Codec Negotiation

The process of agreeing on audio and video codecs (G.711, G.722, Opus, H.264, VP8) between SIP or WebRTC endpoints during SDP offer/answer exchange. The offerer lists supported codecs in priority order; the answerer selects a subset from the offered list. Codec mismatches result in call failure (488 Not Acceptable Here) or require a transcoding B2BUA. Codec choice balances audio quality, bandwidth consumption, and hardware acceleration availability.