Cisco CP-7911G-CH1 Administration Guide - Page 259
Matching Endpoint Capabilities, Retrieving Video Codec Information, Call Fallback to Audio-Only,
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Setting Video Parameters Information About Setting Video Parameters with Cisco Unified CM. However, you must enter call-manager-fallback configuration mode to set video parameters for Cisco Unified SRST. The feature set for video is the same as that for Cisco Unified SRST audio calls. To set video parameters, you should understand the following concepts: • Matching Endpoint Capabilities, page 259 • Retrieving Video Codec Information, page 259 • Call Fallback to Audio-Only, page 259 • Call Setup for Video Endpoints, page 259 • Flow of the RTP Video Stream, page 260 Matching Endpoint Capabilities Endpoint capabilities are stored in the Cisco Unified SRST during phone registration. These capabilities are used to match with other endpoints during call setup. Endpoints can update at any time; however, the router recognizes endpoint-capability changes only during call setup. If a video feature is added to a phone, the information about it is updated in the router's internal data structure, but that information does not take effect until the next call. If a video feature is removed, the router continues to see the video capability until the call is terminated but no video stream is exchanged between the two endpoints. Note The endpoint-capability match is executed every time a new call is set up or an existing call is resumed. Retrieving Video Codec Information Voice gateways use dial-peer configurations to retrieve codec information for audio codecs. Video codec selection is done by the endpoints and is not controlled by the H.323 service-provider interface (SPI) through dial-peer or other configuration. The video-codec information is retrieved from the SCCP endpoint using a capabilities request during call setup. Call Fallback to Audio-Only When a video-capable endpoint connects to an audio-only endpoint, the call falls back to an audio-only connection. Also, for certain features such as conferencing, where video support is not available, the call falls back to audio-only. Cisco Unified SRST routers use a call-type flag to indicate whether the call is video-capable or audio-only. The call-type flag is set to video when the video capability is matched or set to audio-only when connecting to an audio-only TDM or an audio-only SIP endpoint. Note During an audio-only connection, all video-related media messages are skipped. Call Setup for Video Endpoints The process for handling SCCP video endpoints is the same as that for handling SCCP audio endpoints. The video call must be part of the audio call. If the audio call setup fails, the video call fails. OL-13143-04 Cisco Unified SCCP and SIP SRST System Administrator Guide 259