Error detection and control for the parametric information in CELP coders

Optimum quantization and code assignment schemes are described which minimize the subjective quality degradations introduced into the output speech of code excited linear predictive (CELP) coders by channel degradations. The background and basis for use of minimum redundancy for error control are examined. Greater emphasis is placed on adjustment of corrupted parameters to minimize subjective degradation rather than outright bit-by-bit error correction. These schemes are mostly tested on the CELP baseband coder, but they should be applicable to any linear predictive coder. They raise the bit rate of a 4.8-kb/s coder by about 12.5% and its MOS at 2×10^-2 bit error rate by about 21.1% (scale 1-5)