LCOV - code coverage report
Current view: top level - libavdevice - timefilter.c (source / functions) Hit Total Coverage
Test: coverage.info Lines: 0 28 0.0 %
Date: 2017-10-24 00:14:43 Functions: 0 6 0.0 %

          Line data    Source code
       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             : #include "libavutil/common.h"
      26             : #include "libavutil/mem.h"
      27             : 
      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             : /* 1 - exp(-x) using a 3-order power series */
      41           0 : static double qexpneg(double x)
      42             : {
      43           0 :     return 1 - 1 / (1 + x * (1 + x / 2 * (1 + x / 3)));
      44             : }
      45             : 
      46           0 : TimeFilter *ff_timefilter_new(double time_base,
      47             :                               double period,
      48             :                               double bandwidth)
      49             : {
      50           0 :     TimeFilter *self       = av_mallocz(sizeof(TimeFilter));
      51           0 :     double o               = 2 * M_PI * bandwidth * period * time_base;
      52             : 
      53           0 :     if (!self)
      54           0 :         return NULL;
      55             : 
      56           0 :     self->clock_period     = time_base;
      57           0 :     self->feedback2_factor = qexpneg(M_SQRT2 * o);
      58           0 :     self->feedback3_factor = qexpneg(o * o) / period;
      59           0 :     return self;
      60             : }
      61             : 
      62           0 : void ff_timefilter_destroy(TimeFilter *self)
      63             : {
      64           0 :     av_freep(&self);
      65           0 : }
      66             : 
      67           0 : void ff_timefilter_reset(TimeFilter *self)
      68             : {
      69           0 :     self->count = 0;
      70           0 : }
      71             : 
      72           0 : double ff_timefilter_update(TimeFilter *self, double system_time, double period)
      73             : {
      74           0 :     self->count++;
      75           0 :     if (self->count == 1) {
      76           0 :         self->cycle_time = system_time;
      77             :     } else {
      78             :         double loop_error;
      79           0 :         self->cycle_time += self->clock_period * period;
      80           0 :         loop_error = system_time - self->cycle_time;
      81             : 
      82           0 :         self->cycle_time   += FFMAX(self->feedback2_factor, 1.0 / self->count) * loop_error;
      83           0 :         self->clock_period += self->feedback3_factor * loop_error;
      84             :     }
      85           0 :     return self->cycle_time;
      86             : }
      87             : 
      88           0 : double ff_timefilter_eval(TimeFilter *self, double delta)
      89             : {
      90           0 :     return self->cycle_time + self->clock_period * delta;
      91             : }

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