[FFmpeg-devel] Removing the "multicast=" tag from UDP URLs

Luca Abeni lucabe72
Mon Apr 14 10:03:12 CEST 2008

Hi Luca,

Luca Barbato wrote:
> Luca Abeni wrote:
>> I have a set of patches for removing the need for such
>> tag; I am currently testing them, and I'll post the
>> results on Monday. But I have a question:
>> to make everything as simple as possible, I am assuming
>> that a destination address can be multicast only if it
>> is provided as a numeric address (for example, the SDP
>> generator is not going to resolve an host name to check
>> if it is multicast or not). Is this reasonable?
> I think so even if additionally checking would be nice (resolve the 
> address, check if it is multicast, act accordingly)

Ok; I hope I found a reasonable solution, see attached patches.

0001-Remove-the-multicast-tag.txt removes the usage of the
"multicast=" tag, by using the (hopefully standard) IN_MULTICAST
and IN6_IS_ADDR_MULTICAST macros to understand if an address
is multicast. I added some "#ifdef"s to avoiding breaking
architectures that do not define such macros. The patch is tested
(and seems to work fine) on Linux.
0004-Fix-receiving-from-SDP-with-unicast-destinations.txt fixes
the RTSP demuxer to pass the correct input port to the RTP protocol,
so that unicast SDP files can be correctly played.

There is a remaining usage of "multicast=" in the SDP generator,
and I have some patches for removing it but I am not satisfied yet
with them (I do not want to resolve a host name for generating an
SDP description). The two attached patches actually fix a real bug
(while the SDP generator's patches are only a cleanup), so I think
they should be committed first.

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