[FFmpeg-devel] [PATCH] Fix nonsense non-mod16 AMV flipping code.

[Michael Niedermayer]

On Sun, Apr 29, 2012 at 10:09:52PM +0200, Reimar Döffinger wrote:
> On Sun, Apr 29, 2012 at 09:45:42PM +0200, Michael Niedermayer wrote:
> > On Sat, Apr 28, 2012 at 11:37:08PM +0200, Reimar Döffinger wrote:
> > > It is obviously nonsense since it produces wrong results
> > > or even crashes (crashes should be encode-only though).
> > > Fixes trac issue #1092.
> > > 
> > > Signed-off-by: Reimar Döffinger <Reimar.Doeffinger at gmx.de>
> > > ---
> > >  libavcodec/mjpegdec.c      |    3 +--
> > >  libavcodec/mjpegenc.c      |    2 +-
> > >  libavcodec/mpegvideo_enc.c |    5 -----
> > >  3 files changed, 2 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
> > > index a841384..fe54b45 100644
> > > --- a/libavcodec/mjpegdec.c
> > > +++ b/libavcodec/mjpegdec.c
> > > @@ -972,8 +972,7 @@ static int mjpeg_decode_scan(MJpegDecodeContext *s, int nb_components, int Ah,
> > >          s->coefs_finished[c] |= 1;
> > >          if (s->flipped) {
> > >              // picture should be flipped upside-down for this codec
> > > -            int offset = (linesize[c] * (s->v_scount[i] *
> > > -                         (8 * s->mb_height - ((s->height / s->v_max) & 7)) - 1));
> > > +            int offset = linesize[c] * (s->v_scount[c] * s->height / s->v_max - 1);
> > 
> > this will draw above the image i think, is this ok for all MB sizes
> > and interlacing ?
> 
> Well, at least not more than before, and the tests I made looked ok.
> But I can't tell for sure. I believe the way this is supposed to work
> is like this:
> Since EMU_EDGE may not be set, we have 16 pixels extra all around the
> picture. These we use to both flip and expand the image (since the codec
> is intra-only they aren't really needed for anything else).

the picture size is rounded up first then the edge is added
thus there should be more space at the bottom then top.


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

Why not whip the teacher when the pupil misbehaves? -- Diogenes of Sinope
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