标签：types fft mod cti Dimension required cos end may
webrtc-audioproc-master/modules/audio_processing/utility/fft4g.c
/*
* http://www.kurims.kyoto-u.ac.jp/~ooura/fft.html
* Copyright Takuya OOURA, 1996-2001
*
* You may use, copy, modify and distribute this code for any purpose (include
* commercial use) and without fee. Please refer to this package when you modify
* this code.
*
* Changes:
* Trivial type modifications by the WebRTC authors.
*/
/*
Fast Fourier/Cosine/Sine Transform
dimension :one
data length :power of 2
decimation :frequency
radix :4, 2
data :inplace
table :use
functions
cdft: Complex Discrete Fourier Transform
rdft: Real Discrete Fourier Transform
ddct: Discrete Cosine Transform
ddst: Discrete Sine Transform
dfct: Cosine Transform of RDFT (Real Symmetric DFT)
dfst: Sine Transform of RDFT (Real Anti-symmetric DFT)
function prototypes
void cdft(int, int, float *, int *, float *);
void rdft(int, int, float *, int *, float *);
void ddct(int, int, float *, int *, float *);
void ddst(int, int, float *, int *, float *);
void dfct(int, float *, float *, int *, float *);
void dfst(int, float *, float *, int *, float *);
-------- Complex DFT (Discrete Fourier Transform) --------
[definition]
X[k] = sum_j=0^n-1 x[j]*exp(2*pi*i*j*k/n), 0
X[k] = sum_j=0^n-1 x[j]*exp(-2*pi*i*j*k/n), 0
ip[0] = 0; // first time only
cdft(2*n, 1, a, ip, w);
ip[0] = 0; // first time only
cdft(2*n, -1, a, ip, w);
[parameters]
2*n :data length (int)
n >= 1, n = power of 2
a[0...2*n-1] :input/output data (float *)
input data
a[2*j] = Re(x[j]),
a[2*j+1] = Im(x[j]), 0= 2+sqrt(n)
strictly,
length of ip >=
2+(1 RDFT
R[k] = sum_j=0^n-1 a[j]*cos(2*pi*j*k/n), 0 IRDFT (excluding scale)
a[k] = (R[0] + R[n/2]*cos(pi*k))/2 +
sum_j=1^n/2-1 R[j]*cos(2*pi*j*k/n) +
sum_j=1^n/2-1 I[j]*sin(2*pi*j*k/n), 0
ip[0] = 0; // first time only
rdft(n, 1, a, ip, w);
ip[0] = 0; // first time only
rdft(n, -1, a, ip, w);
[parameters]
n :data length (int)
n >= 2, n = power of 2
a[0...n-1] :input/output data (float *)
output data
a[2*k] = R[k], 0
input data
a[2*j] = R[j], 0= 2+sqrt(n/2)
strictly,
length of ip >=
2+(1 IDCT (excluding scale)
C[k] = sum_j=0^n-1 a[j]*cos(pi*j*(k+1/2)/n), 0 DCT
C[k] = sum_j=0^n-1 a[j]*cos(pi*(j+1/2)*k/n), 0
ip[0] = 0; // first time only
ddct(n, 1, a, ip, w);
ip[0] = 0; // first time only
ddct(n, -1, a, ip, w);
[parameters]
n :data length (int)
n >= 2, n = power of 2
a[0...n-1] :input/output data (float *)
output data
a[k] = C[k], 0= 2+sqrt(n/2)
strictly,
length of ip >=
2+(1 IDST (excluding scale)
S[k] = sum_j=1^n A[j]*sin(pi*j*(k+1/2)/n), 0 DST
S[k] = sum_j=0^n-1 a[j]*sin(pi*(j+1/2)*k/n), 0
ip[0] = 0; // first time only
ddst(n, 1, a, ip, w);
ip[0] = 0; // first time only
ddst(n, -1, a, ip, w);
[parameters]
n :data length (int)
n >= 2, n = power of 2
a[0...n-1] :input/output data (float *)
input data
a[j] = A[j], 0
output data
a[k] = S[k], 0= 2+sqrt(n/2)
strictly,
length of ip >=
2+(1= 2, n = power of 2
a[0...n] :input/output data (float *)
output data
a[k] = C[k], 0= 2+sqrt(n/4)
strictly,
length of ip >=
2+(1= 2, n = power of 2
a[0...n-1] :input/output data (float *)
output data
a[k] = S[k], 0= 2+sqrt(n/4)
strictly,
length of ip >=
2+(1*/
static void makewt(int nw, int *ip, float *w);
static void makect(int nc, int *ip, float *c);
static void bitrv2(int n, int *ip, float *a);
static void bitrv2conj(int n, int *ip, float *a);
static void cftfsub(int n, float *a, float *w);
static void cftbsub(int n, float *a, float *w);
static void cft1st(int n, float *a, float *w);
static void cftmdl(int n, int l, float *a, float *w);
static void rftfsub(int n, float *a, int nc, float *c);
static void rftbsub(int n, float *a, int nc, float *c);
#if 0 // Not used.
