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better, reduced mutliply in real fft

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This commit is contained in:
Mark Borgerding
2003-12-10 05:48:42 +00:00
parent b880c599ef
commit 8a992d0e98
3 changed files with 31 additions and 27 deletions
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17
kiss_fftr.c
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@ -79,25 +79,30 @@ void kiss_fftr(const void * cfg,const kiss_fft_scalar *timedata,kiss_fft_cpx *fr
freqdata[0].r = st->tmpbuf[0].r + st->tmpbuf[0].i;
freqdata[0].i = 0;
for (k=1;k<N;++k) {
kiss_fft_cpx fpnk,fpk,f1k;
for (k=1;k <= N/2 ; ++k ) {
kiss_fft_cpx fpnk,fpk,f1k,f2k,tw;
fpk = st->tmpbuf[k];
fpnk.r = st->tmpbuf[N-k].r;
fpnk.i = -st->tmpbuf[N-k].i;
C_ADD( f1k, fpk , fpnk );
C_SUBFROM( fpk , fpnk );
C_MUL( freqdata[k], fpk , st->super_twiddles[k] );
C_ADDTO(freqdata[k],f1k);
C_SUB( f2k, fpk , fpnk );
C_MUL( tw , f2k , st->super_twiddles[k]);
C_ADD( freqdata[k] , f1k ,tw);
freqdata[k].r /= 2;
freqdata[k].i /= 2;
freqdata[N-k].r = f1k.r - tw.r;
freqdata[N-k].i = - (f1k.i - tw.i);
freqdata[N-k].r /= 2;
freqdata[N-k].i /= 2;
}
freqdata[N].r = st->tmpbuf[0].r - st->tmpbuf[0].i;
freqdata[N].i = 0;
}
void kiss_fftri(const void * cfg,const kiss_fft_cpx *freqdata,kiss_fft_scalar *timedata)
{
/* input buffer timedata is stored row-wise */