JPH0257084A - Moving image encoding processing system - Google Patents

Abstract

PURPOSE:To remove a block-shaped noise to be generated in a background part attributing to the fluctuation of a light source or the like by firstly detecting the background part and preventing the differential signal between frames of the background area from being transmitted by the prevention of the encoding of the part. CONSTITUTION:A background area detection circuit 4 detects a background area block with the use of an input image frame, an input image preceding to one-encoded frame, namely an image frame being stored in a frame memory 2 and a reproduction image preceding to one-encoded frame, namely an image frame being stored in a frame memory 7 and sends out a background area instruction signal to an inter-frame prediction circuit 3 with a movement compensation and an inter-frame differential image encoding circuit 5. The prediction circuit 3 calculates the inter-frame differential image executing the movement compensation through the input image and the reproduction image preceding to one-encoded frame. In this case, the movement compensation is not executed in the background part. The encoding circuit 5 encodes the inter-frame differential image and outputs an output code and the local decoding signal of the inter-frame differential image. The background part is encoded so that the local decoding signal may turn to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] In a video encoding processing method in which inter-frame differences are divided into blocks and encoded for each block, a phenomenon occurs in which block-like noise stands out in the background. The present invention removes this block noise and obtains a high-quality reproduced image. Particularly in moving images such as video conferences and video calls, the brightness of the background changes to some extent due to fluctuations in the light source and the like. If this amount of change is a value near the boundary between whether or not that part is determined to be a moving area and transmitted, the difference value of a certain background block will be transmitted, but the difference value of the background block next to it will be transmitted. A phenomenon occurs in which the difference value is not transmitted. The reproduced image observed in such a case contains block-like noise in the background, giving an unnatural impression to the viewer. In the present invention, the background portion is first detected.

Furthermore, by not encoding that portion, generation of block noise based on the above principle is suppressed.

[Industrial application field]

The present invention relates to a high-efficiency video encoding processing method.

[Conventional technology]

Conventionally, three images are divided into blocks and a method with high coding efficiency, such as orthogonal transform coding or vector quantization, is applied to the interframe difference image, which improves the video coding efficiency. It has been planned.

[Problems to be Solved by the Invention] However, in a video encoding processing method in which inter-frame differences are divided into blocks and encoded for each block, differences in brightness or color may appear in the background area of the reproduced image. occurs,
It gave an unnatural impression to the observer. This occurs due to the following reasons. That is, in moving images such as video conferences and video calls, the brightness of the background changes to some extent due to fluctuations in the light source and the like. If this amount of change is a value near the boundary between whether or not that part is determined to be a moving area and transmitted, the difference value of a certain background block will be transmitted, but the difference value of the background block next to it will be transmitted. A phenomenon occurs in which the difference value is not transmitted. In such a case, the reproduced image observed will contain block-like noise in the background.

[Means for solving problems]

In order to solve these problems, the present invention detects the background area in the input image and treats that area as a still part of the moving image, thereby eliminating block noise occurring in the background area. Remove. Furthermore, the input image is divided into blocks, and it is determined for each block whether or not the block is a background area. first.

(i) Input image frame r1 at a certain time.

(ii) Image frame f2 created manually before fl
and.

(iii) In the image frame g2 obtained by decoding f2, the average value of the difference between [1 and f2 of a certain block is a1
, the variance is vl.

(iv) The variance of the difference between fl and g2 of the block is v2
゜ (V) The three thresholds are th1, th1, th2, th3
When.

If a1<th1, vl<th2, and v2<th3, the block is determined to be a background area.

Blocks determined to be background regions are regarded as static regions and are not subjected to motion compensation processing or quantization processing.

[For production]

By applying the present invention, it is possible to remove block noise that occurs in the background due to fluctuations of a light source or the like.

〔Example〕

FIG. 1 shows the configuration of an embodiment of the present invention. In the figure, 1 is an input terminal, 2 is a frame memory, 3 is a motion compensation material interframe prediction circuit, and 4 is a background area detection circuit.

5 is an inter-frame differential image encoding circuit, 6 is a frame memory update circuit, 7 is a frame memory, and 8 is an output terminal. Note that in the figure, the portion surrounded by a chain line may be considered to be a portion added in the present invention.

An input image is input from input terminal 1. The background area detection circuit 4 inputs an input image frame f1, an input image of one encoded frame before, ie, an image frame f2 stored in the frame memory 2, and a reproduced image of one encoded frame before, ie, stored in the frame memory 7. image frame g
2 is input. And block by block.

(i) Average value a1 and variance vl of the difference between fl and f2 (ii) Calculate the variance of the difference between fl and g2 of the block, using three appropriate thresholds th1, th2, and th3.

a 1 < t h 1 and vl < th2 and v2 < t
A block with h3 is defined as a background area block, and a block with no h3 is defined as a moving area block. The information is sent to the motion compensation material interframe prediction circuit 3 and the interframe difference image encoding circuit 5 as a background area instruction signal. The motion compensation material inter-frame prediction circuit 3 calculates an inter-frame difference image subjected to motion compensation from the input image and the reproduced image one encoded frame before. At this time, according to the background area instruction signal.

Motion compensation is not performed on the background part of the input image. The interframe difference image encoding circuit 5 encodes the interframe difference image and outputs an output code and a locally decoded signal of the interframe difference image. At this time, according to the background area instruction signal,
In the background part of the input image.

Encoding is performed so that the locally decoded signal of the interframe difference image becomes zero. The frame memory update circuit 6 calculates a reproduced image from the locally decoded signal of the inter-frame difference signal and the reproduced image one encoded frame before.

It is stored in the frame memory 7. The output sign is output terminal 8
is output from.

FIG. 2 shows a flowchart of the main part of the present invention.

Process (2) corresponds to the process for selecting fl, f2, and g2 in the above. Process (2) corresponds to the process for determining al, vl, and v2 in the above. Process (2) corresponds to the process of checking whether the above conditions al<thL, vl<th1, th2, and v2<th3 are satisfied. The process (2) corresponds to the encoding process for the moving area block, and the process (2) corresponds to the encoding process for the background area.

〔Effect of the invention〕

As described above, according to the second aspect of the present invention, since the inter-frame difference signal of the background area is not transmitted, it is possible to remove block noise generated in the background area due to fluctuations of the light source or the like.

[Brief explanation of the drawing]

FIG. 1 shows the configuration of an embodiment of the present invention, and FIG. 2 shows a flowchart of the main parts of the present invention. 1 is an input terminal, 2 is a frame memory, 3 is a motion compensation material interframe prediction circuit, 4 is a background area detection circuit, 5 is an inter-frame differential image encoding circuit, 6 is a frame memory update circuit, 7 is a frame memory, and 8 is an output terminal. Patent applicant Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] (1) In a method that performs a video encoding processing method by encoding an inter-frame difference image or an inter-frame difference image with motion compensation, an input image is separated into a background area and a moving area in advance, and the background A moving image encoding processing method characterized in that a region is treated as a completely still region, and a differential image of the background region is not transmitted. (2) Divide the input image into blocks, and divide the input image frame f1, the image frame f2 that was input before the frame f1, and the image frame g2 obtained by decoding the frame f2 into blocks. The average value of the difference between f1 and the above f2 is a1, the variance is v1,
The variance of the difference between the above f1 and the above g2 of the block is v2
, when the three thresholds are th1, th2, and th3,
2. The video encoding processing method according to claim 1, wherein when a1<th1, v1<th2, and v2<th3, the block is set as a background region.