static void dctsub(int n, float *a, int nc, float *c)
static void dstsub(int n, float *a, int nc, float *c)
#endif
void WebRtc_cdft(int n, int isgn, float *a, int *ip, float *w)
{
if (n > (ip[0] 2)) {
makewt(n >> 2, ip, w);
}
if (n > 4) {
if (isgn >= 0) {
bitrv2(n, ip + 2, a);
cftfsub(n, a, w);
} else {
bitrv2conj(n, ip + 2, a);
cftbsub(n, a, w);
}
} else if (n == 4) {
cftfsub(n, a, w);
}
}
void WebRtc_rdft(int n, int isgn, float *a, int *ip, float *w)
{
int nw, nc;
float xi;
nw = ip[0];
if (n > (nw 2)) {
nw = n >> 2;
makewt(nw, ip, w);
}
nc = ip[1];
if (n > (nc 2)) {
nc = n >> 2;
makect(nc, ip, w + nw);
}
if (isgn >= 0) {
if (n > 4) {
bitrv2(n, ip + 2, a);
cftfsub(n, a, w);
rftfsub(n, a, nc, w + nw);
} else if (n == 4) {
cftfsub(n, a, w);
}
xi = a[0] - a[1];
a[0] += a[1];
a[1] = xi;
} else {
a[1] = 0.5f * (a[0] - a[1]);
a[0] -= a[1];
if (n > 4) {
rftbsub(n, a, nc, w + nw);
bitrv2(n, ip + 2, a);
cftbsub(n, a, w);
} else if (n == 4) {
cftfsub(n, a, w);
}
}
}
#if 0 // Not used.
static void ddct(int n, int isgn, float *a, int *ip, float *w)
{
int j, nw, nc;
float xr;
nw = ip[0];
if (n > (nw 2)) {
nw = n >> 2;
makewt(nw, ip, w);
}
nc = ip[1];
if (n > nc) {
nc = n;
makect(nc, ip, w + nw);
}
if (isgn 0) {
xr = a[n - 1];
for (j = n - 2; j >= 2; j -= 2) {
a[j + 1] = a[j] - a[j - 1];
a[j] += a[j - 1];
}
a[1] = a[0] - xr;
a[0] += xr;
if (n > 4) {
rftbsub(n, a, nc, w + nw);
bitrv2(n, ip + 2, a);
cftbsub(n, a, w);
} else if (n == 4) {
cftfsub(n, a, w);
}
}
dctsub(n, a, nc, w + nw);
if (isgn >= 0) {
if (n > 4) {
bitrv2(n, ip + 2, a);
cftfsub(n, a, w);
rftfsub(n, a, nc, w + nw);
} else if (n == 4) {
cftfsub(n, a, w);
}
xr = a[0] - a[1];
a[0] += a[1];
for (j = 2; j 2) {
a[j - 1] = a[j] - a[j + 1];
a[j] += a[j + 1];
}
a[n - 1] = xr;
}
}
static void ddst(int n, int isgn, float *a, int *ip, float *w)
{
int j, nw, nc;
float xr;
nw = ip[0];
if (n > (nw 2)) {
nw = n >> 2;
makewt(nw, ip, w);
}
nc = ip[1];
if (n > nc) {
nc = n;
makect(nc, ip, w + nw);
}
if (isgn 0) {
xr = a[n - 1];
for (j = n - 2; j >= 2; j -= 2) {
a[j + 1] = -a[j] - a[j - 1];
a[j] -= a[j - 1];
}
a[1] = a[0] + xr;
a[0] -= xr;
if (n > 4) {
rftbsub(n, a, nc, w + nw);
bitrv2(n, ip + 2, a);
cftbsub(n, a, w);
} else if (n == 4) {
cftfsub(n, a, w);
}
}
dstsub(n, a, nc, w + nw);
if (isgn >= 0) {
if (n > 4) {
bitrv2(n, ip + 2, a);
cftfsub(n, a, w);
