* MDCT/IMDCT transforms
* Copyright (c) 2002 Fabrice Bellard.
*
- * This library is free software; you can redistribute it and/or
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
- * version 2 of the License, or (at your option) any later version.
+ * version 2.1 of the License, or (at your option) any later version.
*
- * This library is distributed in the hope that it will be useful,
+ * FFmpeg 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "dsputil.h"
-/*
- * init MDCT or IMDCT computation
+/**
+ * @file mdct.c
+ * MDCT/IMDCT transforms.
+ */
+
+// Generate a Kaiser-Bessel Derived Window.
+#define BESSEL_I0_ITER 50 // default: 50 iterations of Bessel I0 approximation
+void ff_kbd_window_init(float *window, float alpha, int n)
+{
+ int i, j;
+ double sum = 0.0, bessel, tmp;
+ double local_window[n];
+ double alpha2 = (alpha * M_PI / n) * (alpha * M_PI / n);
+
+ for (i = 0; i < n; i++) {
+ tmp = i * (n - i) * alpha2;
+ bessel = 1.0;
+ for (j = BESSEL_I0_ITER; j > 0; j--)
+ bessel = bessel * tmp / (j * j) + 1;
+ sum += bessel;
+ local_window[i] = sum;
+ }
+
+ sum++;
+ for (i = 0; i < n; i++)
+ window[i] = sqrt(local_window[i] / sum);
+}
+
+/**
+ * init MDCT or IMDCT computation.
*/
int ff_mdct_init(MDCTContext *s, int nbits, int inverse)
{
int n, n4, i;
- float alpha;
+ double alpha;
memset(s, 0, sizeof(*s));
n = 1 << nbits;
s->tcos[i] = -cos(alpha);
s->tsin[i] = -sin(alpha);
}
- if (fft_init(&s->fft, s->nbits - 2, inverse) < 0)
+ if (ff_fft_init(&s->fft, s->nbits - 2, inverse) < 0)
goto fail;
return 0;
fail:
/* complex multiplication: p = a * b */
#define CMUL(pre, pim, are, aim, bre, bim) \
{\
- float _are = (are);\
- float _aim = (aim);\
- float _bre = (bre);\
- float _bim = (bim);\
+ double _are = (are);\
+ double _aim = (aim);\
+ double _bre = (bre);\
+ double _bim = (bim);\
(pre) = _are * _bre - _aim * _bim;\
(pim) = _are * _bim + _aim * _bre;\
}
* @param input N/2 samples
* @param tmp N/2 samples
*/
-void ff_imdct_calc(MDCTContext *s, FFTSample *output,
+void ff_imdct_calc(MDCTContext *s, FFTSample *output,
const FFTSample *input, FFTSample *tmp)
{
int k, n8, n4, n2, n, j;
in1 += 2;
in2 -= 2;
}
- fft_calc(&s->fft, z);
+ ff_fft_calc(&s->fft, z);
/* post rotation + reordering */
/* XXX: optimize */
* @param out N/2 samples
* @param tmp temporary storage of N/2 samples
*/
-void ff_mdct_calc(MDCTContext *s, FFTSample *out,
+void ff_mdct_calc(MDCTContext *s, FFTSample *out,
const FFTSample *input, FFTSample *tmp)
{
int i, j, n, n8, n4, n2, n3;
CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
}
- fft_calc(&s->fft, x);
-
+ ff_fft_calc(&s->fft, x);
+
/* post rotation */
for(i=0;i<n4;i++) {
re = x[i].re;
{
av_freep(&s->tcos);
av_freep(&s->tsin);
- fft_end(&s->fft);
+ ff_fft_end(&s->fft);
}