JUCE/modules/juce_audio_basics/synthesisers/juce_Synthesiser.cpp

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited

   JUCE is an open source library subject to commercial or open-source
   licensing.

   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. 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.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

SynthesiserSound::SynthesiserSound() {}
SynthesiserSound::~SynthesiserSound() {}

//==============================================================================
SynthesiserVoice::SynthesiserVoice() {}
SynthesiserVoice::~SynthesiserVoice() {}

bool SynthesiserVoice::isPlayingChannel (const int midiChannel) const
{
    return currentPlayingMidiChannel == midiChannel;
}

void SynthesiserVoice::setCurrentPlaybackSampleRate (const double newRate)
{
    currentSampleRate = newRate;
}

bool SynthesiserVoice::isVoiceActive() const
{
    return getCurrentlyPlayingNote() >= 0;
}

void SynthesiserVoice::clearCurrentNote()
{
    currentlyPlayingNote = -1;
    currentlyPlayingSound = nullptr;
    currentPlayingMidiChannel = 0;
}

void SynthesiserVoice::aftertouchChanged (int) {}
void SynthesiserVoice::channelPressureChanged (int) {}

bool SynthesiserVoice::wasStartedBefore (const SynthesiserVoice& other) const noexcept
{
    return noteOnTime < other.noteOnTime;
}

void SynthesiserVoice::renderNextBlock (AudioBuffer<double>& outputBuffer,
                                        int startSample, int numSamples)
{
    AudioBuffer<double> subBuffer (outputBuffer.getArrayOfWritePointers(),
                                   outputBuffer.getNumChannels(),
                                   startSample, numSamples);

    tempBuffer.makeCopyOf (subBuffer, true);
    renderNextBlock (tempBuffer, 0, numSamples);
    subBuffer.makeCopyOf (tempBuffer, true);
}

//==============================================================================
Synthesiser::Synthesiser()
{
    for (int i = 0; i < numElementsInArray (lastPitchWheelValues); ++i)
        lastPitchWheelValues[i] = 0x2000;
}

Synthesiser::~Synthesiser()
{
}

//==============================================================================
SynthesiserVoice* Synthesiser::getVoice (const int index) const
{
    const ScopedLock sl (lock);
    return voices [index];
}

void Synthesiser::clearVoices()
{
    const ScopedLock sl (lock);
    voices.clear();
}

SynthesiserVoice* Synthesiser::addVoice (SynthesiserVoice* const newVoice)
{
    SynthesiserVoice* voice;

    {
        const ScopedLock sl (lock);
        newVoice->setCurrentPlaybackSampleRate (sampleRate);
        voice = voices.add (newVoice);
    }

    {
        const ScopedLock sl (stealLock);
        usableVoicesToStealArray.ensureStorageAllocated (voices.size() + 1);
    }

    return voice;
}

void Synthesiser::removeVoice (const int index)
{
    const ScopedLock sl (lock);
    voices.remove (index);
}

void Synthesiser::clearSounds()
{
    const ScopedLock sl (lock);
    sounds.clear();
}

SynthesiserSound* Synthesiser::addSound (const SynthesiserSound::Ptr& newSound)
{
    const ScopedLock sl (lock);
    return sounds.add (newSound);
}

void Synthesiser::removeSound (const int index)
{
    const ScopedLock sl (lock);
    sounds.remove (index);
}

void Synthesiser::setNoteStealingEnabled (const bool shouldSteal)
{
    shouldStealNotes = shouldSteal;
}

void Synthesiser::setMinimumRenderingSubdivisionSize (int numSamples, bool shouldBeStrict) noexcept
{
    jassert (numSamples > 0); // it wouldn't make much sense for this to be less than 1
    minimumSubBlockSize = numSamples;
    subBlockSubdivisionIsStrict = shouldBeStrict;
}

//==============================================================================
void Synthesiser::setCurrentPlaybackSampleRate (const double newRate)
{
    if (! approximatelyEqual (sampleRate, newRate))
    {
        const ScopedLock sl (lock);
        allNotesOff (0, false);
        sampleRate = newRate;

        for (auto* voice : voices)
            voice->setCurrentPlaybackSampleRate (newRate);
    }
}

template <typename floatType>
void Synthesiser::processNextBlock (AudioBuffer<floatType>& outputAudio,
                                    const MidiBuffer& midiData,
                                    int startSample,
                                    int numSamples)
{
    // must set the sample rate before using this!
    jassert (! exactlyEqual (sampleRate, 0.0));
    const int targetChannels = outputAudio.getNumChannels();

    auto midiIterator = midiData.findNextSamplePosition (startSample);

    bool firstEvent = true;

    const ScopedLock sl (lock);

