Fixed Rate - Polycom RealPresence RMX 1500 Administrator's Manual

Highest Common Calculation Depending on Content Settings
For Graphics, Hi-res Graphics and Live Video (see
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
content rates as determined by system flags, see

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
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
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
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.
Polycom®, Inc.
H.264 Highest Common Content Rates
Endpoints).
Sharing Content During Conferences
Content Settings), the highest common content is
Tables. For information on minimum
H.264 HD System Flags.
Highest Common and Fixed Content Bit Rate
Tables, and the high/base profile configured by the user.
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