AN APPLICATION OF DIGITAL SPEECH INTERPOLATION TO VARIABLE RATE CODING

摘要

A theoretical method of evaluating degradations of variable rate coders in a Digital Speech Interpolation (DSI) system is developed.The DSI system carries a fixed bit rate;however,each of the coder has a variable rate.During periods of high activity all active users are served,but at a reduced rate depending on the demand.Comparisons of the degradations are made between the theoretical results and computer simulated results for two types of variable rate coders.Close agreement is observed.Objective quality measures made for speech indicate that a 2:1 compression over the 16 Kb/s fixed rate subband coder can be achieved with a degradation of less than 1 dB if the trunk size of the DSI system is greater than 40.