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ffmpeg / libavformat / timefilter.c @ bd51c013

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/*
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 * Delay Locked Loop based time filter
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 * Copyright (c) 2009 Samalyse
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 * Copyright (c) 2009 Michael Niedermayer
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 * Author: Olivier Guilyardi <olivier samalyse com>
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 *         Michael Niedermayer <michaelni gmx at>
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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#include "config.h"
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#include "avformat.h"
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#include "timefilter.h"
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struct TimeFilter {
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    /// Delay Locked Loop data. These variables refer to mathematical
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    /// concepts described in: http://www.kokkinizita.net/papers/usingdll.pdf
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    double cycle_time;
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    double feedback2_factor;
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    double feedback3_factor;
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    double clock_period;
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    int count;
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};
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TimeFilter * ff_timefilter_new(double clock_period, double feedback2_factor, double feedback3_factor)
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{
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    TimeFilter *self        = av_mallocz(sizeof(TimeFilter));
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    self->clock_period      = clock_period;
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    self->feedback2_factor  = feedback2_factor;
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    self->feedback3_factor  = feedback3_factor;
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    return self;
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}
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void ff_timefilter_destroy(TimeFilter *self)
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{
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    av_freep(&self);
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}
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void ff_timefilter_reset(TimeFilter *self)
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{
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    self->count      = 0;
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}
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double ff_timefilter_update(TimeFilter *self, double system_time, double period)
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{
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    self->count++;
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    if (self->count==1) {
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        /// init loop
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        self->cycle_time    = system_time;
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    } else {
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        double loop_error;
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        self->cycle_time   += self->clock_period * period;
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        /// calculate loop error
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        loop_error          = system_time - self->cycle_time;
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        /// update loop
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        self->cycle_time   += FFMAX(self->feedback2_factor, 1.0/(self->count)) * loop_error;
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        self->clock_period += self->feedback3_factor * loop_error / period;
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    }
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    return self->cycle_time;
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}
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#ifdef TEST
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#undef rand
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int main(void)
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{
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    double n0,n1;
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#define SAMPLES 1000
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    double ideal[SAMPLES];
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    double samples[SAMPLES];
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#if 1
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    for(n0= 0; n0<40; n0=2*n0+1){
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        for(n1= 0; n1<10; n1=2*n1+1){
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#else
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    {{
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        n0=7;
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        n1=1;
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#endif
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            double best_error= 1000000000;
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            double bestpar0=1;
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            double bestpar1=0.001;
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            int better, i;
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            srandom(123);
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            for(i=0; i<SAMPLES; i++){
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                ideal[i]  = 10 + i + n1*i/(1000);
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                samples[i]= ideal[i] + n0*(rand()-RAND_MAX/2)/(RAND_MAX*10LL);
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            }
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            do{
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                double par0, par1;
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                better=0;
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                for(par0= bestpar0*0.8; par0<=bestpar0*1.21; par0+=bestpar0*0.05){
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                    for(par1= bestpar1*0.8; par1<=bestpar1*1.21; par1+=bestpar1*0.05){
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                        double error=0;
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                        TimeFilter *tf= ff_timefilter_new(1, par0, par1);
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                        for(i=0; i<SAMPLES; i++){
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                            double filtered;
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                            filtered=  ff_timefilter_update(tf, samples[i], 1);
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                            error += (filtered - ideal[i]) * (filtered - ideal[i]);
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                        }
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                        ff_timefilter_destroy(tf);
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                        if(error < best_error){
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                            best_error= error;
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                            bestpar0= par0;
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                            bestpar1= par1;
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                            better=1;
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                        }
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                    }
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                }
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            }while(better);
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#if 0
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            double lastfil=9;
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            TimeFilter *tf= ff_timefilter_new(1, bestpar0, bestpar1);
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            for(i=0; i<SAMPLES; i++){
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                double filtered;
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                filtered=  ff_timefilter_update(tf, samples[i], 1);
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                printf("%f %f %f %f\n", i - samples[i] + 10, filtered - samples[i], samples[FFMAX(i, 1)] - samples[FFMAX(i-1, 0)], filtered - lastfil);
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                lastfil= filtered;
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            }
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            ff_timefilter_destroy(tf);
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#else
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            printf(" [%f %f %f]", bestpar0, bestpar1, best_error);
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#endif
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        }
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        printf("\n");
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    }
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    return 0;
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}
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#endif