/* * Delay Locked Loop based time filter * Copyright (c) 2009 Samalyse * Copyright (c) 2009 Michael Niedermayer * Author: Olivier Guilyardi <olivier samalyse com> * Michael Niedermayer <michaelni gmx at> * * 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 "timefilter.h" #include "libavutil/mem.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 #include "libavutil/lfg.h" #define LFG_MAX ((1LL << 32) - 1) #undef printf int main(void) { AVLFG prng; double n0,n1; #define SAMPLES 1000 double ideal[SAMPLES]; double samples[SAMPLES]; #if 1 for(n0= 0; n0<40; n0=2*n0+1){ for(n1= 0; n1<10; n1=2*n1+1){ #else {{ n0=7; n1=1; #endif double best_error= 1000000000; double bestpar0=1; double bestpar1=0.001; int better, i; av_lfg_init(&prng, 123); for(i=0; i<SAMPLES; i++){ ideal[i] = 10 + i + n1*i/(1000); samples[i] = ideal[i] + n0 * (av_lfg_get(&prng) - LFG_MAX / 2) / (LFG_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); #if 0 double lastfil=9; TimeFilter *tf= ff_timefilter_new(1, bestpar0, bestpar1); for(i=0; i<SAMPLES; i++){ double filtered; filtered= ff_timefilter_update(tf, samples[i], 1); printf("%f %f %f %f\n", i - samples[i] + 10, filtered - samples[i], samples[FFMAX(i, 1)] - samples[FFMAX(i-1, 0)], filtered - lastfil); lastfil= filtered; } ff_timefilter_destroy(tf); #else printf(" [%f %f %9f]", bestpar0, bestpar1, best_error); #endif } printf("\n"); } return 0; } #endif