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failed attempt -- DOES NOT WORK!
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Mark Borgerding
parent
a2cca1b70e
commit
18e5e8e360
99
kiss_fft.c
99
kiss_fft.c
@ -15,6 +15,7 @@ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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#include <stdlib.h>
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#include <stdio.h>
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#include <math.h>
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#include <memory.h>
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#include "kiss_fft.h"
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/*
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* kiss_fft.h
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@ -32,16 +33,21 @@ typedef struct {
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kiss_fft_cpx * twiddle;
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}kiss_fft_stage;
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const double pi=3.14159265358979323846264338327;
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#define MAX_STAGES 20
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typedef struct {
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int nfft;
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int nstages;
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int allocsize;
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kiss_fft_stage stages[MAX_STAGES];
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int * unscramble_indices;
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kiss_fft_cpx * buf1;
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}kiss_fft_state;
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#ifdef FIXED_POINT
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# define TWIDDLE_RANGE ( (1<<FIXED_POINT_FRAC_BITS) - 1 )
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@ -81,17 +87,26 @@ typedef struct {
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#endif
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static
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kiss_fft_cpx cexp(double phase)
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{
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kiss_fft_cpx x;
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x.r = cos(phase);
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x.i = -sin(phase);
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return x;
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}
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// create the twiddle factors
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static
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void make_twiddles(kiss_fft_cpx * twiddle,int ntwid,int symmetry,int inverse_fft)
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{
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const double pi=3.14159265358979323846264338327;
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int n;
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int denom = ntwid*symmetry;
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for (n=0;n<ntwid;++n) {
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twiddle[n].r = cos(2*pi*n/denom);
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twiddle[n].i = -sin(2*pi*n/denom);
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twiddle[n] = cexp( 2*pi*n/denom );
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//twiddle[n].r = cos(2*pi*n/denom);
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//twiddle[n].i = -sin(2*pi*n/denom);
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// inverse fft uses complex conjugate twiddle factors
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if (inverse_fft)
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twiddle[n].i *= -1;
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@ -144,35 +159,68 @@ void undo_bit_rev( kiss_fft_cpx * f, const int * swap_indices,int nswap)
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}
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}
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static kiss_fft_cpx cadd(kiss_fft_cpx a,kiss_fft_cpx b)
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{
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kiss_fft_cpx c;
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C_ADD(c,a,b);
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return c;
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}
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static kiss_fft_cpx cmul(kiss_fft_cpx a,kiss_fft_cpx b)
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{
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kiss_fft_cpx c;
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C_MUL(c,a,b);
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return c;
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}
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// the heart of the fft
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static
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void fft_work( kiss_fft_cpx * f,const kiss_fft_stage * stage , int nstages )
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void fft_work( kiss_fft_cpx * h,kiss_fft_cpx * h2,const kiss_fft_stage * stage , int nstages )
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{
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int n;
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// only works for 2s
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{ // declare automatic variables in here to reduce stack usage
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kiss_fft_cpx csum,cdiff;
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kiss_fft_cpx *f1 = f;
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kiss_fft_cpx *f2 = f+ stage->nr;
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const kiss_fft_cpx * twid = stage->twiddle;
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for ( n = 0 ; n < stage->nr ; ++n )
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{
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C_ADD( csum, *f1 , *f2 );
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C_SUB( cdiff, *f1 , *f2 );
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*f1++ = csum;
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C_MUL(*f2, cdiff, *twid);
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++f2;
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++twid;
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int nx,ny,Nx,Ny;
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kiss_fft_cpx twid;
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double inc1 = -2*pi/(stage->radix * stage->nr);
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Ny = stage->nr;
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Nx = stage->radix;
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for (ny=0;ny<Ny; ++ny) {
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for ( nx=0 ; nx<Nx ; ++nx ) {
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h2[ny] = h[ny];
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h2[ny] = cadd( h2[ny] , cmul( twid ,h[ nx * nr + ny ] ) );
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}
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twid = cexp();
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cmul(h2[ny]);
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}
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/*
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h2[n] = h[n] + h[n+N/2]
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h2[n+N/2] = ( h[n] - h[n+N/2] ) * exp ( n * j*2*pi/N)
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for ( n = 0 ; n < stage->nr ; ++n )
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{
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C_ADD( csum, *f1 , *f2 );
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C_SUB( cdiff, *f1 , *f2 );
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C_MUL(*f2, cdiff, *twid);
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*f1++ = csum;
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++f2;
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++twid;
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}
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*/
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}
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if ( nstages == 1 )
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return;
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for (n=0;n<stage->radix;++n)
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fft_work( f + n * stage->nr ,stage+1,nstages-1);
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for (n=0;n<stage->radix;++n) {
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int offset = n * stage->nr;
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fft_work( h2 + offset , h + offset ,stage+1,nstages-1);
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}
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}
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static
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kiss_fft_state * decompose( kiss_fft_state * st, int * pnfft,int radix,int inverse_fft)
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{
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@ -213,12 +261,14 @@ void * kiss_fft_alloc(int nfft,int inverse_fft)
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kiss_fft_state * st=NULL;
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int tmp;
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int i;
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int allocsize=sizeof(kiss_fft_state) + nfft*sizeof(int);
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int allocsize=sizeof(kiss_fft_state) + nfft*( sizeof(int) + sizeof(kiss_fft_cpx) );
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st = ( kiss_fft_state *)malloc( allocsize );
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st->nfft=nfft;
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st->nstages=0;
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st->allocsize=allocsize;
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st->unscramble_indices = (int*)(st+1);// just past end of buffer
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st->buf1 = (kiss_fft_cpx*)( st->unscramble_indices + nfft);
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for (i=0;i<nfft;++i)
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st->unscramble_indices[i] = i;
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@ -242,5 +292,8 @@ void * kiss_fft_alloc(int nfft,int inverse_fft)
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void kiss_fft(const void * cfg,kiss_fft_cpx *f)
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{
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const kiss_fft_state * st = cfg;
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fft_work( f, st->stages , st->nstages );
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fft_work( f,st->buf1, st->stages , st->nstages );
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if (st->nstages&1) {
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memcpy( st->buf1 , f,sizeof(kiss_fft_cpx) * st->nfft );
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}
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}
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