Some Possibilities of Picture Signal Bandwidth Compression

An experimental appraisal of the Cherry-Gouriet proposals, for the bandwidth compression of television signals by variable-velocity coding, has been made. A flying-spot variablevelocity scanner was built for this purpose. The encoding of the signal in this system is done by a nonlinear feedback loop. Qualitative studies on the stability of the loop have been made. It has been found that the effect of the source noise on the encoder performance is extremely important. It is concluded that owing to the limitations of the devices, the variable-velocity scanner is not practically feasible for television transmissions. However, this system seems ideally suited for LF transmission of pictures. The potential bandwidth compression of the B.B.C. test card C has been determined from its run-length statistics. An open-loop system of bandwidth compression has been described which uses variable-rate sampling. Using the statistics obtained from the test card C, the storage requirement of the open-loop system has been assessed.