[Matroska-users] Some questions about matroska.....

Steve Lhomme steve.lhomme at free.fr
Wed Jan 12 09:49:06 CET 2005

Fabio Bizzi a écrit :
> Hi matroska guys,


> I'm new with matroska and I've some questions to this list, I've 
> searched in the docs but I haven't found what I'm looking for.
> The first question is: Is Matroska "streammable" in multicast ?
> I've looked around for any documentation about streaming matroska in 
> unicast / multicast but I'ven't fond any at all. :(

No. Multicast/RTP requires too many changes to the format to be usable. 
The only streaming we recommend/support/endores is on TCP. UDP could 
work as the format is working even with data loss. But RTP has more 
constraint that would make it hard to work.

We had a discussion about that maybe 2 years ago and decided that it was 
  not a top priority to have this. But if you really want a definitive 
answer we could have a look again.

 From what I remember multicasting is good if the UDP packets are small 
and "atomic". That means it represents a valid basic part of the stream. 
But in Matroska the smaller level that can have error checking is the 
BlockGroup, which can be huge for video since it contains a complete 
frame (can be a few kilobytes)... Now for audio without lacing these 
packets could be small and therefore usable.

> If Yes, Can I use RTP ? or what else ?
> DO I need a SAP server for announcements and Header, Meta Seek 
> Information, Segment Information and Track ? Or What else ?
> Where I can found docs about it ?
> Thanks a lot.

All the doc we have is on the website or the ML. But if you have more 
background on multicasting it could be helpful for us if you share it :) 
Maybe I'm wrong about the needed atomic aspect of RTP/UDP. As even for a 
1 Mbps stream the UDP packets for video will never match a video frame, 
regardless of the format used.


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