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Collaboration, Voice & AV · Foundational

Codec

A coder-decoder algorithm that converts analog audio or video to compressed digital form and back.

Definition

In collaboration systems a codec defines the sampling rate, bit rate, compression method and quality of the media stream. Audio codecs include G.711, G.722, G.729, iLBC and Opus, while video codecs include H.264, H.265 and AV1. Endpoints negotiate a common codec in SDP or H.245, and if none matches a transcoder is required. In AV, codec also refers to a video conferencing hardware endpoint such as a Cisco Room Kit.

Example

CUCM regions limit calls between a branch and headquarters to G.729 at 8 kbps to save WAN bandwidth.

Exam tip

Codec choice is the main lever for voice bandwidth per call; know payload rates of common codecs.

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