[FFmpeg-devel] [PATCH 2/3] ffmpeg: open encoders after decoders

[Aurelien Jacobs]

On Wed, Aug 11, 2010 at 06:25:02PM +0200, Michael Niedermayer wrote:
> On Tue, Aug 10, 2010 at 10:39:37PM +0200, Aurelien Jacobs wrote:
> > On Tue, Aug 10, 2010 at 02:10:35PM +0200, Michael Niedermayer wrote:
> > > On Sun, Aug 08, 2010 at 02:26:57AM +0200, Aur?lien Jacobs wrote:
> > > > From: Aurelien Jacobs <aurel at gnuage.org>
> > > > 
> > > > ---
> > > >  ffmpeg.c |   46 +++++++++++++++++++++++-----------------------
> > > >  1 files changed, 23 insertions(+), 23 deletions(-)
> > > 
> > > this should be unneeded, av_find_stream_info() should cause all the things
> > > to be set
> > 
> > It currently don't. So I've tried to force av_find_stream_info() to fill
> > the subtitle_header field with the attached patch. With this,
> > av_find_stream_info() indeed fills subtitle_header, but after it finishes
> > probing parameters, it calls avcodec_close() which effectively free the
> > subtitle_header buffer.
> > So after av_find_stream_info() call, subtitle_header is NULL again...
> > 
> > Any better alternative ?
> 
> what problems are there with using extradata?

Regarding the decoder, extradata is an input parameter which will
contain the "header" in native subtitle format. The decoder then need to
export the "decoded header" into generic format (ASS). That's what I
added subtitle_header for. Trying to re-use extradata instead would mean
overwritting something provided by the calling app, which might have
been allocated with something else than av_malloc(), or that might even
point to a static const buffer.
The situation is exactly the same for the encoder, but reverted. It is
supposed to output extradata in native encoded format and take the
generic subtitle_header as input.

So re-using extradata for this sounds like a dead-end to me.

Any other idea ?

Aurel