[FFmpeg-devel] H.263 packetizing into RTP

[Luca Abeni]

Hi Martin,

On Fri, 2009-04-03 at 21:08 +0300, Martin Storsj? wrote:
[...]
> > > also i suspect that packets should be split at slices/gobs
> > 
> > RFC 2190 states that pictures should be split either at gob level
> > (mode A), at MB boundaries (mode B) or at MB boundaires of P-frames
> > with PB-frame mode.
> 
> As far as I know (I found the original patch in a mailing list post from 
> Luca Abeni), this is an implementation of RFC 4629 (and 2429); this is a 
> different RTP packetization scheme than the one in RFC 2190. As of RFC 
> 4629, this is the recommended scheme for all variants of H.263.

Yes, this is my understanding too.


> In this packetization scheme, the frame can be split into packets 
> regardless of GOB/MB boundaries or anything else. From RFC 4629, section 
> 6.2:
> 
>    A Follow-on Packet contains a number of bytes of coded H.263+ data
>    that do not start at a synchronization point.  That is, a Follow-on
>    Packet does not start with a Picture, GOB, Slice, EOS, or EOSBS
>    header, and it may or may not start at a macroblock boundary.
> 
> Splitting packets according to such boundaries would perhaps give better 
> handling of dropped packets, but isn't mandated.

Right. This is why I said that the patch is (IMHO) correct but
suboptimal.


			Thanks,
				Luca