G.729 Annex A speech coder was developed for use in multimedia simultaneous voice and data applications like DSVD. The coder processes signals with 10 ms frames and has a 5 ms look-ahead which results in a total of 15 ms algorithmic delay. The input/output of this algorithm is 16 bit linear PCM samples that are converted from/to 8 kbps compressed data stream.
G.729 Annex B provides a high level description of the Voice Activity Detection (VAD), Discontinuous Transmission (DTX), and Comfort Noise Generator (CNG) algorithms. These algorithms are used to reduce the transmission rate during silence periods of speech. They are designed and optimized to work in conjunction with Recommendation V.70. Recommendation V.70 mandates the use of Annex A/G.729 (G.729A) speech coding methods. However, when it is desirable, the full version of Recommendation G.729 can also be used to improve the quality of the speech.
The line interface may be an analog front end (codec and DAA) or a digital interface such as T1/E1, switched 56 and ISDN. The upper end of this software offers a direct binary and speech frame interface.
- Passes ITU test vectors.
- Common compressed speech frame stream interface to support systems with multiple speech coders (G.729 Annex A/B, G.723, G.728, G.726 et al).
- Optimized for high performance on leading edge DSP architectures.
- Multi-tasking environment compatible.
- DAA interface using linear codec at 8.0 kHz sample rate.
- Direct interface to 8.0 kHz PCM data stream (A-law or µ-Law).
- North American/International Telephony (including caller ID) support available.
- Simultaneous DTMF detector operation available - (less than 150 hits on Bellcore test tape typical).
- MF tone detectors, general purpose programmable tone detectors/generators available.
- Line echo cancellation (G.165 compliant) available.
- Where multiple speech coders (G.729, G.723, G.728, G.726 et al.) are available, coder selection can occur at run-time.
- Data/Facsimile/Voice Distinction available.
- Data/Facsimile/Voice command sets available.
- Various startup procedures available (V.8 and V.8bis).
- Multiple ports can be executed on a single DSP.