Add MLS+ noise

OpenSoundMeter.pro

@@ -38,6 +38,7 @@ SOURCES += src/main.cpp \
     src/filtersource.cpp \
     src/generator/burstnoise.cpp \
     src/generator/channelmodel.cpp \
+    src/generator/mlsplus.cpp \
     src/generator/wav.cpp \
     src/inputdevice.cpp \
     src/common/appearance.cpp \
@@ -157,6 +158,7 @@ HEADERS += \
     src/filtersource.h \
     src/generator/burstnoise.h \
     src/generator/channelmodel.h \
+    src/generator/mlsplus.h \
     src/generator/wav.h \
     src/inputdevice.h \
     src/common/appearance.h \

src/generator/generatorthread.cpp

@@ -25,6 +25,7 @@
 #include "sinsweep.h"
 #include "mnoise.h"
 #include "burstnoise.h"
+#include "mlsplus.h"
 
 GeneratorThread *GeneratorThread::s_instance = nullptr;
 
@@ -102,6 +103,8 @@ void GeneratorThread::init()
     m_sources << new SinSweep(this);
     m_sources << new MNoise(this);
     m_sources << new BurstNoise(this);
+    m_sources << new MLSPlus(this);
+
     for (auto &source : m_sources) {
         connect(source, &OutputDevice::sampleError, this, &GeneratorThread::deviceError);
         connect(source, &OutputDevice::sampleOut, this, &GeneratorThread::sampleOut, Qt::DirectConnection);

src/generator/mlsplus.cpp

@@ -0,0 +1,67 @@
+/**
+ *  OSM
+ *  Copyright (C) 2023  Pavel Smokotnin
+
+ *  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 "mlsplus.h"
+
+MLSPlus::MLSPlus(QObject *parent)
+    : OutputDevice{parent}, m_state{}
+{
+    m_name = "MLS+";
+    std::fill(m_state.begin(), m_state.end(), false);
+    m_state[0] = true;
+}
+
+Sample MLSPlus::sample()
+{
+    static std::size_t counter = 0;
+    if (++counter == 65'536) {
+        counter = 0;
+        return { 0 };
+    }
+    /*
+     * W. Stahnke.
+     * Primitive binary polynomials.
+     * Mathematics of Computation, 27:977-980, 1973.
+     *
+     * @url https://www.ams.org/journals/mcom/1973-27-124/S0025-5718-1973-0327722-7/S0025-5718-1973-0327722-7.pdf
+     */
+    bool input  = m_state[16];
+    m_state[16] = m_state[15];
+    m_state[15] = m_state[14];
+    m_state[14] = m_state[13];
+    m_state[13] = m_state[12];
+    m_state[12] = m_state[11];
+    m_state[11] = m_state[10];
+    m_state[10] = m_state[9];
+    m_state[9]  = m_state[8];
+    m_state[8]  = m_state[7];
+    m_state[7]  = m_state[6];
+    m_state[6]  = m_state[5];
+    m_state[5]  = m_state[4] != input;
+    m_state[4]  = m_state[3];
+    m_state[3]  = m_state[2] != input;
+    m_state[2]  = m_state[1] != input;
+    m_state[1]  = m_state[0];
+    m_state[0]  = input;
+
+    Sample s = { m_state[16] ? 1.f : -1.f };
+
+    // -18dB to align rms level with pink noise
+    s.f *= m_gain / 8;
+
+    return s;
+}

src/generator/mlsplus.h

@@ -0,0 +1,35 @@
+/**
+ *  OSM
+ *  Copyright (C) 2023  Pavel Smokotnin
+
+ *  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/>.
+ */
+#ifndef MLSPLUS_H
+#define MLSPLUS_H
+
+#include "outputdevice.h"
+
+class MLSPlus : public OutputDevice
+{
+    Q_OBJECT
+
+public:
+    explicit MLSPlus(QObject *parent = nullptr);
+    Sample sample() override;
+
+private:
+    std::array<bool, 17>  m_state;
+};
+
+#endif // MLSPLUS_H