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/*
* Delay Locked Loop based time filter
* Copyright (c) 2009 Samalyse
* Author: Olivier Guilyardi <olivier samalyse com>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "config.h"
#include "avformat.h"
#include "timefilter.h"
struct TimeFilter {
/// Delay Locked Loop data. These variables refer to mathematical
/// concepts described in: http://www.kokkinizita.net/papers/usingdll.pdf
double cycle_time;
double feedback2_factor;
double feedback3_factor;
double clock_period;
int count;
};
TimeFilter * ff_timefilter_new(double clock_period, double feedback2_factor, double feedback3_factor)
{
TimeFilter *self = av_mallocz(sizeof(TimeFilter));
self->clock_period = clock_period;
self->feedback2_factor = feedback2_factor;
self->feedback3_factor = feedback3_factor;
return self;
}
void ff_timefilter_destroy(TimeFilter *self)
{
av_freep(&self);
}
void ff_timefilter_reset(TimeFilter *self)
{
self->count = 0;
}
double ff_timefilter_update(TimeFilter *self, double system_time, double period)
{
self->count++;
if (self->count==1) {
/// init loop
self->cycle_time = system_time;
} else {
double loop_error;
self->cycle_time += self->clock_period * period;
/// calculate loop error
loop_error = system_time - self->cycle_time;
/// update loop
self->cycle_time += FFMAX(self->feedback2_factor, 1.0/(self->count)) * loop_error;
self->clock_period += self->feedback3_factor * loop_error / period;
}
return self->cycle_time;
}
#ifdef TEST
main(){
double n0,n1;
#define SAMPLES 1000
double ideal[SAMPLES];
double samples[SAMPLES];
for(n0= 0; n0<40; n0=2*n0+1){
for(n1= 0; n1<10; n1=2*n1+1){
double best_error= 1000000000;
double bestpar0=1;
double bestpar1=0.001;
int better, i;
srandom(123);
for(i=0; i<SAMPLES; i++){
ideal[i] = 10 + i + n1*i/(1000);
samples[i]= ideal[i] + n0*(rand()-RAND_MAX/2)/(RAND_MAX*10LL);
}
do{
double par0, par1;
better=0;
for(par0= bestpar0*0.8; par0<=bestpar0*1.21; par0+=bestpar0*0.05){
for(par1= bestpar1*0.8; par1<=bestpar1*1.21; par1+=bestpar1*0.05){
double error=0;
TimeFilter *tf= ff_timefilter_new(1, par0, par1);
for(i=0; i<SAMPLES; i++){
double filtered;
filtered= ff_timefilter_update(tf, samples[i], 1);
error += (filtered - ideal[i]) * (filtered - ideal[i]);
}
ff_timefilter_destroy(tf);
if(error < best_error){
best_error= error;
bestpar0= par0;
bestpar1= par1;
better=1;
}
}
}
}while(better);
printf(" [%f %f %f]", bestpar0, bestpar1, best_error);
}
printf("\n");
}
}
#endif
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