[Ffmpeg-devel] global headers

[Michael Niedermayer]

Hi

On Sun, Mar 19, 2006 at 02:17:12PM +0000, M?ns Rullg?rd wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> 
> > Hi
> >
> > On Sun, Mar 19, 2006 at 01:33:58PM +0000, M?ns Rullg?rd wrote:
> >> Michael Niedermayer <michaelni at gmx.at> writes:
> >> 
> >> > Hi
> >> >
> >> > On Sun, Mar 19, 2006 at 12:05:22AM +0000, M?ns Rullg?rd wrote:
> >> >> Michael Niedermayer <michaelni at gmx.at> writes:
> >> >> 
> >> >> > could we use the same format and convert the global one in the mov/mp4
> >> >> > (de)muxer?
> >> >> 
> >> >> We're doing the opposite right now.  I don't like this, since
> >> >> whichever way it's done, several muxers will need to do the
> >> >> conversion.  E.g. ADTS format is required for raw ADTS, MPEG-TS and
> >> >> MPEG-PS.  MP4 requires the other format.  Matroska, as is to be
> >> >> expected, uses it's own bastardized variant.
> >> >
> >> > fine, so what do you suggest? demuxer -> muxer must work even if the
> >> > AAC variants differ ...
> >> >
> >> > so if a demuxer has ADTS internally what should be done, remove ADTS
> >> > headers in the demuxer? in a middle layer? or the muxer?
> >> >
> >> > should it be optional or always be removed?
> >> > always will break if the headers change (switching channels, movies, ...)
> >> > allowed or not it will happen and must be supported
> >> 
> >> To me, the cleanest solution would be a middle layer for transforming
> >> between the different formats.  Doing it in the demuxer or muxer will
> >> inevitably lead to the same work being done in multiple places.
> >
> > fine, do you volunteer to implement it?
> 
> I'm afraid I don't have time right now.

neither do i (for implementing a intermediate layer, a simple write/remove
global header thingy would have been alot easier ...)


> 
> >> Could we perhaps use AVCodecContext.sub_id here?
> >
> > hmm, maybe but somehow i think its not a good idea
> 
> OK, but we need some method of indicating which variety we are dealing
> with.  The GLOBAL_HEADER flag isn't sufficient when there are several
> formats the global header can take on.

yes, but sub_id is used for things like the layer of mpeg-audio so its
not a good choice here, we need to add a new field ...

[...]
-- 
Michael