JP2509164B2 - Video signal coding method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a video signal coding system, and more particularly to a coding mode control system in an inter-frame decoding differential coding system having a preprocessing filter.

[Background of technology]

As an encoding method for transmitting a television (TV) signal or the like, an inter-frame difference encoding method in which an inter-frame difference value is encoded and transmitted is generally used. In such an inter-frame differential encoding method, the amount of transmission information increases when the input signal changes, that is, when the screen moves rapidly. Therefore, if the encoding accuracy is constant, the amount of information becomes too large and the buffer memory overflows, and the encoding of the pixels of the entire screen is not completed. To deal with this, before the input signal is encoded, the inter-frame difference information amount is detected by the pre-processing filter, and the encoding mode is controlled according to the change of the information amount, so that when the information amount is large, It is necessary to reduce the amount of information using a coarse coding mode.

[Prior Art and Problems] The coding mode control in the inter-frame differential coding method of the prior art is mainly performed based on the occupied amount and the change of the buffer memory. By the way, when the input signal changes abruptly (for example, a static screen to a dynamic screen, or a dynamic screen to a static screen), the switching of the encoding mode is delayed, and the transcoding of the full screen is not performed, The accuracy of transcoding may be insufficient. Therefore, discontinuity may occur in the reproduced image.

[Object of the Invention]

In view of the above problems, an object of the present invention is to provide a video image in which discontinuity does not occur by switching the coding mode by following the rapid change of the input signal. It is to provide a signal coding method.

[Structure of Invention]

In order to achieve the above-mentioned object, in the present invention, in a video signal encoding method in which an inter-frame difference value of each pixel data of a video signal is encoded and transmitted, before encoding an input signal, A preprocessing filter for detecting the inter-frame difference information amount for each frame is provided, and in the control of the coding mode for switching the coding accuracy, the buffer memory occupation amount, the past coding mode, and the preprocessing filter There is provided a video signal coding method, characterized in that a current coding mode is determined based on a change ratio of an inter-frame difference information amount.

Example of Invention

A video signal encoding system according to an embodiment of the present invention,
It will be described below with reference to the drawings. FIG. 1 shows a circuit configuration for encoding a video signal.

In FIG. 1, 1 is a preprocessing filter, 2 is an encoding circuit, 3 is an encoding mode control circuit, 4 is a code conversion circuit, and 5 is a code conversion circuit.
Is a buffer memory (BM).

The preprocessing filter 1 has a subtraction circuit 11, an addition circuit 12, a frame memory (FM1) 13, and a difference value information amount detection circuit 14. The encoding circuit 2 forms an outer loop for obtaining a difference value between frames and an inner loop for obtaining a difference value between pixels in a frame, and the outer loop is a subtraction circuit 2
1, the difference suppression unit 22, the inner loop circuit 23, the difference expansion unit 24,
It consists of an adder circuit 25 and a frame memory (EM2) 26,
The inner loop circuit 23 includes a subtraction circuit 231, a quantization circuit 232, an addition circuit 233, and a prediction value circuit 234.

In the encoding system shown in FIG. 1, the input signal IN
, The amount of difference information from the previous frame is detected in the preprocessing filter 1. In the preprocessing filter 1, the pixel information for the previous frame stored in the frame memory 13 is output in synchronization with the input signal, and is supplied to the subtraction circuit 11 and at the same time is supplied to the encoding circuit 2. In the subtraction circuit 11, the interframe difference value for the input frame is obtained, supplied to the information amount detection circuit 14, and the input signal is reproduced by the addition circuit 12 and stored in the frame memory 13.

The encoding circuit 14 obtains an interframe difference value for the pixel information of the previous frame supplied from the preprocessing filter 1, and further obtains a difference between the interframe difference value and the predicted value. The composite difference value thus obtained is converted by the code conversion circuit 4 into a variable length code having a code length according to the amount of information, and is supplied to the buffer memory 5. Therefore, when the amount of information about the coded frame is large, the buffer memory 5 overflows before the entire screen is coded. In order to prevent this, the coding mode control circuit 3
Thus, the control of the encoding mode is performed. Encoding circuit 2
As the encoding mode in, the switching of the inter-frame difference value suppression / expansion characteristics for the output of the subtraction circuit 21, the sampling value thinning, and the like are used.

A coding mode control system in the coding system of FIG. 1 will be described. In the encoding mode control circuit 3, the ratio I _{PF of} the frame to be encoded and the frame previously encoded with respect to the inter-frame difference information amount from the information amount detection circuit 14 is calculated.
Is input, and the buffer memory 5 occupies the buffer memory occupied amount of the encoded data for the previously encoded frame.
BOC is input. The coding mode control circuit 3 compares the difference information amount ratio I _PF with a predetermined threshold value I _TH (for example, 2). When the information amount ratio I _PF is larger than the threshold value I _TH , it means that the difference information amount of the frame to be encoded next time is rapidly increasing. In this case, the next coding mode is switched from the previous coding mode to the mode which is coarser by the amount corresponding to the information amount ratio I _PF . When the information amount ratio I _PF is smaller than the threshold value I _TH , the next coding mode is determined from the previous coding mode and the buffer memory occupation amount B _OC . The encoding mode control circuit 3 is composed of, for example, a comparator 31, a ROM 32, and a flip-flop 33 as shown in FIG.

In this way, in the encoding system of FIG. 1, the encoding mode can be switched in advance when the screen changes abruptly, whereby the entire screen can be encoded as much as possible.

〔The invention's effect〕

According to the present invention, in the video signal coding system, it is possible to obtain a reproduced image without discontinuity by appropriately switching the coding mode even when the input signal changes abruptly.

[Brief description of drawings]

FIG. 1 is a diagram showing a video signal encoding system as an embodiment of the present invention, and FIG. 2 is a diagram showing an example of the configuration of an encoding mode control circuit in FIG. (Description of symbols) 1 ... Preprocessing filter, 11 ... Subtraction circuit, 12 ... Addition circuit, 13 ... Frame memory, 14 ... Information amount detection circuit, 2
... Encoding circuit, 21 ... Subtraction circuit, 22 ... Difference suppression unit, 23
…… Inner loop circuit, 231 …… Subtraction circuit, 232 …… Quantization circuit, 233 …… Addition circuit, 234 …… Prediction value circuit, 24 …… Differential expansion unit, 25 …… Addition circuit, 26 …… Frame memory Three
...... Encoding mode control circuit, 31 …… Comparator, 32 …… RO
M, 33 ... Flip-flop, 4 ... Code conversion circuit, 5
…… Buffer memory.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Fukuda 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Fujitsu Limited (72) Inventor Shinichi Maki 1015 Kamikotanaka, Nakahara-ku, Kawasaki-shi, Fujitsu Limited (72) Invention Toshitaka Tsuda 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Fujitsu Limited (56) References IEICE Technical Report, IE81-53 P. 79-84

Claims (1)

(57) [Claims] 1. A video signal encoding system in which an inter-frame difference value of each pixel data of a video signal is encoded and transmitted, and an inter-frame difference information amount for each frame is calculated before an input signal is encoded. A preprocessing filter for detection is provided, and in the control of the coding mode for switching the coding accuracy, the buffer memory occupation amount, the past coding mode, and the change ratio of the inter-frame difference information amount from the preprocessing filter are calculated. A video signal encoding method characterized in that the current encoding mode is determined based on the original.