JPH0346481A - Movement compensation error correction system - Google Patents

Abstract

PURPOSE:To obtain a reproduced picture with excellent quality by using an estimate moving vector so as to extract a picture element block, replacing the block into other picture element block so as to correct the transmission error. CONSTITUTION:Address information ad1 of a picture element block affected by a transmission error is inputted to a delay circuit 1 for one block line delay and retarded address information ad2 is inputted to an address generating circuit 2, from which an address ad3 of a surrounding picture element block is generated and when the production of all addresses is finished, a timing signal tm1 is outputted. Then the information ad3 is inputted to a moving vector memory 3, revised by a moving vector mv1 from a moving vector decoder and the extracted moving vector my2 is sequentially inputted to a moving vector estimate circuit 4. When the signal tm1 is inputted, an estimate vector mv3 is outputted and fed to a frame memory 5, a picture element block signal cd is outputted, which is used for error correction.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for encoding and transmitting digital video signals for each pixel block, such as in video conferences and video telephone calls, and in particular, the present invention relates to a method for encoding and transmitting digital video signals for each pixel block, such as video conferences and video calls. The present invention relates to a method for performing motion compensated interframe coding using the detected data.

(Prior art) In a system that digitizes and encodes a video signal, such as a video conference or video telephone, to reduce the transmission bit rate and transmit the video signal, the video signal is encoded independently for each pixel block. There are many ways to convert. for example,
Some methods have been put into practical use, such as those that perform discrete cosine transformation on the prediction error signal obtained by predictive coding, and those that similarly perform vector quantization. Furthermore, in such encoding systems, it is widely practiced to detect a motion vector from a moving image signal and use this to perform motion compensated interframe prediction.

If a transmission error occurs in such a communication system and a normal signal is lost, a portion of the reproduced image will be destroyed on the receiving side. A conventional method to deal with this problem is to notify the transmitting side when a -degree transmission error occurs, and stop decoding until a new forced intra-frame encoded image frame is transmitted. A method is known in which a pixel block affected by a transmission error is replaced with a block at the same position in the previous frame.

(Problem to be solved by the invention) However, in the former case, every time a transmission error occurs, the reproduction (
(reception) video images are interrupted, significantly impairing service quality. Furthermore, the latter has the problem that if there is movement in the image portion affected by the transmission error, very noticeable deterioration occurs in the reproduced image.

An object of the present invention is to obtain a reproduced (received) image of good quality even when a transmission error occurs and a normal image signal is lost.

(Means for Solving the Problem) In order to achieve this object, the present invention relates to a pixel block in an image frame in which a normal signal is lost due to a transmission error on the receiving side. , by estimating the motion vector of the pixel block using Tor, extracting a pixel block corresponding to the pixel block from the previous image frame using this estimated motion vector, and replacing it with the pixel block. It is characterized by correcting transmission errors.

(Principle of the invention) The present invention will be explained in detail using FIG.

FIG. 1 shows an image frame A including an image block in which a normal signal is lost due to a transmission error, and an image frame B just before it.

X on image frame A is a pixel block on image frame A that has been affected by a transmission error (hereinafter referred to as error pixel block X). A, B, C, and D are pixel blocks surrounding the error pixel block X (hereinafter referred to as surrounding pixel blocks).

Xo is a pixel block on image frame B at the same position as the error pixel block X (hereinafter referred to as the same position pixel block X°
That's what it means. ). M is a pixel block on image frame B that can be estimated to have the same content as error pixel block X (hereinafter,
This is called an estimated pixel block M. ). Note that although the number of peripheral pixel blocks is set to 4 here as an example, this value is not limited in the present invention.

Now, in FIG. 1, if pixel block X is affected by a transmission error, surrounding pixel blocks (A, B, C, D
) is extracted from the received data. This is Va
, ■b, ■c, and ■d.

Next, the motion vector V of the error pixel block X is estimated from the motion vectors of surrounding pixel blocks.

In the present invention, the method for estimating the motion vector (2) is not particularly limited. For example, there are two methods: ■ A method to take the vector arithmetic average, ■ A method to take an intermediate value, etc. In the case of ■, the estimated motion vector V is calculated using the following formula. The motion vector V can be estimated with high accuracy. Using this motion vector V, an estimated pixel block M that is reversely shifted by the motion vector ■ from the same position pixel block X° of the previous image frame B is extracted, and the error pixel block X is replaced with the estimated pixel block M.

By performing motion compensation as described above and correcting pixel blocks affected by transmission errors, a reproduced image with high image quality can be obtained.

(Embodiment) FIG. 2 is a block diagram of an apparatus in an embodiment according to the present invention.

The address information adl of the pixel block affected by the transmission error is manually input to the delay circuit 1 corresponding to one block line. The reason for the delay is that 1 as a peripheral pixel block.
This is because the block at the block line destination is used. The delayed address information ad2 is input to the address generation circuit 2.

The address generation circuit 2 generates an address ad3 of a peripheral pixel block of the block having the address ad2. Note that since there are a plurality of peripheral pixel blocks, ad3 is generated multiple times, and the timing signal tml is output when generation of all addresses is completed. Next, ad3 is input to the motion vector memory 3.

The motion vector memory 3 stores the motion vector of each pixel block, and the motion vector mvl from the motion vector decoder
It is updated sequentially.

The motion vector mv2 of the peripheral pixel block taken out from the motion vector memory 3 by ad3 is sequentially input to the motion vector estimation circuit 4. The motion vector estimating circuit 4 is a circuit that estimates a motion vector of a pixel block affected by a transmission error from a plurality of mv2, and outputs an estimated motion vector mv3 when tml is input.

mv3 is added to the frame memory 5 in which the previous image frame is stored, and thereby the pixel block signal cd on the previous image frame corresponding to the pixel block affected by the transmission error is output and used for error correction.

At the same time, the address ad (same as ad2) of the pixel block affected by the transmission error is output.

(Effects of the Invention) As described above, the present invention relates to a pixel block in an image frame in which a normal signal is lost due to a transmission error on the receiving side, and uses the motion vectors of the surrounding pixel blocks of the pixel block to The estimated motion vector is used to extract a pixel block corresponding to the pixel block from the previous image frame and replace it with the pixel block, thereby reducing transmission errors while suppressing image quality deterioration. can be corrected. Moreover, this can be realized with a simple device using the configuration shown in FIG.

Therefore, the present invention can correct errors without deteriorating image quality even if a transmission error occurs in a service such as a video conference or a video telephone that encodes and transmits a digital video signal for each pixel block. This effect is significant.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the present invention in detail. FIG. 2 is a block diagram of a device in an embodiment according to the present invention. DESCRIPTION OF SYMBOLS 1... Delay circuit, 2... Address generation circuit, 3... Motion vector memory, 4... Motion vector estimation circuit, 5... Frame memory.

Claims (1)

[Claims] In a method in which a digital moving image signal is encoded for each pixel block and transmitted together with the motion vector of each block, on the receiving side, regarding a pixel block in an image frame in which a normal signal is lost due to a transmission error. , estimate the motion vector of the pixel block using the motion vectors of the surrounding pixel blocks of the pixel block, extract the pixel block corresponding to the pixel block from the previous image frame using this estimated motion vector, and extract the pixel block corresponding to the pixel block from the previous image frame. A motion compensation error correction method that corrects transmission errors by replacing the pixel block with the pixel block.