Old code needed about 6 times as long as new with defaults in afftfilt
Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
---
libavfilter/window_func.h | 20 +++++---------------
1 file changed, 5 insertions(+), 15 deletions(-)
diff --git a/libavfilter/window_func.h b/libavfilter/window_func.h
index 02b5def9dd..13236d8593 100644
--- a/libavfilter/window_func.h
+++ b/libavfilter/window_func.h
@@ -25,6 +25,7 @@
#include <math.h>
#include "libavutil/avassert.h"
#include "libavutil/common.h"
+#include "libavutil/timer.h"
enum WindowFunc { WFUNC_RECT, WFUNC_HANNING, WFUNC_HAMMING, WFUNC_BLACKMAN,
WFUNC_BARTLETT, WFUNC_WELCH, WFUNC_FLATTOP,
@@ -59,19 +60,6 @@ enum WindowFunc { WFUNC_RECT, WFUNC_HANNING,
WFUNC_HAMMING, WFUNC_BLACKMAN,
{ "bohman", "Bohman", 0, AV_OPT_TYPE_CONST,
{.i64=WFUNC_BOHMAN}, 0, 0, flag, "win_func" }, \
{ "kaiser", "Kaiser", 0, AV_OPT_TYPE_CONST,
{.i64=WFUNC_KAISER}, 0, 0, flag, "win_func" }
-static inline double get_i0(double x)
-{
- double y = 1.0, prev = 1.0, i = 1.0;
-
- while (fabs(prev) > 1e-20) {
- double summand = prev * x * x / (4 * i * i);
- y += summand;
- prev = summand;
- i++;
- }
-
- return y;
-}
static inline void generate_window_func(float *lut, int N, int win_func,
float *overlap)
@@ -232,13 +220,15 @@ static inline void generate_window_func(float *lut, int
N, int win_func,
*overlap = 0.75;
break;
case WFUNC_KAISER:
+ {
+ double scale = 1.0 / av_bessel_i0(12.);
for (n = 0; n < N; n++) {
double x = 2.0 / (double)(N - 1);
-
- lut[n] = get_i0(12. * sqrt(1. - SQR(n * x - 1.))) / get_i0(12.);
+ lut[n] = av_bessel_i0(12. * sqrt(1. - SQR(n * x - 1.))) * scale;
}
*overlap = 0.75;
break;
+ }
default:
av_assert0(0);
}
--
2.17.1
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