Cisco TelePresence MCU 4200 Series

Improving content channel quality on MCU Series

How can I improve the quality of the content channel on the Cisco TelePresence MCU?

This article applies to the following products:

  • Cisco TelePresence MCU 4200 Series
  • Cisco TelePresence MCU 4500 Series
  • Cisco TelePresence MCU 5300 Series
  • Cisco TelePresence MCU MSE Series

Unfortunately video will always be poor over a poor network link; therefore the most important factor for higher quality video is to improve the network over which it is sent.

Under ideal conditions the quality of the content channel from Cisco TelePresence MCUs is very high; however, when some or all the network links are experiencing problems then the shared content channel (which is sent to all content receivers) can reduce in quality. The MCU has various mechanisms to alleviate the problems that poor network links cause.

  • If one endpoint is sending excessive Fast Update Requests, asking for the picture to be refreshed, this can cause blockiness on the content channel. To prevent this, go to Settings > Content and from the Video fast update request filtering setting select Enabled. This ignores excessive fast update requests, thereby maintaining a higher quality picture for the other content viewers.
  • If one connection is at a lower bandwidth than the others, then the bandwidth to all viewers will be affected. This can be due to one participant having a slower connection, or due to endpoints reducing the speed of the call when they experience network problems. To prevent one slow participant reducing the bandwidth for all content viewers, you can stop the content channel to that participant in the Conference > Participants page by clicking the disable link for that participant's content. They will continue to receive the content channel in the main video layout. Connections with reduced content bandwidth can normally be seen because the main video channel also shows a reduced bandwidth. Some endpoints can disable the setting which reduces the call bandwidth when they experience errors; consult your endpoint manufacturer for details.
  • In a similar way, if one connection is at a lower resolution than the others it will cause all other participants to see that low resolution. Note that the participant who is limiting the resolution could be different to the participant limiting the bandwidth. To see which endpoint is limiting the resolution go to Participant > Diagnostics, and check the extended maximum size for either H.263+ or H.264, whichever your MCU is set to use in the content channel (shown in the Conferences > <Conference name> > Configuration page). Disabling content to that participant will result in the other participants receiving a higher bandwidth.
  • The "Hybrid and passthrough content" feature introduced in MCU version 4.3 can also help improve quality if endpoints with a range of bandwidth or resolution capabilities are connected to a conference. Please see the Release Notes for more details.
  • On the Conferences > <Conference name> > Configuration page under Content is the Minimum outgoing bitrate setting. If this is set to a value other than <no minimum>, the MCU will only send content to endpoints capable of that bitrate or higher. This will prevent the MCU sending the content stream to everyone at, say, 128k when all endpoints perhaps apart from one are capable of 786k, for example.

If it is known in advance that an endpoint might have network problems, content can be disabled before the call is made. This can be done when calling out from the Add Participant page by setting Content receive to Disabled. Alternatively, you can configure an endpoint on the MCU with that option disabled, then call out using those settings. Configuring an endpoint also enables you to match incoming calls from a given IP address: if the endpoint calls in, the MCU will apply the same settings and not send content.

April 17th, 2013 TAA_KB_156