void LoopbackCaptureFor(IMMDevice* mmDevice, std::string filename, int secs)
{
    // open new file
    MMIOINFO mi = { 0 };

    // some flags cause mmioOpen write to this buffer
    // but not any that we're using
    std::wstring wsFilename(filename.begin(), filename.end()); // mmioOpen wants a wstring
    HMMIO file = mmioOpen(const_cast<LPWSTR>(wsFilename.c_str()), &mi, MMIO_WRITE | MMIO_CREATE);

    time_t startTime = time(nullptr);

    // activate an IAudioClient
    IAudioClient* audioClient;
    HRESULT hr = mmDevice->Activate(__uuidof(IAudioClient), CLSCTX_ALL, nullptr, (void**)&audioClient);
    if (FAILED(hr))
    {
        fprintf(stderr, "IMMDevice::Activate(IAudioClient) failed: hr = 0x%08x", hr);
        return;
    }

    // get the default device periodicity
    REFERENCE_TIME hnsDefaultDevicePeriod;
    hr = audioClient->GetDevicePeriod(&hnsDefaultDevicePeriod, nullptr);
    if (FAILED(hr))
    {
        fprintf(stderr, "IAudioClient::GetDevicePeriod failed: hr = 0x%08x\n", hr);
        audioClient->Release();
        return;
    }

    // get the default device format
    WAVEFORMATEX* waveform;
    hr = audioClient->GetMixFormat(&waveform);
    if (FAILED(hr))
    {
        fprintf(stderr, "IAudioClient::GetMixFormat failed: hr = 0x%08x\n", hr);
        CoTaskMemFree(waveform);
        audioClient->Release();
        return;
    }

    // coerce int-16 wave format
    // can do this in-place since we're not changing the size of the format
    // also, the engine will auto-convert from float to int for us
    switch (waveform->wFormatTag)
    {
        case WAVE_FORMAT_IEEE_FLOAT:
            waveform->wFormatTag = WAVE_FORMAT_PCM;
            waveform->wBitsPerSample = BITS_PER_SAMPLE;
            waveform->nBlockAlign = BLOCK_ALIGN;
            waveform->nAvgBytesPerSec = BYTE_RATE;
            break;
        case WAVE_FORMAT_EXTENSIBLE:
        {
            // naked scope for case-local variable
            PWAVEFORMATEXTENSIBLE pEx = reinterpret_cast<PWAVEFORMATEXTENSIBLE>(waveform);
            if (IsEqualGUID(KSDATAFORMAT_SUBTYPE_IEEE_FLOAT, pEx->SubFormat))
            {
                pEx->SubFormat = KSDATAFORMAT_SUBTYPE_PCM;
                pEx->Samples.wValidBitsPerSample = BITS_PER_SAMPLE;
                waveform->wBitsPerSample = BITS_PER_SAMPLE;
                waveform->nBlockAlign = waveform->nChannels * BYTE_PER_SAMPLE;
                waveform->nAvgBytesPerSec = waveform->nBlockAlign * waveform->nSamplesPerSec;
            }
            break;
        }
    }

    MMCKINFO ckRIFF = { 0 };
    MMCKINFO ckData = { 0 };
    hr = WriteWaveHeader(file, waveform, &ckRIFF, &ckData);

    // create a periodic waitable timer
    HANDLE hWakeUp = CreateWaitableTimer(nullptr, FALSE, nullptr);
    UINT32 nBlockAlign = waveform->nBlockAlign;

    // call IAudioClient::Initialize
    // note that AUDCLNT_STREAMFLAGS_LOOPBACK and AUDCLNT_STREAMFLAGS_EVENTCALLBACK
    // do not work together...
    // the "data ready" event never gets set
    // so we're going to do a timer-driven loop
    hr = audioClient->Initialize(AUDCLNT_SHAREMODE_SHARED, AUDCLNT_STREAMFLAGS_LOOPBACK, 0, 0, waveform, 0);
    if (FAILED(hr))
    {
        fprintf(stderr, "IAudioClient::Initialize failed: hr = 0x%08x\n", hr);
        CloseHandle(hWakeUp);
        audioClient->Release();
        return;
    }

    // free up waveform
    CoTaskMemFree(waveform);

    // activate an IAudioCaptureClient
    IAudioCaptureClient* audioCaptureClient;
    hr = audioClient->GetService(__uuidof(IAudioCaptureClient), (void**)&audioCaptureClient);

    // register with MMCSS
    DWORD nTaskIndex = 0;
    HANDLE hTask = AvSetMmThreadCharacteristics(L"Capture", &nTaskIndex);
    if (hTask == nullptr)
    {
        DWORD dwErr = GetLastError();
        fprintf(stderr, "AvSetMmThreadCharacteristics failed: last error = %u\n", dwErr);
        audioCaptureClient->Release();
        CloseHandle(hWakeUp);
        audioClient->Release();
        return;
    }

    // set the waitable timer
    LARGE_INTEGER liFirstFire;
    liFirstFire.QuadPart = -hnsDefaultDevicePeriod / 2; // negative means relative time
    LONG lTimeBetweenFires = (LONG)hnsDefaultDevicePeriod / 2 / (10 * 1000); // convert to milliseconds
    if (!SetWaitableTimer(hWakeUp, &liFirstFire, lTimeBetweenFires, nullptr, nullptr, FALSE))
    {
        DWORD dwErr = GetLastError();
        fprintf(stderr, "SetWaitableTimer failed: last error = %u\n", dwErr);
        AvRevertMmThreadCharacteristics(hTask);
        audioCaptureClient->Release();
        CloseHandle(hWakeUp);
        audioClient->Release();
        return;
    }

    // call IAudioClient::Start
    hr = audioClient->Start();

    // loopback capture loop
    DWORD dwWaitResult;

