[FFmpeg-devel] h264_annexbtomp4 filter ideas, was: Collection of patches

[Michael Niedermayer]

On Fri, Apr 25, 2008 at 02:33:28PM +0200, Benoit Fouet wrote:
> Hi,
> 
> Thorsten Jordan wrote:
> > Thorsten Jordan schrieb:
> >   
> >> Loren Merritt schrieb:
> >>     
> >>> On Thu, 24 Apr 2008, Thorsten Jordan wrote:
> >>>       
> >>>> Baptiste Coudurier schrieb:
> >>>>         
> >>>>> Thorsten Jordan wrote:
> >>>>>           
> >>>>>> Thorsten Jordan schrieb:
> >>>>>>
> >>>>>>             
> > [...]
> >   
> >> To fix all this, one needs to know:
> >> * which SEI messages apply to the whole stream and only keep them (there
> >> are 22 types of SEI messages according to spec - do you know which one
> >> are global?)
> >> * should they get stored after SPS/PPS in extra data or keep their
> >> possibly mixed order
> >> * How the split API could be modified to do all this (see my other mail
> >> in reply to Michael)
> >>     
> >
> > Ok, to summarize:
> >
> > - a h264_annexbtomp4 bitstream filter is desired.
> > - parts of it are similar to what a h264-parser-split() function would do
> > - it has to be researched which SEI messages may be stored in global headers
> >   
> 
> should there be any for MP4 ?
> quoting ISO/IEC 14496-15:2004(E) 5.2.2 (by hand, as I only have a paper
> version):
> SEI message NAL Units: All SEI message NAL units shall be contained in
> the sample whose decoding time is that before which the SEI messages
> come into effect instantaneously. The order of SEI messages within a
> sample is as defined in ISO/IEC 14496-10, 7.4.1.2. This means that the
> SEI messages for a picture shall be included in the sample containing
> that picture and that SEI messages pertaining to a sequence of pictures
> shall be included in the sample containing the first picture of the
> sequence to which the SEI message pertains.
> 
> and extradata (that's to say avc1 box) doesn't have room for SEI data.

Yes, ive also (yesterday?) first thought that there are global SEIs but
after a quick look over the SEIs in H.264 none looked global. User data
should in principle be global in some cases but i dont see how that
could be decided in a parser/(de)muxer. Its ironic that with all the
complexity in H.264 such quite important things like to what user data
applies are not clear (that is sequence, gop, frame, slice, ...)

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If a bugfix only changes things apparently unrelated to the bug with no
further explanation, that is a good sign that the bugfix is wrong.
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