Statistics
| Branch: | Revision:

ffmpeg / libavformat / timefilter.c @ bc3057f4

History | View | Annotate | Download (3.9 KB)

1
/*
2
 * Delay Locked Loop based time filter
3
 * Copyright (c) 2009 Samalyse
4
 * Author: Olivier Guilyardi <olivier samalyse com>
5
 *
6
 * This file is part of FFmpeg.
7
 *
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.
12
 *
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.
17
 *
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
21
 */
22

    
23

    
24
#include "config.h"
25
#include "avformat.h"
26
#include "timefilter.h"
27

    
28
struct TimeFilter {
29
    /// Delay Locked Loop data. These variables refer to mathematical
30
    /// concepts described in: http://www.kokkinizita.net/papers/usingdll.pdf
31
    double cycle_time;
32
    double feedback2_factor;
33
    double feedback3_factor;
34
    double clock_period;
35
    int count;
36
};
37

    
38
TimeFilter * ff_timefilter_new(double clock_period, double feedback2_factor, double feedback3_factor)
39
{
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;
44
    return self;
45
}
46

    
47
void ff_timefilter_destroy(TimeFilter *self)
48
{
49
    av_freep(&self);
50
}
51

    
52
void ff_timefilter_reset(TimeFilter *self)
53
{
54
    self->count      = 0;
55
}
56

    
57
double ff_timefilter_update(TimeFilter *self, double system_time, double period)
58
{
59
    self->count++;
60
    if (self->count==1) {
61
        /// init loop
62
        self->cycle_time    = system_time;
63
    } else {
64
        double loop_error;
65
        self->cycle_time   += self->clock_period * period;
66
        /// calculate loop error
67
        loop_error          = system_time - self->cycle_time;
68

    
69
        /// update loop
70
        self->cycle_time   += FFMAX(self->feedback2_factor, 1.0/(self->count)) * loop_error;
71
        self->clock_period += self->feedback3_factor * loop_error / period;
72
    }
73
    return self->cycle_time;
74
}
75

    
76
#ifdef TEST
77
main(){
78
    double n0,n1;
79
#define SAMPLES 1000
80
    double ideal[SAMPLES];
81
    double samples[SAMPLES];
82
    for(n0= 0; n0<40; n0=2*n0+1){
83
        for(n1= 0; n1<10; n1=2*n1+1){
84
            double best_error= 1000000000;
85
            double bestpar0=1;
86
            double bestpar1=0.001;
87
            int better, i;
88

    
89
            srandom(123);
90
            for(i=0; i<SAMPLES; i++){
91
                ideal[i]  = 10 + i + n1*i/(1000);
92
                samples[i]= ideal[i] + n0*(rand()-RAND_MAX/2)/(RAND_MAX*10LL);
93
            }
94

    
95
            do{
96
                double par0, par1;
97
                better=0;
98
                for(par0= bestpar0*0.8; par0<=bestpar0*1.21; par0+=bestpar0*0.05){
99
                    for(par1= bestpar1*0.8; par1<=bestpar1*1.21; par1+=bestpar1*0.05){
100
                        double error=0;
101
                        TimeFilter *tf= ff_timefilter_new(1, par0, par1);
102
                        for(i=0; i<SAMPLES; i++){
103
                            double filtered;
104
                            filtered=  ff_timefilter_update(tf, samples[i], 1);
105
                            error += (filtered - ideal[i]) * (filtered - ideal[i]);
106
                        }
107
                        ff_timefilter_destroy(tf);
108
                        if(error < best_error){
109
                            best_error= error;
110
                            bestpar0= par0;
111
                            bestpar1= par1;
112
                            better=1;
113
                        }
114
                    }
115
                }
116
            }while(better);
117
            printf(" [%f %f %f]", bestpar0, bestpar1, best_error);
118
        }
119
        printf("\n");
120
    }
121
}
122
#endif