Commit 4eb7a735 authored by Robert Swain's avatar Robert Swain Committed by Andreas Öman

Make the Kaiser-Bessel window generator a common function

Patch by Robert Swain, robert d swain a gmail d com

Originally committed as revision 11514 to svn://svn.ffmpeg.org/ffmpeg/trunk
parent f5b41031
......@@ -196,30 +196,6 @@ typedef struct {
AVCodecContext *avctx; ///< parent context
} AC3DecodeContext;
/**
* Generate a Kaiser-Bessel Derived Window.
*/
static void ac3_window_init(float *window)
{
int i, j;
double sum = 0.0, bessel, tmp;
double local_window[256];
double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0);
for (i = 0; i < 256; i++) {
tmp = i * (256 - i) * alpha2;
bessel = 1.0;
for (j = 100; j > 0; j--) /* default to 100 iterations */
bessel = bessel * tmp / (j * j) + 1;
sum += bessel;
local_window[i] = sum;
}
sum++;
for (i = 0; i < 256; i++)
window[i] = sqrt(local_window[i] / sum);
}
/**
* Symmetrical Dequantization
* reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
......@@ -301,7 +277,7 @@ static int ac3_decode_init(AVCodecContext *avctx)
ac3_tables_init();
ff_mdct_init(&s->imdct_256, 8, 1);
ff_mdct_init(&s->imdct_512, 9, 1);
ac3_window_init(s->window);
ff_kbd_window_init(s->window);
dsputil_init(&s->dsp, avctx);
av_init_random(0, &s->dith_state);
......
......@@ -645,6 +645,12 @@ typedef struct MDCTContext {
FFTContext fft;
} MDCTContext;
/**
* Generate a Kaiser-Bessel Derived Window.
* @param window pointer to half window
*/
void ff_kbd_window_init(float *window);
int ff_mdct_init(MDCTContext *s, int nbits, int inverse);
void ff_imdct_calc(MDCTContext *s, FFTSample *output,
const FFTSample *input, FFTSample *tmp);
......
......@@ -25,6 +25,28 @@
* MDCT/IMDCT transforms.
*/
// Generate a Kaiser-Bessel Derived Window.
void ff_kbd_window_init(float *window)
{
int i, j;
double sum = 0.0, bessel, tmp;
double local_window[256];
double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0);
for (i = 0; i < 256; i++) {
tmp = i * (256 - i) * alpha2;
bessel = 1.0;
for (j = 100; j > 0; j--) /* default to 100 iterations */
bessel = bessel * tmp / (j * j) + 1;
sum += bessel;
local_window[i] = sum;
}
sum++;
for (i = 0; i < 256; i++)
window[i] = sqrt(local_window[i] / sum);
}
/**
* init MDCT or IMDCT computation.
*/
......
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