Adaptive forward-backward quantizer for low bit rate high-quality speech coding

A novel variable-rate linear predictive coding (LPC) parameter quantization scheme is proposed, in which linear prediction is done by using either the current (forward LPC) or previously decoded (backward LPC) speech blocks. The proposed LPC quantization scheme was integrated into the FS1016 Federal Standard CELP coder. Significant LPC bit rate reduction is achieved without compromising the decoded speech quality.