Add Metronome example

Signed-off-by: falkTX <falktx@falktx.com>

Makefile

@@ -24,6 +24,7 @@ examples: dgl
 	$(MAKE) all -C examples/Info
 	$(MAKE) all -C examples/Latency
 	$(MAKE) all -C examples/Meters
+	$(MAKE) all -C examples/Metronome
 	$(MAKE) all -C examples/MidiThrough
 	$(MAKE) all -C examples/Parameters
 	$(MAKE) all -C examples/SendNote
@@ -66,6 +67,7 @@ clean:
 	$(MAKE) clean -C examples/Info
 	$(MAKE) clean -C examples/Latency
 	$(MAKE) clean -C examples/Meters
+	$(MAKE) clean -C examples/Metronome
 	$(MAKE) clean -C examples/MidiThrough
 	$(MAKE) clean -C examples/Parameters
 	$(MAKE) clean -C examples/SendNote

examples/CVPort/ExamplePluginCVPort.cpp

@@ -1,6 +1,7 @@
 /*
  * DISTRHO Plugin Framework (DPF)
  * Copyright (C) 2012-2021 Filipe Coelho <falktx@falktx.com>
+ * Copyright (C) 2020 Takamitsu Endo
  *
  * Permission to use, copy, modify, and/or distribute this software for any purpose with
  * or without fee is hereby granted, provided that the above copyright notice and this

examples/Metronome/DistrhoPluginInfo.h

@@ -0,0 +1,29 @@
+/*
+ * DISTRHO Plugin Framework (DPF)
+ * Copyright (C) 2012-2021 Filipe Coelho <falktx@falktx.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any purpose with
+ * or without fee is hereby granted, provided that the above copyright notice and this
+ * permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
+ * TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN
+ * NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+ * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
+ * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef DISTRHO_PLUGIN_INFO_H_INCLUDED
+#define DISTRHO_PLUGIN_INFO_H_INCLUDED
+
+#define DISTRHO_PLUGIN_BRAND "DISTRHO"
+#define DISTRHO_PLUGIN_NAME "Metronome"
+#define DISTRHO_PLUGIN_URI "http://distrho.sf.net/examples/Metronome"
+
+#define DISTRHO_PLUGIN_IS_RT_SAFE 1
+#define DISTRHO_PLUGIN_NUM_INPUTS 0
+#define DISTRHO_PLUGIN_NUM_OUTPUTS 1
+#define DISTRHO_PLUGIN_WANT_TIMEPOS 1
+
+#endif // DISTRHO_PLUGIN_INFO_H_INCLUDED

