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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:
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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.
The endpoint-capability match is executed every time a new call is set up or an existing call is resumed.
Note
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.
During an audio-only connection, all video-related media messages are skipped.
Note
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
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
Information About Setting Video Parameters
Cisco Unified SCCP and SIP SRST System Administrator Guide
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Troubleshooting
