2 Copyright (C) 2014-2021 Carl Hetherington <cth@carlh.net>
4 This file is part of DCP-o-matic.
6 DCP-o-matic is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2 of the License, or
9 (at your option) any later version.
11 DCP-o-matic is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with DCP-o-matic. If not, see <http://www.gnu.org/licenses/>.
21 #ifndef DCPOMATIC_AUDIO_FILTER_H
22 #define DCPOMATIC_AUDIO_FILTER_H
30 struct audio_filter_impulse_input_test;
33 /** An audio filter which can take AudioBuffers and apply some filtering operation,
34 * returning filtered samples
39 explicit AudioFilter (float transition_bandwidth)
41 _M = 4 / transition_bandwidth;
47 virtual ~AudioFilter () {}
49 std::shared_ptr<AudioBuffers> run (std::shared_ptr<const AudioBuffers> in);
54 friend struct audio_filter_impulse_kernel_test;
55 friend struct audio_filter_impulse_input_test;
57 std::vector<float> sinc_blackman (float cutoff, bool invert) const;
59 std::vector<float> _ir;
61 std::shared_ptr<AudioBuffers> _tail;
65 class LowPassAudioFilter : public AudioFilter
68 /** Construct a windowed-sinc low-pass filter using the Blackman window.
69 * @param transition_bandwidth Transition bandwidth as a fraction of the sampling rate.
70 * @param cutoff Cutoff frequency as a fraction of the sampling rate.
72 LowPassAudioFilter (float transition_bandwidth, float cutoff);
76 class HighPassAudioFilter : public AudioFilter
79 /** Construct a windowed-sinc high-pass filter using the Blackman window.
80 * @param transition_bandwidth Transition bandwidth as a fraction of the sampling rate.
81 * @param cutoff Cutoff frequency as a fraction of the sampling rate.
83 HighPassAudioFilter (float transition_bandwidth, float cutoff);
87 class BandPassAudioFilter : public AudioFilter
90 /** Construct a windowed-sinc band-pass filter using the Blackman window.
91 * @param transition_bandwidth Transition bandwidth as a fraction of the sampling rate.
92 * @param lower Lower cutoff frequency as a fraction of the sampling rate.
93 * @param higher Higher cutoff frequency as a fraction of the sampling rate.
95 BandPassAudioFilter (float transition_bandwidth, float lower, float higher);