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/*
Copyright (C) 2014-2021 Carl Hetherington <cth@carlh.net>
This file is part of DCP-o-matic.
DCP-o-matic is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
DCP-o-matic 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with DCP-o-matic. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef DCPOMATIC_AUDIO_FILTER_H
#define DCPOMATIC_AUDIO_FILTER_H
#include <memory>
#include <vector>
class AudioBuffers;
struct audio_filter_impulse_input_test;
/** An audio filter which can take AudioBuffers and apply some filtering operation,
* returning filtered samples
*/
class AudioFilter
{
public:
explicit AudioFilter (float transition_bandwidth)
{
_M = 4 / transition_bandwidth;
if (_M % 2) {
++_M;
}
}
virtual ~AudioFilter () {}
std::shared_ptr<AudioBuffers> run (std::shared_ptr<const AudioBuffers> in);
void flush ();
protected:
friend struct audio_filter_impulse_kernel_test;
friend struct audio_filter_impulse_input_test;
std::vector<float> sinc_blackman (float cutoff, bool invert) const;
std::vector<float> _ir;
int _M;
std::shared_ptr<AudioBuffers> _tail;
};
class LowPassAudioFilter : public AudioFilter
{
public:
/** Construct a windowed-sinc low-pass filter using the Blackman window.
* @param transition_bandwidth Transition bandwidth as a fraction of the sampling rate.
* @param cutoff Cutoff frequency as a fraction of the sampling rate.
*/
LowPassAudioFilter (float transition_bandwidth, float cutoff);
};
class HighPassAudioFilter : public AudioFilter
{
public:
/** Construct a windowed-sinc high-pass filter using the Blackman window.
* @param transition_bandwidth Transition bandwidth as a fraction of the sampling rate.
* @param cutoff Cutoff frequency as a fraction of the sampling rate.
*/
HighPassAudioFilter (float transition_bandwidth, float cutoff);
};
class BandPassAudioFilter : public AudioFilter
{
public:
/** Construct a windowed-sinc band-pass filter using the Blackman window.
* @param transition_bandwidth Transition bandwidth as a fraction of the sampling rate.
* @param lower Lower cutoff frequency as a fraction of the sampling rate.
* @param higher Higher cutoff frequency as a fraction of the sampling rate.
*/
BandPassAudioFilter (float transition_bandwidth, float lower, float higher);
};
#endif
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