High Speed Codebook Searching Algorithm for the CELP Vocoder in the Internet-Based Environment
In general CELP type vocoders provide good speech quality around 4.8kbps. Among them, G.723.1 developed for Internet Phone and videoconferencing includes two vocoders, 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 real 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 about 30% of codebook search time. We first decide the grid bit, and then search the codebook. Grid bit is selected by comparison between the DC-removed original speech and synthesized speech, which is synthesized with only even or odd pulses of target vector.
KeywordsTarget Vector Pulse Position Speech Codec Experimental Result Computer Simulation Rate Communication System
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