Extron Electronics VN-Matrix 250 User Guide - Manual (Page 67)

Decoder video bandwidth tab
To access the video Bandwidth tab from the Device tab, click the Display0 link and, in the
Display tab, click the video link.
Figure 42. Video Bandwidth Tab
This page provides statistics on the video stream and allows the decoder video buffer to be
monitored and configured, if necessary.
If required, modify the
Window Name by editing the current value and clicking Update . It is
not necessary to name this field for normal operation.
Decoder video buffer
The delay time between the data being input to the encoder and output on the decoder is
controlled by setting the
Channel Delay and the Frame Delay . The channel delay is unique
to each channel of video, audio, or data and is set in seconds. The frame delay can only be
modified on the video channel and is converted from frames to seconds depending on the
video frame rate that the decoder is currently receiving. The delay time is the sum of these
two values and is shown in the
Total Delay field.
In normal operation on a LAN, Channel Delay should be set to 0.0 and Frame Delay should
be set to 6 frames. This will give an end to end delay of 100ms on a 60 fps signal.
On a WAN the Channel Delay parameter should be used to add an amount corresponding
to the one‑way network delay.
Under normal operational circumstances, there is no requirement to adjust the Frame Delay
setting and the buffer is managed automatically.
The hardware has a minimum delay requirement of 2.5 frames in progressive mode and
3.5 fields in interlace mode. Setting a
Total Delay less than these values results in uneven
playback and pipeline underflow alarms.
NOTE: There is one exception to this rule — setting the Total Delay to 0.0 (zero)
places the system in a special minimum‑latency mode. When operating with minimum
latency, the display attempts to decode data as soon as it arrives. This reduces the
elastic feel when using a remote cursor but can cause the display to be more jumpy
and the lip sync to an audio stream to be lost.
Excessively long delays cause data to build up in a software buffer within the decoder. When
the build up exceeds 10 video frames, frames of data are discarded, which may cause
on‑screen artefacts.
VNM 250 • VNM 250 GUI Overview 61