[Live-devel] 2 SSRC on the same RTP stream

[Ross Finlayson]

>                  Thanks for the quick reply. In fact I stream each video on a separate multicast addresses:
> ·         The first on 239.20.31.1:5004 which works fine. the SSRC is always the same on all RTP packets
> ·         The second on 239.20.31.2:5004

Are you running Linux?  Linux has a bug (though some people don’t want to call it a ‘bug’) whereby if more than one process joins the same multicast group - but with a different port number - then all of these processes will receive copies of all multicast packets for all of these port numbers.  (Note that other Unix variants (including BSD) - as well as Windows - don’t have this behavior; it’s a problem just with Linux.)

Modern versions of Linux, however (starting, apparently, with Linux kernel version 2.6.31), have a “setsockopt()” option - called IP_MULTICAST_ALL - that allows you to disable this behavior.  The “LIVE555 Streaming Media” code (since version 2013.10.03) automatically calls “setsockopt()” to disable this behavior - if “IP_MULTICAST_ALL” is defined.

So, make sure that you’re using a sufficiently modern version of Linux - one in which the IP_MULTICAST_ALL setsockopt() option is defined.  That should solve your problem.

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

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