Low delay 8 kbits/s CELP speech coder with an algebraic trellis coded excitation and multistage search

This work presents a low delay 8 kbits/s code excitation linear prediction (CELP) coder narrowband speech coder with a buffering delay of 2.5 ms is introduced. The trained codebook in the G.728 standard is replaced by 15 bits binary algebraic shape codebook and 5 bits gain codebook. A new technique of search called "trellis search"- inspired from the TCQ (trellis code quantization) and the multistage search of the joint position and amplitude search (JPAS) technique-was introduced into an algebraic dictionary. Objective speech quality measurements on a large corpus of a testing database shows that the trellis structured algebraic codebook with a multistage search achieves the same performance as the position exhaustive search (backward sign) search technique with the advantage that it requires only 25% of the of the computer execution time.