[Ffmpeg-devel] global headers

[Måns Rullgård]

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.

>> 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.

-- 
M?ns Rullg?rd
mru at inprovide.com