K.J. Byun, H.B. Jung, K.S. Kim, and M. Hahn (Korea)
Speech coding, scalable coder, wideband speech, CELP,algebraic codebook, AMR-WB
This paper presents a new bitrate scalable wideband speech coder based on the Adaptive Multi-Rate Wideband (AMR-WB) standard codec recently selected by the Third Generation Partnership Project (3GPP) for the third generation mobile communication system. The proposed scalable coder consists of three different bitrate codecs where the two lower bitrates can be embedded into the highest bitrate. The bitrate scalability was achieved by modifying the algebraic codebook search method adopted for the AMR-WB codec. Our proposed method needs no additional computation for obtaining two different code vectors of the lower bitrate modes. Our coder provides the scalability while maintaining the same quality for the highest bitrate mode with slightly increased bitrate caused by the decreased coding efficiency of the algebraic codebook. It also works at the same bit rate with the slightly degraded speech quality with the lowest bitrate mode.
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