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Commonly confused · Collaboration, Voice & AV

G.711 vs G.729: What's the Difference?

G.711 is an uncompressed voice codec using 64 kbps PCM, delivering toll-quality audio at the cost of bandwidth. G.729 compresses voice to 8 kbps with slightly lower quality and more processing, making it useful over constrained WAN links.

G.711G.729
Codec bit rate64 kbps8 kbps
Bandwidth per call with IP/UDP/RTP overhead (Ethernet, 20 ms)About 87 kbpsAbout 31 kbps
CompressionNone (PCM, mu-law or A-law)CS-ACELP compression
Voice quality (MOS)About 4.1-4.4About 3.9
CPU/DSP loadLowHigher
Fax and modem supportGoodPoor; use G.711 or T.38
Typical useLAN calls, high-quality trunksWAN links with limited bandwidth
Remember it

G.711 is the full 64k; G.729 squeezes the call to 8k.

Exam tip

Expect bandwidth calculations and codec selection for low-bandwidth WAN links (G.729). Remember codec rate is not the whole story; Layer 2 and IP/UDP/RTP headers add significant overhead.

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