Complete Communications Engineering

G.729A vocoder
G.729A is a reduced complexity CS-ACELP speech compression algorithm

G.729A codec

G.729A codec is used as an internet wideband audio codec for VoIP or similar applications. Contact us to discuss your G.729A vocoder application requirements.

download brochure request demo

VOCAL’s G.729A codec source code is optimized for performance on leading DSPs and conventional processors from TI, ADI, ARM, Intel and other vendors. It is available as a standalone voice compression algorithm, as part of a modular software library suite, as well as with a VoIP stack. Custom designs are also available to meet your specific requirements.


G.729A is a reduced complexity Conjugate-Structure Algebraic-Code-Excited Linear Prediction (CS-ACELP) speech compression algorithm defined in ITU-T G.729 Annex A. G.729A is interoperable with the G.729 codec. The reduction in complexity may result in a small decrease in voice quality. G.729A may be used as an internet wideband audio codec for VoIP or similar applications using multimedia, voice, and/or data although the G.729AB codec may be better in reducing bandwidth usage.

G.729A requires 10 ms input frames and generates frames of 80 bits in length. Since G.729A is based on the Code-Excited Linear Prediction (CELP) model, each 80 bit frame produced contains linear prediction coefficients, excitation code book indices, and gain parameters that are used by the decoder in order to reproduce speech. The inputs/outputs of G.729A are 16 bit linear PCM samples that are converted from/to an 8 kbps compressed data stream. G.729A has the same total algorithmic delay of 15 ms as the G.729 speech coder.

The majority of the changes made to reduce complexity were in the G.729A encoder. The perceptual weighting filter uses instead the Linear Prediction Filter Co-efficients, making computation of the weighted synthesis filtering much easier. Decimation is used in the open-loop pitch analysis to compute correlations with weighted speech. Searches of both the adaptive and fixed algebraic codebooks were simplified as well. In the G.729A decoder, some modifications were made in the adaptive postfilter.





VOCAL’s vocoder software is available for the following Platforms. Please contact us for specific G.729A supported platforms.

ProcessorsOperating Systems
  • Texas Instruments – C6000 (TMS320C62x, TMS320C64x, TMS320C645x, TMS320C66x, TMS320C67x), DaVinci, OMAP, C5000 (TMS320C54x, TMS320C55x)
  • Analog Devices – Blackfin, ADSP-21xx, TigerSHARC, SHARC
  • PowerPC
  • MIPS – MIPS32, MIPS64, MIPS4Kc
  • ARM – ARM7, ARM9, ARM9E, ARM10E, ARM11, StrongARM, ARM Cortex-A8, Cortex-M1
  • Intel / AMD – x86, x64 (both 32 and 64 bit modes)
  • Google Android
  • Apple iOS / iPhone / iPad & MacOS
  • Unix,  Linux, μClinux, BSD
  • Microsoft Windows ACM / RTC / CE / Mobile
  • Symbian
  • eCOS / eCOSPro
  • Wind River VxWorks
  • Green Hills Integrity
  • Micrium μCOS

More Information