Polycom 1500/1800/2000/4000 manual Multiple Content Resolutions, Fixed Rate

Sharing Content During Conferences

Highest Common Calculation Depending on Content Settings

For Graphics, Hi-res Graphics and Live Video (see Content Settings), the highest common content is calculated for the conference each time an endpoint connects. Highest Common content bit rate is calculated using:

●For H.263 - Line rate

●For H.264 - Line rate, resolution, and frame rate.

Therefore, when endpoints with lower capabilities connect to an ongoing conference, content parameters are re-calculated and decreased accordingly.

During content sharing, the MCU does not permit endpoints to increase their content bit rate, only their content resolution.

For more information, see H.264 Highest Common Content Rates Tables. For information on minimum content rates as determined by system flags, see H.264 HD System Flags.

Fixed Rate

This method must be used for cascaded conferences.

In this method the content rate is fixed, and endpoints not supporting this rate do not receive content over the content channel. Endpoints whose capabilities are too low, can only view content over the people video layout (see Sending Content to Legacy Endpoints).

For H.263 cascaded conferences, the MCU automatically uses a fixed rate (once a cascaded link is detected) according to the content rates described in Highest Common and Fixed Content Bit Rate Allocation for H.263.

For H.264 cascaded conferences, the MCU uses a fixed rate according to the content rates described in H.264 Cascade Optimized (Fixed) Content Rates Tables, and the high/base profile configured by the user.

Multiple Content Resolutions

This method is often related to as content transcoding.

In this method, the content is shared in multiple streams, one for each video protocol: H.263 (optional) and H.264HD (mandatory). Separate video resources are used for processing the content for each of the required content streams. The MCU then applies the Highest-Common principle for sharing content with each group of endpoints.

In cascading conferences, an additional resource is dedicated for the cascading link(s), the H.264 Cascade option must be selected, and content is shared over the cascaded link(s) using fixed rates.

As a consequence, using this method allows endpoints with different capabilities to connect/disconnect without having to repeatedly restart content sharing process.

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