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/*
* Copyright (C) 2000-2003 the xine project
*
* This file is part of xine, a free video player.
*
* xine is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* xine is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110, USA
*
* FFT code by Steve Haehnichen, originally licensed under GPL v1
* modified by Thibaut Mattern (tmattern@noos.fr) to remove global vars
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "fft.h"
/**************************************************************************
* fft specific decode functions
*************************************************************************/
# define SINE(x) (fft->SineTable[(x)])
# define COSINE(x) (fft->CosineTable[(x)])
# define WINDOW(x) (fft->WinTable[(x)])
#define PERMUTE(x, y) reverse((x), (y))
/* Number of samples in one "frame" */
#define SAMPLES (1 << bits)
#define REAL(x) wave[(x)].re
#define IMAG(x) wave[(x)].im
#define ALPHA 0.54
/*
* Bit reverser for unsigned ints
* Reverses 'bits' bits.
*/
static inline const unsigned int
reverse (unsigned int val, int bits)
{
unsigned int retn = 0;
while (bits--)
{
retn <<= 1;
retn |= (val & 1);
val >>= 1;
}
return (retn);
}
/*
* Here is the real work-horse.
* It's a generic FFT, so nothing is lost or approximated.
* The samples in wave[] should be in order, and they
* will be decimated when fft() returns.
*/
void fft_compute (fft_t *fft, complex_t wave[])
{
register int loop, loop1, loop2;
unsigned i1; /* going to right shift this */
int i2, i3, i4, y;
double a1, a2, b1, b2, z1, z2;
int bits = fft->bits;
i1 = SAMPLES / 2;
i2 = 1;
/* perform the butterflys */
for (loop = 0; loop < bits; loop++)
{
i3 = 0;
i4 = i1;
for (loop1 = 0; loop1 < i2; loop1++)
{
y = PERMUTE(i3 / (int)i1, bits);
z1 = COSINE(y);
z2 = -SINE(y);
for (loop2 = i3; loop2 < i4; loop2++)
{
a1 = REAL(loop2);
a2 = IMAG(loop2);
b1 = z1 * REAL(loop2+i1) - z2 * IMAG(loop2+i1);
b2 = z2 * REAL(loop2+i1) + z1 * IMAG(loop2+i1);
REAL(loop2) = a1 + b1;
IMAG(loop2) = a2 + b2;
REAL(loop2+i1) = a1 - b1;
IMAG(loop2+i1) = a2 - b2;
}
i3 += (i1 << 1);
i4 += (i1 << 1);
}
i1 >>= 1;
i2 <<= 1;
}
}
/*
* Initializer for FFT routines. Currently only sets up tables.
* - Generates scaled lookup tables for sin() and cos()
* - Fills a table for the Hamming window function
*/
fft_t *fft_new (int bits)
{
fft_t *fft;
int i;
const double TWOPIoN = (atan(1.0) * 8.0) / (double)SAMPLES;
const double TWOPIoNm1 = (atan(1.0) * 8.0) / (double)(SAMPLES - 1);
/* printf("fft_new: bits=%d\n", bits); */
fft = (fft_t*)malloc(sizeof(fft_t));
if (!fft)
return NULL;
fft->bits = bits;
fft->SineTable = malloc (sizeof(double) * SAMPLES);
fft->CosineTable = malloc (sizeof(double) * SAMPLES);
fft->WinTable = malloc (sizeof(double) * SAMPLES);
for (i=0; i < SAMPLES; i++)
{
fft->SineTable[i] = sin((double) i * TWOPIoN);
fft->CosineTable[i] = cos((double) i * TWOPIoN);
/*
* Generalized Hamming window function.
* Set ALPHA to 0.54 for a hanning window. (Good idea)
*/
fft->WinTable[i] = ALPHA + ((1.0 - ALPHA)
* cos (TWOPIoNm1 * (i - SAMPLES/2)));
}
return fft;
}
void fft_dispose(fft_t *fft)
{
free(fft->SineTable);
free(fft->CosineTable);
free(fft->WinTable);
free(fft);
}
/*
* Apply some windowing function to the samples.
*/
void fft_window (fft_t *fft, complex_t wave[])
{
int i;
int bits = fft->bits;
for (i = 0; i < SAMPLES; i++)
{
REAL(i) *= WINDOW(i);
IMAG(i) *= WINDOW(i);
}
}
/*
* Calculate amplitude of component n in the decimated wave[] array.
*/
double fft_amp (int n, complex_t wave[], int bits)
{
n = PERMUTE (n, bits);
return (hypot (REAL(n), IMAG(n)));
}
/*
* Calculate phase of component n in the decimated wave[] array.
*/
double fft_phase (int n, complex_t wave[], int bits)
{
n = PERMUTE (n, bits);
if (REAL(n) != 0.0)
return (atan (IMAG(n) / REAL(n)));
else
return (0.0);
}
/*
* Scale sampled values.
* Do this *before* the fft.
*/
void fft_scale (complex_t wave[], int bits)
{
int i;
for (i = 0; i < SAMPLES; i++) {
wave[i].re /= SAMPLES;
wave[i].im /= SAMPLES;
}
}
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