High Pitch Delay Resolution Technique for Tonal Language Speech Coding Based on Multi-Pulse Based Code Excited Linear Prediction Algorithm

Problem statement: In spontaneous speech communication, speech coding is an important process that should be taken into account, since the quality of coded speech depends on the efficiency of the speech coding algorithm. As for tonal language which tone plays important role not only on the naturalness and also the intelligibility of the speech, tone must be treated appropriately. Approach: This study proposes a modification of flexible Multi-Pulse based Code Excited Linear Predictive (MP-CELP) coder with multiple bitrates and bitrate scalabilities for tonal language speech in the multimedia applications. The coder consists of a core coder and bitrate scalable tools. The High Pitch Delay Resolutions (HPDR) are applied to the adaptive codebook of core coder for tonal language speech quality improvement. The bitrate scalable tool employs multi-stage excitation coding based on an embedded-coding approach. The multi-pulse excitation codebook at each stage is adaptively produced depending on the selected excitation signal at the previous stage. Results: The experimental results show that the speech quality of the proposed coder is improved above the speech quality of the conventional coder without pitch-resolution adaptation. Conclusion: From the study, it is a strong evidence to further apply the proposed technique in the speech coding systems or other speech processing technologies.