rftfsub(n, a, nc, w + nw);
} else if (n == 4) {
cftfsub(n, a, w);
}
xr = a[0] - a[1];
a[0] += a[1];
for (j = 2; j 2) {
a[j - 1] = -a[j] - a[j + 1];
a[j] -= a[j + 1];
}
a[n - 1] = -xr;
}
}
static void dfct(int n, float *a, float *t, int *ip, float *w)
{
int j, k, l, m, mh, nw, nc;
float xr, xi, yr, yi;
nw = ip[0];
if (n > (nw 3)) {
nw = n >> 3;
makewt(nw, ip, w);
}
nc = ip[1];
if (n > (nc 1)) {
nc = n >> 1;
makect(nc, ip, w + nw);
}
m = n >> 1;
yi = a[m];
xi = a[0] + a[n];
a[0] -= a[n];
t[0] = xi - yi;
t[m] = xi + yi;
if (n > 2) {
mh = m >> 1;
for (j = 1; j ) {
k = m - j;
xr = a[j] - a[n - j];
xi = a[j] + a[n - j];
yr = a[k] - a[n - k];
yi = a[k] + a[n - k];
a[j] = xr;
a[k] = yr;
t[j] = xi - yi;
t[k] = xi + yi;
}
t[mh] = a[mh] + a[n - mh];
a[mh] -= a[n - mh];
dctsub(m, a, nc, w + nw);
if (m > 4) {
bitrv2(m, ip + 2, a);
cftfsub(m, a, w);
rftfsub(m, a, nc, w + nw);
} else if (m == 4) {
cftfsub(m, a, w);
}
a[n - 1] = a[0] - a[1];
a[1] = a[0] + a[1];
for (j = m - 2; j >= 2; j -= 2) {
a[2 * j + 1] = a[j] + a[j + 1];
a[2 * j - 1] = a[j] - a[j + 1];
}
l = 2;
m = mh;
while (m >= 2) {
dctsub(m, t, nc, w + nw);
if (m > 4) {
bitrv2(m, ip + 2, t);
cftfsub(m, t, w);
rftfsub(m, t, nc, w + nw);
} else if (m == 4) {
cftfsub(m, t, w);
}
a[n - l] = t[0] - t[1];
a[l] = t[0] + t[1];
k = 0;
for (j = 2; j 2) {
k += l 2;
a[k - l] = t[j] - t[j + 1];
a[k + l] = t[j] + t[j + 1];
}
l 1;
mh = m >> 1;
for (j = 0; j ) {
k = m - j;
t[j] = t[m + k] - t[m + j];
t[k] = t[m + k] + t[m + j];
}
t[mh] = t[m + mh];
m = mh;
}
a[l] = t[0];
a[n] = t[2] - t[1];
a[0] = t[2] + t[1];
} else {
a[1] = a[0];
a[2] = t[0];
a[0] = t[1];
}
}
static void dfst(int n, float *a, float *t, int *ip, float *w)
{
int j, k, l, m, mh, nw, nc;
float xr, xi, yr, yi;
nw = ip[0];
if (n > (nw 3)) {
nw = n >> 3;
makewt(nw, ip, w);
}
nc = ip[1];
if (n > (nc 1)) {
nc = n >> 1;
makect(nc, ip, w + nw);
}
if (n > 2) {
m = n >> 1;
mh = m >> 1;
for (j = 1; j ) {
k = m - j;
xr = a[j] + a[n - j];
xi = a[j] - a[n - j];
yr = a[k] + a[n - k];
yi = a[k] - a[n - k];
a[j] = xr;
a[k] = yr;
t[j] = xi + yi;
t[k] = xi - yi;
}
t[0] = a[mh] - a[n - mh];
a[mh] += a[n - mh];
a[0] = a[m];
dstsub(m, a, nc, w + nw);
if (m > 4) {
bitrv2(m, ip + 2, a);
cftfsub(m, a, w);
rftfsub(m, a, nc, w + nw);
} else if (m == 4) {
cftfsub(m, a, w);
}
a[n - 1] = a[1] - a[0];
a[1] = a[0] + a[1];
for (j = m - 2; j >= 2; j -= 2) {
a[2 * j + 1] = a[j] - a[j + 1];
a[2 * j - 1] = -a[j] - a[j + 1];
}
l = 2;
m = mh;
while (m >= 2) {
dstsub(m, t, nc, w + nw);
if (m > 4) {
bitrv2(m, ip + 2, t);
cftfsub(m, t, w);
rftfsub(m, t, nc, w + nw);
} else if (m == 4) {
cftfsub(m, t, w);
}
a[n - l] = t[1] - t[0];
a[l] = t[0] + t[1];
k = 0;
for (j = 2; j 2) {
k += l 2;
a[k - l] = -t[j] - t[j + 1];
a[k + l] = t[j] - t[j + 1];
}
l 1;
mh = m >> 1;
for (j = 1; j ) {
k = m - j;
t[j] = t[m + k] + t[m + j];
t[k] = t[m + k] - t[m + j];
}
t[0] = t[m + mh];
m = mh;
}
a[l] = t[0];
}
a[0] = 0;
}
#endif // Not used.
/* -------- initializing routines -------- */
#include static void makewt(int nw, int *ip, float *w)
{
int j, nwh;
float delta, x, y;
ip[0] = nw;
ip[1] = 1;
if (nw > 2) {
nwh = nw >> 1;
delta = (float)atan(1.0f) / nwh;
w[0] = 1;
w[1] = 0;
w[nwh] = (float)cos(delta * nwh);
w[nwh + 1] = w[nwh];
if (nwh > 2) {
for (j = 2; j 2) {
x = (float)cos(delta * j);
y = (float)sin(delta * j);
w[j] = x;
w[j + 1] = y;
w[nw - j] = y;
w[nw - j + 1] = x;
}
bitrv2(nw, ip + 2, w);
}
}
}
static void makect(int nc, int *ip, float *c)
{
int j, nch;
float delta;
ip[1] = nc;
if (nc > 1) {
nch = nc >> 1;
delta = (float)atan(1.0f) / nch;
c[0] = (float)cos(delta * nch);
c[nch] = 0.5f * c[0];
for (j = 1; j ) {
c[j] = 0.5f * (float)cos(delta * j);
c[nc - j] = 0.5f * (float)sin(delta * j);
}
}
}
/* -------- child routines -------- */
static void bitrv2(int n, int *ip, float *a)
{
int j, j1, k, k1, l, m, m2;
float xr, xi, yr, yi;
ip[0] = 0;
l = n;
m = 1;
while ((m 3) l) {
l >>= 1;
for (j = 0; j ) {
ip[m + j] = ip[j] + l;
}
m 1;
}
m2 = 2 * m;
if ((m 3) == l) {
for (k = 0; k ) {
for (j = 0; j ) {
j1 = 2 * j + ip[k];
k1 = 2 * k + ip[j];
xr = a[j1];
xi = a[j1 + 1];
yr = a[k1];
yi = a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
j1 += m2;
k1 += 2 * m2;
xr = a[j1];
xi = a[j1 + 1];
yr = a[k1];
yi = a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
j1 += m2;
k1 -= m2;
xr = a[j1];
xi = a[j1 + 1];
yr = a[k1];
yi = a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
j1 += m2;
k1 += 2 * m2;
xr = a[j1];
xi = a[j1 + 1];
yr = a[k1];
yi = a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
}
j1 = 2 * k + m2 + ip[k];
k1 = j1 + m2;
xr = a[j1];
xi = a[j1 + 1];
yr = a[k1];
yi = a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
}
} else {
for (k = 1; k ) {
