Some considerations relating to the performance of variable-information-rate-source to constant-transmission-rate schemes of data compression

Some aspects relating to the performance of variable-source-rate to constant-transmission-rate schemes of data compression are considered. The question of buffering at the transmitter and the receiver is considered, and expressions are derived for the necessary minimum delay that has to be introduced at the transmitter and the receiver if distortion is to be avoided. Also, a ‘symbol-injection’ system is considered, and an expression is derived for the system delay necessary to avoid distortion. The results of a statistical analysis of lowpass filtered speech are presented, and these results are then used to obtain estimates of the necessary minimum overall system delay, and the necessary buffer sizes, in a system of speech coding based on the use of the waveform segments between the real zeros of speech. Also, estimates are provided of the period of time that the output will contain distortion if a delay is used that is less than the minimum necessary to avoid distortion.