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The ITU-T G.729 Annex A fixed-rate speech coder provides toll quality at very low bandwidth. G.729 compresses narrowband linear speech signals at a sample rate of 8kHz to 8kbps, using Conjugate-Structure, Algebraic Code-Excited Linear Prediction (CS-ACELP). The encoder extracts the parameters of the CELP coding model from 10-msec frames. G.729 Annex A is a less mathematically complex version of G.729. It requires roughly one half the cycles of G.729, yet is interoperable with it, with barely any loss of fidelity.
G.729 Annex A encoder is widely used in applications that require robust quality, including videoconferencing, internet, multimedia communications, satellite communications, and store/forward.
The G.729 Annex A has been extremely optimized by DSP Wizard to execute on a Win32 PC or any other multipurpose processor and yet remain bit-exact to the ITU-T standard. DSP Wizard’s G.729 Annex A will execute nine times faster than the source code published by ITU. On a typical PC with a 3.0GHz processor, encoding and decoding a channel of speech requires only 4% of the processor’s CPU cycles. So a user should be able to process 25 independent channels of speech. This should be fast enough for most real-time applications.
DSP Wizard’s G.729 Annex A implementation was designed for low resource requirements without sacrificing quality. The speed is extremely fast compared to the published standard, yet it is still bit-exact to the ITU-T standard test suite. Furthermore, the code should be portable to any machine that supports the C language.