Conferencing Modes Overview
Polycom®, Inc. 9

CP conferencing is defined in the Conference profile by setting the following main

features:

●Setting the Conferencing Mode to CP only
●Conference Line Rate
●Video Layout

Video Protocol Support in CP Conferences

The video protocol selected by the system determines the video compression standard used by the
endpoints. In Continuous Presence conferences, the system selects the best video protocol for each of the
endpoint according to he endpoint’s capabilities.
The following Video protocols are supported in CP conferences:
●H.261 - the legacy video compression algorithm mandatory to all endpoints. It is used by endpoints
that do not support other protocols.
●H.263 - a video compression algorithm that provides a better video quality than H.261. This standard
is not supported by all endpoints.
●H.264 Base Profile - a video compression standard that offers improved video quality, especially at
line rates lower than 384 Kbps.
H.264 High Profile allows higher quality video to be transmitted at lower line rates.
●RTV - a video protocol that provides high quality video conferencing capability to Microsoft OCS
(Office Communicator Server) endpoints at resolutions up to HD720p30. (SIP only).
AVC Basic Conferencing Parameters
The main parameters that define the quality of an AVC-based video conference and its display are:
●Line (Bit) Rate - The transfer rate of video and audio streams. The higher the line (bit) rate, the better
the video quality. The MCU supports the following line rates:
CP Conferences: 64kbps to 4096kbps
●Audio Algorithm - The audio compression algorithm determines the quality of the conference audio.
●Video protocol, video format, frame rate, annexes, and interlaced video mode - These
parameters define the quality of the video images. The Collaboration Server will send video at the
best possible resolution supported by endpoints regardless of the resolution received from the
endpoints.
When Sharpness is selected as the Video Quality setting in the Conference Profile, the
Collaboration Server will send 4CIF (H.263) at 15fps instead of CIF (H.264) at 30fps.
H.264 High Profile protocol provides better compression of video images in line rates lower than
384 Kbps and it will be automatically selected for the endpoint if it supports H.264 High Profile. If
the endpoint does not support H.264 High Profile, the Collaboration Server will try H.264 Base
Profile which provides good compression of video images in line rates lower than 384Kbps (better
than H.263 and not as good as H.264 High Profile).
When working with Collaboration Servers at low bit rates (128, 256, or 384Kbps), HDX endpoints
will transmit SD15 resolution instead of 2CIF resolution.
When using a full screen (1x1) conference layout, the Collaboration Server transmits the same
resolution it receives from the endpoint.
●Video resolution: