The VideoLAN Forums

Hello

Newbie question about IGMP-messages and VLC. I have switch and two laptops. When I connect two laptops to switch and use first stream DVD movie to udp://224.0.0.1:1234 ja I use second laptop to receive udp://224.0.0.1:1234. Stream propagates like a broadcast. On switch "IGMP snooping" is off. Everything works ok, but there's unneccessary 9Mbit/s port utilization on those ports who do not want to see movie.

After that I configure switch and turn "IGMP-snooping" option on. That should configure switch behavior so that stream is sent only to ports who are joined to multicast group. Ok that seems to work, stream doesn't propagate anymore to ports who are not joined to IGMP-group.

Problem is that VLC seems to be passive listener, it doesn't send any "Hey I want to join 224.0.0.1" messages.


Does (or should) VLC send IGMP messages?

You're right about everything in your post. You have to tell VLC that you're streaming on a multicast address : just use udp://@[multicat address]

(the @ is important

Hi,

I dunno much about IGMP... but is it possible to specify an IGMP group name? I mean... when VLC serves out a multicast stream, how does it go about joining (creating) a multicast group? For example, if I send the output to udp://@239.1.2.3:1234, what does VLC send out as the 'group' name? Can you specify a different name? Is it possible to send two streams out on the same multicast IP address and port, and a VLC client pick which stream it wants to receive just by asking to join a specific group name?

thanks,
Scott

the multicast group is addressed by it's ip/port. Just like every computer resource on a ip network is adressed by ip/port. If you want several stream then give time a new ip.

So you can't arbitrarily come up with your own multicast 'group name' ? I mean, in VLC, when you specify like '239.1.2.3' and port '1234' as a UDP 'output' method, what tells VLC that you want to just use UDP as opposed to creating a udp MULTICAST session?