Low-delay CELP with multi-pulse VQ and fast search for GSM EFR

This paper proposes a speech codec, named MP-CELP (multi-pulse-based CELP), with a 10 msec frame length, which has been developed for the GSM EFR (enhanced full-rate) codec standardization. A novel multi-pulse excitation signal quantization method is proposed, where the pulse amplitudes are vector-quantized (VQ). The combination search of the pulse position and the amplitude VQ remarkably enhances the performance. By restricting the pulse positions based on the algebraic-type structure, the search complexity and the bits are reduced. The divided pulse position search drastically reduces the position search complexity. The speech quality for MP-CELP is higher than that for G.728 LD-CELP. MP-CELP also satisfies all the speech quality requirements of the GSM EFR standardization except for the background noise condition