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>
8 * This file is part of FFmpeg.
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.
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.
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
28 #include "timefilter.h"
31 /// Delay Locked Loop data. These variables refer to mathematical
32 /// concepts described in: http://www.kokkinizita.net/papers/usingdll.pdf
34 double feedback2_factor;
35 double feedback3_factor;
40 TimeFilter * ff_timefilter_new(double clock_period, double feedback2_factor, double feedback3_factor)
42 TimeFilter *self = av_mallocz(sizeof(TimeFilter));
43 self->clock_period = clock_period;
44 self->feedback2_factor = feedback2_factor;
45 self->feedback3_factor = feedback3_factor;
49 void ff_timefilter_destroy(TimeFilter *self)
54 void ff_timefilter_reset(TimeFilter *self)
59 double ff_timefilter_update(TimeFilter *self, double system_time, double period)
64 self->cycle_time = system_time;
67 self->cycle_time += self->clock_period * period;
68 /// calculate loop error
69 loop_error = system_time - self->cycle_time;
72 self->cycle_time += FFMAX(self->feedback2_factor, 1.0/(self->count)) * loop_error;
73 self->clock_period += self->feedback3_factor * loop_error / period;
75 return self->cycle_time;
79 #include "libavutil/lfg.h"
80 #define LFG_MAX ((1LL << 32) - 1)
89 double ideal[SAMPLES];
90 double samples[SAMPLES];
92 for(n0= 0; n0<40; n0=2*n0+1){
93 for(n1= 0; n1<10; n1=2*n1+1){
99 double best_error= 1000000000;
101 double bestpar1=0.001;
104 av_lfg_init(&prng, 123);
105 for(i=0; i<SAMPLES; i++){
106 ideal[i] = 10 + i + n1*i/(1000);
107 samples[i] = ideal[i] + n0 * (av_lfg_get(&prng) - LFG_MAX / 2)
114 for(par0= bestpar0*0.8; par0<=bestpar0*1.21; par0+=bestpar0*0.05){
115 for(par1= bestpar1*0.8; par1<=bestpar1*1.21; par1+=bestpar1*0.05){
117 TimeFilter *tf= ff_timefilter_new(1, par0, par1);
118 for(i=0; i<SAMPLES; i++){
120 filtered= ff_timefilter_update(tf, samples[i], 1);
121 error += (filtered - ideal[i]) * (filtered - ideal[i]);
123 ff_timefilter_destroy(tf);
124 if(error < best_error){
135 TimeFilter *tf= ff_timefilter_new(1, bestpar0, bestpar1);
136 for(i=0; i<SAMPLES; i++){
138 filtered= ff_timefilter_update(tf, samples[i], 1);
139 printf("%f %f %f %f\n", i - samples[i] + 10, filtered - samples[i], samples[FFMAX(i, 1)] - samples[FFMAX(i-1, 0)], filtered - lastfil);
142 ff_timefilter_destroy(tf);
144 printf(" [%f %f %9f]", bestpar0, bestpar1, best_error);