for (j = 0; j ) {
j1 = 2 * j + ip[k];
k1 = 2 * k + ip[j];
xr = a[j1];
xi = a[j1 + 1];
yr = a[k1];
yi = a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
j1 += m2;
k1 += m2;
xr = a[j1];
xi = a[j1 + 1];
yr = a[k1];
yi = a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
}
}
}
}
static void bitrv2conj(int n, int *ip, float *a)
{
int j, j1, k, k1, l, m, m2;
float xr, xi, yr, yi;
ip[0] = 0;
l = n;
m = 1;
while ((m 3) l) {
l >>= 1;
for (j = 0; j ) {
ip[m + j] = ip[j] + l;
}
m 1;
}
m2 = 2 * m;
if ((m 3) == l) {
for (k = 0; k ) {
for (j = 0; j ) {
j1 = 2 * j + ip[k];
k1 = 2 * k + ip[j];
xr = a[j1];
xi = -a[j1 + 1];
yr = a[k1];
yi = -a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
j1 += m2;
k1 += 2 * m2;
xr = a[j1];
xi = -a[j1 + 1];
yr = a[k1];
yi = -a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
j1 += m2;
k1 -= m2;
xr = a[j1];
xi = -a[j1 + 1];
yr = a[k1];
yi = -a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
j1 += m2;
k1 += 2 * m2;
xr = a[j1];
xi = -a[j1 + 1];
yr = a[k1];
yi = -a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
}
k1 = 2 * k + ip[k];
a[k1 + 1] = -a[k1 + 1];
j1 = k1 + m2;
k1 = j1 + m2;
xr = a[j1];
xi = -a[j1 + 1];
yr = a[k1];
yi = -a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
k1 += m2;
a[k1 + 1] = -a[k1 + 1];
}
} else {
a[1] = -a[1];
a[m2 + 1] = -a[m2 + 1];
for (k = 1; k ) {
for (j = 0; j ) {
j1 = 2 * j + ip[k];
k1 = 2 * k + ip[j];
xr = a[j1];
xi = -a[j1 + 1];
yr = a[k1];
yi = -a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
j1 += m2;
k1 += m2;
xr = a[j1];
xi = -a[j1 + 1];
yr = a[k1];
yi = -a[k1 + 1];
a[j1] = yr;
a[j1 + 1] = yi;
a[k1] = xr;
a[k1 + 1] = xi;
}
k1 = 2 * k + ip[k];
a[k1 + 1] = -a[k1 + 1];
a[k1 + m2 + 1] = -a[k1 + m2 + 1];
}
}
}
static void cftfsub(int n, float *a, float *w)
{
int j, j1, j2, j3, l;
float x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;
l = 2;
if (n > 8) {
cft1st(n, a, w);
l = 8;
while ((l 2) n) {
cftmdl(n, l, a, w);
l 2;
}
}
if ((l 2) == n) {
for (j = 0; j 2) {
j1 = j + l;
j2 = j1 + l;
j3 = j2 + l;
x0r = a[j] + a[j1];
x0i = a[j + 1] + a[j1 + 1];
x1r = a[j] - a[j1];
x1i = a[j + 1] - a[j1 + 1];
x2r = a[j2] + a[j3];
x2i = a[j2 + 1] + a[j3 + 1];
x3r = a[j2] - a[j3];
x3i = a[j2 + 1] - a[j3 + 1];
a[j] = x0r + x2r;
a[j + 1] = x0i + x2i;
a[j2] = x0r - x2r;
a[j2 + 1] = x0i - x2i;
a[j1] = x1r - x3i;
a[j1 + 1] = x1i + x3r;
