blob: ad6485d5e7807a29ee33a158c5cd3b3d3fa12b06
| 1 | /* |
| 2 | * Delay Locked Loop based time filter |
| 3 | * Copyright (c) 2009 Samalyse |
| 4 | * Copyright (c) 2009 Michael Niedermayer |
| 5 | * Author: Olivier Guilyardi <olivier samalyse com> |
| 6 | * Michael Niedermayer <michaelni gmx at> |
| 7 | * |
| 8 | * This file is part of FFmpeg. |
| 9 | * |
| 10 | * FFmpeg is free software; you can redistribute it and/or |
| 11 | * modify it under the terms of the GNU Lesser General Public |
| 12 | * License as published by the Free Software Foundation; either |
| 13 | * version 2.1 of the License, or (at your option) any later version. |
| 14 | * |
| 15 | * FFmpeg is distributed in the hope that it will be useful, |
| 16 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 17 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 18 | * Lesser General Public License for more details. |
| 19 | * |
| 20 | * You should have received a copy of the GNU Lesser General Public |
| 21 | * License along with FFmpeg; if not, write to the Free Software |
| 22 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 23 | */ |
| 24 | |
| 25 | #include "libavutil/common.h" |
| 26 | #include "libavutil/mem.h" |
| 27 | |
| 28 | #include "timefilter.h" |
| 29 | |
| 30 | struct TimeFilter { |
| 31 | // Delay Locked Loop data. These variables refer to mathematical |
| 32 | // concepts described in: http://www.kokkinizita.net/papers/usingdll.pdf |
| 33 | double cycle_time; |
| 34 | double feedback2_factor; |
| 35 | double feedback3_factor; |
| 36 | double clock_period; |
| 37 | int count; |
| 38 | }; |
| 39 | |
| 40 | /* 1 - exp(-x) using a 3-order power series */ |
| 41 | static double qexpneg(double x) |
| 42 | { |
| 43 | return 1 - 1 / (1 + x * (1 + x / 2 * (1 + x / 3))); |
| 44 | } |
| 45 | |
| 46 | TimeFilter *ff_timefilter_new(double time_base, |
| 47 | double period, |
| 48 | double bandwidth) |
| 49 | { |
| 50 | TimeFilter *self = av_mallocz(sizeof(TimeFilter)); |
| 51 | double o = 2 * M_PI * bandwidth * period * time_base; |
| 52 | |
| 53 | if (!self) |
| 54 | return NULL; |
| 55 | |
| 56 | self->clock_period = time_base; |
| 57 | self->feedback2_factor = qexpneg(M_SQRT2 * o); |
| 58 | self->feedback3_factor = qexpneg(o * o) / period; |
| 59 | return self; |
| 60 | } |
| 61 | |
| 62 | void ff_timefilter_destroy(TimeFilter *self) |
| 63 | { |
| 64 | av_freep(&self); |
| 65 | } |
| 66 | |
| 67 | void ff_timefilter_reset(TimeFilter *self) |
| 68 | { |
| 69 | self->count = 0; |
| 70 | } |
| 71 | |
| 72 | double ff_timefilter_update(TimeFilter *self, double system_time, double period) |
| 73 | { |
| 74 | self->count++; |
| 75 | if (self->count == 1) { |
| 76 | self->cycle_time = system_time; |
| 77 | } else { |
| 78 | double loop_error; |
| 79 | self->cycle_time += self->clock_period * period; |
| 80 | loop_error = system_time - self->cycle_time; |
| 81 | |
| 82 | self->cycle_time += FFMAX(self->feedback2_factor, 1.0 / self->count) * loop_error; |
| 83 | self->clock_period += self->feedback3_factor * loop_error; |
| 84 | } |
| 85 | return self->cycle_time; |
| 86 | } |
| 87 | |
| 88 | double ff_timefilter_eval(TimeFilter *self, double delta) |
| 89 | { |
| 90 | return self->cycle_time + self->clock_period * delta; |
| 91 | } |
| 92 |