    for (; numSamples > 0; ++midiIterator)
    {
        if (midiIterator == midiData.cend())
        {
            if (targetChannels > 0)
                renderVoices (outputAudio, startSample, numSamples);

            return;
        }

        const auto metadata = *midiIterator;
        const int samplesToNextMidiMessage = metadata.samplePosition - startSample;

        if (samplesToNextMidiMessage >= numSamples)
        {
            if (targetChannels > 0)
                renderVoices (outputAudio, startSample, numSamples);

            handleMidiEvent (metadata.getMessage());
            break;
        }

        if (samplesToNextMidiMessage < ((firstEvent && ! subBlockSubdivisionIsStrict) ? 1 : minimumSubBlockSize))
        {
            handleMidiEvent (metadata.getMessage());
            continue;
        }

        firstEvent = false;

        if (targetChannels > 0)
            renderVoices (outputAudio, startSample, samplesToNextMidiMessage);

        handleMidiEvent (metadata.getMessage());
        startSample += samplesToNextMidiMessage;
        numSamples  -= samplesToNextMidiMessage;
    }

    std::for_each (midiIterator,
                   midiData.cend(),
                   [&] (const MidiMessageMetadata& meta) { handleMidiEvent (meta.getMessage()); });
}

// explicit template instantiation
template void Synthesiser::processNextBlock<float>  (AudioBuffer<float>&,  const MidiBuffer&, int, int);
template void Synthesiser::processNextBlock<double> (AudioBuffer<double>&, const MidiBuffer&, int, int);

void Synthesiser::renderNextBlock (AudioBuffer<float>& outputAudio, const MidiBuffer& inputMidi,
                                   int startSample, int numSamples)
{
    processNextBlock (outputAudio, inputMidi, startSample, numSamples);
}

void Synthesiser::renderNextBlock (AudioBuffer<double>& outputAudio, const MidiBuffer& inputMidi,
                                   int startSample, int numSamples)
{
    processNextBlock (outputAudio, inputMidi, startSample, numSamples);
}

void Synthesiser::renderVoices (AudioBuffer<float>& buffer, int startSample, int numSamples)
{
    for (auto* voice : voices)
        voice->renderNextBlock (buffer, startSample, numSamples);
}

void Synthesiser::renderVoices (AudioBuffer<double>& buffer, int startSample, int numSamples)
{
    for (auto* voice : voices)
        voice->renderNextBlock (buffer, startSample, numSamples);
}

void Synthesiser::handleMidiEvent (const MidiMessage& m)
{
    const int channel = m.getChannel();

    if (m.isNoteOn())
    {
        noteOn (channel, m.getNoteNumber(), m.getFloatVelocity());
    }
    else if (m.isNoteOff())
    {
        noteOff (channel, m.getNoteNumber(), m.getFloatVelocity(), true);
    }
    else if (m.isAllNotesOff() || m.isAllSoundOff())
    {
        allNotesOff (channel, true);
    }
    else if (m.isPitchWheel())
    {
        const int wheelPos = m.getPitchWheelValue();
        lastPitchWheelValues [channel - 1] = wheelPos;
        handlePitchWheel (channel, wheelPos);
    }
    else if (m.isAftertouch())
    {
        handleAftertouch (channel, m.getNoteNumber(), m.getAfterTouchValue());
    }
    else if (m.isChannelPressure())
    {
        handleChannelPressure (channel, m.getChannelPressureValue());
    }
    else if (m.isController())
    {
        handleController (channel, m.getControllerNumber(), m.getControllerValue());
    }
    else if (m.isProgramChange())
    {
        handleProgramChange (channel, m.getProgramChangeNumber());
    }
}

//==============================================================================
void Synthesiser::noteOn (const int midiChannel,
                          const int midiNoteNumber,
                          const float velocity)
{
    const ScopedLock sl (lock);

    for (auto* sound : sounds)
    {
        if (sound->appliesToNote (midiNoteNumber) && sound->appliesToChannel (midiChannel))
        {
            // If hitting a note that's still ringing, stop it first (it could be
            // still playing because of the sustain or sostenuto pedal).
            for (auto* voice : voices)
                if (voice->getCurrentlyPlayingNote() == midiNoteNumber && voice->isPlayingChannel (midiChannel))
                    stopVoice (voice, 1.0f, true);

            startVoice (findFreeVoice (sound, midiChannel, midiNoteNumber, shouldStealNotes),
                        sound, midiChannel, midiNoteNumber, velocity);
        }
    }
}

void Synthesiser::startVoice (SynthesiserVoice* const voice,
                              SynthesiserSound* const sound,
                              const int midiChannel,
                              const int midiNoteNumber,
                              const float velocity)
{
    if (voice != nullptr && sound != nullptr)
    {
        if (voice->currentlyPlayingSound != nullptr)
            voice->stopNote (0.0f, false);

