Based on the Code Excited Linear Prediction (CELP) coding model, the G.729 codec delivers toll-quality speech, similar in quality to 32-kbps ADPCM but at one-quarter the bitrate. With the low rate of 8 kbps, G.729 is the lowest-bitrate ITU-T standard with toll quality, offering opportunities for significant increases in bandwidth utilization in existing telephony and wireless applications. G.729 operates on 10-ms frames, allowing moderate transmission delays, so applications such as VoIP, where quality, delay and bandwidth are all important, benefit substantially from this codec.
Annex A (G.729A) has approximately half the complexity of G.729. G.729 and G.729A are totally interoperable.
Annex B (G.729B) is a discontinuous transmission (DTX) functionality that interrupts the transmission during silence for VoIP communication. This functionality can be merged with G.729A to form G.729AB.
Annex D (G.729D) is a 6.4-kbps CS-ACELP speech coding algorithm.
Annex E (G.729E) is an 11.8-kbps CS-ACELP speech coding algorithm.
Annexes F, G, H and I are combinations respectively of annexes B&D, B&E, D&E and B&D&E.
The memory and CPU details are generic Standard specifications.
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