of a two-dimensional array in an embodiment of the encoding device of the present invention.

FIG. 3 is a diagram showing a scan order of transform coefficient sequences in the embodiment.

FIG. 4 is a diagram showing a conversion coefficient sequence of a one-dimensional array in the same embodiment.

FIG. 5 is a diagram showing a quantized transform coefficient string in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Orthogonal transformer 2 Quantizer 3 Encoder 4 Dividing means 5 Variable length encoder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toyohiko Matsuda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. An orthogonal transformer for dividing a television signal into blocks to perform orthogonal transformation, a quantizer for quantizing a transform sequence of each block obtained by the orthogonal transformer, and a quantizer. The obtained quantized transform coefficient sequence of each block is configured by an encoder that encodes, and the coder performs the variable length encoding of the quantized transform coefficient sequence of each block, each block Of the quantized transform coefficient sequence is divided into M partial coefficient sequences, each partial coefficient sequence is variable-length coded, an end code indicating the end of encoding is set for each partial coefficient sequence, and the end code is continuous. When appearing, the coding device is characterized in that only the trailing end code of the continuous end codes is used. 2. A coding apparatus according to claim 1, wherein the variable length coding table of each partial coefficient sequence of the encoder is changed for each partial coefficient sequence. 3. The orthogonal transform of the orthogonal transformer is a two-dimensional orthogonal transform, and the partial coefficient string is composed of two partial coefficient strings (M = 2) of a low band and a high band in a two-dimensional frequency band. The encoding device according to claim 1 or 2, characterized in that. 4. The orthogonal transform of the orthogonal transformer is a three-dimensional orthogonal transform, and the partial coefficient string is composed of two partial coefficient strings (M = 2) of a low band and a high band in a three-dimensional frequency band. The encoding device according to claim 1 or 2, characterized in that. 5. The encoding apparatus according to claim 1, wherein when the quantizer performs quantization, one quantization table is used regardless of the number of end codes.