Codecs & Media

G.729

G.729 is a narrowband audio codec at 8 kbps — one-eighth the bandwidth of G.711, useful for satellite, mobile, or constrained-network links. Patent royalties expired in 2017, so it is now royalty-free.

Specs

• Sample rate: 8 kHz
• Bitrate: 8 kbps (Annex A: 6.4 kbps low-rate, Annex B: VAD/CNG silence suppression)
• Frame: 10ms (typical packetization 20-30ms = 2-3 frames per RTP packet)
• MOS: ~3.9 (vs 4.2 for G.711)

When to use it

• Satellite or mobile-data links where bandwidth is the bottleneck.
• Branch offices on slow VPNs.
• Not recommended as a default — the bandwidth difference is rarely worth the quality drop on modern broadband.

Transcoding cost

G.729 is more CPU-expensive to encode/decode than G.711. PBX-to-carrier traffic in G.729 forces the carrier to transcode for the PSTN side, which can degrade quality further. Prefer G.711 unless you have a measurable bandwidth constraint.

Related terms