A low-delay wideband speech coder at 24-kbps

A novel low-delay wideband speech coder, called multiband CELP (MB-CELP) achieves a delay of about 10 ms, by exploiting time-domain correlations with a two stage linear prediction scheme. A low-order forward adaptive LP stage models the coarse shape, and a high order backward-adaptive LP stage models the fine structure of the input spectrum. A conditional pitch prediction method improves the performance of the coder for speech without degrading the music performance. A multi-band bank of off-line filtered codebooks generates the excitation signal. A 24 kbps version of the coder has nine multi-band codebooks with a nonuniform bandwidth. Subjective comparison tests show that this coder outperforms the G.722 coder at the bit-rate of 56 kbps