Nec Corporation

Syuzo Tsugane

Mitsuo Nishiwaki

A system for coding video signals e.g. television signals in block units is disclosed. The coding system comprises a synchronization detector for detecting a frame synchronization from the video signal, and a block former operative to divide the video signal in block units per a predetermined number of lines by using a picture frame synchronization signal detected by the synchronization detector as a reference. When the number of lines included in a block immediately before the subsequent picture frame synchronization signal is less than the predetermined number of lines, the block former designates the block as an ineffective block. The coding system further comprises a coder operative to apply a coding processing to the blocks except for the ineffective block designated by the block former in accordnace with a predetermined coding procedure, and transmitter operative to multiplex coded data outputted from the block former and coder, position information of the first block immediately after the picture frame synchronization signal, and the number of lines within the ineffective block so as to transmit the multiplexed signal thus obtained. Thus, when the input video signal is asynchronously switched, the coding system necessarily executes only a processing per each block, thus providing a reproduced picture image free from distortion on the side of a receiving station.

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Tokyo, Japan

Syuzo Tsugane