Move everything into a separate futatabi/ subdir, for the upcoming merge with Futatabi.

[nageru] / nageru / correlation_measurer.cpp

diff --git a/nageru/correlation_measurer.cpp b/nageru/correlation_measurer.cpp
new file mode 100644 (file)
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+++ b/nageru/correlation_measurer.cpp
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+// Adapted from Adriaensen's project Zita-mu1 (as of January 2016).
+// Original copyright follows:
+//
+//  Copyright (C) 2008-2015 Fons Adriaensen <fons@linuxaudio.org>
+//    
+//  This program 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 3 of the License, or
+//  (at your option) any later version.
+//
+//  This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#include "correlation_measurer.h"
+
+#include <assert.h>
+#include <cmath>
+#include <cstddef>
+
+using namespace std;
+
+CorrelationMeasurer::CorrelationMeasurer(unsigned sample_rate,
+                                         float lowpass_cutoff_hz,
+                                        float falloff_seconds)
+    : w1(2.0 * M_PI * lowpass_cutoff_hz / sample_rate),
+      w2(1.0 / (falloff_seconds * sample_rate))
+{
+}
+
+void CorrelationMeasurer::reset()
+{
+       zl = zr = zll = zlr = zrr = 0.0f;
+}
+
+void CorrelationMeasurer::process_samples(const std::vector<float> &samples)
+{
+       assert(samples.size() % 2 == 0);
+
+       // The compiler isn't always happy about modifying members,
+       // since it doesn't always know they can't alias on <samples>.
+       // Help it out a bit.
+       float l = zl, r = zr, ll = zll, lr = zlr, rr = zrr;
+       const float w1c = w1, w2c = w2;
+
+       for (size_t i = 0; i < samples.size(); i += 2) {
+               // The 1e-15f epsilon is to avoid denormals.
+               // TODO: Just set the SSE flush-to-zero flags instead.
+               l += w1c * (samples[i + 0] - l) + 1e-15f;
+               r += w1c * (samples[i + 1] - r) + 1e-15f;
+               lr += w2c * (l * r - lr);
+               ll += w2c * (l * l - ll);
+               rr += w2c * (r * r - rr);
+       }
+
+       zl = l;
+       zr = r;
+       zll = ll;
+       zlr = lr;
+       zrr = rr;
+}
+
+float CorrelationMeasurer::get_correlation() const
+{
+       // The 1e-12f epsilon is to avoid division by zero.
+       // zll and zrr are both always non-negative, so we do not risk negative values.
+       return zlr / sqrt(zll * zrr + 1e-12f);
+}