Minimal WASAPI

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Minimal WASAPI

Minimal WASAPI reference implementation. Runnable console application contained in a single function and laid out in a linear, step-by-step fashion. No modern C++ / OOP / obscuring cruft. Produces a steady sine wave sound.

(This is a re-post of the same gist I posted a few years earlier, simply due to me wanting the Minimal D3D11 series to be listed contiguously and it's not possible to hide or rearrange gists).

code.cpp

#pragma comment(lib, "ole32")

///////////////////////////////////////////////////////////////////////////////////////////////////

#include <windows.h>
#include <mmdeviceapi.h>
#include <audioclient.h>
#include <math.h> // for sine

///////////////////////////////////////////////////////////////////////////////////////////////////

int main()
{
    CoInitializeEx(nullptr, COINIT_MULTITHREADED | COINIT_DISABLE_OLE1DDE);

    ///////////////////////////////////////////////////////////////////////////////////////////////

    IMMDeviceEnumerator* deviceEnumerator;

    CoCreateInstance(__uuidof(MMDeviceEnumerator), nullptr, CLSCTX_INPROC_SERVER, __uuidof(IMMDeviceEnumerator), reinterpret_cast<void**>(&deviceEnumerator));

    ///////////////////////////////////////////////////////////////////////////////////////////////

    IMMDevice* audioDevice;

    deviceEnumerator->GetDefaultAudioEndpoint(eRender, eConsole, &audioDevice);

    ///////////////////////////////////////////////////////////////////////////////////////////////

    IAudioClient3* audioClient;

    audioDevice->Activate(__uuidof(IAudioClient3), CLSCTX_INPROC_SERVER, nullptr, reinterpret_cast<void**>(&audioClient));

    ///////////////////////////////////////////////////////////////////////////////////////////////

    REFERENCE_TIME defaultPeriod;
    REFERENCE_TIME minimumPeriod;

    audioClient->GetDevicePeriod(&defaultPeriod, &minimumPeriod);

    WAVEFORMATEX* mixFormat;

    audioClient->GetMixFormat(&mixFormat);

    audioClient->Initialize(AUDCLNT_SHAREMODE_SHARED, AUDCLNT_STREAMFLAGS_EVENTCALLBACK, minimumPeriod, 0, mixFormat, nullptr);

    IAudioRenderClient* audioRenderClient;

    audioClient->GetService(__uuidof(IAudioRenderClient), reinterpret_cast<void**>(&audioRenderClient));

    UINT32 bufferSize;

    audioClient->GetBufferSize(&bufferSize);

    HANDLE bufferReady = CreateEventA(nullptr, FALSE, FALSE, nullptr);

    audioClient->SetEventHandle(bufferReady);

    ///////////////////////////////////////////////////////////////////////////////////////////////

    double time = 0.0;

    audioClient->Start();

    while (WaitForSingleObject(bufferReady, INFINITE) == WAIT_OBJECT_0)
    {
        UINT32 bufferPadding;

        audioClient->GetCurrentPadding(&bufferPadding);

        UINT32 frameCount = bufferSize - bufferPadding;
        float* buffer;

        audioRenderClient->GetBuffer(frameCount, reinterpret_cast<BYTE**>(&buffer));

        for (UINT32 frameIndex = 0; frameIndex < frameCount; frameIndex++)
        {
            float amplitude = static_cast<float>(sin(time));

            *buffer++ = amplitude; // left
            *buffer++ = amplitude; // right

            time += 0.05;
        }

        audioRenderClient->ReleaseBuffer(frameCount, 0);
    }

    audioClient->Stop();

    ///////////////////////////////////////////////////////////////////////////////////////////////

    return 0;
}