[FFmpeg-devel] Fixpoint FFT optimization, with MDCT and IMDCT wrappers for audio optimization

[Marc Hoffman]

On 7/28/07, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Sat, Jul 28, 2007 at 08:49:52PM -0400, Marc Hoffman wrote:
> > On 7/27/07, Michael Niedermayer <michaelni at gmx.at> wrote:
> > > Hi
> > >
> > > On Fri, Jul 27, 2007 at 09:56:34PM -0400, Marc Hoffman wrote:
> > > > Hi,
> > > >
> > > > On 7/27/07, Michael Niedermayer <michaelni at gmx.at> wrote:
> > > > > Hi
> > > > >
> > > > > On Fri, Jul 27, 2007 at 05:40:14PM -0400, mmh wrote:
> > > > > [...]
> > > > > > +/*
> > >
> > > >
> > > > >
> > > > > also several iterations have trivial (1/-1/0) w* these should not be done
> > > > > in this generic way
> > > > ?
> > >
> > > these things called twiddle factors, which are represented by wwr and wwi in
> > > your code have values like 1/-1/0, well 32768/-32768/0 as its fixedpoint
> > > in some iterations and its very lame to do a full complex multiplication
> > > for w being one of 1,-1,i,-i
> > >
> >
> > So you want to see the trivial stage pulled?  Is the use of N/2
> > acceptable to you here?
>
> no, N>>1 is better

ok if it makes you happy :)