JPH02217087A - Decoder for moving picture signal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a moving picture signal encoding device used in a teleconferencing system, a teleconference system, etc. The configuration of the device is shown.

In FIG. 3, orthogonal transform coefficients are obtained by orthogonally transforming the inter-frame difference signal and original image signal of a moving image in blocks of 8 pixels x 8 lines, for example, using an orthogonal transform circuit 11, and the orthogonal transform coefficients are converted into quantum It is quantized by the quantizer 12, and the quantization level is output as is by the coefficient truncation circuit 33, or is truncated to 10'', and the quantization level is encoded by the coefficient encoding circuit 34 and temporarily stored in the transmission buffer 10. and send.

Here, the coefficient truncation determination circuit 36 determines whether the amount of information remaining and accumulated in the transmission buffer 19 exceeds the listening limit, and if it exceeds the listening limit, blocks the coefficient truncation instruction signal. It is output to the coefficient truncation circuit 33 in units. In response to this coefficient truncation instruction signal, the coefficient truncation circuit 33 sets the quantization level from the quantizer 12 to "0".
It is output to the coefficient encoding circuit 34 as

Therefore, according to the conventional example, when the previous block has a large amount of code, the orthogonal transformation coefficients of the next block are discarded, so that the amount of information to be transmitted can be compressed.

Problems to be Solved by the Invention However, in the above-mentioned conventional video signal encoding device,
When the subject moves a lot or when the entire screen changes (scene change), the inter-frame difference signal becomes large and many orthogonal transformation coefficients are generated. If the orthogonal transform coefficients of the block are simply discarded, there is a problem in that the quality of the image reproduced on the receiving side deteriorates.

In view of the above conventional problems, the present invention aims to provide a video signal encoding device that can compress the amount of information to be transmitted and can prevent the quality of reproduced images on the receiving side from deteriorating. purpose.

Means for Solving the Problems In order to achieve the above object, the present invention encodes the quantization levels of DC coefficient components and AC coefficient components of orthogonal transform coefficients when the code amount of the previous block is relatively small, On the other hand, when the code amount of the previous block is relatively large, the AC coefficient component of the orthogonal transform coefficient is discarded and the quantization level of the DC coefficient component is encoded.

With the above configuration, the present invention cuts off the AC coefficient component of the orthogonal transform coefficient when the code amount of the previous block is relatively large, so the amount of information to be transmitted can be compressed, and the DC coefficient component is not truncated, so the playback quality on the receiving side does not deteriorate.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a moving picture signal encoding device according to the present invention, FIG. 2 is an explanatory diagram of the operation of the coefficient encoding circuit of FIG. 1, and the configuration shown in FIG. The same reference numerals are given to the same parts.

In FIG. 1, reference numeral 11 denotes an orthogonal transformation circuit that orthogonally transforms the inter-frame difference signal or original image signal of a moving image in units of blocks of 8 pixels x 8 lines, for example, to obtain orthogonal transformation coefficients; 12; is orthogonal transform circuit 1
A quantizer 13 quantizes the orthogonal transform coefficients obtained by quantizer 12.
As will be described later, this is an AC component truncation circuit that outputs the AC coefficient component as is or cuts off the quantization level of the AC coefficient component and outputs the quantization level as "0".

14, when the amount of code of the previous block is relatively small,
There is a mode that encodes the quantization level of the DC coefficient component and AC coefficient component of the orthogonal transform coefficient, and when the code amount of the previous block is relatively large, the AC coefficient component of the orthogonal transform coefficient is truncated and the quantization level of the DC coefficient component is This is an encoding mode switching circuit that switches the mode for encoding the encoding level.

As shown in FIG. 2 fa), the encoding mode switching circuit 14 encodes the quantization levels of the DC coefficient component and the AC coefficient component, and outputs mode information (
1 bit), the codes of the luminance signal Y, color difference signals Cr and Cb in the block, and the code EOB indicating the boundary of each signal. As shown, the quantization level of only the DC coefficient component is encoded, and mode information indicating the encoding mode of that block, a luminance signal Y, and a color difference signal Cr for that block are encoded.

