for an externally arranged frame synchronizer is avoided the decoding system itself incorporates a frame synchronization function in one form the decoding system comprises a buffer memory for temporarily storing video signals that have coded by a predetermined coding algorithm a frame sync signal detector detects frame sync signals out of the video signals temporarily stored in the buffer memory and generates sync detection signals a reference sync signal detector detects reference sync signals provided from outside and generates reference sync detection signals a decoder is responsive to the frame sync and reference sync detection signals to read the video signals out of the buffer memory and to decode the video signals application_number US 37289689 A description in order to facilitate comprehension of the present invention the prior art will be described first fig1 is a block diagram illustrating a video signal transmission system of the prior art a video signal fed to a high efficiency coder 10 via line 1000 is coded by a high efficiency coding algorithm such as predictive coding and supplied to a variable length coder 11 the coded video signal is variable length coded into a variable length vl coded video signal for instance a huffman code by the vl coder 11 the vl coded video signal after being matched to the data transmission speed of a transmission line 3000 by a buffer memory 12 is outputted to the transmission line 3000 another buffer memory 13 temporarily stores the vl coded video signal received via the transmission line 3000 and outputs stored video signal to a line.