1 // Adapted from Adriaensen's project Zita-mu1 (as of January 2016).
2 // Original copyright follows:
4 // Copyright (C) 2008-2015 Fons Adriaensen <fons@linuxaudio.org>
6 // This program 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 3 of the License, or
9 // (at your option) any later version.
11 // This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
19 #include "correlation_measurer.h"
29 CorrelationMeasurer::CorrelationMeasurer(unsigned sample_rate,
30 float lowpass_cutoff_hz,
31 float falloff_seconds)
32 : w1(2.0 * M_PI * lowpass_cutoff_hz / sample_rate),
33 w2(1.0 / (falloff_seconds * sample_rate))
37 void CorrelationMeasurer::reset()
39 zl = zr = zll = zlr = zrr = 0.0f;
42 void CorrelationMeasurer::process_samples(const std::vector<float> &samples)
44 assert(samples.size() % 2 == 0);
46 // The compiler isn't always happy about modifying members,
47 // since it doesn't always know they can't alias on <samples>.
49 float l = zl, r = zr, ll = zll, lr = zlr, rr = zrr;
50 const float w1c = w1, w2c = w2;
52 for (size_t i = 0; i < samples.size(); i += 2) {
53 // The 1e-15f epsilon is to avoid denormals.
54 // TODO: Just set the SSE flush-to-zero flags instead.
55 l += w1c * (samples[i + 0] - l) + 1e-15f;
56 r += w1c * (samples[i + 1] - r) + 1e-15f;
57 lr += w2c * (l * r - lr);
58 ll += w2c * (l * l - ll);
59 rr += w2c * (r * r - rr);
69 float CorrelationMeasurer::get_correlation() const
71 // The 1e-12f epsilon is to avoid division by zero.
72 // zll and zrr are both always non-negative, so we do not risk negative values.
73 return zlr / sqrt(zll * zrr + 1e-12f);