ref: fc68b29d4f34ab444b30032638cc39a14ff7b0d9
dir: /transfo.c/
#include <math.h>
#include "transfo.h"
#ifdef USE_ORIG_FFT
double FFTarray [1024]; /* the array for in-place FFT */
#else
fftw_complex_d FFTarray[512]; /* the array for in-place FFT */
extern int unscambled64[64]; /* the permutation array for FFT64*/
extern int unscambled512[512]; /* the permutation array for FFT512*/
int unscambled;
#endif
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
#ifndef M_PI_2
#define M_PI_2 1.57079632679489661923
#endif
/*****************************
Fast MDCT Code
*****************************/
void MDCT (double *data, int N) {
#ifndef USE_ORIG_FFT
static int init = 1;
#endif
double tempr, tempi, c, s, cold, cfreq, sfreq; /* temps for pre and post twiddle */
double freq = 2.0 * M_PI / N;
double fac,cosfreq8,sinfreq8;
int i, n;
int isign = 1;
int b = N >> 1;
int N4 = N >> 2;
int N2 = N >> 1;
int a = N - b;
int a2 = a >> 1;
int a4 = a >> 2;
int b4 = b >> 2;
#ifndef USE_ORIG_FFT
if (init) {
init = 0;
MakeFFTOrder();
}
#endif
/* Choosing to allocate 2/N factor to Inverse Xform! */
fac = 2.; /* 2 from MDCT inverse to forward */
/* prepare for recurrence relation in pre-twiddle */
cfreq = cos (freq);
sfreq = sin (freq);
cosfreq8 = cos (freq * 0.125);
sinfreq8 = sin (freq * 0.125);
c = cosfreq8;
s = sinfreq8;
for (i = 0; i < N4; i++) {
/* calculate real and imaginary parts of g(n) or G(p) */
n = N / 2 - 1 - 2 * i;
if (i < b4) {
tempr = data [a2 + n] + data [N + a2 - 1 - n]; /* use second form of e(n) for n = N / 2 - 1 - 2i */
} else {
tempr = data [a2 + n] - data [a2 - 1 - n]; /* use first form of e(n) for n = N / 2 - 1 - 2i */
}
n = 2 * i;
if (i < a4) {
tempi = data [a2 + n] - data [a2 - 1 - n]; /* use first form of e(n) for n=2i */
} else {
tempi = data [a2 + n] + data [N + a2 - 1 - n]; /* use second form of e(n) for n=2i*/
}
/* calculate pre-twiddled FFT input */
#ifdef USE_ORIG_FFT
FFTarray [2 * i] = tempr * c + tempi * s;
FFTarray [2 * i + 1] = tempi * c - tempr * s;
#else
FFTarray [i].re = tempr * c + tempi * s;
FFTarray [i].im = tempi * c - tempr * s;
#endif
/* use recurrence to prepare cosine and sine for next value of i */
cold = c;
c = c * cfreq - s * sfreq;
s = s * cfreq + cold * sfreq;
}
/* Perform in-place complex FFT of length N/4 */
#ifdef USE_ORIG_FFT
FFT (FFTarray, N4, -1);
#else
switch (N) {
case 256: pfftw_d_64(FFTarray);
break;
case 2048:pfftw_d_512(FFTarray);
}
#endif
/* prepare for recurrence relations in post-twiddle */
c = cosfreq8;
s = sinfreq8;
/* post-twiddle FFT output and then get output data */
for (i = 0; i < N4; i++) {
/* get post-twiddled FFT output */
/* Note: fac allocates 4/N factor from IFFT to forward and inverse */
#ifdef USE_ORIG_FFT
tempr = fac * (FFTarray [2 * i] * c + FFTarray [2 * i + 1] * s);
tempi = fac * (FFTarray [2 * i + 1] * c - FFTarray [2 * i] * s);
#else
switch (N) {
case 256:
unscambled = unscambled64[i];
break;
case 2048:
unscambled = unscambled512[i];
}
tempr = fac * (FFTarray [unscambled].re * c + FFTarray [unscambled].im * s);
tempi = fac * (FFTarray [unscambled].im * c - FFTarray [unscambled].re * s);
#endif
/* fill in output values */
data [2 * i] = -tempr; /* first half even */
data [N2 - 1 - 2 * i] = tempi; /* first half odd */
data [N2 + 2 * i] = -tempi; /* second half even */
data [N - 1 - 2 * i] = tempr; /* second half odd */
/* use recurrence to prepare cosine and sine for next value of i */
cold = c;
c = c * cfreq - s * sfreq;
s = s * cfreq + cold * sfreq;
}
}
#ifdef USE_ORIG_FFT /* OLD FFT */
#define SWAP(a,b) tempr=a;a=b;b=tempr
void FFT (double *data, int nn, int isign) {
/* Varient of Numerical Recipes code from off the internet. It takes nn
interleaved complex input data samples in the array data and returns nn interleaved
complex data samples in place where the output is the FFT of input if isign==1 and it
is nn times the IFFT of the input if isign==-1.
(Note: it doesn't renormalize by 1/N when doing the inverse transform!!!)
(Note: this follows physicists convention of +i, not EE of -j in forward
transform!!!!)
*/
/* Press, Flannery, Teukolsky, Vettering "Numerical
* Recipes in C" tuned up ; Code works only when nn is
* a power of 2 */
int n, mmax, m, j, i;
double wtemp, wr, wpr, wpi, wi, theta, wpin;
double tempr, tempi, datar, datai;
double data1r, data1i;
n = nn << 1;
/* bit reversal */
j = 0;
for (i = 0; i < n; i += 2) {
if (j > i) { /* could use j>i+1 to help compiler analysis */
SWAP (data [j], data [i]);
SWAP (data [j + 1], data [i + 1]);
}
m = nn;
while (m >= 2 && j >= m) {
j -= m;
m >>= 1;
}
j += m;
}
// theta = 3.141592653589795 * 0.5;
theta = M_PI_2;
if (isign < 0)
theta = -theta;
wpin = 0; /* sin(+-PI) */
for (mmax = 2; n > mmax; mmax <<= 1) {
wpi = wpin;
wpin = sin (theta);
wpr = 1 - wpin * wpin - wpin * wpin; /* cos(theta*2) */
theta *= .5;
wr = 1;
wi = 0;
for (m = 0; m < mmax; m += 2) {
j = m + mmax;
tempr = wr * (data1r = data [j]);
tempi = wi * (data1i = data [j + 1]);
for (i = m; i < n - mmax * 2; i += mmax * 2) {
/* mixed precision not significantly more
* accurate here; if removing float casts,
* tempr and tempi should be double */
tempr -= tempi;
tempi = wr *data1i + wi *data1r;
/* don't expect compiler to analyze j > i + 1 */
data1r = data [j + mmax * 2];
data1i = data [j + mmax * 2 + 1];
data [i] = (datar = data [i]) + tempr;
data [i + 1] = (datai = data [i + 1]) + tempi;
data [j] = datar - tempr;
data [j + 1] = datai - tempi;
tempr = wr *data1r;
tempi = wi *data1i;
j += mmax * 2;
}
tempr -= tempi;
tempi = wr * data1i + wi *data1r;
data [i] = (datar = data [i]) + tempr;
data [i + 1] = (datai = data [i + 1]) + tempi;
data [j] = datar - tempr;
data [j + 1] = datai - tempi;
wr = (wtemp = wr) * wpr - wi * wpi;
wi = wtemp * wpi + wi * wpr;
}
}
}
#endif /* OLD FFT*/