User Guide

NETNode Operations Guide
Commercial in
Confidence
IP Mesh Systems
000-130
R1.8 2015-07-24
Commercial in
Confidence
Page 2-36
In this mode of operation the slider bar on VLC can be moved to navigate to different parts
of the recording.
Note: Playback will always start on the next 30 second chunk. The Network Time Protocol
(NTP) timestamps in the data contain the time the recording was transferred to SD card.
Step 7: Transferring the Files
Individual recorded files can be transferred to the PC using the Web interface to download
the files. To do this operation, simply right click on the file.
The SD card can also be removed and inserted into a card slot on the PC to read the files.
The SD card format is FAT16 with the date stored in UTC format.
2.11 Video Flow Control
Video flow control allows the video bitrate to be varied depending on the MESH bandwidth
available. This prevents corruption of the video when MESH bandwidth drops, and allows the
picture quality to adapt accordingly.
The VFC operates by monitoring the latency from the video encoder to the MESH endpoint or
endpoints (this is where the video emerges from the MESH network). At the endpoint a
special acknowledgement packet (RACK) is sent back to the source. The system tries to
maintain the round trip to the target latency.
Video flow control requires the internal encoder to be upgraded to version 1.4 or greater.
See the H264 encoder upgrade instructions to see how to do this.
To setup the video flow control, first check that the streaming protocol on the global settings
plane is set to RTSP unicast or multicast. On the configuration plane set the video bitrate on
the encoder tab to the lower of maximum value that the link will support, and what is
required to give the required picture quality. This value will not be exceeded. Setting this
value too high will degrade performance.
At this time, go to the streamer plane, and enable Video Flow Control. It can be necessary to
adjust the Target Latency depending on the network. Too low a value will drop the actual
bitrate, too high a value will increase latency and cause overflow in the internal FIFOs, which
will corrupt the video. The value must be chosen so it is just big enough to give full capacity.
In most cases the default value of 80ms will operate well. It is possible to reduce the value a
little to give spare capacity for other services.