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.

G.729/A/B/C/D/E/F/G/H/I Codec Overview

The memory and CPU details are generic Standard specifications.

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G.729 Codec Technical Specifications

  • Bandwidth: 200-3400 Hz
  • Standardized: ITU-T 1995
  • Technology: ACELP
  • Bit rate: 8 kbps
  • Delay (msec): 15
  • Frame size (msec): 10
  • Lookahead (msec): 5
  • Quality: Narrowband / PSTN
  • Complexity (MIPS): 20
  • ROM (bytes): 50K
  • RAM (bytes): 4K + 3K/ch