2 * Delay Locked Loop based time filter
3 * Copyright (c) 2009 Samalyse
4 * Author: Olivier Guilyardi <olivier samalyse com>
6 * This file is part of FFmpeg.
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
26 #include "timefilter.h"
29 /// Delay Locked Loop data. These variables refer to mathematical
30 /// concepts described in: http://www.kokkinizita.net/papers/usingdll.pdf
32 double feedback2_factor;
33 double feedback3_factor;
38 TimeFilter * ff_timefilter_new(double clock_period, double feedback2_factor, double feedback3_factor)
40 TimeFilter *self = av_mallocz(sizeof(TimeFilter));
41 self->clock_period = clock_period;
42 self->feedback2_factor = feedback2_factor;
43 self->feedback3_factor = feedback3_factor;
47 void ff_timefilter_destroy(TimeFilter *self)
52 void ff_timefilter_reset(TimeFilter *self)
57 double ff_timefilter_update(TimeFilter *self, double system_time, double period)
62 self->cycle_time = system_time;
65 self->cycle_time += self->clock_period * period;
66 /// calculate loop error
67 loop_error = system_time - self->cycle_time;
70 self->cycle_time += FFMAX(self->feedback2_factor, 1.0/(self->count)) * loop_error;
71 self->clock_period += self->feedback3_factor * loop_error / period;
73 return self->cycle_time;
82 double ideal[SAMPLES];
83 double samples[SAMPLES];
85 for(n0= 0; n0<40; n0=2*n0+1){
86 for(n1= 0; n1<10; n1=2*n1+1){
92 double best_error= 1000000000;
94 double bestpar1=0.001;
98 for(i=0; i<SAMPLES; i++){
99 ideal[i] = 10 + i + n1*i/(1000);
100 samples[i]= ideal[i] + n0*(rand()-RAND_MAX/2)/(RAND_MAX*10LL);
106 for(par0= bestpar0*0.8; par0<=bestpar0*1.21; par0+=bestpar0*0.05){
107 for(par1= bestpar1*0.8; par1<=bestpar1*1.21; par1+=bestpar1*0.05){
109 TimeFilter *tf= ff_timefilter_new(1, par0, par1);
110 for(i=0; i<SAMPLES; i++){
112 filtered= ff_timefilter_update(tf, samples[i], 1);
113 error += (filtered - ideal[i]) * (filtered - ideal[i]);
115 ff_timefilter_destroy(tf);
116 if(error < best_error){
127 TimeFilter *tf= ff_timefilter_new(1, bestpar0, bestpar1);
128 for(i=0; i<SAMPLES; i++){
130 filtered= ff_timefilter_update(tf, samples[i], 1);
131 printf("%f %f %f %f\n", i - samples[i] + 10, filtered - samples[i], samples[FFMAX(i, 1)] - samples[FFMAX(i-1, 0)], filtered - lastfil);
134 ff_timefilter_destroy(tf);
136 printf(" [%f %f %f]", bestpar0, bestpar1, best_error);