[Ffmpeg-devel] [BUG] H.264 + AltiVec == heavy artefacts

Diego Biurrun diego
Fri Sep 30 22:42:49 CEST 2005

On Fri, Sep 23, 2005 at 09:25:10AM +0200, Romain Dolbeau wrote:
> Diego Biurrun wrote:
> >and it shows really bad artefacts, black blocks all over the image.  Any
> >other H.264 movie will do as well.  ffplay has the same issues, which go
> >away if I compile with --disable-altivec.
> >I'm trying to find out which function exactly is causing the problems
> >but I haven't quite figured out yet how h264.c falls back to AltiVec or
> >other CPU-specific optimizations (yes, I'm lame and I know all about
> >it).  Any helpful pointers would be appreciated.
> relevant files are libavcodec/ppc/dsputil_h264_altivec.c and
> libavcodec/ppc/dsputil_h264_template_altivec.c for h264-
> specific stuff.
> dsputil_h264_altivec.c::dsputil_h264_init_ppc() set up
> the various functions.
> Please let me know if you find the problematic function (I'm
> sorry I don't have time to investigate myself ATM), I'll see
> what I can do to fix.

If I comment out

  dspfunc(put_h264_qpel, 0, 16);
  dspfunc(avg_h264_qpel, 0, 16);

in libavcodec/dsputil_h264_altivec.c lines 255 and 256 the artifacts go


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