| /* | |
| * 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 | |
| */ | |
| /** | |
| * 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 | |
| * | |
| * 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 | |
| */ | |
| TimeFilter * ff_timefilter_new(double time_base, double period, double bandwidth); | |
| /** | |
| * 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 *); | |