        voice->currentlyPlayingNote = midiNoteNumber;
        voice->currentPlayingMidiChannel = midiChannel;
        voice->noteOnTime = ++lastNoteOnCounter;
        voice->currentlyPlayingSound = sound;
        voice->setKeyDown (true);
        voice->setSostenutoPedalDown (false);
        voice->setSustainPedalDown (sustainPedalsDown[midiChannel]);

        voice->startNote (midiNoteNumber, velocity, sound,
                          lastPitchWheelValues [midiChannel - 1]);
    }
}

void Synthesiser::stopVoice (SynthesiserVoice* voice, float velocity, const bool allowTailOff)
{
    jassert (voice != nullptr);

    voice->stopNote (velocity, allowTailOff);

    // the subclass MUST call clearCurrentNote() if it's not tailing off! RTFM for stopNote()!
    jassert (allowTailOff || (voice->getCurrentlyPlayingNote() < 0 && voice->getCurrentlyPlayingSound() == nullptr));
}

void Synthesiser::noteOff (const int midiChannel,
                           const int midiNoteNumber,
                           const float velocity,
                           const bool allowTailOff)
{
    const ScopedLock sl (lock);

    for (auto* voice : voices)
    {
        if (voice->getCurrentlyPlayingNote() == midiNoteNumber
              && voice->isPlayingChannel (midiChannel))
        {
            if (auto sound = voice->getCurrentlyPlayingSound())
            {
                if (sound->appliesToNote (midiNoteNumber)
                     && sound->appliesToChannel (midiChannel))
                {
                    jassert (! voice->keyIsDown || voice->isSustainPedalDown() == sustainPedalsDown [midiChannel]);

                    voice->setKeyDown (false);

                    if (! (voice->isSustainPedalDown() || voice->isSostenutoPedalDown()))
                        stopVoice (voice, velocity, allowTailOff);
                }
            }
        }
    }
}

void Synthesiser::allNotesOff (const int midiChannel, const bool allowTailOff)
{
    const ScopedLock sl (lock);

    for (auto* voice : voices)
        if (midiChannel <= 0 || voice->isPlayingChannel (midiChannel))
            voice->stopNote (1.0f, allowTailOff);

    sustainPedalsDown.clear();
}

void Synthesiser::handlePitchWheel (const int midiChannel, const int wheelValue)
{
    const ScopedLock sl (lock);

    for (auto* voice : voices)
        if (midiChannel <= 0 || voice->isPlayingChannel (midiChannel))
            voice->pitchWheelMoved (wheelValue);
}

void Synthesiser::handleController (const int midiChannel,
                                    const int controllerNumber,
                                    const int controllerValue)
{
    switch (controllerNumber)
    {
        case 0x40:  handleSustainPedal   (midiChannel, controllerValue >= 64); break;
        case 0x42:  handleSostenutoPedal (midiChannel, controllerValue >= 64); break;
        case 0x43:  handleSoftPedal      (midiChannel, controllerValue >= 64); break;
        default:    break;
    }

    const ScopedLock sl (lock);

    for (auto* voice : voices)
        if (midiChannel <= 0 || voice->isPlayingChannel (midiChannel))
            voice->controllerMoved (controllerNumber, controllerValue);
}

void Synthesiser::handleAftertouch (int midiChannel, int midiNoteNumber, int aftertouchValue)
{
    const ScopedLock sl (lock);

    for (auto* voice : voices)
        if (voice->getCurrentlyPlayingNote() == midiNoteNumber
              && (midiChannel <= 0 || voice->isPlayingChannel (midiChannel)))
            voice->aftertouchChanged (aftertouchValue);
}

void Synthesiser::handleChannelPressure (int midiChannel, int channelPressureValue)
{
    const ScopedLock sl (lock);

    for (auto* voice : voices)
        if (midiChannel <= 0 || voice->isPlayingChannel (midiChannel))
            voice->channelPressureChanged (channelPressureValue);
}

void Synthesiser::handleSustainPedal (int midiChannel, bool isDown)
{
    jassert (midiChannel > 0 && midiChannel <= 16);
    const ScopedLock sl (lock);

    if (isDown)
    {
        sustainPedalsDown.setBit (midiChannel);

        for (auto* voice : voices)
            if (voice->isPlayingChannel (midiChannel) && voice->isKeyDown())
                voice->setSustainPedalDown (true);
    }
    else
    {
        for (auto* voice : voices)
        {
            if (voice->isPlayingChannel (midiChannel))
            {
                voice->setSustainPedalDown (false);

                if (! (voice->isKeyDown() || voice->isSostenutoPedalDown()))
                    stopVoice (voice, 1.0f, true);
            }
        }

