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LibDSP: Create Classic synth
The Classic synthesizer is a replication of Piano's old synthesizer engine that is removed in the next commit.
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4 changed files with 221 additions and 1 deletions
146
Userland/Libraries/LibDSP/Synthesizers.cpp
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146
Userland/Libraries/LibDSP/Synthesizers.cpp
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/*
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* Copyright (c) 2021, kleines Filmröllchen <malu.bertsch@gmail.com>.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/HashMap.h>
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#include <AK/Math.h>
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#include <AK/Random.h>
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#include <LibDSP/Envelope.h>
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#include <LibDSP/Processor.h>
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#include <LibDSP/Synthesizers.h>
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#include <math.h>
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namespace LibDSP::Synthesizers {
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Classic::Classic(NonnullRefPtr<Transport> transport)
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: LibDSP::SynthesizerProcessor(transport)
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, m_waveform("Waveform"sv, Waveform::Saw)
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, m_attack("Attack"sv, 0, 2000, 5)
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, m_decay("Decay"sv, 0, 20'000, 80)
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, m_sustain("Sustain"sv, 0, 1, 0.725)
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, m_release("Release", 0, 6'000, 120)
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{
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m_parameters.append(m_waveform);
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m_parameters.append(m_attack);
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m_parameters.append(m_decay);
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m_parameters.append(m_sustain);
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m_parameters.append(m_release);
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}
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Signal Classic::process_impl(Signal const& input_signal)
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{
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auto& in = input_signal.get<RollNotes>();
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Sample out;
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SinglyLinkedList<PitchedEnvelope> playing_envelopes;
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// "Press" the necessary notes in the internal representation,
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// and "release" all of the others
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for (u8 i = 0; i < note_count; ++i) {
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if (auto maybe_note = in.get(i); maybe_note.has_value())
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m_playing_notes.set(i, maybe_note.value());
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if (m_playing_notes.contains(i)) {
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Envelope note_envelope = m_playing_notes.get(i)->to_envelope(m_transport->time(), m_attack * m_transport->ms_sample_rate(), m_decay * m_transport->ms_sample_rate(), m_release * m_transport->ms_sample_rate());
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if (!note_envelope.is_active()) {
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m_playing_notes.remove(i);
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continue;
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}
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playing_envelopes.append(PitchedEnvelope { note_envelope, i });
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}
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}
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for (auto envelope : playing_envelopes) {
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double volume = volume_from_envelope(envelope);
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double wave = wave_position(envelope.note);
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out += volume * wave;
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}
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return out;
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}
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double Classic::volume_from_envelope(Envelope envelope)
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{
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switch (static_cast<EnvelopeState>(envelope)) {
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case EnvelopeState::Off:
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return 0;
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case EnvelopeState::Attack:
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return envelope.attack();
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case EnvelopeState::Decay:
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return (1. - envelope.decay()) * m_sustain + m_sustain;
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case EnvelopeState::Sustain:
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return m_sustain;
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case EnvelopeState::Release:
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return (1. - envelope.release()) * m_sustain;
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}
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VERIFY_NOT_REACHED();
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}
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double Classic::wave_position(u8 note)
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{
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switch (m_waveform) {
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case Sine:
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return sin_position(note);
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case Triangle:
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return triangle_position(note);
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case Square:
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return square_position(note);
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case Saw:
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return saw_position(note);
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case Noise:
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return noise_position(note);
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}
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VERIFY_NOT_REACHED();
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}
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double Classic::samples_per_cycle(u8 note)
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{
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return m_transport->sample_rate() / note_frequencies[note];
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}
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double Classic::sin_position(u8 note)
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{
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double spc = samples_per_cycle(note);
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double cycle_pos = m_transport->time() / spc;
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return AK::sin(cycle_pos * 2 * AK::Pi<double>);
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}
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// Absolute value of the saw wave "flips" the negative portion into the positive, creating a ramp up and down.
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double Classic::triangle_position(u8 note)
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{
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double saw = saw_position(note);
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return AK::fabs(saw) * 2 - 1;
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}
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// The first half of the cycle period is 1, the other half -1.
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double Classic::square_position(u8 note)
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{
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double spc = samples_per_cycle(note);
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double progress = AK::fmod(static_cast<double>(m_transport->time()), spc) / spc;
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return progress >= 0.5 ? -1 : 1;
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}
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// Modulus creates inverse saw, which we need to flip and scale.
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double Classic::saw_position(u8 note)
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{
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double spc = samples_per_cycle(note);
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double unscaled = spc - AK::fmod(static_cast<double>(m_transport->time()), spc);
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return unscaled / (samples_per_cycle(note) / 2.) - 1;
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}
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// We resample the noise twenty times per cycle.
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double Classic::noise_position(u8 note)
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{
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double spc = samples_per_cycle(note);
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u32 getrandom_interval = max(static_cast<u32>(spc / 2), 1);
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// Note that this code only works well if the processor is called for every increment of time.
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if (m_transport->time() % getrandom_interval == 0)
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last_random[note] = (get_random<u16>() / static_cast<double>(NumericLimits<u16>::max()) - .5) * 2;
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return last_random[note];
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}
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}
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