Design and Real-Time Implementation of a Robust APC Coder for Speech Transmission over 16 Kb/s Noisy Channels. Volume I. Algorithm Design and Simulation

摘要

This report describes the design and development of a real-time robust APC speech coder that transmits high-quality speech over a 16 kb/s channel with fit-error rates of up to 1%. This volume (Vol. I) describes the development, experimental investigation, and speech-quality optimization of 16 kb/s adaptive predictive coders. Important among the various topics treated in this report are: extensive investigation of several existing and new methods for coding the APC residual, adaptive spectral shaping of the quantization noise, causes for an effective remedy of the limit-cycle behavior of the quantizer output, different APC configurations, optimization of APC coders for error-free channels and for error-full channels, tradeoff between voice data rate and error-protection data rate, tandeming of the optimized 16 kb/s APC coder with the 2.4 kb/s LPC-10 coder, and coder performance in noisy backgrounds typical in offices and in air-borne command post environments. Most impressive of the numerous interesting and useful results described in this report is that the final optimized, robust coder design yields speech quality that degrades only slightly as the bit-error rate is increased from 0% to 1%. (Author)