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Sharing Content During Conferences
Polycom®, Inc. 132
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
Highest Common
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.
LPR has no effect on content rate, though due to the increased number of frames, video rate is
decreased.
This method is applied for single MCU conferences.