Telepresence is a set of technologies that allow video conferencing in such a way that the user feels as if they are actually at the remote site. Cisco sells a variety of platforms in the telepresence space supporting up to three 65” high definition video displays, at up to 1080p resolution and 48khz wide-band spatial audio.
This post will investigate the bandwidth requirements of these Cisco telepresence products. The bandwidth requirements are required for capacity planning of wide area network circuits and to properly provision QoS policies for telepresence.
The bandwidth requirement of each video screen is based on the resolution and compression level of each screen, multiplied by the number of screens. Uncompressed 1080p video is approximately 1.5Gbps per video stream, but the Cisco telepresence codecs compresses this video significantly, as can be seen in the video table below.
|Bandwidth||4 Mbps||3.5 Mbps||3 Mbps||2.25 Mbps||1.5 Mbps||1 Mbps|
The Cisco telepresence solution uses the advanced audio coding–low delay (AAC-LD) audio codec at a rate of 64kbps each. AAC-LD is a high definition audio codec with much better quality level than G.711, and arguably better than the ITU G.722 wideband audio codec introduced in Cisco Unified Communications Manager 6.0.
At 1080p resolution and best quality, 4.064 Mbps will be required per screen in the telepresence solution. QoS best practices recommend adding 20% overhead bandwidth to accommodate layer 2, 3, and 4 overhead, resulting in approximately 5Mbps per screen (4.064 * 1.2 = 4.8768 Mbps).
The 3-screen CTS-3000 telepresence solution has three video and three audio channels resulting in a bandwidth requirement of approximately 15Mbps. A fourth auxiliary audio and video channel may be used, which will increase the bandwidth requirements differently depending on the version of telepresence.
For more information on this topic, check out the links in the references section below.
Author: Dennis Hartmann
Cisco TelePresence Network Systems 2.0 Design Guide - particularly tables 4-1, 4-2, and 4-3
Advanced Audio Coding – Low Delay