The reduction of the search time by the pre-determination of the grid bit in the g.723.1 MP-MLQ

In general CELP type vocoders provide good speech qu ality around 4.8kbps. Among them, G.723.1 developed f or Internet Phone and videoconferencing includes two v ocoders, 5.3kbps ACELP and 6.3kbps MP-MLQ. Since 6.3kbps MP-MLQ requires large amount of computation for the fixed codebook search, it is difficult to realize r eal time processing for the Internet-based environment. In order to improve the problem this paper proposes the new method that reduces the processing time up to abo ut 50% of codebook search time. We first decide the gr id bit, and then search the codebook. Grid bit is selecte d by comparison between the DC-removed original spee ch and synthesized speech, which is synthesized with o nly even or odd pulses of target vector.