MosaicExampleSetup
Contents
Example set-up for a conference: Plans
Problem description
For a conference we needed a web stream for participants who were not able to come. The set-up needed to be flexible as well transportable, since the conference took place at two venues which were several hundred meters apart. VLC was chosen because there was already a somehow working set-up available which was modified for this conference.
Hardware
We were using a dual-core AMD box (Athlon X2 4600+) with 1 GB of memory and only two PCI slots (Fujitsu Siemens PC). So nothing out of the ordinary. We had two PolyCom remote controllable cameras which can output SVIDEO signals which we feed into to BT878 based grabber cards.
Software
We used the vlc version coming with Ubuntu Gutsy 0.8.6c along with xawtv for direct control of the cameras (the encoding process and buffering of the clients usually introduce a lag of a few seconds which makes it hard to steer the camera efficiently.
Network distribution
One of our problems was that at one of the conference venues the network bandwidth was somehow limited and we feared to overload that network. We thus decided to stream only to a single dedicated box which is connected to a network with a much larger bandwidth. This box was restreaming the content to anyone interested.
Details
Needed devices
Video
Grabber cards registered their devices where the camera output can be viewed from:
/dev/video0 /dev/video1
The very first step is to check, if these are working. For this, start
xawtv -c /dev/video0
and we saw a blue window, because xawtv sets the input mode to composite not SVIDEO. To change this, right-click on the blue window, and change the input to SVIDEO. I have not found a possibility to change this via the command line.
If video0 is working, try the same with video1 it should work as well.
Audio
The grabber cards I used, do have audio input but I only got very bad quality. With the on-board audio I got a much better quality so this was used. If you are a fan of a graphical interface try to record input from /dev/dsp (need the OSS kernel modules) with audacity. Don't simply connect the output of the sound card to loudspeakers and the input of your microphone to the microphone input of your computer. The sound card may directly connect those two channels without the software having the possibility to record anything.
more to come