    UINT32 frames = 0;
    for (UINT32 passes = 0; ; passes++)
    {
        // drain data while it is available
        UINT32 nextPacketSize;
        for (hr = audioCaptureClient->GetNextPacketSize(&nextPacketSize);
            SUCCEEDED(hr) && nextPacketSize > 0;
            hr = audioCaptureClient->GetNextPacketSize(&nextPacketSize))
        {
            // get the captured data
            BYTE* data;
            UINT32 framesToRead;
            DWORD dwFlags;

            hr = audioCaptureClient->GetBuffer(&data, &framesToRead, &dwFlags, nullptr, nullptr);
            if (FAILED(hr))
            {
                fprintf(stderr, "IAudioCaptureClient::GetBuffer failed on pass %u after %u frames: hr = 0x%08x\n", passes, frames, hr);
                audioClient->Stop();
                CancelWaitableTimer(hWakeUp);
                AvRevertMmThreadCharacteristics(hTask);
                audioCaptureClient->Release();
                CloseHandle(hWakeUp);
                audioClient->Release();
                return;
            }

            // this type of error seems to happen often, ignore it
            if (dwFlags == AUDCLNT_BUFFERFLAGS_DATA_DISCONTINUITY)
                ;
            else if (dwFlags != 0) {
                fprintf(stderr, "IAudioCaptureClient::GetBuffer set flags to 0x%08x on pass %u after %u frames\n", dwFlags, passes, frames);
                audioClient->Stop();
                CancelWaitableTimer(hWakeUp);
                AvRevertMmThreadCharacteristics(hTask);
                audioCaptureClient->Release();
                CloseHandle(hWakeUp);
                audioClient->Release();
                return;
            }

            if (framesToRead == 0)
            {
                fprintf(stderr, "IAudioCaptureClient::GetBuffer said to read 0 frames on pass %u after %u frames\n", passes, frames);
                audioClient->Stop();
                CancelWaitableTimer(hWakeUp);
                AvRevertMmThreadCharacteristics(hTask);
                audioCaptureClient->Release();
                CloseHandle(hWakeUp);
                audioClient->Release();
                return;
            }

            LONG lBytesToWrite = framesToRead * nBlockAlign;
#pragma prefast(suppress: __WARNING_INCORRECT_ANNOTATION, "IAudioCaptureClient::GetBuffer SAL annotation implies a 1-byte buffer")
            LONG lBytesWritten = mmioWrite(file, reinterpret_cast<PCHAR>(data), lBytesToWrite);
            if (lBytesToWrite != lBytesWritten)
            {
                fprintf(stderr, "mmioWrite wrote %u bytes on pass %u after %u frames: expected %u bytes\n", lBytesWritten, passes, frames, lBytesToWrite);
                audioClient->Stop();
                CancelWaitableTimer(hWakeUp);
                AvRevertMmThreadCharacteristics(hTask);
                audioCaptureClient->Release();
                CloseHandle(hWakeUp);
                audioClient->Release();
                return;
            }

            frames += framesToRead;

            hr = audioCaptureClient->ReleaseBuffer(framesToRead);
        }

        dwWaitResult = WaitForSingleObject(hWakeUp, INFINITE);

        if (time(nullptr) - startTime > secs)
            break;
    }

    FinishWaveFile(file, &ckData, &ckRIFF);
    audioClient->Stop();
    CancelWaitableTimer(hWakeUp);
    AvRevertMmThreadCharacteristics(hTask);
    audioCaptureClient->Release();
    CloseHandle(hWakeUp);
    audioClient->Release();


    // everything went well... fixup the fact chunk in the file
    MMRESULT result = mmioClose(file, 0);
    file = nullptr;
    if (result != MMSYSERR_NOERROR)
    {
        fprintf(stderr, "mmioClose failed: MMSYSERR = %u\n", result);
        return;
    }

    // reopen the file in read/write mode
    mi = { 0 };
    file = mmioOpen(const_cast<LPWSTR>(wsFilename.c_str()), &mi, MMIO_READWRITE);
    if (file == nullptr)
    {
        fprintf(stderr, "mmioOpen(\"%ls\", ...) failed. wErrorRet == %u\n", filename, mi.wErrorRet);
        return;
    }

    // descend into the RIFF/WAVE chunk
    ckRIFF = { 0 };
    ckRIFF.ckid = MAKEFOURCC('W', 'A', 'V', 'E'); // this is right for mmioDescend
    result = mmioDescend(file, &ckRIFF, nullptr, MMIO_FINDRIFF);
    if (result != MMSYSERR_NOERROR)
    {
        fprintf(stderr, "mmioDescend(\"WAVE\") failed: MMSYSERR = %u\n", result);
        return;
    }

    // descend into the fact chunk
    MMCKINFO ckFact = { 0 };
    ckFact.ckid = MAKEFOURCC('f', 'a', 'c', 't');
    result = mmioDescend(file, &ckFact, &ckRIFF, MMIO_FINDCHUNK);
    if (result != MMSYSERR_NOERROR) {
        fprintf(stderr, "mmioDescend(\"fact\") failed: MMSYSERR = %u\n", result);
        return;
    }

    // write the correct data to the fact chunk
    LONG lBytesWritten = mmioWrite(file, reinterpret_cast<PCHAR>(&frames), sizeof(frames));
    if (lBytesWritten != sizeof(frames))
    {
        fprintf(stderr, "Updating the fact chunk wrote %u bytes; expected %u\n", lBytesWritten, (UINT32)sizeof(frames));
        return;
    }

    // ascend out of the fact chunk
    result = mmioAscend(file, &ckFact, 0);
    if (result != MMSYSERR_NOERROR)
        fprintf(stderr, "mmioAscend(\"fact\") failed: MMSYSERR = %u\n", result);
}
//HRESULT LoopbackCapture(
//    IMMDevice *pMMDevice,
//    bool bInt16,
//    HANDLE hStartedEvent,
//    HANDLE hStopEvent,
//    PUINT32 pnFrames,
//	HMMIO hFile,
//	AudioBuffer *pBuffer
//)
HRESULT LoopbackCapture::Process()
{
    HRESULT hr;

