Polycom Audio and Video manual Preferred Speed for

Chapter 3 - Configuring Network Use

4.Select to go to the Preferred Speeds screens and configure these settings:

Setting	Description
Preferred Speed for	Enter the speed that will be used for calls placed from this system
Placing Calls	in either of these cases:
	• When Call Quality is set to Auto on the home screen and
	Directory screen
	• When the Call Quality option is not available for users
	If the far-site system does not support the speed you select, the
	system automatically negotiates a lower speed.
	Note: Cable and DSL modems typically have bandwidth
	restrictions for upload (transmit) and download (receive).
	Therefore, if you’re making calls through a cable or DSL modem,
	you need to find out what your upload and download capabilities
	are in order to select the correct speed for your system. If you
	don’t know, ask your ISP.
Maximum Speed	If you want to restrict the bandwidth used when receiving calls,
for Receiving Calls	enter the speed here. For example, if you have a DSL connection
	that it is limited to 384 Kbps upload and 1.5 MB download, you
	should restrict your calls to 384 Kbps or less for better call results.
	If the far site attempts to call the system at a higher speed than
	selected here, the call is re-negotiated at the speed specified in
	this field.

One way to determine what your optimal call speeds should be is to select the lowest call speed for each direction: upload and download. Try the call at that speed and see how it looks. You can then keep increasing the call speeds and checking the results until you find your optimal call speed for each direction.

Keep in mind, however, that optimal call speeds may vary at different times of day depending on the traffic on the network. Also, if another system in the video call cannot upload at the speed you specified, the call may suffer from poor video quality or you may not be able to view video at all (black screen). Call speeds also do not reflect additional IP overhead (such as timestamps) of approximately 20%.

5.Select to go to the Call Speeds screen and specify the call speeds to make available to users, if you are allowing them to choose speeds on a call-by-call basis.

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