The VideoLAN Forums

vlc on a linux box transmits a multicast feed to Windows boxes running vlc which play fine. When OSX is plugged into the same port, it doesn't play.

I did a trace and found that vlc on OSX subscribes to the feed (IP_ADD_MEMBERSHIP) and the UDP data starts flooding in, but vlc never sees nor plays it.

Wireshark Screenshot (request is packet 284 and you can see all the red UDP data packets after that)

When I start vlc in the terminal with:

/Applications/VLC.app/Contents/MacOS/vlc -vvvvvvvvv --stats udp:@239.255.10.10:12345

I get:

[00000287] ipv4 access debug: cannot configure socket (SO_RCVBUF: No buffer space available)
[00000287] ipv4 access debug: cannot configure socket (SO_SNDBUF: No buffer space available)

and eventually I get the famous "cannot pre fill buffer".

full vlc trace output

Has anybody else had a problem with this? Any suggestions on why vlc isn't seeing the multicast data it successfully subscribes to?

I have found the same thing. I have tried recompiling from SVN and I get the exact same issue.

I have this replicated on 5 machines at this point. I'm running VLC 0.8.5.

My working theory at this point is that the kernel isn't giving the packets to VLC. Does anyone know how to ask the OSX kernel what multicast streams are subscribed to what applications? Is there any other multicast debugging I can expose?

that sounds like multicast is not present on the default MacOS network (the topmost one).

If you have multiple networks, try changing the order of them in the Network control panel.

I have mcast on my non-primary interface, and use this terminal command enter a route for the mcast address space:

sudo route add 224.0.0.0 192.168.2.0 240.0.0.0

where my second network with mcast is 192.168.2.0

macOSX VLC 0.8.6 works great with multicast when it's present.

Perhaps your router is filtering the mcast?

George