[FFmpeg-devel] [PATCH 2/2] avcodec/h264_slice: Never call get_format() for just checking if the format matches

[Michael Niedermayer]

On Sun, Oct 11, 2015 at 09:39:32PM +0200, wm4 wrote:
> On Sun, 11 Oct 2015 21:16:27 +0200
> Michael Niedermayer <michaelni at gmx.at> wrote:
> 
> > From: Michael Niedermayer <michael at niedermayer.cc>
> > 
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> >  libavcodec/h264_slice.c |    4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/libavcodec/h264_slice.c b/libavcodec/h264_slice.c
> > index cce97d9..daa3737 100644
> > --- a/libavcodec/h264_slice.c
> > +++ b/libavcodec/h264_slice.c
> > @@ -985,6 +985,10 @@ static enum AVPixelFormat get_pixel_format(H264Context *h, int force_callback)
> >      for (i=0; choices[i] != AV_PIX_FMT_NONE; i++)
> >          if (non_j_pixfmt(choices[i]) == non_j_pixfmt(h->avctx->pix_fmt) && !force_callback)
> >              return choices[i];
> > +
> > +    if (!force_callback)
> > +        return AV_PIX_FMT_NONE;
> > +
> >      return ff_thread_get_format(h->avctx, choices);
> >  }
> >  
> 
> So if I can see this right, the whole purpose of this is to check
> whether the h264 parameters map to a lavc pixfmt, and bail out or
> reinitialize if it doesn't. Why can't this be delayed later? What
> actually needs it sooner than the first "real" get_format? For dealing

> with paramater changes, why can't it check the raw parameters instead?

The raw parameters are checked as well but iam not sure these checks
are complete, they are more complex.


> Doing it this way seems a bit convoluted. (I understand it now that I
> thought about it, but normally I'd think it's VERY weird that it
> somehow can go on without using the user-decided pixfmt, or that the
> user-decided pixfmt sometimes doesn't seem to matter?)


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

It is dangerous to be right in matters on which the established authorities
are wrong. -- Voltaire
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