[FFmpeg-devel] dealing with tables in DV codec

Roman V. Shaposhnik rvs
Thu Sep 11 04:27:13 CEST 2008

On Wed, 2008-09-10 at 23:06 +0200, Michael Niedermayer wrote:
> 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
> is.

Seems like you've confused the threads, then. I fail to see the
relevance of this war story to the issue at hand -- should the
change that is a toss up on x86 and ~3% performance degradation
on SPARC be included or not. 

> 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 ...

It is actually pretty decent. At least the portions I used to
make the DV codec go. Once again -- I'm talking exclusively
about SPARC. I have no interest in mlib on x86.

> Divx4-bugs/Lorenna_McKennit-Mummers_Dance-Mononoke_Hime-gabucino.avi
> on samples.mplayerhq.hu is a good one to test idcts.

Do you mean just comparing PSNRs or a more involved test?

> > 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, 

repeat after me: there are no stupid questions, there are no stupid
questions ;-)

> Though honestly my gut feeling is that anyone knowing VIS and sparc asm

Do you have anyone like that on the horizon?


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