A Perceptually Based Embedded Subband Speech Coder - Speech and Audio Processing, IEEE Transactions on

A new scheme for robust, high-quality, embedded speech coding based on subband decomposition and perceptually optimized bit allocation and prioritization is presented. An infinte impulse response (IIR) quadrature mirror filterbank (QMF) performs subband decomposition. A perceptual model, computed using subband spectral analysis, optimizes the coder’s perceptual quality. Dynamic bit allocation and prioritization is combined with embedded quantization resulting in little performance degradation relative to a nonembedded implementation. The coder output is scalable from high quality at higher bit rates to lower quality at lower bit rates, supporting a wide range of service and resource utilization. The lower bit-rate representation is obtained simply through truncation of the higher bit-rate representation. Since source-rate adaptation is performed through truncation of the encoded stream, interaction with the coder is not required, making the embedded coder ideally suited for rateadaptive communication systems. Performance for both speech and music was verified through subjective listening tests.