/*
  * 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 "libavutil/mem.h"

 #include "config.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;

 };
 

 /* 1 - exp(-x) using a 3-order power series */
 static double qexpneg(double x)
 {
     return 1 - 1 / (1 + x * (1 + x / 2 * (1 + x / 3)));
 }
 
 TimeFilter *ff_timefilter_new(double time_base,
                               double period,
                               double bandwidth)

 {

     TimeFilter *self       = av_mallocz(sizeof(TimeFilter));

     double o               = 2 * M_PI * bandwidth * period * time_base;
     self->clock_period     = time_base;
     self->feedback2_factor = qexpneg(M_SQRT2 * o);

     self->feedback3_factor = qexpneg(o * o) / period;

     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;

     }
     return self->cycle_time;
 }

 double ff_timefilter_eval(TimeFilter *self, double delta)
 {
     return self->cycle_time + self->clock_period * delta;
 }
 

 #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];

     double samplet[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   = 1;

             int better, i;
 

             av_lfg_init(&prng, 123);

             for (i = 0; i < SAMPLES; i++) {

                 samplet[i] = 10 + i + (av_lfg_get(&prng) < LFG_MAX/2 ? 0 : 0.999);
                 ideal[i]   = samplet[i] + n1 * i / (1000);

                 samples[i] = ideal[i] + n0 * (av_lfg_get(&prng) - LFG_MAX / 2) / (LFG_MAX * 10LL);

                 if(i && samples[i]<samples[i-1])
                     samples[i]=samples[i-1]+0.001;

             }
 

             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], i ? (samplet[i] - samplet[i-1]) : 1);
                             if(filtered < 0 || filtered > 1000000000)
                                 printf("filter is unstable\n");

                             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