diff --git a/libswresample/resample.c b/libswresample/resample.c index 82f004c802..072e0d6a78 100644 --- a/libswresample/resample.c +++ b/libswresample/resample.c @@ -1,6 +1,7 @@ /* * audio resampling * Copyright (c) 2004-2012 Michael Niedermayer + * bessel function: Copyright (c) 2006 Xiaogang Zhang * * This file is part of FFmpeg. * @@ -28,38 +29,108 @@ #include "libavutil/avassert.h" #include "resample.h" +static inline double eval_poly(const double *coeff, int size, double x) { + double sum = coeff[size-1]; + int i; + for (i = size-2; i >= 0; --i) { + sum *= x; + sum += coeff[i]; + } + return sum; +} + /** * 0th order modified bessel function of the first kind. - */ -static double bessel(double x){ - double lastv=0; - double t, v; - int i; - static const double inv[100]={ - 1.0/( 1* 1), 1.0/( 2* 2), 1.0/( 3* 3), 1.0/( 4* 4), 1.0/( 5* 5), 1.0/( 6* 6), 1.0/( 7* 7), 1.0/( 8* 8), 1.0/( 9* 9), 1.0/(10*10), - 1.0/(11*11), 1.0/(12*12), 1.0/(13*13), 1.0/(14*14), 1.0/(15*15), 1.0/(16*16), 1.0/(17*17), 1.0/(18*18), 1.0/(19*19), 1.0/(20*20), - 1.0/(21*21), 1.0/(22*22), 1.0/(23*23), 1.0/(24*24), 1.0/(25*25), 1.0/(26*26), 1.0/(27*27), 1.0/(28*28), 1.0/(29*29), 1.0/(30*30), - 1.0/(31*31), 1.0/(32*32), 1.0/(33*33), 1.0/(34*34), 1.0/(35*35), 1.0/(36*36), 1.0/(37*37), 1.0/(38*38), 1.0/(39*39), 1.0/(40*40), - 1.0/(41*41), 1.0/(42*42), 1.0/(43*43), 1.0/(44*44), 1.0/(45*45), 1.0/(46*46), 1.0/(47*47), 1.0/(48*48), 1.0/(49*49), 1.0/(50*50), - 1.0/(51*51), 1.0/(52*52), 1.0/(53*53), 1.0/(54*54), 1.0/(55*55), 1.0/(56*56), 1.0/(57*57), 1.0/(58*58), 1.0/(59*59), 1.0/(60*60), - 1.0/(61*61), 1.0/(62*62), 1.0/(63*63), 1.0/(64*64), 1.0/(65*65), 1.0/(66*66), 1.0/(67*67), 1.0/(68*68), 1.0/(69*69), 1.0/(70*70), - 1.0/(71*71), 1.0/(72*72), 1.0/(73*73), 1.0/(74*74), 1.0/(75*75), 1.0/(76*76), 1.0/(77*77), 1.0/(78*78), 1.0/(79*79), 1.0/(80*80), - 1.0/(81*81), 1.0/(82*82), 1.0/(83*83), 1.0/(84*84), 1.0/(85*85), 1.0/(86*86), 1.0/(87*87), 1.0/(88*88), 1.0/(89*89), 1.0/(90*90), - 1.0/(91*91), 1.0/(92*92), 1.0/(93*93), 1.0/(94*94), 1.0/(95*95), 1.0/(96*96), 1.0/(97*97), 1.0/(98*98), 1.0/(99*99), 1.0/(10000) - }; + * Algorithm taken from the Boost project, source: + * https://searchcode.com/codesearch/view/14918379/ + * Use, modification and distribution are subject to the + * Boost Software License, Version 1.0 (see notice below). + * Boost Software License - Version 1.0 - August 17th, 2003 +Permission is hereby granted, free of charge, to any person or organization +obtaining a copy of the software and accompanying documentation covered by +this license (the "Software") to use, reproduce, display, distribute, +execute, and transmit the Software, and to prepare derivative works of the +Software, and to permit third-parties to whom the Software is furnished to +do so, all subject to the following: - x= x*x/4; - t = x; - v = 1 + x; - for(i=1; v != lastv; i+=2){ - t *= x*inv[i]; - v += t; - lastv=v; - t *= x*inv[i + 1]; - v += t; - av_assert2(i<98); +The copyright notices in the Software and this entire statement, including +the above license grant, this restriction and the following disclaimer, +must be included in all copies of the Software, in whole or in part, and +all derivative works of the Software, unless such copies or derivative +works are solely in the form of machine-executable object code generated by +a source language processor. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT +SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE +FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE, +ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER +DEALINGS IN THE SOFTWARE. + */ + +static double bessel(double x) { +// Modified Bessel function of the first kind of order zero +// minimax rational approximations on intervals, see +// Blair and Edwards, Chalk River Report AECL-4928, 1974 + static const double p1[] = { + -2.2335582639474375249e+15, + -5.5050369673018427753e+14, + -3.2940087627407749166e+13, + -8.4925101247114157499e+11, + -1.1912746104985237192e+10, + -1.0313066708737980747e+08, + -5.9545626019847898221e+05, + -2.4125195876041896775e+03, + -7.0935347449210549190e+00, + -1.5453977791786851041e-02, + -2.5172644670688975051e-05, + -3.0517226450451067446e-08, + -2.6843448573468483278e-11, + -1.5982226675653184646e-14, + -5.2487866627945699800e-18, + }; + static const double q1[] = { + -2.2335582639474375245e+15, + 7.8858692566751002988e+12, + -1.2207067397808979846e+10, + 1.0377081058062166144e+07, + -4.8527560179962773045e+03, + 1.0L, + }; + static const double p2[] = { + -2.2210262233306573296e-04, + 1.3067392038106924055e-02, + -4.4700805721174453923e-01, + 5.5674518371240761397e+00, + -2.3517945679239481621e+01, + 3.1611322818701131207e+01, + -9.6090021968656180000e+00, + }; + static const double q2[] = { + -5.5194330231005480228e-04, + 3.2547697594819615062e-02, + -1.1151759188741312645e+00, + 1.3982595353892851542e+01, + -6.0228002066743340583e+01, + 8.5539563258012929600e+01, + -3.1446690275135491500e+01, + 1.0L, + }; + double y, r, factor; + if (x == 0) + return 1.0; + x = fabs(x); + if (x <= 15) { + y = x * x; + return eval_poly(p1, FF_ARRAY_ELEMS(p1), y) / eval_poly(q1, FF_ARRAY_ELEMS(q1), y); + } + else { + y = 1 / x - 1.0 / 15; + r = eval_poly(p2, FF_ARRAY_ELEMS(p2), y) / eval_poly(q2, FF_ARRAY_ELEMS(q2), y); + factor = exp(x) / sqrt(x); + return factor * r; } - return v; } /**