    // activate an IAudioClient
    IAudioClient *pAudioClient;
    hr = pMMDevice->Activate(
             __uuidof(IAudioClient),
             CLSCTX_ALL, NULL,
             (void**)&pAudioClient
         );
    if (FAILED(hr)) {
        printf("IMMDevice::Activate(IAudioClient) failed: hr = 0x%08x", hr);
        return hr;
    }

    // get the default device periodicity
    REFERENCE_TIME hnsDefaultDevicePeriod;
    hr = pAudioClient->GetDevicePeriod(&hnsDefaultDevicePeriod, NULL);
    if (FAILED(hr)) {
        printf("IAudioClient::GetDevicePeriod failed: hr = 0x%08x\n", hr);
        pAudioClient->Release();
        return hr;
    }

    // get the default device format
    WAVEFORMATEX *pwfx;
    hr = pAudioClient->GetMixFormat(&pwfx);
    if (FAILED(hr)) {
        printf("IAudioClient::GetMixFormat failed: hr = 0x%08x\n", hr);
        CoTaskMemFree(pwfx);
        pAudioClient->Release();
        return hr;
    }

    if (pwfx->wFormatTag == WAVE_FORMAT_EXTENSIBLE)
    {
        PWAVEFORMATEXTENSIBLE pEx = reinterpret_cast<PWAVEFORMATEXTENSIBLE>(pwfx);
        //pEx->SubFormat = KSDATAFORMAT_SUBTYPE_PCM;
        printf("WAVE_FORMAT_EXTENSIBLE\n");
        if (IsEqualGUID(KSDATAFORMAT_SUBTYPE_IEEE_FLOAT, pEx->SubFormat))
        {
            printf("float\n");
        }//
        else if (IsEqualGUID(KSDATAFORMAT_SUBTYPE_PCM, pEx->SubFormat))
        {
            printf("PCM\n");
        }//KSDATAFORMAT_SUBTYPE_WAVEFORMATEX
        else if (IsEqualGUID(KSDATAFORMAT_SUBTYPE_WAVEFORMATEX, pEx->SubFormat))
        {
            printf("WAVEFORMATEX\n");
        }
    }

    if (bInt16) {
        // coerce int-16 wave format
        // can do this in-place since we're not changing the size of the format
        // also, the engine will auto-convert from float to int for us
        switch (pwfx->wFormatTag) {
        case WAVE_FORMAT_IEEE_FLOAT:
            pwfx->wFormatTag = WAVE_FORMAT_PCM;
            pwfx->wBitsPerSample = 16;
            pwfx->nBlockAlign = pwfx->nChannels * pwfx->wBitsPerSample / 8;
            pwfx->nAvgBytesPerSec = pwfx->nBlockAlign * pwfx->nSamplesPerSec;
            break;

        case WAVE_FORMAT_EXTENSIBLE:
        {
            // naked scope for case-local variable
            PWAVEFORMATEXTENSIBLE pEx = reinterpret_cast<PWAVEFORMATEXTENSIBLE>(pwfx);
            if (IsEqualGUID(KSDATAFORMAT_SUBTYPE_IEEE_FLOAT, pEx->SubFormat)) {
                pEx->SubFormat = KSDATAFORMAT_SUBTYPE_PCM;
                pEx->Samples.wValidBitsPerSample = 16;
                pwfx->wBitsPerSample = 16;
                pwfx->nBlockAlign = pwfx->nChannels * pwfx->wBitsPerSample / 8;
                pwfx->nAvgBytesPerSec = pwfx->nBlockAlign * pwfx->nSamplesPerSec;
            } else {
                printf("Don't know how to coerce mix format to int-16\n");
                CoTaskMemFree(pwfx);
                pAudioClient->Release();
                return E_UNEXPECTED;
            }
        }
        break;

        default:
            printf("Don't know how to coerce WAVEFORMATEX with wFormatTag = 0x%08x to int-16\n", pwfx->wFormatTag);
            CoTaskMemFree(pwfx);
            pAudioClient->Release();
            return E_UNEXPECTED;
        }
    }

    MMCKINFO ckRIFF = {0};
    MMCKINFO ckData = {0};
    if (hFile!=NULL)
        hr = WriteWaveHeader(hFile, pwfx, &ckRIFF, &ckData);
    if (pBuffer)
    {
        bool isFloat = false;
        switch (pwfx->wFormatTag) {
        case WAVE_FORMAT_IEEE_FLOAT:
            isFloat = true;
            break;

        case WAVE_FORMAT_EXTENSIBLE:
        {
            // naked scope for case-local variable
            PWAVEFORMATEXTENSIBLE pEx = reinterpret_cast<PWAVEFORMATEXTENSIBLE>(pwfx);
            if (IsEqualGUID(KSDATAFORMAT_SUBTYPE_IEEE_FLOAT, pEx->SubFormat)) {
                isFloat = true;
            }
        }
        break;
        default:
            break;
        }
        pBuffer->SetAudioInfo(pwfx->nSamplesPerSec,pwfx->nBlockAlign,pwfx->nChannels,pwfx->wBitsPerSample,isFloat);
    }

    if (FAILED(hr)) {
        // WriteWaveHeader does its own logging
        CoTaskMemFree(pwfx);
        pAudioClient->Release();
        return hr;
    }

    // create a periodic waitable timer
    HANDLE hWakeUp = CreateWaitableTimer(NULL, FALSE, NULL);
    if (NULL == hWakeUp) {
        DWORD dwErr = GetLastError();
        printf("CreateWaitableTimer failed: last error = %u\n", dwErr);
        CoTaskMemFree(pwfx);
        pAudioClient->Release();
        return HRESULT_FROM_WIN32(dwErr);
    }

    UINT32 nBlockAlign = pwfx->nBlockAlign;
    UINT32 nChannels = pwfx->nChannels;
    nFrames = 0;

