[FFmpeg-devel] dealing with tables in DV codec

Michael Niedermayer michaelni
Wed Sep 10 23:06:38 CEST 2008

On Wed, Sep 10, 2008 at 12:46:22PM -0700, Roman Shaposhnik wrote:
> On Wed, 2008-09-10 at 21:37 +0200, Michael Niedermayer wrote:
> > > Thanks for saying this. On one hand Michael uses embedded systems
> > > as a constant argument in favor of optimizing for such
> > > platforms, but on the other hand there's a clear x86 tilt
> > > that I see. 
> > 
> > /me cleans romans glasses.
> > 
> > I suggest you ask balatoni denes about how easy it was to get a half optimal
> > sparc vis idct into ffmpeg.
> I'm actually unaware of what you are referring to. Please educate me.

balatoni denes tried to get a half optimized idct in and i nicely told
him that it has to include all tricks and optimizations we could think of.
We ended up with something that was clearly quite a bit faster than
what he submitted first, that is between all the complaints about how
little time he had and how evil we were for not just acceptiing it as

> What I'm aware of, though, is that Sun's medialib on SPARC seems to
> perform better than what's currently in FFmpeg (for obvious reasons).

our shiny idct isnt enabled by default as its not bitexact to any other
ANSI C idct.

That besides reminds me that rumors say the mlib idct is so inaccurate
that its practically useless.
As iam not able to test, i wonder how bad it really is ...

on samples.mplayerhq.hu is a good one to test idcts.

> So one of the things I'm trying to do is to see whether the code
> that is really needed for FFmpeg (medialib is huge, we only need
> like 2% of it) could be OSed under a reasonable license that would
> allow direct inclusion into FFmpeg sources.
> Should I stop it?

stupid question, its of course always nice if things are open source.
Though honestly my gut feeling is that anyone knowing VIS and sparc asm
could do more good in less time than trying to convince a large corporation
to open source something, that is especially if it has to be under a license
that we can include (GPL/LGPL/BSD/public domain)


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have often repented speaking, but never of holding my tongue.
-- Xenocrates
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