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

[Diego Biurrun]

On Thu, Oct 06, 2005 at 04:06:47PM +0200, Romain Dolbeau wrote:
> Diego Biurrun wrote:
> 
> >OK, I'll try to narrow it down a bit more.
> 
> >Any H.264 sample will exhibit the problem and be completely unwatchable.
> 
> This is becoming interesting. I just tried 2 different samples, one
> that use a subset of the functions, one that use them all. Both
> decode to perfect bit-exactness compared to the C implementation.
> The resulting YUV also looked fine to me (but my eyes are not to
> be trusted :-( ).

Anybody's eyes can be trusted for the kind of artifacts I am seeing:

http://mplayerhq.hu/~diego/h264_altivec.jpg

> So now let's try the usual suspects: what compiler, what OS, what CPU(s),
> what extra compiler option(s) are you using ?

Debian unstable
PowerBook G4 7447A processor running at 1500MHz
gcc (GCC) 4.0.2 (Debian 4.0.2-2)

I get the same results with

gcc-3.3 (GCC) 3.3.6 (Debian 1:3.3.6-10)
gcc-3.4 (GCC) 3.4.5 20050821 (prerelease) (Debian 3.4.4-8)

> And a common sample between us would be useful, too.

OK, let's settle on this one:

http://mplayerhq.hu/~diego/bbc-africa_m720p.mov

Diego