/mcpYou should consider relaxing both region and location bandwidth restrictions for H.239 calls, so the H.239 devices are allowed to readjust and balance load for both the video channels without Cisco Unified Communications Manager intervention. Note Number of Video Channels Allowed Unified Communications Manager supports only a maximum of two video channels due to the following reasons: • Both Cisco and Polycom only support two video channels, one of which is for main video, and the other is for presentation. • H.239 only defines an Additional Media Channel (AMC) for H.320-based system to partition the traditional H.320 video channel for the purpose of presentation. H.239 Commands and Indication Messages Command and Indication (C&I) messages get used for H.239 to manage tokens for the Presentation and Live roles and to permit devices to request release of video flow control to enable the operation of additional media channels. Cisco Unified Communications Manager supports all the C & I messages. Whenever Cisco Unified Communications Manager receives C&I messages, it relays them to the call party accordingly. Be aware that the flow control release request and response messages can be used to request that the far end release flow control, so it allows an endpoint to send the indicated channel at the indicated bit rate. Be aware that the call party may or may not honor the request as is indicated by flow control release response. Note The Presentation role token messages allow an H.239 device to acquire the token for presentation. The other call party may accept or reject the request. The presenter device sends out a token release message when it is no longer needed. Topology and Protocol Interoperability Limitation Cisco Unified Communications Manager supports only H.239 in H.323 to H.323 calls. Cisco Unified Communications Manager allows H.239 calls to be established across H.323 intercluster trunk or multiple nodes. If an H.239-enabled device attempts to make a call with a non-H323 end, the H.239 capabilities will get ignored and the call will get conducted like the traditional video calls that are supported by Cisco Unified Communications Manager. Cisco Unified Communications Manager does not support a second video channel when a media termination point or transcoder is inserted into the call. If it happens, the call will fall back to normal video calls. Midcall Feature Limitation Cisco Unified Communications Manager supports opening second video channels only in direct H.323 to H.323 calls. Feature Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs 869 SIP Interoperability Number of Video Channels Allowed