    // call IAudioClient::Initialize
    // note that AUDCLNT_STREAMFLAGS_LOOPBACK and AUDCLNT_STREAMFLAGS_EVENTCALLBACK
    // do not work together...
    // the "data ready" event never gets set
    // so we're going to do a timer-driven loop
    hr = pAudioClient->Initialize(
             AUDCLNT_SHAREMODE_SHARED,
             AUDCLNT_STREAMFLAGS_LOOPBACK,
             0, 0, pwfx, 0
         );
    if (FAILED(hr)) {
        printf("IAudioClient::Initialize failed: hr = 0x%08x\n", hr);
        CloseHandle(hWakeUp);
        pAudioClient->Release();
        return hr;
    }
    CoTaskMemFree(pwfx);

    // activate an IAudioCaptureClient
    IAudioCaptureClient *pAudioCaptureClient;
    hr = pAudioClient->GetService(
             __uuidof(IAudioCaptureClient),
             (void**)&pAudioCaptureClient
         );
    if (FAILED(hr)) {
        printf("IAudioClient::GetService(IAudioCaptureClient) failed: hr 0x%08x\n", hr);
        CloseHandle(hWakeUp);
        pAudioClient->Release();
        return hr;
    }

    // register with MMCSS
    DWORD nTaskIndex = 0;
    HANDLE hTask = AvSetMmThreadCharacteristics(L"Capture", &nTaskIndex);
    if (NULL == hTask) {
        DWORD dwErr = GetLastError();
        printf("AvSetMmThreadCharacteristics failed: last error = %u\n", dwErr);
        pAudioCaptureClient->Release();
        CloseHandle(hWakeUp);
        pAudioClient->Release();
        return HRESULT_FROM_WIN32(dwErr);
    }

    // set the waitable timer
    LARGE_INTEGER liFirstFire;
    liFirstFire.QuadPart = -hnsDefaultDevicePeriod / 2; // negative means relative time
    LONG lTimeBetweenFires = (LONG)hnsDefaultDevicePeriod / 2 / (10 * 1000); // convert to milliseconds
    BOOL bOK = SetWaitableTimer(
                   hWakeUp,
                   &liFirstFire,
                   lTimeBetweenFires,
                   NULL, NULL, FALSE
               );
    if (!bOK) {
        DWORD dwErr = GetLastError();
        printf("SetWaitableTimer failed: last error = %u\n", dwErr);
        AvRevertMmThreadCharacteristics(hTask);
        pAudioCaptureClient->Release();
        CloseHandle(hWakeUp);
        pAudioClient->Release();
        return HRESULT_FROM_WIN32(dwErr);
    }

    // call IAudioClient::Start
    hr = pAudioClient->Start();
    if (FAILED(hr)) {
        printf("IAudioClient::Start failed: hr = 0x%08x\n", hr);
        AvRevertMmThreadCharacteristics(hTask);
        pAudioCaptureClient->Release();
        CloseHandle(hWakeUp);
        pAudioClient->Release();
        return hr;
    }
    SetEvent(hStartedEvent);

    // loopback capture loop
    HANDLE waitArray[2] = { hStopEvent, hWakeUp };
    DWORD dwWaitResult;
    DWORD immdState;

    bool bDone = false;
    bool bFirstPacket = true;
    for (UINT32 nPasses = 0; !bDone; nPasses++) {
        dwWaitResult = WaitForMultipleObjects(
                           ARRAYSIZE(waitArray), waitArray,
                           FALSE, INFINITE
                       );

        if (WAIT_OBJECT_0 == dwWaitResult) {
            //printf("Received stop event after %u passes and %u frames\n", nPasses, nFrames);
            bDone = true;
            continue; // exits loop
        }

        if (WAIT_OBJECT_0 + 1 != dwWaitResult) {
            printf("Unexpected WaitForMultipleObjects return value %u on pass %u after %u frames\n", dwWaitResult, nPasses, nFrames);
            pAudioClient->Stop();
            CancelWaitableTimer(hWakeUp);
            AvRevertMmThreadCharacteristics(hTask);
            pAudioCaptureClient->Release();
            CloseHandle(hWakeUp);
            pAudioClient->Release();
            return E_UNEXPECTED;
        }

        printf("'");

        // got a "wake up" event - see if there's data
        UINT32 nNextPacketSize;
        hr = pAudioCaptureClient->GetNextPacketSize(&nNextPacketSize);
        if (FAILED(hr)) {
            if (hr == AUDCLNT_E_SERVICE_NOT_RUNNING)
                printf("AUDCLNT_E_SERVICE_NOT_RUNNING : \n");
            else if (hr == AUDCLNT_E_DEVICE_INVALIDATED)
                printf("AUDCLNT_E_DEVICE_INVALIDATED : \n");
            else
                printf("UNKNOWN ERROR!!! : \n");

            printf("IAudioCaptureClient::GetNextPacketSize failed on pass %u after %u frames: hr = 0x%08x\n", nPasses, nFrames, hr);
            pAudioClient->Stop();
            CancelWaitableTimer(hWakeUp);
            AvRevertMmThreadCharacteristics(hTask);
            pAudioCaptureClient->Release();
            CloseHandle(hWakeUp);
            pAudioClient->Release();
            return hr;
        }

        if (0 == nNextPacketSize) {
            // no data yet
            continue;
        }

