[FFmpeg-devel] dealing with tables in DV codec
Thu Sep 11 12:35:45 CEST 2008
On Wed, Sep 10, 2008 at 07:27:13PM -0700, Roman V. Shaposhnik wrote:
> 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.
It should not be included as such, 3% speed loss is significant.
> > 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.
DV is a intra codec, it never adds 2 idcts on top of each other, all the
mpeg & h26* codecs add idcts on top of each other, that makes them much
more sensitive for idct errors.
> > 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?
i meant ffplay -idct 6 file.avi
and looking at it
for comarission you can look at
-idct 2 (no artifacts)
-idct 1 (minor atifacts)
-idct 4 (major artifacts)
> > > 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?
Do you know sparc & vis asm ? :)
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
If you really think that XML is the answer, then you definitly missunderstood
the question -- Attila Kinali
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