QVidium QVSD - Manual (Page 46)

User‟s Manual v.3 QVidium
®
QVSD H.264 SD Video Codec™
Copyright 2011 QVidium
®
Technologies, Inc.Page 46 of 53
for determining the necessary ARQ delay. The ARQ divides the Target Latency, specified
in milliseconds, by the round-trip time to the video encoding source to determine the
number of request attempts. Unless Robust Mode is enabled, it sets a minimum ARQ
latency of one round-trip time. A larger Target Latency allows the system to increase the
number or repeat requests, although the system will limit the maximum number of retries
to a maximum of 5, even if the Target Latency value would have otherwise allowed more
retries. Thus depending upon the Round-Trip time, the maximum delay may end up being
less than the specified Target Latency value.
Max Burst Drop: Burst packet losses are common occurrences in many IP networks and
the Internet. IP networks may dynamically change paths in response to load balancing,
link failure avoidance, and for other reasons. During a re-route, a sequence of queued
packets on a discontinued path may be dropped. A burst of packets may be dropped when
higher priority packets stall a lower priority buffer. ARQ will notice a burst packet loss
when the first packet after the loss arrives at the codec. Setting the Max Burst Drop Delay
(in milliseconds) will delay the ARQ repeat request by this amount to handle packet burst
losses.
Robust Mode: Normally, the ARQ will only require that a minimum of one repeat request
is sent to the video encoding source device, regardless of the Target Latency. However,
enabling Robust Mode will increase the minimum number of repeat requests to a minimum
of two retries.
ARQ Port: By default, ARQ normally sends upstream retransmission request packets on
UDP port 7020. You can change this ARQ Port setting to any valid and non-conflicting
UDP port. However, you must make certain that you specify the same port number at both
the encoder and the decoder.