        // get the captured data
        BYTE *pData;
        UINT32 nNumFramesToRead;
        DWORD dwFlags;

        hr = pAudioCaptureClient->GetBuffer(
                 &pData,
                 &nNumFramesToRead,
                 &dwFlags,
                 NULL,
                 NULL
             );
        if (FAILED(hr)) {
            printf("IAudioCaptureClient::GetBuffer failed on pass %u after %u frames: hr = 0x%08x\n", nPasses, nFrames, hr);
            pAudioClient->Stop();
            CancelWaitableTimer(hWakeUp);
            AvRevertMmThreadCharacteristics(hTask);
            pAudioCaptureClient->Release();
            CloseHandle(hWakeUp);
            pAudioClient->Release();
            return hr;
        }

        if (bFirstPacket && AUDCLNT_BUFFERFLAGS_DATA_DISCONTINUITY == dwFlags) {
            printf("Probably spurious glitch reported on first packet\n");
        }
        else if (dwFlags & AUDCLNT_BUFFERFLAGS_SILENT)
        {
            printf("#");
        }
        else if (dwFlags & AUDCLNT_BUFFERFLAGS_DATA_DISCONTINUITY)
        {
            printf("!");
        }
        else if (0 != dwFlags) {
            printf("IAudioCaptureClient::GetBuffer set flags to 0x%08x on pass %u after %u frames\n", dwFlags, nPasses, nFrames);
            pAudioClient->Stop();
            CancelWaitableTimer(hWakeUp);
            AvRevertMmThreadCharacteristics(hTask);
            pAudioCaptureClient->Release();
            CloseHandle(hWakeUp);
            pAudioClient->Release();
            return E_UNEXPECTED;
        }

        if (0 == nNumFramesToRead) {
            // no data yet
            continue;
        }

        //if (0 == nNumFramesToRead) {
        //    printf("IAudioCaptureClient::GetBuffer said to read 0 frames on pass %u after %u frames\n", nPasses, nFrames);
        //    pAudioClient->Stop();
        //    CancelWaitableTimer(hWakeUp);
        //    AvRevertMmThreadCharacteristics(hTask);
        //    pAudioCaptureClient->Release();
        //    CloseHandle(hWakeUp);
        //    pAudioClient->Release();
        //    return E_UNEXPECTED;
        //}

        LONG lBytesToWrite = nNumFramesToRead * nBlockAlign;
#pragma prefast(suppress: __WARNING_INCORRECT_ANNOTATION, "IAudioCaptureClient::GetBuffer SAL annotation implies a 1-byte buffer")

        if (hFile!=NULL)
        {
            LONG lBytesWritten = mmioWrite(hFile, reinterpret_cast<PCHAR>(pData), lBytesToWrite);
            if (lBytesToWrite != lBytesWritten) {
                printf("mmioWrite wrote %u bytes on pass %u after %u frames: expected %u bytes\n", lBytesWritten, nPasses, nFrames, lBytesToWrite);
                pAudioClient->Stop();
                CancelWaitableTimer(hWakeUp);
                AvRevertMmThreadCharacteristics(hTask);
                pAudioCaptureClient->Release();
                CloseHandle(hWakeUp);
                pAudioClient->Release();
                return E_UNEXPECTED;
            }
        }
        if (pBuffer)
        {
            //switch (nBlockAlign/nChannels)
            //{
            //case 1:
            //	ShowPCM((unsigned char*)pData,nNumFramesToRead,nChannels,1024,60,"SYS_Byte");
            //	break;
            //case 2:
            //	ShowPCM((short*)pData,nNumFramesToRead,nChannels,1024,60,"SYS_Short");
            //	break;
            //case 4:
            //	ShowPCM((int*)pData,nNumFramesToRead,nChannels,1024,60,"SYS_Int");
            //	//ShowPCM((float*)pData,nNumFramesToRead,nChannels,1024,60,"SYS_float");
            //	break;
            //}


            pBuffer->PushBuffer(pData,lBytesToWrite);
        }
        nFrames += nNumFramesToRead;

        hr = pAudioCaptureClient->ReleaseBuffer(nNumFramesToRead);
        if (FAILED(hr)) {
            printf("IAudioCaptureClient::ReleaseBuffer failed on pass %u after %u frames: hr = 0x%08x\n", nPasses, nFrames, hr);
            pAudioClient->Stop();
            CancelWaitableTimer(hWakeUp);
            AvRevertMmThreadCharacteristics(hTask);
            pAudioCaptureClient->Release();
            CloseHandle(hWakeUp);
            pAudioClient->Release();
            return hr;
        }

        bFirstPacket = false;
    } // capture loop

    if (hFile!=NULL)
        hr = FinishWaveFile(hFile, &ckData, &ckRIFF);


    if (FAILED(hr)) {
        // FinishWaveFile does it's own logging
        pAudioClient->Stop();
        CancelWaitableTimer(hWakeUp);
        AvRevertMmThreadCharacteristics(hTask);
        pAudioCaptureClient->Release();
        CloseHandle(hWakeUp);
        pAudioClient->Release();
        return hr;
    }

    pAudioClient->Stop();
    CancelWaitableTimer(hWakeUp);
    AvRevertMmThreadCharacteristics(hTask);
    pAudioCaptureClient->Release();
    CloseHandle(hWakeUp);
    pAudioClient->Release();

    return hr;
}
示例#3
0
int _tmain(int argc, _TCHAR* argv[]) {
  IMMDeviceEnumerator *enumerator = 0;
  IMMDevice *device = 0;
  FILE *f;
	f=fopen("c:/1.wav","w");
  CoInitialize(0);
  CoCreateInstance(__uuidof(MMDeviceEnumerator), NULL, CLSCTX_ALL, __uuidof(IMMDeviceEnumerator), 
    (void**) &enumerator);
  enumerator->GetDefaultAudioEndpoint(eRender, eConsole, &device);

  HANDLE processOutWrite, processOutRead, processInWrite, processInRead;    

  /*wchar_t processCommand[2000];
  {
    FILE* commandFile;
    fopen_s(&commandFile, "command.txt", "r");
    char cmd[2000];
    fread(cmd, sizeof(char), 2000, commandFile);
    fclose(commandFile);
    size_t count;
    mbstowcs_s(&count, processCommand, cmd, 2000);
  }*/

