Television – Bandwidth reduction system – Data rate reduction
Patent
1996-09-30
1998-09-22
Chin, Tommy P.
Television
Bandwidth reduction system
Data rate reduction
348699, 3488451, H04N 732
Patent
active
058121986
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a video coding decoding apparatus which is capable of effectively refreshing a picture and recovering degradation of a picture caused by code error, in a short time.
BACKGROUND ART
Heretofore, there is known a system, as a technique for coding a video, in which a picture in a single frame is divided into blocks of M.times.N (where M and N are natural numbers, respectively). In the technique, data showing the frame, data showing the number of each block and data of a picture belonging to the blocks are coded in a hierarchical structure, and those data are coded by means of a two-dimensional discrete cosine transform (DCT) and a Huffman code (ITU-T Recommendation H. 261). If, at that time, a motion on each block in the continuous inter-frames is estimated, data can be coded in an efficient manner by compensating the motion from a reference data and without coding all of the picture data.
Here, in the example shown in FIG. 1, the block numbers are assigned such that a number assigned to a block located on a left upper end of the explanatory view is "1" and the numbers are gradually sequentially increased toward the right of the same horizontal row. When a block located on the right extremity of the row is reached, a new row is started and a new block number is assigned to each block on this new row from left to right in the same manner as the first row. It should be noted that FIG. 1 shows only one example showing a way for assigning block numbers and any other suitable way for assigning block numbers may be employed in accordance with necessity. In a video coding decoding apparatus in which the above-mentioned coding system is employed, a refreshing operation is carried out in a sequential order of the block numbers for each frame (see arrows of the broken lines). Presuming that the number of a block in which a refreshing operation is carried out in an i-th frame is "1", the number of another block in which a refreshing operation is carried out in the subsequent (i+1)-th frame is "2". It should be noted that such a refreshing operation is carried out on a premise that a communication line, in which a transmission error is negligible, is employed and no consideration is given to a possible degradation caused by code error.
However, in the event that a code error has occurred in an area where a motion compensation is being carried out and this particular area is not to be refreshed in the subsequent frame, degradation of a picture is accumulated without being recovered even when no code error has occurred in the above-mentioned subsequent frame. Consequently, in accordance with the conventional refreshing operation, once a picture degradation occurs, it takes about several dozens of seconds to recover the picture from degradation in the worst case.
DISCLOSURE OF INVENTION
The present invention has been accomplished in view of the above-mentioned problems. It is, therefore, an object of the invention to provide a video coding decoding apparatus in which a refreshing operation for recovering degradation of a picture caused by code error can be carried out efficiently.
In order to achieve the above object, there is provided a video coding decoding apparatus in which a picture in a single frame is divided into blocks of M.times.N (where M and N are natural numbers) and in which an interframe motion compensation prediction is carried out, the video coding decoding apparatus comprising: a motion compensation area and the remaining area and then detecting a shape of the motion compensation area by distinguishing between the motion compensation area and the remaining area; overall motion compensation area from a motion vector in the motion compensation area; and point of the estimated motion vector toward the motion vector, in the motion compensation area.
According to the present invention, a motion compensation area in a video in a single frame is detected by the area shape detecting means, a motion vector (moving direction) of the overall motion compensating area is
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Miki Toshio
Saigusa Masahito
Chin Tommy P.
Johnson John T.
Le Vu
NTT Mobile Communications Network Inc.
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