[FFmpeg-devel] Fw: [foms] Paper submissions to LCA

Carl Eugen Hoyos cehoyos
Fri Jul 17 10:26:06 CEST 2009

M?ns Rullg?rd <mans <at> mansr.com> writes:

> On that topic, does anyone know why so many FATE tests are failing
> with icc?

(It exclusively fails for 11.x 64bit and I wrote a wiki page about it.)
Some files are mis-compiled at optimisations > 0:

Earlier this year, I looked into wmv2dec.c (it is the shortest of these files),
and found that the problem is wmv2_pred_motion(). (Adding printf's after the
initialisation of *C shows that mot_val, A[], B[] and C[] often differ from
compilation with -O0 while xy and wrap are unchanged.)
Perhaps you could have a look what is so special about this (short) function?
I could upload the assembly of O0 and O1 if you want.

I reported the problem to Intel, but it took them some time to reproduce the
problem. It is reproduced (escalated) now (issue 540759):
"I've narrowed down the problem to one of our internal modules"

I have no idea if the other files have the same problem (there is some
indication that vc1.c has a different problem), but they are rather big making
it difficult to find the failing function.

Carl Eugen

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