The VideoLAN Forums

Hi,
First, thanks for taking the time to read my post.

I own a bowling alley and I am trying to figure out how I could send video to the many monitors I have above the lanes. I have twelve monitors (probably more) available for video display and I want to be able to display different video feeds on different monitors (e.g. different sports channels, in-house advertising, etc.). I think that I would probably have a total of five sources, 2 TV channels, 1 DVD player, 1 show controller with DVD output and a PC with an in-house advertising video stream. In some circumstances I would also like to have all the monitor displaying the same stream (music video DVDs) with music playing through the bowling center's sound system.

My electronics room is maybe 300 feet from the furthest monitor. I have looked into running video over cat-5 cable and then having some sort of cat-5 based video matrix switch to allow me to connect the various video sources to particular video monitors but this is really expensive. Another option is to have a distribution amplifier in my electronics room send all the video feeds to all the monitors and then switch each monitor to a particular video feed. This is sort of clumsy and I have cable length problems in this configuration.

Since I am planning on having an embedded linux system at each monitor (for some other purposes) it occurred to me that I could multicast my various videos sources to the various linux systems controling each over-the-lane monitor. Each linux system could select which multicast feed it wants to attend to. This seems like it would work fine to me--but I really don't know much about this.

One issue is that the audio associated with the video would not go through the mpeg encoding-decoding path. The audio would be available in my electronics room (from the DVD player or the TV cable box) and that audio would go right into the centers audio amplifier system. I do see a problem here, the audio may lead the video in time due to the delays in the encoding and decoding of the video stream. I could insert a constant delay in the audio though I don't know if the encode-decode delay would be constant. And I don't know if there would be any video lag between the various monitors above the lanes. If things were not all synchronized well, it could be a problem.

I have never done much work with video and streaming so I don't know if these are simple or serious problems. Maybe someone out there would share there thoughts with me about this. I think that if this would work, it would give me lots of flexibility.

Thanks,
Greg Laird

What about one system streaming in Multicast on your network all the channels and buy some STB to display them on each monitor?

I am going to have an embedded PC at each monitor, so this embed PC could play the multicasted video. And if I run a fast enough network, it should be able to handle 4-5 channels with good resolution. I am using 42 inch monitors with 1920 x 1080 resolution.

I have done some experiments using VLC to stream and to receive network video. The resolution seems good when I set the bit rate up around 5 Mbps. I did notice a long delay (1-2 seconds) from when I stopped the streaming software until the video on the receiving PC stopped. There is some buffering going on somewhere it seems.

One thing that I am worried about is the synchronization of the various monitors--they will all be getting the same feed but each will have its own processor. It seems like it would be unlikely that there would be skew between monitors but I have no experience with this.

Secondly, I am concerned that I might have problems with audio synchronization. The reason for this possibility is that I will not have any audio connection at each monitor. The audio will run through the buildings audio system that will be fed from program source--e.g. cable stb, dvd player, etc. I know there will be some encoding-transmission-decoding delay and I could allow for this by delaying the audio--but I don't know if this delay will be constant. One option would be to extract the audio from a PC receiving the media stream and then run extracted audio into the buildings audio system. This would take care of the delay problems if there wasn't any skew between stream playback devices.

If I could figure this out and get it to work reliably, it sure would be slick.

1) PC playing the same streams should be synchronised with nothing to do with them.
2) Yeah, this might be an issue, you might need to have a PC reading the stream and outputting the audio, to have correct synchro with the video.