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

[Romain Dolbeau]

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.

Damn.

> 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.

Some (all?) functions in dsputil_h264_template_altivec.c assume
that stride % 16 == 0, it may be a starting point to check if it
is true...

-- 
Romain Dolbeau
<romain at dolbeau.org>