Chapter 2-Additional Conferencing Information

H.239

The H.239 protocol allows compliant endpoints to transmit and receive two simultaneous video streams:

People Conference – Continuous Presence or Video Switched conference

Content Conference – Video Switching conference for content sharing

By default, all conferences, Entry Queues, and Meeting Rooms launched on the RMX 2000/RMX 4000 have H.239 capabilities.

To view Content, endpoints must use the same Bit Rate, Protocol, and Resolution. An endpoint may not send Content while connecting to an Entry Queue.

Endpoints without H.239 capability can connect to the video conference without Content.

Cascade links declare H.239 capabilities and they are supported in Star and MIH cascading topologies. For more details, see "Cascading Conferences - H.239-enabled MIH Topology” on page 2-61.

Content Transmission Modes

The Content channel can transmit one of the following modes:

Graphics – default mode, for standard graphics

Hi-res Graphics – requiring a higher bit rate, for high quality display or highly detailed graphics

Live Video – highest bit rate, for video clips or live video display

The highest common Content bit rate is calculated for the conference each time an endpoint connects. Therefore, if an endpoint connects to an ongoing conference at a lower bit rate than the current bit rate, the Content bit rate for the current conference is re-calculated and decreased.

Bit rate allocation by the MCU is dynamic during the conference and when the Content channel closes, the video bit rate of the People conference is restored to its maximum.

During a conference the MCU will not permit an endpoint to increase its bit rate, it can however change its Content resolution. The RMX can decrease the allocated Content bit rate during a conference.

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Polycom 2000/4000 manual 239, Content Transmission Modes