[FFmpeg-devel] [RFC] WC3 decoder without AVPaletteControl

[Baptiste Coudurier]

On Wed, Apr 15, 2009 at 11:55:48PM +0200, Michael Niedermayer wrote:
> > > > > [....]
> > > > >
> > > > > the first sample file i picked has
> > > > > 87 palette chunks and a duration of 7.8 seconds (at 12fps)
> > > > > are you sure that 3600*30 stsd chunks in mov will work?
> > > > 
> > > > Well it will work for sure. 
> > > 
> > > how exactly would the libvaformat mov demuxer pass these palettes
> > > to the decoder?
> > 
> > Using the same way it does currently ?
> 
> You mean the one that causes race conditions and doesnt work with threaded
> players like ffplay ...
> The one why we try to change because it doesnt work ...

ffmpeg kinda works. Yes there is a race problem and there are some
ways to fix it. I strongly believe we can reach an agreement here.

> [...]
> > > > [...]
> > > > 
> > > > IIRC the race condition happens because demuxer sets palette to
> > > > AVCodecContext _directly_.
> > > > 
> > > > Storing it in AVFormatContext should avoid this race, or is there
> > > > something I'm forgetting ?
> > > 
> > > you forget that the palette from AVFormatContext must reach the decoder
> > > and what you do is that you would just remove the code that does that
> > > that fixes the race condition but it removes palette support pretty much
> > 
> > I don't forget, application will update AVCodecContext palette
> > accordingly, of course. This does not remove palette support at all,
> > and avoids changing decoders and fixes the race condition IMHO since
> > now AVCodecContext does not get updated by the demuxer but the application.
> 
> Which application?
> 

One you don't know about ? ;)
This is still one solution.

There are at least 3 solutions:
- append palette to pkt->data
- use pkt->palette_data
- use AVFormatContext palette

If the third is not ok for anybody then fine.

I find the second reasonable and should satisfy everybody IMHO.
Palette is passed through AVPacket and it avoids parsing in pkt->data,
though it grows a bit AVPacket struct. It's not like we are afraid of
growing structs usually ;)

Besides, avcodec_decode_video2 now uses AVPacket.

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