QVidium QVSD - Manual (Page 45)

User‟s Manual v.3 QVidium
®
QVSD H.264 SD Video Codec™
Copyright 2011 QVidium
®
Technologies, Inc.Page 45 of 53
jitter or variability in the delivery of data to the decoder. If you notice audio clicks or
pauses, or if the decoded video occasionally freezes or loses lip-sync, especially over long
network distances, increasing this value may help. The default value should be 300ms, but
for operation over a WAN, we would suggest increasing this value to 500ms or larger.
Increasing this value will increase overall latency, so you should minimize this value to
minimize latency.
Out-of-Order buffer: When in ARQ mode, the decoder includes an optional additional
buffer, in addition to the Jitter Buffer, that reorders incoming packets in case the network
is causing some of the packets in the incoming video stream to arrive out of order. This
buffer will re-order any packets within it to be output in the order of the RTP sequence
number. To enable this feature, you must specify a buffer size in terms of the number of
packets this buffer must hold until any packets are output to the decoder. This feature is
most useful if you choose to use Network Bonding on the decoder which causes the
outgoing video stream to be interleaved between the two Ethernet ports. In this case,
varying network delays may cause packets to arrive out of sequence, which this feature
helps to fix.
Detect video break: This feature only works for Network input. It monitors the PCR
timestamps in the incoming MPEG2 Transport Stream for discontinuities and unexpected
values and then automatically restarts the decoder when it detects a problem.
Detect video break limit: This parameter lets you set the minimum discontinuity time-out
of between 100ms and 2000ms (2 seconds). If the decoder detects a break in the incoming
IP stream larger than this value, then it will restart the decoder to prevent the decoder
from getting into a bad state.
ARQ Parameters
The parameters below ONLY pertain to QVidium ARQ error correction. They will be
ignored unless ARQ is selected for IP Transport.
Mode: Auto or Manual. In “Auto” mode, immediately after clicking on Start, the
decoder sends out a series of packets upstream to the encoder to measure the round-trip
time and automatically set the number of retries and round-trip time parameters based on
the Target Latency parameter. The results of these measurements can be seen in the
decoder’s log file by clicking on Show Log and scrolling towards the bottom of the log
file. Clicking on Status will show the resulting value of these parameter based on the
measurements seen in the log file.
In “Manual” mode, the codec uses the Number Retries and Round Trip Time
parameters to create an ARQ buffer with the ARQ delay = Number Retries *
Round Trip Time. In Manual mode, the decoder’s ARQ mechanism ignores the
Target Latency parameter and does not take any upstream link measurements.
Target Latency: QVidium’s ARQ error correction operates through the addition of a
small additional buffering delay to provide enough time to request and receive
replacement for each lost packet. Target Latency gives the ARQ mechanism a target value