mirror of https://github.com/VDR4Arch/vdr.git
306 lines
6.4 KiB
C
306 lines
6.4 KiB
C
/*
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* srfft.c
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*
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* Copyright (C) Yuqing Deng <Yuqing_Deng@brown.edu> - April 2000
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*
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* 64 and 128 point split radix fft for ac3dec
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*
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* The algorithm is desribed in the book:
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* "Computational Frameworks of the Fast Fourier Transform".
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*
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* The ideas and the the organization of code borrowed from djbfft written by
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* D. J. Bernstein <djb@cr.py.to>. djbff can be found at
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* http://cr.yp.to/djbfft.html.
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*
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* srfft.c is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* srfft.c is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNU Make; see the file COPYING. If not, write to
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* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*/
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#include <stdio.h>
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#include "srfft.h"
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#include "srfftp.h"
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void fft_8 (complex_t *x);
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void fft_4(complex_t *x)
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{
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/* delta_p = 1 here */
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/* x[k] = sum_{i=0..3} x[i] * w^{i*k}, w=e^{-2*pi/4}
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*/
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register float yt_r, yt_i, yb_r, yb_i, u_r, u_i, vi_r, vi_i;
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yt_r = x[0].re;
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yb_r = yt_r - x[2].re;
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yt_r += x[2].re;
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u_r = x[1].re;
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vi_i = x[3].re - u_r;
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u_r += x[3].re;
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u_i = x[1].im;
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vi_r = u_i - x[3].im;
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u_i += x[3].im;
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yt_i = yt_r;
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yt_i += u_r;
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x[0].re = yt_i;
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yt_r -= u_r;
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x[2].re = yt_r;
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yt_i = yb_r;
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yt_i += vi_r;
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x[1].re = yt_i;
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yb_r -= vi_r;
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x[3].re = yb_r;
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yt_i = x[0].im;
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yb_i = yt_i - x[2].im;
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yt_i += x[2].im;
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yt_r = yt_i;
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yt_r += u_i;
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x[0].im = yt_r;
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yt_i -= u_i;
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x[2].im = yt_i;
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yt_r = yb_i;
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yt_r += vi_i;
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x[1].im = yt_r;
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yb_i -= vi_i;
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x[3].im = yb_i;
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}
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void fft_8 (complex_t *x)
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{
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/* delta_p = diag{1, sqrt(i)} here */
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/* x[k] = sum_{i=0..7} x[i] * w^{i*k}, w=e^{-2*pi/8}
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*/
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register float wT1_r, wT1_i, wB1_r, wB1_i, wT2_r, wT2_i, wB2_r, wB2_i;
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wT1_r = x[1].re;
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wT1_i = x[1].im;
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wB1_r = x[3].re;
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wB1_i = x[3].im;
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x[1] = x[2];
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x[2] = x[4];
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x[3] = x[6];
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fft_4(&x[0]);
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/* x[0] x[4] */
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wT2_r = x[5].re;
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wT2_r += x[7].re;
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wT2_r += wT1_r;
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wT2_r += wB1_r;
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wT2_i = wT2_r;
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wT2_r += x[0].re;
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wT2_i = x[0].re - wT2_i;
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x[0].re = wT2_r;
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x[4].re = wT2_i;
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wT2_i = x[5].im;
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wT2_i += x[7].im;
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wT2_i += wT1_i;
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wT2_i += wB1_i;
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wT2_r = wT2_i;
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wT2_r += x[0].im;
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wT2_i = x[0].im - wT2_i;
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x[0].im = wT2_r;
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x[4].im = wT2_i;
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/* x[2] x[6] */
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wT2_r = x[5].im;
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wT2_r -= x[7].im;
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wT2_r += wT1_i;
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wT2_r -= wB1_i;
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wT2_i = wT2_r;
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wT2_r += x[2].re;
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wT2_i = x[2].re - wT2_i;
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x[2].re = wT2_r;
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x[6].re = wT2_i;
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wT2_i = x[5].re;
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wT2_i -= x[7].re;
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wT2_i += wT1_r;
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wT2_i -= wB1_r;
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wT2_r = wT2_i;
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wT2_r += x[2].im;
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wT2_i = x[2].im - wT2_i;
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x[2].im = wT2_i;
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x[6].im = wT2_r;
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/* x[1] x[5] */
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wT2_r = wT1_r;
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wT2_r += wB1_i;
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wT2_r -= x[5].re;
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wT2_r -= x[7].im;
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wT2_i = wT1_i;
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wT2_i -= wB1_r;
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wT2_i -= x[5].im;
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wT2_i += x[7].re;
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wB2_r = wT2_r;
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wB2_r += wT2_i;