a[j3] = x1r + x3i;
a[j3 + 1] = x1i - x3r;
}
} else {
for (j = 0; j 2) {
j1 = j + l;
x0r = a[j] - a[j1];
x0i = a[j + 1] - a[j1 + 1];
a[j] += a[j1];
a[j + 1] += a[j1 + 1];
a[j1] = x0r;
a[j1 + 1] = x0i;
}
}
}
static void cftbsub(int n, float *a, float *w)
{
int j, j1, j2, j3, l;
float x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;
l = 2;
if (n > 8) {
cft1st(n, a, w);
l = 8;
while ((l 2) n) {
cftmdl(n, l, a, w);
l 2;
}
}
if ((l 2) == n) {
for (j = 0; j 2) {
j1 = j + l;
j2 = j1 + l;
j3 = j2 + l;
x0r = a[j] + a[j1];
x0i = -a[j + 1] - a[j1 + 1];
x1r = a[j] - a[j1];
x1i = -a[j + 1] + a[j1 + 1];
x2r = a[j2] + a[j3];
x2i = a[j2 + 1] + a[j3 + 1];
x3r = a[j2] - a[j3];
x3i = a[j2 + 1] - a[j3 + 1];
a[j] = x0r + x2r;
a[j + 1] = x0i - x2i;
a[j2] = x0r - x2r;
a[j2 + 1] = x0i + x2i;
a[j1] = x1r - x3i;
a[j1 + 1] = x1i - x3r;
a[j3] = x1r + x3i;
a[j3 + 1] = x1i + x3r;
}
} else {
for (j = 0; j 2) {
j1 = j + l;
x0r = a[j] - a[j1];
x0i = -a[j + 1] + a[j1 + 1];
a[j] += a[j1];
a[j + 1] = -a[j + 1] - a[j1 + 1];
a[j1] = x0r;
a[j1 + 1] = x0i;
}
}
}
static void cft1st(int n, float *a, float *w)
{
int j, k1, k2;
float wk1r, wk1i, wk2r, wk2i, wk3r, wk3i;
float x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;
x0r = a[0] + a[2];
x0i = a[1] + a[3];
x1r = a[0] - a[2];
x1i = a[1] - a[3];
x2r = a[4] + a[6];
x2i = a[5] + a[7];
x3r = a[4] - a[6];
x3i = a[5] - a[7];
a[0] = x0r + x2r;
a[1] = x0i + x2i;
a[4] = x0r - x2r;
a[5] = x0i - x2i;
a[2] = x1r - x3i;
a[3] = x1i + x3r;
a[6] = x1r + x3i;
a[7] = x1i - x3r;
wk1r = w[2];
x0r = a[8] + a[10];
x0i = a[9] + a[11];
x1r = a[8] - a[10];
x1i = a[9] - a[11];
x2r = a[12] + a[14];
x2i = a[13] + a[15];
x3r = a[12] - a[14];
x3i = a[13] - a[15];
a[8] = x0r + x2r;
a[9] = x0i + x2i;
a[12] = x2i - x0i;
a[13] = x0r - x2r;
x0r = x1r - x3i;
x0i = x1i + x3r;
a[10] = wk1r * (x0r - x0i);
a[11] = wk1r * (x0r + x0i);
x0r = x3i + x1r;
x0i = x3r - x1i;
a[14] = wk1r * (x0i - x0r);
a[15] = wk1r * (x0i + x0r);
k1 = 0;
for (j = 16; j 16) {
k1 += 2;
k2 = 2 * k1;
wk2r = w[k1];
wk2i = w[k1 + 1];
wk1r = w[k2];
wk1i = w[k2 + 1];
wk3r = wk1r - 2 * wk2i * wk1i;
wk3i = 2 * wk2i * wk1r - wk1i;
x0r = a[j] + a[j + 2];
x0i = a[j + 1] + a[j + 3];
x1r = a[j] - a[j + 2];
x1i = a[j + 1] - a[j + 3];
x2r = a[j + 4] + a[j + 6];
x2i = a[j + 5] + a[j + 7];
x3r = a[j + 4] - a[j + 6];
x3i = a[j + 5] - a[j + 7];
a[j] = x0r + x2r;
