Pitch synchronous multi-band (PSMB) coding of speech signals

Abstract

A novel speech coding algorithm, named pitch synchronous multi-band (PSMB), is proposed. The new coding algorithm uses the multi-band excitation (MBE) model to generate a representative pitch-cycle waveform (PCW) for each frame. The representative PCW of a frame is encoded by two out of three codebooks depending upon whether the frame is related or unrelated to the previous frame. When a frame is related to its previous frame, the PCW is encoded by a length-converted-excitation (LCE) codebook and a stochastic codebook. The codevectors of the LCE codebook are derived from the previous PCW. When a frame is unrelated to its previous frame, it is encoded by a bandlimited single pulse excitation (BSPE) codebook and the stochastic codebook. The new speech coder introduces a pitch-period-based coding feature. It overcomes some weaknesses existing in the improved MBE (IMBE) speech coder. The PSMB coder operating at 4 kbps outperforms the Inmarsat 4.15 kbps IMBE coder by a clear margin. Our listening tests also indicate that it is slightly better than the FS1016 4.8 kbps code excited linear predictive (CELP) coder in terms of perceptual quality. Fast search algorithms for the three codebooks used in PSMB are also developed. The fast algorithms render the new speech coder comparable to the FS1016 CELP coder, in terms of computational complexity.