kiss_fftr()

void kiss_fftr	(	kiss_fftr_cfg	st,
		const kiss_fft_scalar *	timedata,
		kiss_fft_cpx *	freqdata )

Definition at line 82 of file kiss_fftr.cpp.hpp.

{ // ok no noexcept: preserve vendor C declaration (#4773)
    /* input buffer timedata is stored row-wise */
    int k,ncfft;
    kiss_fft_cpx fpnk,fpk,f1k,f2k,tw,tdc;
 
    if ( st->substate->inverse) {
        //fprintf(stderr,"kiss fft usage error: improper alloc\n");
        FL_WARN("kiss fft usage error: improper alloc");
        fl::exit(1);
    }
 
    ncfft = st->substate->nfft;
 
    /*perform the parallel fft of two real signals packed in real,imag*/
    kiss_fft( st->substate , (const kiss_fft_cpx*)timedata, st->tmpbuf );
    /* The real part of the DC element of the frequency spectrum in st->tmpbuf
     * contains the sum of the even-numbered elements of the input time sequence
     * The imag part is the sum of the odd-numbered elements
     *
     * The sum of tdc.r and tdc.i is the sum of the input time sequence. 
     *      yielding DC of input time sequence
     * The difference of tdc.r - tdc.i is the sum of the input (dot product) [1,-1,1,-1... 
     *      yielding Nyquist bin of input time sequence
     */
 
    tdc.r = st->tmpbuf[0].r;
    tdc.i = st->tmpbuf[0].i;
    C_FIXDIV(tdc,2);
    CHECK_OVERFLOW_OP(tdc.r ,+, tdc.i);
    CHECK_OVERFLOW_OP(tdc.r ,-, tdc.i);
    freqdata[0].r = tdc.r + tdc.i;
    freqdata[ncfft].r = tdc.r - tdc.i;
#ifdef USE_SIMD    
    freqdata[ncfft].i = freqdata[0].i = _mm_set1_ps(0);
#else
    freqdata[ncfft].i = freqdata[0].i = 0;
#endif
 
    for ( k=1;k <= ncfft/2 ; ++k ) {
        fpk    = st->tmpbuf[k]; 
        fpnk.r =   st->tmpbuf[ncfft-k].r;
        fpnk.i = - st->tmpbuf[ncfft-k].i;
        C_FIXDIV(fpk,2);
        C_FIXDIV(fpnk,2);
 
        C_ADD( f1k, fpk , fpnk );
        C_SUB( f2k, fpk , fpnk );
        C_MUL( tw , f2k , st->super_twiddles[k-1]);
 
        freqdata[k].r = HALF_OF(f1k.r + tw.r);
        freqdata[k].i = HALF_OF(f1k.i + tw.i);
        freqdata[ncfft-k].r = HALF_OF(f1k.r - tw.r);
        freqdata[ncfft-k].i = HALF_OF(tw.i - f1k.i);
    }
}

References C_ADD, C_FIXDIV, C_MUL, C_SUB, CHECK_OVERFLOW_OP, fl::exit(), FL_WARN, HALF_OF, kiss_fft_cpx::i, kiss_fft_state::inverse, kiss_fft(), kiss_fft_scalar, kiss_fft_state::nfft, kiss_fft_cpx::r, kiss_fftr_state::substate, kiss_fftr_state::super_twiddles, and kiss_fftr_state::tmpbuf.

Referenced by _generate_kernel(), and fl::audio::fft::fl_fft_real_forward().

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