ITU-T-G.729 ANNEX-A - REDUCED COMPLEXITY 8 KB S CS-ACELP CODEC FOR DIGITAL SIMULTANEOUS VOICE AND DATA/

This article describes the recently adopted ITU-T Recommendation G.729 Annex A (G.729A) for encoding speech signals at 8 kb/s with low compl exity. G.729A is the standard speech coding algorithm for multimedia d igital simultaneous voice and data (DSVD). G.729A is bitstream interop erable with G.729; that is, speech coded with G.729A can be decoded wi th G.729, and vice versa. Like C.729, it uses the conjugate-structure algebraic code excited linear prediction (CS-ACELP) algorithm with 10 ms frames. However, several algorithmic changes have been introduced w hich result in a 50 percent reduction in complexity. This article desc ribes the algorithm introduced to achieve the low complexity goal whil e meeting the terms of reference. Subjective tests showed that the per formance of G.729A is equivalent to both G.729 and C.726 at 32 kb/s in most operating conditions; however, it is slightly worse in the case of three tandems and in the presence of background noise. A breakdown of the complexities of both G.729 and G.729A is given at the end of th e article.