Cisco Cisco WebEx Meeting Center WBS30 White Paper
© 2015 Cisco and/or its affiliates. All rights reserved. This document is Cisco Public Information.
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About the WebEx Video Codec
The Cisco WebEx Meeting Center has adopted the H.264 standards-based Scalable Video Coding (SVC) for video
compression to deliver adaptive standard-quality (SQ), high-quality (HQ), and high- definition (HD) video. HD
(720p) video is currently available in Meeting Center and Training center.
The video engine consists of all the fundamental video processing modules, including capture, encoding,
transmission, receiving, decoding, and rendering. It also includes supporting modules for error control, congestion
control, bit-rate adaptation, and encryption.
The SVC encoding protocol allows the captured video to be separated into multiple layers of resolutions, frame
rates, and quality. In the WebEx video encoder implementation, raw video sequences are compressed into a single
base layer and several enhancement layers before they are transmitted to the receiving clients. The base layer in
the compressed video bit streams provides a relatively low video quality and can be independently decoded.
Enhancement layers serve as add-ons for the base layer to improve the video experience. If more bandwidth is
available, then more enhancement layers will send, resulting in better video quality.
Similarly, when network congestion occurs for any participants, the clients could save bandwidth by receiving fewer
enhancement layers, gradually degrading the video quality while maintaining the best video experience and
dynamically adjusting the quality to changing conditions of the network or the participant’s computer.
dynamically adjusting the quality to changing conditions of the network or the participant’s computer.
Depending on various conditions, such as user eligibility, subscription modes of the receivers, capability of camera
and PC, network conditions, and others, one or more of the available resolutions can be encoded at the same time
that the video is sent. On the receiving side, the client automatically selects and decodes one specific resolution.
This encoding and decoding capability results in a higher bandwidth requirement for transmitting video compared
to receiving video.
Frame-Rate Range
WebEx supports various frame-rate ranges. On the sender side, it depends on the camera capture capability and
available computing and bandwidth resources. On the receiver side, it depends on the bandwidth and computing
resources.
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Up to 30-fps HQ and HD video is supported in a one-on-one meeting (only two participants point to point
[P2P]).
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Up to 24-fps HQ and HD video is supported in a multipoint meeting (three or more participants).
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Up to 18-fps 180p video is supported in a one-on-one meeting (only two participants P2P).
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Up to 12-fps 180p video is supported in a multipoint meeting (three and more participants).
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The WebEx client may stop sending and receiving the video if the network or hardware environment
conditions deteriorate drastically.
Site-Level Control
Administrators cannot control the default and maximum bandwidth levels for multipoint HQ and HD video.
The levels and frame rates are controlled automatically by software, and administrators cannot override the
software control. Administrators can choose to disable the HQ/HD mode and limit the video to 180p resolution.
Refer to Figure 5 for the “Turn on high-quality video” or “Turn on high-definition video” checkboxes. This setting is a
Refer to Figure 5 for the “Turn on high-quality video” or “Turn on high-definition video” checkboxes. This setting is a
site wide-
setting that affects all users. Refer to the site administrator’s guide for more details.