From 0c7a0514e3d2b30ba081968d2829ca751a835967 Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Tue, 23 May 2023 00:03:31 +0200 Subject: [PATCH] avfilter/window_func: Use av_bessel_i0() Old code needed about 6 times as long as new with defaults in afftfilt Signed-off-by: Michael Niedermayer --- libavfilter/window_func.h | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-) diff --git a/libavfilter/window_func.h b/libavfilter/window_func.h index 02b5def9dd..d0de63b5a8 100644 --- a/libavfilter/window_func.h +++ b/libavfilter/window_func.h @@ -59,19 +59,6 @@ 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 +219,15 @@ 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); }