[Live-devel] Broadcasting to UDP?

[Ross Finlayson]

> I am building an application where several clients should be able to watch a video stream from a CCTV IP camera.
> I think that the best solution bandwidth-wise is to have a single computer in the  network connect to the rtsp stream from the camera, and then broadcast this stream via UDP (to some address like 255.255.255.255) so all other computers in the network only need to "tap" that UDP port to get the video stream.

First, you shouldn’t be sending to the ‘broadcast’ address 255.255.255.255, because that will cause the packets to get received (and then discarded, if inappropriate) by all computers on your LAN.  Instead, you should be using an IP multicast address - which will cause the packets to get delivered only to the computer(s) that have subscribed to that address, and also (with appropriate routing) allows for the possibility of the packets being forwarded beyond a single LAN.

And, of course, you should be using the standard RTP protocol (over UDP), rather than raw UDP.

We have several demo applications - in the “testProgs” directory - that will stream (from a video file) via IP multicast.  You didn’t say what video codec you are using, but if you’re using H.264 (the most commonly-used video codec these days), then you can use our “testH264VideoStreamer” application.

Then, once you have demonstrated multicast streaming from a file (using an appropriate “test*Streamer” demo application), then see here
	http://live555.com/liveMedia/faq.html#liveInput <http://live555.com/liveMedia/faq.html#liveInput>
for tips on how to adapt this to stream from a live video source.


> I implemented this with VLC and it works, but... as the network gets more load from several devices, the VLC instances start falling behind the real time stream from the camera. With one Full HD camera and four standard cameras in the network, VLC (the "source" or re-streaming instance mainly) falls behind at an astonishing rate and after some 10 minutes the output stream is like 5 minutes behind real time!

We can’t help you with VLC problems (because VLC is not our problem), but I wonder if perhaps you’re running into network capacity problems.  Note that if any of your cameras are streaming over WiFi, then broadcast (or multicast) over WiFi is notoriously slow.


Ross Finlayson
Live Networks, Inc.
http://www.live555.com/

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