  /*{	
    //create pipes for plink process
    SECURITY_ATTRIBUTES pipeAttributes = {0};
    pipeAttributes.nLength = sizeof(SECURITY_ATTRIBUTES);
    pipeAttributes.bInheritHandle = TRUE;
    pipeAttributes.lpSecurityDescriptor= NULL;
    CreatePipe(&processOutRead, &processOutWrite, &pipeAttributes, 0);
    CreatePipe(&processInRead,  &processInWrite,  &pipeAttributes, 0);
    STARTUPINFO startupInfo;
    ZeroMemory(&startupInfo, sizeof(STARTUPINFO));
    startupInfo.cb = sizeof(STARTUPINFO);
    startupInfo.hStdError = processOutWrite;
    startupInfo.hStdOutput = processOutWrite;
    startupInfo.hStdInput = processInRead;
    startupInfo.dwFlags |= STARTF_USESTDHANDLES;
    PROCESS_INFORMATION processInfo = {0};
    //launch process
    CreateProcess(NULL, processCommand, NULL, NULL, TRUE, 0, NULL, NULL, &startupInfo, &processInfo);

    //wait for plink to connect to minimze sound delay  (magic number)
    Sleep(2500);

  }*/

  HRESULT hr;
  // activate an IAudioClient
  IAudioClient *audioClient;
  hr = device->Activate(__uuidof(IAudioClient), CLSCTX_ALL, NULL, (void**) &audioClient); 
  if (FAILED(hr)) {
    printf("IMMDevice::Activate(IAudioClient) failed: hr = 0x%08x", hr);
    return hr;
  }

  // get the default device format
  WAVEFORMATEX *waveFormat;
  hr = audioClient->GetMixFormat(&waveFormat);
  if (FAILED(hr)) {
    printf("IAudioClient::GetMixFormat failed: hr = 0x%08x\n", hr);
    CoTaskMemFree(waveFormat);
    audioClient->Release();
    return hr;
  }

  // coerce int-16 wave format
  // can do this in-place since we're not changing the size of the format
  // also, the engine will auto-convert from float to int for us
  switch (waveFormat->wFormatTag) {
  case WAVE_FORMAT_IEEE_FLOAT:
    waveFormat->wFormatTag = WAVE_FORMAT_PCM;
    waveFormat->wBitsPerSample = 16;
    waveFormat->nBlockAlign = waveFormat->nChannels * waveFormat->wBitsPerSample / 8;
    waveFormat->nAvgBytesPerSec = waveFormat->nBlockAlign * waveFormat->nSamplesPerSec;
    break;

  case WAVE_FORMAT_EXTENSIBLE:
    {
      // naked scope for case-local variable
      PWAVEFORMATEXTENSIBLE waveFormatEx = reinterpret_cast<PWAVEFORMATEXTENSIBLE>(waveFormat);
      if (IsEqualGUID(KSDATAFORMAT_SUBTYPE_IEEE_FLOAT, waveFormatEx->SubFormat)) {
        waveFormatEx->SubFormat = KSDATAFORMAT_SUBTYPE_PCM;
        waveFormatEx->Samples.wValidBitsPerSample = 16;
        waveFormat->wBitsPerSample = 16;
        waveFormat->nBlockAlign = waveFormat->nChannels * waveFormat->wBitsPerSample / 8;
        waveFormat->nAvgBytesPerSec = waveFormat->nBlockAlign * waveFormat->nSamplesPerSec;
      } else {
        printf("Don't know how to coerce mix format to int-16\n");
        CoTaskMemFree(waveFormat);
        audioClient->Release();
        return E_UNEXPECTED;
      }
    }
    break;

  default:
    printf("Don't know how to coerce WAVEFORMATEX with wFormatTag = 0x%08x to int-16\n", waveFormat->wFormatTag);
    CoTaskMemFree(waveFormat);
    audioClient->Release();
    return E_UNEXPECTED;
  }

  UINT32 blockAlign = waveFormat->nBlockAlign;

  // call IAudioClient::Initialize
  // note that AUDCLNT_STREAMFLAGS_LOOPBACK and AUDCLNT_STREAMFLAGS_EVENTCALLBACK do not work together...
  // the "data ready" event never gets set, so we're going to do a timer-driven loop
  hr = audioClient->Initialize(
    AUDCLNT_SHAREMODE_SHARED,
    AUDCLNT_STREAMFLAGS_LOOPBACK,
    10000000, 0, waveFormat, 0
    );
  if (FAILED(hr)) {
    printf("IAudioClient::Initialize failed: hr = 0x%08x\n", hr);
    audioClient->Release();
    return hr;
  }
  CoTaskMemFree(waveFormat);

  // activate an IAudioCaptureClient
  IAudioCaptureClient *audioCaptureClient;
  hr = audioClient->GetService(__uuidof(IAudioCaptureClient), (void**) &audioCaptureClient);
  if (FAILED(hr)) {
    printf("IAudioClient::GetService(IAudioCaptureClient) failed: hr 0x%08x\n", hr);
    audioClient->Release();
    return hr;
  }

  hr = audioClient->Start();
  if (FAILED(hr)) {
    printf("IAudioClient::Start failed: hr = 0x%08x\n", hr);
    audioCaptureClient->Release();
    audioClient->Release();
    return hr;
  }