examples/Metronome/ExamplePluginMetronome.cpp

@@ -0,0 +1,364 @@
+/*
+ * DISTRHO Plugin Framework (DPF)
+ * Copyright (C) 2012-2021 Filipe Coelho <falktx@falktx.com>
+ * Copyright (C) 2020 Takamitsu Endo
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any purpose with
+ * or without fee is hereby granted, provided that the above copyright notice and this
+ * permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
+ * TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN
+ * NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+ * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
+ * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "DistrhoPlugin.hpp"
+
+START_NAMESPACE_DISTRHO
+
+// -----------------------------------------------------------------------------------------------------------
+
+/**
+  1-pole lowpass filter to smooth out parameters and envelopes.
+  This filter is guaranteed not to overshoot.
+ */
+class Smoother {
+    float kp;
+
+public:
+    float value;
+
+    Smoother()
+        : kp(0.0f),
+          value(0.0f) {}
+
+    /**
+      Set kp from cutoff frequency in Hz.
+      For derivation, see the answer of Matt L. on the url below. Equation 3 is used.
+
+      Computation is done on double for accuracy. When using float, kp will be inaccurate
+      if the cutoffHz is below around 3.0 to 4.0 Hz.
+
+      Reference:
+      - Single-pole IIR low-pass filter - which is the correct formula for the decay coefficient?
+        https://dsp.stackexchange.com/questions/54086/single-pole-iir-low-pass-filter-which-is-the-correct-formula-for-the-decay-coe
+     */
+    void setCutoff(float sampleRate, float cutoffHz) {
+        double omega_c = 2.0 * M_PI * cutoffHz / sampleRate;
+        double y = 1.0 - std::cos(omega_c);
+        kp = float(-y + std::sqrt((y + 2.0) * y));
+    }
+
+    float process(float input) {
+        return value += kp * (input - value);
+    }
+};
+
+// -----------------------------------------------------------------------------------------------------------
+
+/**
+  Plugin that demonstrates tempo sync in DPF.
+  The tempo sync implementation is on the first if branch in run() method.
+ */
+class ExamplePluginMetronome : public Plugin
+{
+public:
+    ExamplePluginMetronome()
+        : Plugin(4, 0, 0), // 4 parameters, 0 programs, 0 states
+          sampleRate(getSampleRate()),
+          counter(0),
+          phase(0.0f),
+          decay(0.0f),
+          gain(0.5f),
+          semitone(72),
+          cent(0),
+          decayTime(0.2f)
+    {
+    }
+
+protected:
+   /* --------------------------------------------------------------------------------------------------------
+    * Information */
+
+   /**
+      Get the plugin label.
+      A plugin label follows the same rules as Parameter::symbol, with the exception that it can start with numbers.
+    */
+    const char* getLabel() const override
+    {
+        return "Metronome";
+    }
+
+   /**
+      Get an extensive comment/description about the plugin.
+    */
+    const char* getDescription() const override
+    {
+        return "Simple metronome plugin which outputs impulse at the start of every beat.";
+    }
+
+   /**
+      Get the plugin author/maker.
+    */
+    const char* getMaker() const override
+    {
+        return "DISTRHO";
+    }
+
+   /**
+      Get the plugin homepage.
+    */
+    const char* getHomePage() const override
+    {
+        return "https://github.com/DISTRHO/DPF";
+    }
+
+   /**
+      Get the plugin license name (a single line of text).
+      For commercial plugins this should return some short copyright information.
+    */
+    const char* getLicense() const override
+    {
+        return "ISC";
+    }
+
+   /**
+      Get the plugin version, in hexadecimal.
+    */
+    uint32_t getVersion() const override
+    {
+        return d_version(1, 0, 0);
+    }
+
+   /**
+      Get the plugin unique Id.
+      This value is used by LADSPA, DSSI and VST plugin formats.
+    */
+    int64_t getUniqueId() const override
+    {
+        return d_cconst('d', 'M', 'e', 't');
+    }
+
+   /* --------------------------------------------------------------------------------------------------------
+    * Init */
+
+   /**
+      Initialize the parameter @a index.
+      This function will be called once, shortly after the plugin is created.
+    */
+    void initParameter(uint32_t index, Parameter& parameter) override
+    {
+        parameter.hints = kParameterIsAutomable;
+
+        switch (index)
+        {
+        case 0:
+            parameter.name = "Gain";
+            parameter.hints |= kParameterIsLogarithmic;
+            parameter.ranges.min = 0.0f;
+            parameter.ranges.max = 1.0f;
+            parameter.ranges.def = 0.5f;
+            break;
+        case 1:
+            parameter.name = "DecayTime";
+            parameter.hints |= kParameterIsLogarithmic;
+            parameter.ranges.min = 0.001f;
+            parameter.ranges.max = 1.0f;
+            parameter.ranges.def = 0.2f;
+            break;
+        case 2:
+            parameter.name = "Semitone";
+            parameter.hints |= kParameterIsInteger;
+            parameter.ranges.min = 0;
+            parameter.ranges.max = 127;
+            parameter.ranges.def = 72;
+            break;
+        case 3:
+            parameter.name = "Cent";
+            parameter.hints |= kParameterIsInteger;
+            parameter.ranges.min = -100;
+            parameter.ranges.max = 100;
+            parameter.ranges.def = 0;
+            break;
+        }
+
+        parameter.symbol = parameter.name;
+    }
+
+   /* --------------------------------------------------------------------------------------------------------
+    * Internal data */
+
+   /**
+      Get the current value of a parameter.
+    */
