libavformat/timefilter.c

   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
  26 #include "config.h"
  27 #include "avformat.h"
  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 TimeFilter * ff_timefilter_new(double clock_period, double feedback2_factor, double feedback3_factor)
  41 {
  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;
  46     return self;
  47 }
  48
  49 void ff_timefilter_destroy(TimeFilter *self)
  50 {
  51     av_freep(&self);
  52 }
  53
  54 void ff_timefilter_reset(TimeFilter *self)
  55 {
  56     self->count      = 0;
  57 }
  58
  59 double ff_timefilter_update(TimeFilter *self, double system_time, double period)
  60 {
  61     self->count++;
  62     if (self->count==1) {
  63         /// init loop
  64         self->cycle_time    = system_time;
  65     } else {
  66         double loop_error;
  67         self->cycle_time   += self->clock_period * period;
  68         /// calculate loop error
  69         loop_error          = system_time - self->cycle_time;
  70
  71         /// update loop
  72         self->cycle_time   += FFMAX(self->feedback2_factor, 1.0/(self->count)) * loop_error;
  73         self->clock_period += self->feedback3_factor * loop_error / period;
  74     }
  75     return self->cycle_time;
  76 }
  77
  78 #ifdef TEST
  79 #include "libavutil/lfg.h"
  80 #define LFG_MAX ((1LL << 32) - 1)
  81
  82 int main(void)
  83 {
  84     AVLFG prng;
  85     double n0,n1;
  86 #define SAMPLES 1000
  87     double ideal[SAMPLES];
  88     double samples[SAMPLES];
  89 #if 1
  90     for(n0= 0; n0<40; n0=2*n0+1){
  91         for(n1= 0; n1<10; n1=2*n1+1){
  92 #else
  93     {{
  94         n0=7;
  95         n1=1;
  96 #endif
  97             double best_error= 1000000000;
  98             double bestpar0=1;
  99             double bestpar1=0.001;
 100             int better, i;
 101
 102             av_lfg_init(&prng, 123);
 103             for(i=0; i<SAMPLES; i++){
 104                 ideal[i]  = 10 + i + n1*i/(1000);
 105                 samples[i] = ideal[i] + n0 * (av_lfg_get(&prng) - LFG_MAX / 2)
 106                                            / (LFG_MAX * 10LL);
 107             }
 108
 109             do{
 110                 double par0, par1;
 111                 better=0;
 112                 for(par0= bestpar0*0.8; par0<=bestpar0*1.21; par0+=bestpar0*0.05){
 113                     for(par1= bestpar1*0.8; par1<=bestpar1*1.21; par1+=bestpar1*0.05){
 114                         double error=0;
 115                         TimeFilter *tf= ff_timefilter_new(1, par0, par1);
 116                         for(i=0; i<SAMPLES; i++){
 117                             double filtered;
 118                             filtered=  ff_timefilter_update(tf, samples[i], 1);
 119                             error += (filtered - ideal[i]) * (filtered - ideal[i]);
 120                         }
 121                         ff_timefilter_destroy(tf);
 122                         if(error < best_error){
 123                             best_error= error;
 124                             bestpar0= par0;
 125                             bestpar1= par1;
 126                             better=1;
 127                         }
 128                     }
 129                 }
 130             }while(better);
 131 #if 0
 132             double lastfil=9;
 133             TimeFilter *tf= ff_timefilter_new(1, bestpar0, bestpar1);
 134             for(i=0; i<SAMPLES; i++){
 135                 double filtered;
 136                 filtered=  ff_timefilter_update(tf, samples[i], 1);
 137                 printf("%f %f %f %f\n", i - samples[i] + 10, filtered - samples[i], samples[FFMAX(i, 1)] - samples[FFMAX(i-1, 0)], filtered - lastfil);
 138                 lastfil= filtered;
 139             }
 140             ff_timefilter_destroy(tf);
 141 #else
 142             printf(" [%f %f %9f]", bestpar0, bestpar1, best_error);
 143 #endif
 144         }
 145         printf("\n");
 146     }
 147     return 0;
 148 }
 149 #endif