Audio/Visual Best Practices (8.5) 

Best Practices for ensuring a good audio/visual experience

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Always use the latest manufacturer camera drivers

• Install drivers before connecting camera.  Otherwise camera may use Generic UVC driver.
• Check manufacturer for latest drivers, or use provided update mechanism
• Verify drivers against Windows Update (most large manufacturers update drivers in both places.)
• Do not use Generic UVC drivers, unless no other drivers are available
• If using Generic UVC drivers, you must be at Windows XP SP2 or greater

Crashes in audio/visual are known to occur if not using the latest and greatest drivers, especially with Windows XP SP1 and earlier UVC drivers.

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Always use latest manufacturer video card drivers

• Video decompression is highly CPU intensive.  Better DirectDraw drivers move CPU load to GPU (graphics processing unit) 
• Download the drivers either from computer manufacturer, video card manufacturer, or Windows Update.
• Video Card should have minimum required video memory - 128M.  Lower memory sometimes works, but will have poor experience and is not supported.  < 32M will always fail

There have been problem reports where video performance was terrible, with constant issues with pixelation, that were not seen again after updating to latest video drivers.

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Verify function with clients on same network subnet first

• Sametime 8.5 does not support NAT traversal, and also requires clients and servers to be able to connect in both directions.
• Audio/Visual data uses UDP, not TCP, which many firewalls (client and infrastructure) do not pass.  Connection ports are assigned dynamically, complicating opening firewalls.
• This complicates debugging in situations with firewalls, VPNs, remote subnets.
• Always verify the function of the Sametime Media Manager Server first with clients on the same subnet as the server, with their client firewalls disabled. 
• When verified, then move clients out to other network points.

There have multiple problem reports opened, and the issue turned out to be caused by a firewall only passing UDP traffic in one direction.  The use of the network in AV is complicated as there is lots of data moving on multiple ports, with multiple UDP and TCP traffic.  (Its not simple like just opening port 80 inbound HTTP traffic)

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Use bitrate appropriate for your users / equipment / environment

• Default bitrate (CIF 352x288@15Fps 384kbps) is probably good for most setups. Good for machines 1-3 years old, Cable or DSL, most webcams
• Higher bitrates, with more resolution, more frames per second, require: higher bandwidth, more processing power, better video cards, and better cameras. When all of this is available, the quality improvement is noticeable
• Lower bitrates, with less resolution, less frames per second, require: less bandwidth, less processing power, slower video cards, and standard cameras. They allow older, slower networks to be acceptable, but at lower video quality.

It may be necessary to tune their bandwidth settings to what is appropriate for them. As the setting is global, they will not be able to tune the value to work for all users, unless all users have the same environment and equipment.

Related articles:

Open Mic recording: Sametime 8.5 audio and video installation and limitations