+    float getParameterValue(uint32_t index) const override
+    {
+        switch (index)
+        {
+        case 0:
+            return gain;
+        case 1:
+            return decayTime;
+        case 2:
+            return semitone;
+        case 3:
+            return cent;
+        }
+
+        return 0.0f;
+    }
+
+   /**
+      Change a parameter value.
+    */
+    void setParameterValue(uint32_t index, float value) override
+    {
+        switch (index)
+        {
+        case 0:
+            gain = value;
+            break;
+        case 1:
+            decayTime = value;
+            break;
+        case 2:
+            semitone = value;
+            break;
+        case 3:
+            cent = value;
+            break;
+        }
+    }
+
+   /* --------------------------------------------------------------------------------------------------------
+    * Process */
+
+   /**
+      Run/process function for plugins without MIDI input.
+      `inputs` is commented out because this plugin has no inputs.
+    */
+    void run(const float** /* inputs */, float** outputs, uint32_t frames) override
+    {
+        const TimePosition& timePos(getTimePosition());
+        float* const output = outputs[0];
+
+        if (timePos.playing && timePos.bbt.valid)
+        {
+            // Better to use double when manipulating time.
+            double secondsPerBeat = 60.0 / timePos.bbt.beatsPerMinute;
+            double framesPerBeat  = sampleRate * secondsPerBeat;
+            double beatFraction   = timePos.bbt.tick / timePos.bbt.ticksPerBeat;
+
+            // If beatFraction is zero, next beat is exactly at the start of currenct cycle.
+            // Otherwise, reset counter to the frames to the next beat.
+            counter = d_isZero(beatFraction)
+                    ? 0
+                    : static_cast<uint32_t>(framesPerBeat * (1.0 - beatFraction));
+
+            // Compute deltaPhase in normalized frequency.
+            // semitone is midi note number, which is A4 (440Hz at standard tuning) at 69.
+            // Frequency goes up to 1 octave higher at the start of bar.
+            float frequency = 440.0f * std::pow(2.0f, (100.0f * (semitone - 69.0f) + cent) / 1200.0f);
+            float deltaPhase = frequency / sampleRate;
+            float octave = timePos.bbt.beat == 1 ? 2.0f : 1.0f;
+
+            // Envelope reaches 1e-5 at decayTime after triggering.
+            decay = std::pow(1e-5, 1.0 / (decayTime * sampleRate));
+
+            // Reset phase and frequency at the start of transpose.
+            if (!wasPlaying)
+            {
+                phase = 0.0f;
+
+                deltaPhaseSmoother.value = deltaPhase;
+                gainSmoother.value = 1.0f;
+                envelopeSmoother.value = 0.0f;
+            }
+
+            for (uint32_t i = 0; i < frames; ++i)
+            {
+                if (counter <= 0)
+                {
+                    envelope = 1.0f;
+                    counter = static_cast<uint32_t>(framesPerBeat + 0.5);
+                    octave = (!wasPlaying || timePos.bbt.beat == static_cast<int32_t>(timePos.bbt.beatsPerBar)) ? 2.0f
+                                                                                                                : 1.0f;
+                }
+                --counter;
+
+                envelope *= decay;
+
+                phase += octave * deltaPhaseSmoother.process(deltaPhase);
+                phase -= std::floor(phase);
+
+                output[i] = gainSmoother.process(gain)
+                          * envelopeSmoother.process(envelope)
+                          * std::sin(float(2.0 * M_PI) * phase);
+            }
+        }
+        else
+        {
+            // Stop metronome if not playing or timePos.bbt is invalid.
+            std::memset(output, 0, sizeof(float)*frames);
+        }
+
+        wasPlaying = timePos.playing;
+    }
+
+   /* --------------------------------------------------------------------------------------------------------
+    * Callbacks (optional) */
+
+   /**
+      Optional callback to inform the plugin about a sample rate change.
+      This function will only be called when the plugin is deactivated.
+    */
+    void sampleRateChanged(double newSampleRate) override
+    {
+        sampleRate = newSampleRate;
+
+        // Cutoff value was tuned manually.
+        deltaPhaseSmoother.setCutoff(sampleRate, 100.0f);
+        gainSmoother.setCutoff(sampleRate, 500.0f);
+        envelopeSmoother.setCutoff(sampleRate, 250.0f);
+    }
+
+    // -------------------------------------------------------------------------------------------------------
+
+private:
+    float sampleRate;
+    uint32_t counter; // Stores number of frames to the next beat.
+    bool wasPlaying;  // Used to reset phase and frequency at the start of transpose.
+    float phase;      // Sine wave phase. Normalized in [0, 1).
+    float envelope;   // Current value of gain envelope.
+    float decay;      // Coefficient to decay envelope in a frame.
+
+    Smoother deltaPhaseSmoother;
+    Smoother gainSmoother;
+    Smoother envelopeSmoother;
+
+    // Parameters.
+    float gain;
+    float semitone;
+    float cent;
+    float decayTime;
+
+   /**
+      Set our plugin class as non-copyable and add a leak detector just in case.
+    */
+    DISTRHO_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR(ExamplePluginMetronome)
+};
+
+/* ------------------------------------------------------------------------------------------------------------
+ * Plugin entry point, called by DPF to create a new plugin instance. */
+
+Plugin* createPlugin()
+{
+    return new ExamplePluginMetronome();
+}
+
+// -----------------------------------------------------------------------------------------------------------
+
+END_NAMESPACE_DISTRHO

