[FFmpeg-devel] [patch] fix problem receiving udp multicast

Deti Fliegl deti at fliegl.de
Wed Nov 20 21:45:13 CET 2013

On 20.11.13 21:10, Reimar Döffinger wrote:
> Sure, that would be one step further.
> I was just attacking the part of the problem that made no sense to me.
> Though I could imagine that limiting the issue to the
> RTCP part is still an improvement, particularly since that
> solution isn't OS-specific.
Unfortunately this issue is result of a poor design. The UDP code relies
on the assumption that only these multicast groups have been joined by
the host that are relevant for the current UDP stream. This is not
correct, because multicast groups are always joined system wide. So you
will receive all the multicast packets sent to a single UDP port that
are come from multicast groups joined by the system.
The only way to limit the multicast packets that are sent to a single
multicast group is using bind.
So basically my first patch is the only one that works properly. I will
keep it that way, because it fixes RTP and RTCP reception.


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