mirror of
https://github.com/librempeg/librempeg
synced 2024-11-23 11:39:47 +00:00
111 lines
3.8 KiB
C
111 lines
3.8 KiB
C
/*
|
|
* 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 */
|