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109 lines
3.5 KiB
C++
109 lines
3.5 KiB
C++
/*
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* Copyright 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef SHARED_SYNTH_SOUND_H
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#define SHARED_SYNTH_SOUND_H
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#include <cstdint>
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#include <atomic>
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#include <math.h>
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#include <memory>
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#include "IRenderableAudio.h"
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constexpr float kDefaultFrequency = 440.0;
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constexpr int32_t kDefaultSampleRate = 48000;
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constexpr float kPi = M_PI;
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constexpr float kTwoPi = kPi * 2;
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constexpr int32_t kNumSineWaves = 5;
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constexpr float kSustainMultiplier = 0.99999;
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constexpr float kReleaseMultiplier = 0.999;
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// Stop playing music below this cutoff
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constexpr float kMasterAmplitudeCutOff = 0.01;
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class SynthSound : public IRenderableAudio {
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public:
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SynthSound() {
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}
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~SynthSound() {
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};
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void noteOn() {
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mTrigger = true; // start a note envelope
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mAmplitudeScaler = kSustainMultiplier;
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}
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void noteOff() {
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mAmplitudeScaler = kReleaseMultiplier;
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}
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void setSampleRate(int32_t sampleRate) {
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mSampleRate = sampleRate;
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updatePhaseIncrement();
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};
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void setFrequency(float frequency) {
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mFrequency = frequency;
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updatePhaseIncrement();
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};
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// Amplitudes from https://epubs.siam.org/doi/pdf/10.1137/S00361445003822
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inline void setAmplitude(float amplitude) {
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mAmplitudes[0] = amplitude * .2f;
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mAmplitudes[1] = amplitude;
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mAmplitudes[2] = amplitude * .1f;
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mAmplitudes[3] = amplitude * .02f;
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mAmplitudes[4] = amplitude * .15f;
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};
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// From IRenderableAudio
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void renderAudio(float *audioData, int32_t numFrames) override {
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for (int i = 0; i < numFrames; ++i) {
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if (mTrigger.exchange(false)) {
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mMasterAmplitude = 1.0;
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mPhase = 0.0f;
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} else {
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mMasterAmplitude *= mAmplitudeScaler;
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}
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audioData[i] = 0;
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if (mMasterAmplitude < kMasterAmplitudeCutOff) {
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continue;
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}
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for (int j = 0; j < kNumSineWaves; ++j) {
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audioData[i] += sinf(mPhase * (j + 1)) * mAmplitudes[j] * mMasterAmplitude;
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}
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mPhase += mPhaseIncrement;
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if (mPhase > kTwoPi) {
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mPhase -= kTwoPi;
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}
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}
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};
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private:
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std::atomic<bool> mTrigger { false };
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float mMasterAmplitude = 0.0f;
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std::atomic<float> mAmplitudeScaler { 0.0f };
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std::array<std::atomic<float>, kNumSineWaves> mAmplitudes;
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float mPhase = 0.0f;
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std::atomic<float> mPhaseIncrement { 0 };
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std::atomic<float> mFrequency { kDefaultFrequency };
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std::atomic<int32_t> mSampleRate { kDefaultSampleRate };
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void updatePhaseIncrement(){
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// Note how there is a division here. If this file is changed so that updatePhaseIncrement
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// is called more frequently, please cache 1/mSampleRate. This allows this operation to not
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// need divisions.
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mPhaseIncrement = kTwoPi * mFrequency / static_cast<float>(mSampleRate);
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};
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};
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#endif //SHARED_SYNTH_SOUND_H
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