Conjugate structure celp coder for the ccitt 8-kbit/s standardization candidate
A. Kataoka, Takehiro Moriya, S. Hayashi · 2005
This paper presents a high-quality 8-kbit/s speech coder (Conjugate Structure CELP: CS-CELP) with a 10-ms frame length. CS-CELP is now one of two candidates for the CCITT 8-kbit/s speech coding standard. It uses five unique schemes: LSP quantization using interframe correlation, pre-selection of the codebook search, a conjugate structure, backward adaptation of the vector quantization (VQ) gain, and a cyclic fixed-shape codebook. The first four schemes provide high quality in both error-free and error conditions. The cyclic fixed-shape codebook reduces memory requirements. Subjective testing indicates that the quality of it's coder is equivalent to that of the 32-kbit/s ADPCM under error-free conditions.