Polycom RMX 1800 AVC Conferencing Parameters

Polycom® RMX™ 1800 Administrator’s Guide

2-4 Polycom, Inc.

•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.

AVC Conferencing Parameters

When defining a new video Profile, you select the parameters that determine the video

display on the participant’s endpoint and the quality of the video. When defining a new

conference Profile, the system uses default values for Continuous Presence (CP) standard

conferencing. Continuous Presence conferencing enables several participants to be viewed

simultaneously and each connected endpoint uses its highest video, audio and data

capabilities up to the maximum line rate set for the conference.

The main parameters that define the quality of a video conference are:

•Line (Bit) Rate - The transfer rate of video and audio streams. The higher the line (bit)

rate, the better the video quality.

•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 384Kbps 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.

•Lost Packet Recovery (LPR) - LPR creates additional packets that contain recovery

information used to reconstruct packets that are lost during transmission.

• Supported resolutions:

—H.261 CIF/QCIF – Is supported in Continuous Presence (CP) conferences at

resolutions of 288 x 352 pixels (CIF) and 144 x 176 pixels (QCIF). Both resolutions

are supported at frame rates of up to 30 frames per second.

—H.263 4CIF - A high video resolution available to H.263 endpoints that do not

support H.264. It is only supported for conferences in which the video quality is set

to sharpness and for lines rates of 384kbps to 1920kbps.

—Standard Definition (SD) - A high quality video protocol which uses the H.264

and H.264 High Profile video algorithms. It enables compliant endpoints to