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

Luca Barbato lu_zero
Mon Apr 14 16:51:33 CEST 2008

Luca Abeni wrote:
> 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.

We should check on freebsd and netbsd IIRC.

> 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.

I took some time to look at the rtp -> udp protocol bridge and I think 
that maybe we could avoid reformatting the url (I have a patch to get 
the max_packet_size exposed on rtp but I'm not exactly happy with it)



Luca Barbato
Gentoo Council Member
Gentoo/linux Gentoo/PPC

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