Comrex BRIC-Link Product Manual page 33

buffer size to compensate.
Fixed Delay - This option simply sets the Delay Cushion and Delay Limit at a similar value, so that the delay buffer is
defined to the chosen value and will not increase or decrease significantly.
Delay Cushion - The jitter buffer manager works to keep absolute delay to a minimum. Some applications are not
delay-sensitive and rely less on the jitter buffer manager. The Delay Cushion setting is a way to instruct the manager
not to attempt to drive the delay below a certain value. (For example, if the delay cushion is set to 500 ms, this
amount of fixed delay will be added to the buffer.) If the jitter manager needs to increase the buffer it will do so, but
will not go below the 0.5 second level.
Delay Limit - The inverse of the Delay Cushion, this parameter instructs the manager not to wind the buffer out
beyond a certain delay value, regardless of how many packets are lost. This is useful in applications where staying
below a certain delay figure is essential, but use of the delay limit can result in very poor performance if the
network jitter dramatically exceeds the limit.
Jitter Window - This parameter defines the amount of time (in minutes) that historical network performance is
analyzed in order to make the rest of the calculations. As an example, if the Jitter Window is set to the default
of five minutes, and if a dramatic network event happens and the buffer manager reacts (perhaps by increasing
the buffer), the event will be included in the manager's calculations for the next five minutes. If the network
experiences improved performance over this period, the manager may choose to wind the buffer back down after
the five minutes has passed.
Buffer Management On/Off - This is a diagnostic setting used to troubleshoot buffer manager performance by the
factory. For usage, it should always remain "on".
CrossLock Managed Delay - There are two ways BRIC-Link can calculate its target delay, and, therefore, how much
decoder buffer to add. The first is the BRIC-Normal way, and is the default for non-CrossLock connections. Buffer
size is set based on a histogram of past jitter performance. This will incur the shortest delay possible. For CrossLock
connections, the buffer is increased to allow the use of error correction, so buffer is thus based on a combination
of the jitter histogram, and the round-trip delay as calculated by the system. This will generally result in bigger
decode buffers (and higher delays). Because it is lower, the default setting is to use the jitter histogram for all
connections. This setting allows the profile user to use alternately the CrossLock "error correction friendly" setting,
for connections where delay is less important.
The following three settings are available to users in BRIC Normal mode. They are legacy settings for use in non-
CrossLock connections. Most users should leave these settings as-is, because they can interfere with CrossLock
connections. CrossLock settings now incorporate these functions.
Congestion Avoidance - Enabling this option allows the encoder to dynamically change the number of frames per
packet sent, thereby reducing total data requirements. In addition, in most encode modes, enabling congestion
avoidance provides the system a license to step down to a lower encode data rate if desired. This will happen
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