OVERVIEW AND PERFORMANCE OF CCITT ANSI EMBEDDED ADPCM ALGORITHMS/

Embedded adaptive differential pulse coded modulation (ADPCM) algorith ms quantize the difference between the input signal and the estimated signal into core bits and enhancement bits. This feature gives them an advantage over nonembedded algorithms because they allow an intermedi ate node to drop the enhancement bits without having to exchange contr ol messages with the transmitting end. CCITT Recommendation G.727 desc ribes embedded ADPCM encoding algorithms with 5, 4, 3, and 2 core bits ; it is virtually identical to the corresponding ANSI standard T1.310. This paper highlights the main features of G.727/T1.310 and presents results on its performance. A formal subjective evaluation of the spee ch performance of embedded ADPCM algorithms indicates that a midrise q uantizer provides better voice transmission performance than its midtr ead counterpart when two core bits are used. The subjective data also show that the performance of the 40 kb/s midrise ADPCM algorithm with two feedback bits is indistinguishable from that of 64 kb/s pulse code modulation (PCM) for up to four tandem encodings. Embedded algorithms are therefore recommended for flexible congestion control of integrat ed traffic in multinode networks.