samples/hello-oboe/src/main/cpp/SoundGenerator.cpp

/*
 * Copyright 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "SoundGenerator.h"

SoundGenerator::SoundGenerator(int32_t sampleRate, int32_t channelCount) :
        TappableAudioSource(sampleRate, channelCount)
        , mOscillators(std::make_unique<Oscillator[]>(channelCount)){

    double frequency = 440.0;
    constexpr double interval = 110.0;
    constexpr float amplitude = 1.0;

    // Set up the oscillators
    for (int i = 0; i < mChannelCount; ++i) {
        mOscillators[i].setFrequency(frequency);
        mOscillators[i].setSampleRate(mSampleRate);
        mOscillators[i].setAmplitude(amplitude);
        frequency += interval;
    }
}

void SoundGenerator::renderAudio(float *audioData, int32_t numFrames) {
    // Render each oscillator into its own channel
    std::fill_n(mBuffer.get(), kSharedBufferSize, 0);
    for (int i = 0; i < mChannelCount; ++i) {
        mOscillators[i].renderAudio(mBuffer.get(), numFrames);
        for (int j = 0; j < numFrames; ++j) {
            audioData[(j * mChannelCount) + i] = mBuffer[j];
        }
    }
}

void SoundGenerator::tap(bool isOn) {
    for (int i = 0; i < mChannelCount; ++i) {
        mOscillators[i].setWaveOn(isOn);
    }
}