examples/Metronome/Makefile

@@ -0,0 +1,42 @@
+#!/usr/bin/make -f
+# Makefile for DISTRHO Plugins #
+# ---------------------------- #
+# Created by falkTX
+#
+
+# --------------------------------------------------------------
+# Project name, used for binaries
+
+NAME = d_metronome
+
+# --------------------------------------------------------------
+# Files to build
+
+FILES_DSP = \
+	ExamplePluginMetronome.cpp
+
+# --------------------------------------------------------------
+# Do some magic
+
+include ../../Makefile.plugins.mk
+
+# --------------------------------------------------------------
+# Enable all possible plugin types
+
+ifeq ($(HAVE_JACK),true)
+ifeq ($(HAVE_OPENGL),true)
+TARGETS += jack
+endif
+endif
+
+ifeq ($(HAVE_OPENGL),true)
+TARGETS += lv2_sep
+else
+TARGETS += lv2_dsp
+endif
+
+TARGETS += vst
+
+all: $(TARGETS)
+
+# --------------------------------------------------------------

examples/Metronome/README.md

@@ -0,0 +1,34 @@
+# Metronome example
+
+This example will show tempo sync in DPF.<br/>
+
+This plugin will output sine wave at the start of every beat.<br/>
+The pitch of sine wave is 1 octave higher at the start of every bar.<br/>
+
+4 parameters are avaialble:
+
+- Gain
+- Decay time
+- Semitone
+- Cent
+
+To calculate frames to the next beat from the start of current audio buffer, following implementation is used.<br/>
+
+```c++
+const TimePosition& timePos(getTimePosition());
+
+if (timePos.bbt.valid) {
+    double secondsPerBeat = 60.0 / timePos.bbt.beatsPerMinute;
+    double framesPerBeat  = sampleRate * secondsPerBeat;
+    double beatFraction   = timePos.bbt.tick / timePos.bbt.ticksPerBeat;
+
+    uint32_t framesToNextBeat = beatFraction == 0.0
+        ? 0
+        : static_cast<uint32_t>(framesPerBeat * (1.0 - beatFraction));
+
+    // ...
+}
+```
+
+Reference:
+- [DISTRHO Plugin Framework: TimePosition::BarBeatTick Struct Reference](https://distrho.github.io/DPF/structTimePosition_1_1BarBeatTick.html)