a data transfer system for transferring data between a computer and a video recorder / player is disclosed . generating means generate a video signal . coding means code data received from a computer . mixing means mix the coded data with the video signal to carry the data on the video signal . furthermore , separating means separate coded data from a video signal received from a video recorder / player . decoding means decode data separated by the separating means . settable timing means control the rate of transfer of data between the computer and the video recorder / player . a predetermined number of data bits carried on the video signal are carried on each of a plurality of lines of the video signal . each line carries markers to define the beginning and end of the line and when the video signal is decoded , missing data bits on a line are replaced by a predetermined sequence of bits , and each such sequence of bits is detected by an error detector and reconstituted by the original bits by an error correction process .