Check codec settings before changing a call path

Before changing a codec list, identify both ends of the call and any transcoding device between them. A codec offered by one phone may be unavailable on the carrier leg.

Record the current offer

Save the active codec order, packetisation interval, sample configuration and any transcoding policy. Check the negotiated codec in a known-good call rather than assuming the first configured option is used.

Estimate the network cost

Work from the busiest expected concurrent calls in each direction. Include IP, UDP, RTP and link overhead; a G.729 payload rate of 8 kbps is not a circuit-size estimate. Shorter packet intervals send more headers each second. Leave capacity for other traffic and confirm the provider’s supported packet interval.

After the change, test call setup, intelligibility and two-way audio through every affected leg. Restore the saved policy if negotiation or quality fails.

See the voice codecs guide for codec characteristics and trade-offs.