/*
  * Delay Locked Loop based time filter prototypes and declarations
  * 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
  */
 

 #ifndef AVDEVICE_TIMEFILTER_H
 #define AVDEVICE_TIMEFILTER_H

 
 /**
  * Opaque type representing a time filter state
  *
  * The purpose of this filter is to provide a way to compute accurate time
  * stamps that can be compared to wall clock time, especially when dealing
  * with two clocks: the system clock and a hardware device clock, such as
  * a soundcard.
  */
 typedef struct TimeFilter TimeFilter;
 
 
 /**
  * Create a new Delay Locked Loop time filter
  *
  * feedback2_factor and feedback3_factor are the factors used for the
  * multiplications that are respectively performed in the second and third
  * feedback paths of the loop.
  *
  * Unless you know what you are doing, you should set these as follow:
  *

  * o = 2 * M_PI * bandwidth * period_in_seconds
  * feedback2_factor = sqrt(2) * o

  * feedback3_factor = o * o
  *
  * Where bandwidth is up to you to choose. Smaller values will filter out more
  * of the jitter, but also take a longer time for the loop to settle. A good
  * starting point is something between 0.3 and 3 Hz.
  *

  * @param time_base   period of the hardware clock in seconds
  *                    (for example 1.0/44100)
  * @param period      expected update interval, in input units
  * @param brandwidth  filtering bandwidth, in Hz

  *

  * @return a pointer to a TimeFilter struct, or NULL on error
  *

  * For more details about these parameters and background concepts please see:
  * http://www.kokkinizita.net/papers/usingdll.pdf
  */

 TimeFilter * ff_timefilter_new(double clock_period, double feedback2_factor, double feedback3_factor);

 
 /**
  * Update the filter
  *
  * This function must be called in real time, at each process cycle.
  *

  * @param period the device cycle duration in clock_periods. For example, at
  * 44.1kHz and a buffer size of 512 frames, period = 512 when clock_period
  * was 1.0/44100, or 512/44100 if clock_period was 1.

  *

  * system_time, in seconds, should be the value of the system clock time,
  * at (or as close as possible to) the moment the device hardware interrupt

  * occurred (or any other event the device clock raises at the beginning of a

  * cycle).
  *

  * @return the filtered time, in seconds

  */

 double ff_timefilter_update(TimeFilter *self, double system_time, double period);

 
 /**

  * Evaluate the filter at a specified time
  *
  * @param delta  difference between the requested time and the current time
  *               (last call to ff_timefilter_update).
  * @return  the filtered time
  */
 double ff_timefilter_eval(TimeFilter *self, double delta);
 
 /**

  * Reset the filter
  *
  * This function should mainly be called in case of XRUN.
  *
  * Warning: after calling this, the filter is in an undetermined state until
  * the next call to ff_timefilter_update()
  */
 void ff_timefilter_reset(TimeFilter *);
 
 /**
  * Free all resources associated with the filter
  */
 void ff_timefilter_destroy(TimeFilter *);
 

 #endif /* AVDEVICE_TIMEFILTER_H */