diff options
Diffstat (limited to 'libavcodec/mdct.c')
| -rw-r--r-- | libavcodec/mdct.c | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/libavcodec/mdct.c b/libavcodec/mdct.c index c7008df4f1..e809fcdcbc 100644 --- a/libavcodec/mdct.c +++ b/libavcodec/mdct.c @@ -26,24 +26,25 @@ */ // Generate a Kaiser-Bessel Derived Window. -void ff_kbd_window_init(float *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[256]; - double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0); + double local_window[n]; + double alpha2 = (alpha * M_PI / n) * (alpha * M_PI / n); - for (i = 0; i < 256; i++) { - tmp = i * (256 - i) * alpha2; + for (i = 0; i < n; i++) { + tmp = i * (n - i) * alpha2; bessel = 1.0; - for (j = 100; j > 0; j--) /* default to 100 iterations */ + 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 < 256; i++) + for (i = 0; i < n; i++) window[i] = sqrt(local_window[i] / sum); } |