Source Encoding for Good Quality Speech Communications Systems

摘要

The performance of Pulse Code Modulation (PCM), Differential Pulse Code Modulation (DPCM) and Delta Modulation are compared for speech signals. Formulas are presented for the ratios of signal power to quantizing noise power to be expected from operating systems. User reactions to speech quality are related to these signal to noise ratios. For good quality speech encoding systems bit rates of about 25/kilobits/second will be required. At this bit rate, four bit DPCM is the most efficient encoding system to use. The posture taken is conservative--formulas include the effects of equipment misalignment and tandem operation. Most results used herein are not derived but are quoted from other sources. Application to AACOMS and MALLARD are discussed. Also included are brief sections on equipment complexity, dynamic range, the effect of line errors, encryption, the effect of equipment misalignment and tandem operation. (Author)