[Ffmpeg-devel] RTP patches & RFC

Michael Niedermayer michaelni
Fri Oct 27 21:28:16 CEST 2006


On Fri, Oct 27, 2006 at 11:56:42AM -0500, Ryan Martell wrote:
> >>>>The other part of the issue is that fragmentation packets should be
> >>>>reassembled before handing them to the AVParser, so that if  
> >>>>there is
> >>>>a sequence issue or a missing packet, the entire packet can be
> >>>>dropped without going to the codec to corrupt the stream.  There is
> >>>>no way (IMHO) of doing this, if I just passed the packets up the
> >>>>chain.  I know the parser is resilient, but basically a packet  
> >>>>could
> >>>>be broken anywhere.  it seems like a lot of strain to put on the
> >>>>decoder's error detection/correction, when at my level I KNOW if
> >>>>parts were dropped.
> >>>
> >>>well, but the decoder should be able to decode the part of a NAL  
> >>>unit
> >>>until the missing part, so droping the whole just isnt correct
> >>>but note, i dont know how well this currently works with h264.c,
> >>>its just
> >>>supposed to work and does work with the mpeg/h263 decoders ...
> >>
> >>We can do either.  Here's my thoughts on dropping the entire packet:
> >>	Pros:
> >>		I _know_ that it was not complete.
> >>		That's what the RFC says to do.
> >>		Prevents weird invalid data stream issues in the decode (it
> >>		might  not like it if it doesn't get a certain byte..).
> >
> >invalid data must be handled sanely anyway when the source is the  
> >internet
> Another issue i just thought of is that a fragmented packet is  
> supposed to have the timestamp of the first packet received, not the  
> last packet received.  I don't know whether the server always sends  
> them with the same timestamp or not, but if I did away with the  
> packets in the background, this would not be correct (then the parser  
> would think they were for different frames..)

the parser does NOT use the timestamps to determine frame boundaries


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In the past you could go to a library and read, borrow or copy any book
Today you'd get arrested for mere telling someone where the library is

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