1 /* 2 * Copyright 2018 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 #ifndef SHARED_SYNTH_SOUND_H 17 #define SHARED_SYNTH_SOUND_H 18 #include <cstdint> 19 #include <atomic> 20 #include <math.h> 21 #include <memory> 22 #include "IRenderableAudio.h" 23 constexpr float kDefaultFrequency = 440.0; 24 constexpr int32_t kDefaultSampleRate = 48000; 25 constexpr float kPi = M_PI; 26 constexpr float kTwoPi = kPi * 2; 27 constexpr int32_t kNumSineWaves = 5; 28 constexpr float kSustainMultiplier = 0.99999; 29 constexpr float kReleaseMultiplier = 0.999; 30 // Stop playing music below this cutoff 31 constexpr float kMasterAmplitudeCutOff = 0.01; 32 33 class SynthSound : public IRenderableAudio { 34 35 public: SynthSound()36 SynthSound() { 37 38 } 39 ~SynthSound()40 ~SynthSound() { 41 42 }; 43 noteOn()44 void noteOn() { 45 mTrigger = true; // start a note envelope 46 mAmplitudeScaler = kSustainMultiplier; 47 } 48 noteOff()49 void noteOff() { 50 mAmplitudeScaler = kReleaseMultiplier; 51 } 52 setSampleRate(int32_t sampleRate)53 void setSampleRate(int32_t sampleRate) { 54 mSampleRate = sampleRate; 55 updatePhaseIncrement(); 56 }; setFrequency(float frequency)57 void setFrequency(float frequency) { 58 mFrequency = frequency; 59 updatePhaseIncrement(); 60 }; 61 // Amplitudes from https://epubs.siam.org/doi/pdf/10.1137/S00361445003822 setAmplitude(float amplitude)62 inline void setAmplitude(float amplitude) { 63 mAmplitudes[0] = amplitude * .2f; 64 mAmplitudes[1] = amplitude; 65 mAmplitudes[2] = amplitude * .1f; 66 mAmplitudes[3] = amplitude * .02f; 67 mAmplitudes[4] = amplitude * .15f; 68 }; 69 // From IRenderableAudio renderAudio(float * audioData,int32_t numFrames)70 void renderAudio(float *audioData, int32_t numFrames) override { 71 for (int i = 0; i < numFrames; ++i) { 72 if (mTrigger.exchange(false)) { 73 mMasterAmplitude = 1.0; 74 mPhase = 0.0f; 75 } else { 76 mMasterAmplitude *= mAmplitudeScaler; 77 } 78 79 audioData[i] = 0; 80 if (mMasterAmplitude < kMasterAmplitudeCutOff) { 81 continue; 82 } 83 for (int j = 0; j < kNumSineWaves; ++j) { 84 audioData[i] += sinf(mPhase * (j + 1)) * mAmplitudes[j] * mMasterAmplitude; 85 } 86 mPhase += mPhaseIncrement; 87 if (mPhase > kTwoPi) { 88 mPhase -= kTwoPi; 89 } 90 } 91 }; 92 93 private: 94 std::atomic<bool> mTrigger { false }; 95 float mMasterAmplitude = 0.0f; 96 std::atomic<float> mAmplitudeScaler { 0.0f }; 97 std::array<std::atomic<float>, kNumSineWaves> mAmplitudes; 98 float mPhase = 0.0f; 99 std::atomic<float> mPhaseIncrement { 0 }; 100 std::atomic<float> mFrequency { kDefaultFrequency }; 101 std::atomic<int32_t> mSampleRate { kDefaultSampleRate }; updatePhaseIncrement()102 void updatePhaseIncrement(){ 103 // Note how there is a division here. If this file is changed so that updatePhaseIncrement 104 // is called more frequently, please cache 1/mSampleRate. This allows this operation to not 105 // need divisions. 106 mPhaseIncrement = kTwoPi * mFrequency / static_cast<float>(mSampleRate); 107 }; 108 }; 109 #endif //SHARED_SYNTH_SOUND_H 110