Variable rate embedded ADPCM coding scheme for packet speech on ATM networks

A variable bit rate embedded ADPCM (adaptive differential PCM) coding scheme for packet speech, primarily for use in advanced private networks integrating ATM (asynchronous transfer mode) technology, is presented. The goal is to maintain high-quality speech even with the high percentage of information loss, anticipated in these networks. By varying the number of code bits of an embedded ADPCM coder from 6 bits per sample (48-kbits) for blocks of speech with high prediction gain, to 2 bits (16-kbits) for silent blocks, a good compromise between coding bit rate and speech quality with graceful degradation due to information loss was achieved.<>