[FFmpeg-devel] basic DCT question

Michael Niedermayer michaelni
Mon Feb 23 19:42:12 CET 2009


On Mon, Feb 23, 2009 at 10:24:08AM -0800, Roman V. Shaposhnik wrote:
> On Mon, 2009-02-23 at 19:11 +0100, Michael Niedermayer wrote:
> > On Mon, Feb 23, 2009 at 09:23:46AM -0800, Roman V. Shaposhnik wrote:
> > > Guys,
> > > 
> > > the following is probably going to show just how clueless
> > > I am (still! :-() in the magic of DCT, but I have to ask it 
> > > anyway.
> > 
> > The dct algrithm is selected by the user though the command line argument
> > of matching name.
> > the regression tests should/do not use dct algos that differ between
> > achitectures, like the auto variant that selects the best, instead they
> > use a plain ISO C one.
> 
> Got it! But just to clarify: are you saying that ISO C DCT
> implementation guarantees even the extra 3 bits to be identical
> on all the arcs?

yes, ignoring bugs in the dct (very unlikely) and bugs in gcc (very likely)

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

No great genius has ever existed without some touch of madness. -- Aristotle
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