/* * Delay Locked Loop based time filter * Copyright (c) 2009 Samalyse * Copyright (c) 2009 Michael Niedermayer * Author: Olivier Guilyardi <olivier samalyse com> *         Michael Niedermayer <michaelni gmx at> * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include <math.h>#include <stddef.h> #include "libavutil/macros.h"#include "libavutil/mathematics.h"#include "libavutil/mem.h" #include "timefilter.h" struct TimeFilter {    // Delay Locked Loop data. These variables refer to mathematical    // concepts described in: http://www.kokkinizita.net/papers/usingdll.pdf    double cycle_time;    double feedback2_factor;    double feedback3_factor;    double clock_period;    int count;}; /* 1 - exp(-x) using a 3-order power series */static double qexpneg(double x){    return 1 - 1 / (1 + x * (1 + x / 2 * (1 + x / 3)));} TimeFilter *ff_timefilter_new(double time_base,                              double period,                              double bandwidth){    TimeFilter *self       = av_mallocz(sizeof(TimeFilter));    double o               = 2 * M_PI * bandwidth * period * time_base;     if (!self)        return NULL;     self->clock_period     = time_base;    self->feedback2_factor = qexpneg(M_SQRT2 * o);    self->feedback3_factor = qexpneg(o * o) / period;    return self;} void ff_timefilter_destroy(TimeFilter *self){    av_freep(&self);} void ff_timefilter_reset(TimeFilter *self){    self->count = 0;} double ff_timefilter_update(TimeFilter *self, double system_time, double period){    self->count++;    if (self->count == 1) {        self->cycle_time = system_time;    } else {        double loop_error;        self->cycle_time += self->clock_period * period;        loop_error = system_time - self->cycle_time;         self->cycle_time   += FFMAX(self->feedback2_factor, 1.0 / self->count) * loop_error;        self->clock_period += self->feedback3_factor * loop_error;    }    return self->cycle_time;} double ff_timefilter_eval(TimeFilter *self, double delta){    return self->cycle_time + self->clock_period * delta;}