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wT2_i -= wT2_r;
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wB2_r *= HSQRT2;
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wT2_i *= HSQRT2;
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wT2_r = wB2_r;
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wB2_r += x[1].re;
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wT2_r = x[1].re - wT2_r;
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wB2_i = x[5].re;
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x[1].re = wB2_r;
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x[5].re = wT2_r;
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wT2_r = wT2_i;
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wT2_r += x[1].im;
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wT2_i = x[1].im - wT2_i;
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wB2_r = x[5].im;
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x[1].im = wT2_r;
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x[5].im = wT2_i;
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/* x[3] x[7] */
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wT1_r -= wB1_i;
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wT1_i += wB1_r;
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wB1_r = wB2_i - x[7].im;
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wB1_i = wB2_r + x[7].re;
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wT1_r -= wB1_r;
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wT1_i -= wB1_i;
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wB1_r = wT1_r + wT1_i;
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wB1_r *= HSQRT2;
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wT1_i -= wT1_r;
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wT1_i *= HSQRT2;
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wB2_r = x[3].re;
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wB2_i = wB2_r + wT1_i;
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wB2_r -= wT1_i;
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x[3].re = wB2_i;
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x[7].re = wB2_r;
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wB2_i = x[3].im;
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wB2_r = wB2_i + wB1_r;
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wB2_i -= wB1_r;
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x[3].im = wB2_i;
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x[7].im = wB2_r;
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}
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void fft_asmb(int k, complex_t *x, complex_t *wTB,
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const complex_t *d, const complex_t *d_3)
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{
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register complex_t *x2k, *x3k, *x4k, *wB;
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register float a_r, a_i, a1_r, a1_i, u_r, u_i, v_r, v_i;
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x2k = x + 2 * k;
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x3k = x2k + 2 * k;
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x4k = x3k + 2 * k;
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wB = wTB + 2 * k;
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TRANSZERO(x[0],x2k[0],x3k[0],x4k[0]);
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TRANS(x[1],x2k[1],x3k[1],x4k[1],wTB[1],wB[1],d[1],d_3[1]);
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--k;
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for(;;) {
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TRANS(x[2],x2k[2],x3k[2],x4k[2],wTB[2],wB[2],d[2],d_3[2]);
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TRANS(x[3],x2k[3],x3k[3],x4k[3],wTB[3],wB[3],d[3],d_3[3]);
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if (!--k) break;
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x += 2;
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x2k += 2;
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x3k += 2;
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x4k += 2;
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d += 2;
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d_3 += 2;
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wTB += 2;
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wB += 2;
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}
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}
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void fft_asmb16(complex_t *x, complex_t *wTB)
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{
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register float a_r, a_i, a1_r, a1_i, u_r, u_i, v_r, v_i;
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int k = 2;
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/* transform x[0], x[8], x[4], x[12] */
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TRANSZERO(x[0],x[4],x[8],x[12]);
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/* transform x[1], x[9], x[5], x[13] */
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TRANS(x[1],x[5],x[9],x[13],wTB[1],wTB[5],delta16[1],delta16_3[1]);
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/* transform x[2], x[10], x[6], x[14] */
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TRANSHALF_16(x[2],x[6],x[10],x[14]);
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/* transform x[3], x[11], x[7], x[15] */
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TRANS(x[3],x[7],x[11],x[15],wTB[3],wTB[7],delta16[3],delta16_3[3]);
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}
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void fft_64p_c (complex_t *a)
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{
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fft_8(&a[0]); fft_4(&a[8]); fft_4(&a[12]);
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fft_asmb16(&a[0], &a[8]);
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fft_8(&a[16]), fft_8(&a[24]);
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fft_asmb(4, &a[0], &a[16],&delta32[0], &delta32_3[0]);
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fft_8(&a[32]); fft_4(&a[40]); fft_4(&a[44]);
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fft_asmb16(&a[32], &a[40]);
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fft_8(&a[48]); fft_4(&a[56]); fft_4(&a[60]);
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fft_asmb16(&a[48], &a[56]);
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fft_asmb(8, &a[0], &a[32],&delta64[0], &delta64_3[0]);
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}
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void fft_128p_c (complex_t *a)
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{
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fft_8(&a[0]); fft_4(&a[8]); fft_4(&a[12]);
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fft_asmb16(&a[0], &a[8]);
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fft_8(&a[16]), fft_8(&a[24]);
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fft_asmb(4, &a[0], &a[16],&delta32[0], &delta32_3[0]);
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fft_8(&a[32]); fft_4(&a[40]); fft_4(&a[44]);
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fft_asmb16(&a[32], &a[40]);
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fft_8(&a[48]); fft_4(&a[56]); fft_4(&a[60]);
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fft_asmb16(&a[48], &a[56]);
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fft_asmb(8, &a[0], &a[32],&delta64[0], &delta64_3[0]);
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fft_8(&a[64]); fft_4(&a[72]); fft_4(&a[76]);
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/* fft_16(&a[64]); */
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fft_asmb16(&a[64], &a[72]);
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fft_8(&a[80]); fft_8(&a[88]);
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/* fft_32(&a[64]); */
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fft_asmb(4, &a[64], &a[80],&delta32[0], &delta32_3[0]);
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fft_8(&a[96]); fft_4(&a[104]), fft_4(&a[108]);
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/* fft_16(&a[96]); */
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fft_asmb16(&a[96], &a[104]);
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fft_8(&a[112]), fft_8(&a[120]);
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/* fft_32(&a[96]); */
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fft_asmb(4, &a[96], &a[112], &delta32[0], &delta32_3[0]);
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/* fft_128(&a[0]); */
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fft_asmb(16, &a[0], &a[64], &delta128[0], &delta128_3[0]);
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}
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