Some investigations are presented on subband ADPCM (adaptive differential pulse-code modulation) algorithms, for the coding of medium or high quality sound signals. This technique combines subband coding with a low number of subbands and ADPCM in each subband. Noise shaping is introduced for substantially improving the subjective quality. The study shows that a 120-kb/s high-quality 15-kHz sound coder can be obtained using this technique. Its complexity allows its implementation on commercially available 16 bit DSP chip.
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