Training algorithm of the codebooks

An iterative training method is proposed for the design of random codebooks and channel code mapping tables for a CELP coder. The method is based on a structured excitation source, including a conjugate structure, pitch period repetition, and integrated mapping to channel code. All training procedures use a closed-loop distortion measure, which minimize perceptually weighted distortion between the input and the synthesized speech. The training improves SNR by around 1 dB and improves subjective quality. The channel code mapping and channel-matched distortion measure increase robustness against channel errors.