It includes a coefficient encoding circuit 14b that outputs the code of cb, and switchers 14c and 14d for selecting the coefficient encoding circuits 14a and 14b'i.

Reference numeral 19 denotes a transmission buffer for temporarily storing and transmitting the codes from the coefficient encoding circuits 14a and 14b, and 20 determines whether the amount of information remaining and accumulated in the transmission buffer 19 exceeds a threshold value. and if the threshold is exceeded, the AC
Switcher 1 of AC component truncation circuit 13 and encoding mode switching circuit 14 transmits the coefficient component truncation instruction signal block by block.
This is a coefficient truncation determination circuit that outputs to 4C and 14d.

Next, the operation of the above embodiment will be explained.

In FIG. 1, a coefficient truncation determination circuit 20 determines whether the amount of information remaining and accumulated in the transmission buffer 19 exceeds a threshold value, and if it exceeds the threshold value, an AC coefficient component truncation instruction signal is sent. If the coefficient truncation determination circuit 20 does not output an AC coefficient component truncation instruction signal, the AC component truncation circuit 13
outputs the quantization level from the quantizer 12 as it is to the encoding mode switching circuit 14, and the encoding mode switching circuit 1
4, the coefficient encoding circuit 14a encodes the quantization levels of the C coefficient component and the AC coefficient component as shown in FIG. The codes of the luminance signal Y, color difference signals Cr and Cb in the block, and the code EOB indicating the boundaries of the respective signals are output.

On the other hand, when the coefficient truncation determination circuit 20 outputs the AC coefficient component truncation instruction signal, the AC component truncation circuit 13 truncates the quantization level of the AC coefficient component from the quantizer 12 to quantize only the DC coefficient component. The coefficient encoding circuit 14a outputs the encoding level to the encoding mode switching circuit 14, and the coefficient encoding circuit 14a outputs the encoding level to the encoding mode switching circuit 14.
As shown in FIG. 2, the quantization level of only the DC coefficient component is encoded, and the mode information indicating the encoding mode of the block, the luminance signal Y, and the color difference signal Cr in the block.

Outputs the sign of cb.

Therefore, according to the above embodiment, the orthogonal transform coefficients cut off the quantized AC coefficient components, so the amount of information to be transmitted can be compressed, and since the DC coefficient components are not cut off, the movement of the subject can be reduced. The image quality on the receiving side does not deteriorate even when the screen size is large or when the entire screen changes (scene change).

Further, according to the above embodiment, when the AC coefficient component is to be discarded, the luminance signal Y and the color difference signal Cr are used.

Since the code EOB indicating the boundary of each signal of the cb code is not required, the compression rate is further increased. , the DC coefficient component of the orthogonal transform coefficient and A
The quantization level of the C coefficient component is encoded, and on the other hand, when the code amount of the previous block is relatively large, the AC coefficient component of the orthogonal transform coefficient is truncated and the quantization level of the DC coefficient component is Since the encoding level is encoded, it is possible to compress the amount of information to be transmitted, and it is also possible to prevent the image quality on the receiving side from deteriorating.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a moving image signal encoding device according to the present invention, FIG. 2 is an explanatory diagram of the operation of the coefficient encoding circuit of FIG. 1, and FIG. FIG. 2 is a block diagram showing an image signal encoding device. 11. Orthogonal transform circuit, 12. Quantizer, 13.
AC component truncation circuit, 14..., encoding mode switching circuit, 14a, 14b-coefficient encoding circuit, 1
4C. 14d...Switcher, 19...Transmission buffer, 20...
- Coefficient truncation judgment circuit.

Claims (1)

[Scope of Claims] Orthogonal transform means for orthogonally transforming a moving image signal block by block and outputting orthogonal transform coefficients; means for quantizing the orthogonal transform coefficients; and when the amount of code of the previous block is relatively small. a first encoding means for encoding a quantization level of a DC coefficient component and an AC coefficient component of the orthogonal transform coefficient; a second encoding means for encoding a quantization level of a component.