a[j + 1] = x0i + x2i;
x0r -= x2r;
x0i -= x2i;
a[j + 4] = wk2r * x0r - wk2i * x0i;
a[j + 5] = wk2r * x0i + wk2i * x0r;
x0r = x1r - x3i;
x0i = x1i + x3r;
a[j + 2] = wk1r * x0r - wk1i * x0i;
a[j + 3] = wk1r * x0i + wk1i * x0r;
x0r = x1r + x3i;
x0i = x1i - x3r;
a[j + 6] = wk3r * x0r - wk3i * x0i;
a[j + 7] = wk3r * x0i + wk3i * x0r;
wk1r = w[k2 + 2];
wk1i = w[k2 + 3];
wk3r = wk1r - 2 * wk2r * wk1i;
wk3i = 2 * wk2r * wk1r - wk1i;
x0r = a[j + 8] + a[j + 10];
x0i = a[j + 9] + a[j + 11];
x1r = a[j + 8] - a[j + 10];
x1i = a[j + 9] - a[j + 11];
x2r = a[j + 12] + a[j + 14];
x2i = a[j + 13] + a[j + 15];
x3r = a[j + 12] - a[j + 14];
x3i = a[j + 13] - a[j + 15];
a[j + 8] = x0r + x2r;
a[j + 9] = x0i + x2i;
x0r -= x2r;
x0i -= x2i;
a[j + 12] = -wk2i * x0r - wk2r * x0i;
a[j + 13] = -wk2i * x0i + wk2r * x0r;
x0r = x1r - x3i;
x0i = x1i + x3r;
a[j + 10] = wk1r * x0r - wk1i * x0i;
a[j + 11] = wk1r * x0i + wk1i * x0r;
x0r = x1r + x3i;
x0i = x1i - x3r;
a[j + 14] = wk3r * x0r - wk3i * x0i;
a[j + 15] = wk3r * x0i + wk3i * x0r;
}
}
static void cftmdl(int n, int l, float *a, float *w)
{
int j, j1, j2, j3, k, k1, k2, m, m2;
float wk1r, wk1i, wk2r, wk2i, wk3r, wk3i;
float x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;
m = l 2;
for (j = 0; j 2) {
j1 = j + l;
j2 = j1 + l;
j3 = j2 + l;
x0r = a[j] + a[j1];
x0i = a[j + 1] + a[j1 + 1];
x1r = a[j] - a[j1];
x1i = a[j + 1] - a[j1 + 1];
x2r = a[j2] + a[j3];
x2i = a[j2 + 1] + a[j3 + 1];
x3r = a[j2] - a[j3];
x3i = a[j2 + 1] - a[j3 + 1];
a[j] = x0r + x2r;
a[j + 1] = x0i + x2i;
a[j2] = x0r - x2r;
a[j2 + 1] = x0i - x2i;
a[j1] = x1r - x3i;
a[j1 + 1] = x1i + x3r;
a[j3] = x1r + x3i;
a[j3 + 1] = x1i - x3r;
}
wk1r = w[2];
for (j = m; j 2) {
j1 = j + l;
j2 = j1 + l;
j3 = j2 + l;
x0r = a[j] + a[j1];
x0i = a[j + 1] + a[j1 + 1];
x1r = a[j] - a[j1];
x1i = a[j + 1] - a[j1 + 1];
x2r = a[j2] + a[j3];
x2i = a[j2 + 1] + a[j3 + 1];
x3r = a[j2] - a[j3];
x3i = a[j2 + 1] - a[j3 + 1];
a[j] = x0r + x2r;
a[j + 1] = x0i + x2i;
a[j2] = x2i - x0i;
a[j2 + 1] = x0r - x2r;
x0r = x1r - x3i;
x0i = x1i + x3r;
a[j1] = wk1r * (x0r - x0i);
a[j1 + 1] = wk1r * (x0r + x0i);
x0r = x3i + x1r;
x0i = x3r - x1i;
a[j3] = wk1r * (x0i - x0r);
a[j3 + 1] = wk1r * (x0i + x0r);
}
k1 = 0;
m2 = 2 * m;
for (k = m2; k m2) {
k1 += 2;
k2 = 2 * k1;
wk2r = w[k1];
wk2i = w[k1 + 1];
wk1r = w[k2];
wk1i = w[k2 + 1];
wk3r = wk1r - 2 * wk2i *