What causes codec mismatch failures?

What causes codec mismatch failures?

• A. No common codec due to region/gateway constraints or misconfigured codec preference.
• B. Excessive jitter on network.
• C. IP address conflict causing routing loops.
• D. Mismatched time zones across gateways.

Answer: (A)

Codec negotiation is about both ends agreeing on a common media format before the call can carry audio. During setup, each side offers the codecs it supports and a preferred order. A call will fail to establish if there is no overlap between the two sides’ codec sets. This happens when region or gateway constraints limit which codecs can be used, or when a device is misconfigured to prefer or only offer a specific codec that the other side does not support. In that case, there’s no mutual codec to use, so the media path cannot be established. This is different from issues that affect quality after the call starts, like excessive jitter, which degrades an already established stream rather than preventing negotiation. Routing problems or IP conflicts affect signaling or path topology, not the codec negotiation itself. Time zone differences have no impact on how codecs are negotiated.

Codec negotiation is about both ends agreeing on a common media format before the call can carry audio. During setup, each side offers the codecs it supports and a preferred order. A call will fail to establish if there is no overlap between the two sides’ codec sets. This happens when region or gateway constraints limit which codecs can be used, or when a device is misconfigured to prefer or only offer a specific codec that the other side does not support. In that case, there’s no mutual codec to use, so the media path cannot be established.

This is different from issues that affect quality after the call starts, like excessive jitter, which degrades an already established stream rather than preventing negotiation. Routing problems or IP conflicts affect signaling or path topology, not the codec negotiation itself. Time zone differences have no impact on how codecs are negotiated.