Simple audio playback

Table of Contents

• main.cpp

main.cpp

#define FPL_IMPLEMENTATION
#define FPL_NO_WINDOW
#include <final_platform_layer.h>
#include <math.h> // sinf
 
struct AudioTest {
    uint32_t toneHz;
    uint32_t toneVolume;
    uint32_t runningSampleIndex;
    uint32_t wavePeriod;
    bool useSquareWave;
};
 
static const float PI32 = 3.14159265359f;
 
static uint32_t FillAudioBuffer(const fplAudioFormat *nativeFormat, const uint32_t frameCount, void *outputSamples, void *userData) {
    AudioTest *audioTest = (AudioTest *)userData;
    fplAssert(audioTest != nullptr);
    fplAssert(nativeFormat->type == fplAudioFormatType_S16);
    uint32_t result = 0;
    int16_t *outSamples = (int16_t *)outputSamples;
    uint32_t halfWavePeriod = audioTest->wavePeriod / 2;
    for (uint32_t frameIndex = 0; frameIndex < frameCount; ++frameIndex) {
        int16_t sampleValue;
        if (audioTest->useSquareWave) {
            sampleValue = ((audioTest->runningSampleIndex++ / halfWavePeriod) % 2) ? (int16_t)audioTest->toneVolume : -(int16_t)audioTest->toneVolume;
        } else {
            float t = 2.0f * PI32 * (float)audioTest->runningSampleIndex++ / (float)audioTest->wavePeriod;
            sampleValue = (int16_t)(sinf(t) * audioTest->toneVolume);
        }
        for (uint32_t channelIndex = 0; channelIndex < nativeFormat->channels; ++channelIndex) {
             *outSamples++ = sampleValue;
            ++result;
        }
    }
    return result;
}
 
int main(int argc, char **argv) {
    int result = -1;
 
    // Initialize to default settings which is 48 kHz and 2 Channels
    fplSettings settings;
    fplSetDefaultSettings(&settings);
 
    // Optionally overwrite audio settings if needed
 
    // Setup some state for the sine/square wave generation
    AudioTest audioTest = {};
    audioTest.toneHz = 256;
    audioTest.toneVolume = 1000;
    audioTest.wavePeriod = settings.audio.deviceFormat.sampleRate / audioTest.toneHz;
    audioTest.useSquareWave = false;
 
    // Provide client read callback and optionally user data
    settings.audio.clientReadCallback = FillAudioBuffer;
    settings.audio.userData = &audioTest;
    settings.audio.deviceFormat.type = fplAudioFormatType_S16;
    settings.audio.deviceFormat.channels = 2;
    settings.audio.deviceFormat.sampleRate = 48000;
 
    // Disable auto start/stop of audio playback
    settings.audio.startAuto = false;
    settings.audio.stopAuto = false;
 
    // Find audio device
    if (fplPlatformInit(fplInitFlags_Audio, &settings)) {
        fplAudioDeviceID audioDevices[16] = {};
        uint32_t deviceCount = fplGetAudioDevices(audioDevices, fplArrayCount(audioDevices));
        if (deviceCount > 0) {
            settings.audio.deviceID = audioDevices[0];
            fplConsoleFormatOut("Using audio device: %s\n", settings.audio.deviceID.name);
        }
        fplPlatformRelease();
    }
 
    // Initialize the platform with audio enabled and the settings
    if (fplPlatformInit(fplInitFlags_Audio, &settings)) {
        // You can overwrite the client read callback and user data if you want to
        fplSetAudioClientReadCallback(FillAudioBuffer, &audioTest);
        // Start audio playback (This will start calling clientReadCallback regulary)
        if (fplPlayAudio() == fplAudioResult_Success) {
            // Print out the native audio format
            fplAudioFormat nativeFormat = fplGetAudioHardwareFormat();
            fplConsoleFormatOut("Audio with %lu kHz and %lu channels is playing, press any key to stop playback...\n", nativeFormat.sampleRate, nativeFormat.channels);
            // Wait for any key presses
            fplConsoleWaitForCharInput();
            // Stop audio playback
            fplStopAudio();
        }
        // Release the platform
        fplPlatformRelease();
        result = 0;
    }
    return(result);
}