  // loopback capture loop
  for (UINT32 i = 0; true; i++) {
    UINT32 nextPacketSize;
    hr = audioCaptureClient->GetNextPacketSize(&nextPacketSize);
    if (FAILED(hr)) {
      printf("IAudioCaptureClient::GetNextPacketSize failed on pass %u: hr = 0x%08x\n", i, hr);
      audioClient->Stop();
      audioCaptureClient->Release();
      audioClient->Release();            
      return hr;
    }

    if (nextPacketSize == 0) { // no data yet
      continue;
    }

    // get the captured data
    BYTE *data;
    UINT32 frameCount;
    DWORD bufferFlags;

    hr = audioCaptureClient->GetBuffer(&data, &frameCount, &bufferFlags, NULL, NULL);
    if (FAILED(hr)) {
      printf("IAudioCaptureClient::GetBuffer failed on pass %u: hr = 0x%08x\n", i, hr);
      audioClient->Stop();
      audioCaptureClient->Release();
      audioClient->Release();            
      return hr;            
    }

    if (bufferFlags & AUDCLNT_BUFFERFLAGS_DATA_DISCONTINUITY) {
      printf("IAudioCaptureClient::GetBuffer reports 'data discontinuity' on pass %u\n", i);
    }
    if (bufferFlags & AUDCLNT_BUFFERFLAGS_SILENT) {
      printf("IAudioCaptureClient::GetBuffer reports 'silent' on pass %u\n", i);
    }
    if (bufferFlags & AUDCLNT_BUFFERFLAGS_TIMESTAMP_ERROR) {
      printf("IAudioCaptureClient::GetBuffer reports 'timestamp error' on pass %u\n", i);
    }

    if (frameCount == 0) {
      printf("IAudioCaptureClient::GetBuffer said to read 0 frames on pass %u\n", i);
      audioClient->Stop();
      audioCaptureClient->Release();
      audioClient->Release();            
      return E_UNEXPECTED;            
    }

    LONG bytesToWrite = frameCount * blockAlign;
    DWORD bytesWritten;
	printf("Recording:%d\n",bytesToWrite);
	
		fwrite(data,bytesToWrite,1,f);
		
    /*WriteFile(processInWrite,reinterpret_cast<PCHAR>(data), bytesToWrite, &bytesWritten, NULL);
    if (bytesWritten != bytesToWrite) {
      printf("WriteFile: tried to write %d bytes, but %d bytes written\n", bytesToWrite, bytesWritten);            
    }

    char buf[10000];
    DWORD count;
    DWORD bytesAvailable;
    PeekNamedPipe(processOutRead, NULL, 0, 0, &bytesAvailable, NULL);
    if (bytesAvailable > 0) { 
      ReadFile(processOutRead, buf, 10000, &count, NULL);
      std::cout.write(buf, count);
    }*/


    hr = audioCaptureClient->ReleaseBuffer(frameCount);
    if (FAILED(hr)) {
      printf("IAudioCaptureClient::ReleaseBuffer failed on pass %u: hr = 0x%08x\n", i, hr);
      audioClient->Stop();
      audioCaptureClient->Release();
      audioClient->Release();            
      return hr;            
    }

  } // capture loop

  audioClient->Stop();
  audioCaptureClient->Release();
  audioClient->Release();
  fclose(f);
  return 0;
}
示例#4
0
int main(int argc, char *argv[])
{
	CoInitialize(nullptr);

	listDevices();

	IAudioClient *pAudioClient;
	IMMDevice *device;

	getDefaultDevice(&device);

    HRESULT hr = device->Activate(__uuidof(IAudioClient),
        CLSCTX_ALL, nullptr, (void**)&pAudioClient);
    if (FAILED(hr)) {
        printf("IMMDevice::Activate(IAudioClient) failed: hr = 0x%08x", hr);
        return hr;
    }

	REFERENCE_TIME hnsDefaultDevicePeriod;
    hr = pAudioClient->GetDevicePeriod(&hnsDefaultDevicePeriod, nullptr);
    if (FAILED(hr)) {
        printf("IAudioClient::GetDevicePeriod failed: hr = 0x%08x\n", hr);
        pAudioClient->Release();
        return hr;
    }

	// get the default device format
    WAVEFORMATEX *pwfx;
    hr = pAudioClient->GetMixFormat(&pwfx);
    if (FAILED(hr)) {
        printf("IAudioClient::GetMixFormat failed: hr = 0x%08x\n", hr);
        CoTaskMemFree(pwfx);
        pAudioClient->Release();
        return hr;
    }

    DVAR(pwfx->wFormatTag);
    DVAR(pwfx->wBitsPerSample);
    DVAR(pwfx->nBlockAlign);
    DVAR(pwfx->nAvgBytesPerSec);

    switch (pwfx->wFormatTag) {
        case WAVE_FORMAT_IEEE_FLOAT:
            pwfx->wFormatTag = WAVE_FORMAT_PCM;
            pwfx->wBitsPerSample = 16;
            pwfx->nBlockAlign = pwfx->nChannels * pwfx->wBitsPerSample / 8;
            pwfx->nAvgBytesPerSec = pwfx->nBlockAlign * pwfx->nSamplesPerSec;
            break;

        case WAVE_FORMAT_EXTENSIBLE:
            {
                // naked scope for case-local variable
                PWAVEFORMATEXTENSIBLE pEx = reinterpret_cast<PWAVEFORMATEXTENSIBLE>(pwfx);
                if (IsEqualGUID(KSDATAFORMAT_SUBTYPE_IEEE_FLOAT, pEx->SubFormat)) {
                    pEx->SubFormat = KSDATAFORMAT_SUBTYPE_PCM;
                    pEx->Samples.wValidBitsPerSample = 16;
                    pwfx->wBitsPerSample = 16;
                    pwfx->nBlockAlign = pwfx->nChannels * pwfx->wBitsPerSample / 8;
                    pwfx->nAvgBytesPerSec = pwfx->nBlockAlign * pwfx->nSamplesPerSec;
                } else {
                    printf("Don't know how to coerce mix format to int-16\n");
                    CoTaskMemFree(pwfx);
                    pAudioClient->Release();
                    return E_UNEXPECTED;
                }
            }
            break;

        default:
            printf("Don't know how to coerce WAVEFORMATEX with wFormatTag = 0x%08x to int-16\n", pwfx->wFormatTag);
            CoTaskMemFree(pwfx);
            pAudioClient->Release();
            return E_UNEXPECTED;
    }

    DVAR(pwfx->wFormatTag);
    DVAR(pwfx->wBitsPerSample);
    DVAR(pwfx->nBlockAlign);
    DVAR(pwfx->nAvgBytesPerSec);

	hr = pAudioClient->Initialize(AUDCLNT_SHAREMODE_SHARED, AUDCLNT_STREAMFLAGS_LOOPBACK, 0, 0, pwfx, 0 );
    if (FAILED(hr)) {
        printf("IAudioClient::Initialize failed: hr = 0x%08x\n", hr);
        pAudioClient->Release();
        return hr;
    }

