Technical
Codec choice for call centers: G.729 vs G.711 vs Opus
Compare G.729, G.711 and Opus for contact center calling: bandwidth, audio quality, CPU load and when to use each.
- 6 min read
The codec decides how voice is compressed between your agents and the carrier. Choose badly and you either waste bandwidth or hear robotic audio. Here is how the three most common options compare.
G.711 (a-law and u-law)
Uncompressed narrowband audio at 64 kbps of payload. It is the reference for PSTN quality and uses almost no CPU, but needs roughly 87 kbps per call including packet overhead.
G.729
Compressed to 8 kbps of payload, around 31 kbps with overhead. Quality is slightly lower than G.711 but perfectly acceptable for conversation, which is why it is the workhorse of many call centers.
Opus
A modern adaptive codec that can scale from narrowband to full-band audio and handles packet loss gracefully. It shines between softphones and WebRTC clients; on the PSTN leg it is usually transcoded.
Rule of thumb
- Limited bandwidth or many agents per site: G.729
- Plenty of bandwidth and you want maximum PSTN fidelity: G.711
- Remote agents on variable home connections or WebRTC: Opus