| /* |
| * 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 "libavutil/common.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; |
| } |