Polycom 1500/1800/2000/4000 Content Transmission Methods, Content Video Switching, Highest Common

Sharing Content During Conferences

Content Transmission Methods

There are two methods used for content transmission:

●Content Video Switching

●Multiple Content Resolution - Content Transcoding

Content Transcoding is not supported by Collaboration Server (RMX) 1800-0.

Content Video Switching

When using this method, content sent by endpoints is transmitted as-is to all content-capable participants. The content rate is determined using one of the following methods:

●Highest Common

●Fixed Rate

LPR has no effect on content rate, though due to the increased number of frames, video rate is decreased.

Highest Common

This method is applied for single MCU conferences.

The Highest Common method is applied in a few levels:

●Within the same protocol - The highest common content rate

●Between protocols - H.263 and H.264

●In H.264 - Base and high profile

In this method, the content rate is negotiated to highest common capabilities supported by the endpoints connected to the conference. Therefore, if the conference includes participants supporting both lower and higher content capabilities, the content is sent to all endpoints using the lowest endpoint capabilities.

Note, that for H.263 content, the MCU negotiates the content rate, and the endpoint sharing the content determines the resolution and frame rate. However, for H.264 content, the MCU negotiates profile type, content rate, resolution and frame rate, and the endpoint sharing the content may use lower content parameters.

When a new endpoint with lower content capabilities joins while content is shared, content sharing parameters are downgraded to this endpoint capabilities:

●If downgrade affects the protocol (from H.264 to H.263) or profile type (from high to base), content sharing is terminated, protocol automatically downgrades to H.263, or in H.264, profile downgrades to base profile, and content sharing should be manually resumed.

●If downgrade affects only the content rate, resolution or frame rate (in H.264), the relevant content parameters automatically downgrade during content sharing.

Once this endpoint leaves the conference during content sharing, no change occurs in the content parameters.

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