QVidium QVMP2C-1011 - Manual (Page 17)

User’s Manual v.28 QVidium™ MPEG2+4 Codec
17 of 45 - Copyright 2007-2008 QVidium™ Technologies, Inc.
milliseconds, allotted for the request, retransmission, and recovery process. The ARQ mechanism
will attempt as many retries as possible within this target latency time. Thus, larger target latency
times increase the delay before video is output, but allows for more chances of requesting and
recovering any missing packets.
A Burst Drop delay can also be specified to delay any retransmission requests for a time equal to
the maximum expected packet loss time, such as from dynamic router changes of other sources of
burst loss.
A Robust Mode can also be selected. When selected (checked), a minimum of two tries will be
attempted for recovering any missing packets. Increasing the Target Latency in robust mode will
produce additional retransmission requests to the encoder. When not selected (unchecked), ARQ
will always try at least once to recover any missing packets. Regardless of the Target Latency,
normal (non-robust) mode will never send more than 2 retransmission requests per lost packet.
To help with firewall configuration and to handle potential port conflicts, the user can change the
default port that ARQ uses to send upstream retransmission requests, ARQ Port. However, you
must make certain that the same ARQ port number is set in both the encoder as in the decoder.
Although the automatic measurement of the round-trip time uses multiple measurements to take
into account random network delays, for some networks you might wish to specify a larger round-
trip value, or to specify a larger number of retries in case the upstream link loses some of the
retransmission request messages. In automatic robust-mode of ARQ operation, the system
automatically measures the round-trip time and divides that number into your specified Target
Latency to determine the number of retries to use. However in Manual Mode, you can force ARQ
to always use a specified number or retransmission requests.
Note: For testing ARQ error correction, select ARQ transport at both the encoder and decoder and
use the default ARQ parameters at the decoder (receiver). Please also be certain that ARQ has
also been selected at the encoder. Currently for ARQ, you MUST enable Full Pacing and limit the
video TS bitrate to 6.5 Mbps or less on the encoder.