        sustainPedalsDown.clearBit (midiChannel);
    }
}

void Synthesiser::handleSostenutoPedal (int midiChannel, bool isDown)
{
    jassert (midiChannel > 0 && midiChannel <= 16);
    const ScopedLock sl (lock);

    for (auto* voice : voices)
    {
        if (voice->isPlayingChannel (midiChannel))
        {
            if (isDown)
                voice->setSostenutoPedalDown (true);
            else if (voice->isSostenutoPedalDown())
                stopVoice (voice, 1.0f, true);
        }
    }
}

void Synthesiser::handleSoftPedal ([[maybe_unused]] int midiChannel, bool /*isDown*/)
{
    jassert (midiChannel > 0 && midiChannel <= 16);
}

void Synthesiser::handleProgramChange ([[maybe_unused]] int midiChannel,
                                       [[maybe_unused]] int programNumber)
{
    jassert (midiChannel > 0 && midiChannel <= 16);
}

//==============================================================================
SynthesiserVoice* Synthesiser::findFreeVoice (SynthesiserSound* soundToPlay,
                                              int midiChannel, int midiNoteNumber,
                                              const bool stealIfNoneAvailable) const
{
    const ScopedLock sl (lock);

    for (auto* voice : voices)
        if ((! voice->isVoiceActive()) && voice->canPlaySound (soundToPlay))
            return voice;

    if (stealIfNoneAvailable)
        return findVoiceToSteal (soundToPlay, midiChannel, midiNoteNumber);

    return nullptr;
}

SynthesiserVoice* Synthesiser::findVoiceToSteal (SynthesiserSound* soundToPlay,
                                                 int /*midiChannel*/, int midiNoteNumber) const
{
    // This voice-stealing algorithm applies the following heuristics:
    // - Re-use the oldest notes first
    // - Protect the lowest & topmost notes, even if sustained, but not if they've been released.

    // apparently you are trying to render audio without having any voices...
    jassert (! voices.isEmpty());

    // These are the voices we want to protect (ie: only steal if unavoidable)
    SynthesiserVoice* low = nullptr; // Lowest sounding note, might be sustained, but NOT in release phase
    SynthesiserVoice* top = nullptr; // Highest sounding note, might be sustained, but NOT in release phase

    // All major OSes use double-locking so this will be lock- and wait-free as long as the lock is not
    // contended. This is always the case if you do not call findVoiceToSteal on multiple threads at
    // the same time.
    const ScopedLock sl (stealLock);

    // this is a list of voices we can steal, sorted by how long they've been running
    usableVoicesToStealArray.clear();

    for (auto* voice : voices)
    {
        if (voice->canPlaySound (soundToPlay))
        {
            jassert (voice->isVoiceActive()); // We wouldn't be here otherwise

            usableVoicesToStealArray.add (voice);

            // NB: Using a functor rather than a lambda here due to scare-stories about
            // compilers generating code containing heap allocations..
            struct Sorter
            {
                bool operator() (const SynthesiserVoice* a, const SynthesiserVoice* b) const noexcept { return a->wasStartedBefore (*b); }
            };

            std::sort (usableVoicesToStealArray.begin(), usableVoicesToStealArray.end(), Sorter());

            if (! voice->isPlayingButReleased()) // Don't protect released notes
            {
                auto note = voice->getCurrentlyPlayingNote();

                if (low == nullptr || note < low->getCurrentlyPlayingNote())
                    low = voice;

                if (top == nullptr || note > top->getCurrentlyPlayingNote())
                    top = voice;
            }
        }
    }

    // Eliminate pathological cases (ie: only 1 note playing): we always give precedence to the lowest note(s)
    if (top == low)
        top = nullptr;

    // The oldest note that's playing with the target pitch is ideal..
    for (auto* voice : usableVoicesToStealArray)
        if (voice->getCurrentlyPlayingNote() == midiNoteNumber)
            return voice;

    // Oldest voice that has been released (no finger on it and not held by sustain pedal)
    for (auto* voice : usableVoicesToStealArray)
        if (voice != low && voice != top && voice->isPlayingButReleased())
            return voice;

    // Oldest voice that doesn't have a finger on it:
    for (auto* voice : usableVoicesToStealArray)
        if (voice != low && voice != top && ! voice->isKeyDown())
            return voice;

    // Oldest voice that isn't protected
    for (auto* voice : usableVoicesToStealArray)
        if (voice != low && voice != top)
            return voice;

    // We've only got "protected" voices now: lowest note takes priority
    jassert (low != nullptr);

    // Duophonic synth: give priority to the bass note:
    if (top != nullptr)
        return top;

    return low;
}

} // namespace juce