[Ffmpeg-devel] [RFC] mdct window generation

Michael Niedermayer michaelni
Mon Jul 10 15:14:10 CEST 2006


On Mon, Jul 10, 2006 at 01:23:27PM +0200, Benjamin Larsson wrote:
> Regarding the interpolation of the window, that would make sense on a
> memory constrained system. But otherwise it would just be slower then
> using a table on most systems.

maybe, maybe not, keep in mind the table will eat L1 and L2 cache space
and interpolation is not that slow ...
its just

for(i=0; i<window_size/STEP; i++){
    double w= coeff[i][0];
    double b= coeff[i][1];
    double c= coeff[i][2];
    double d= coeff[i][3];
    for(j=0; j<STEP; j++){
        use w instead of window[i*STEP + j]

for approximation by 3rd order polynomials
thats just 3 additions vs. 1 memory read


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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