	IAudioCaptureClient *pAudioCaptureClient;
    hr = pAudioClient->GetService(__uuidof(IAudioCaptureClient), (void**)&pAudioCaptureClient);
    if (FAILED(hr)) {
        printf("IAudioClient::GetService(IAudioCaptureClient) failed: hr 0x%08x\n", hr);
        pAudioClient->Release();
        return hr;
    }


    hr = pAudioClient->Start();
    if (FAILED(hr)) {
        printf("IAudioClient::Start failed: hr = 0x%08x\n", hr);
        pAudioCaptureClient->Release();
        pAudioClient->Release();
        return hr;
    }


for (int i = 0; i < 10; ++i)
{

	UINT32 nNextPacketSize;
    hr = pAudioCaptureClient->GetNextPacketSize(&nNextPacketSize);
    if (FAILED(hr)) {
        printf("IAudioCaptureClient::GetNextPacketSize failed on pass %u after %u frames: hr = 0x%08x\n", 0, 0, hr);
        pAudioClient->Stop();
        pAudioCaptureClient->Release();
        pAudioClient->Release();
        return hr;
    }


    // get the captured data
    BYTE *pData;
    UINT32 nNumFramesToRead;
    DWORD dwFlags;

    hr = pAudioCaptureClient->GetBuffer(&pData, &nNumFramesToRead, &dwFlags, nullptr,
        nullptr);
    if (FAILED(hr)) {
        printf("IAudioCaptureClient::GetBuffer failed on pass %u after %u frames: hr = 0x%08x\n", 0, 0, hr);
        pAudioClient->Stop();
        pAudioCaptureClient->Release();
        pAudioClient->Release();
        return hr;
    }

    DVAR(nNumFramesToRead);


    // if (bFirstPacket && AUDCLNT_BUFFERFLAGS_DATA_DISCONTINUITY == dwFlags) {
        // printf("Probably spurious glitch reported on first packet\n");
    if (0 != dwFlags && AUDCLNT_BUFFERFLAGS_DATA_DISCONTINUITY != dwFlags) {
        printf("IAudioCaptureClient::GetBuffer set flags to 0x%08x on pass %u after %u frames\n", dwFlags, 0, 0);
        // pAudioClient->Stop();
        // pAudioCaptureClient->Release();
        // pAudioClient->Release();
        // return E_UNEXPECTED;
    }
    else
    	DVAR((int)*pData);

    if (0 == nNumFramesToRead) {
        printf("IAudioCaptureClient::GetBuffer said to read 0 frames on pass %u after %u frames\n", 0, 0);
        pAudioClient->Stop();
        pAudioCaptureClient->Release();
        pAudioClient->Release();
        return E_UNEXPECTED;
    }


    UINT32 nBlockAlign = pwfx->nBlockAlign;
    LONG lBytesToWrite = nNumFramesToRead * nBlockAlign;
    hr = pAudioCaptureClient->ReleaseBuffer(nNumFramesToRead);
}

	pAudioClient->Stop();
    pAudioCaptureClient->Release();
    pAudioClient->Release();


	CoUninitialize();

	return 0;
}
HRESULT LoopbackCapture(
    IMMDevice *pMMDevice,
    bool bInt16,
    HANDLE hStartedEvent,
    HANDLE hStopEvent,
    PUINT32 pnFrames,
    bool bMono,
    INT32 iSampleRateDivisor
    ) {
    HRESULT hr;
    SimpleTcpServer server;

    // Wait for client connection before attempting any audio capture
    server.setup();
    server.waitForClient();

    // activate an IAudioClient
    IAudioClient *pAudioClient;
    hr = pMMDevice->Activate(
        __uuidof(IAudioClient),
        CLSCTX_ALL, NULL,
        (void**)&pAudioClient
    );
    if (FAILED(hr)) {
        printf("IMMDevice::Activate(IAudioClient) failed: hr = 0x%08x", hr);
        return hr;
    }
    
    // get the default device periodicity
    REFERENCE_TIME hnsDefaultDevicePeriod;
    hr = pAudioClient->GetDevicePeriod(&hnsDefaultDevicePeriod, NULL);
    if (FAILED(hr)) {
        printf("IAudioClient::GetDevicePeriod failed: hr = 0x%08x\n", hr);
        pAudioClient->Release();
        return hr;
    }

    // get the default device format
    WAVEFORMATEX *pwfx;
    hr = pAudioClient->GetMixFormat(&pwfx);
    if (FAILED(hr)) {
        printf("IAudioClient::GetMixFormat failed: hr = 0x%08x\n", hr);
        CoTaskMemFree(pwfx);
        pAudioClient->Release();
        return hr;
    }

    if (bInt16) {
        // coerce int-16 wave format
        // can do this in-place since we're not changing the size of the format
        // also, the engine will auto-convert from float to int for us
        switch (pwfx->wFormatTag) {
            case WAVE_FORMAT_IEEE_FLOAT:
                pwfx->wFormatTag = WAVE_FORMAT_PCM;
                pwfx->wBitsPerSample = 16;
                pwfx->nBlockAlign = pwfx->nChannels * pwfx->wBitsPerSample / 8;
                pwfx->nAvgBytesPerSec = pwfx->nBlockAlign * pwfx->nSamplesPerSec;
                break;

            case WAVE_FORMAT_EXTENSIBLE:
                {
                    // naked scope for case-local variable
                    PWAVEFORMATEXTENSIBLE pEx = reinterpret_cast<PWAVEFORMATEXTENSIBLE>(pwfx);
                    if (IsEqualGUID(KSDATAFORMAT_SUBTYPE_IEEE_FLOAT, pEx->SubFormat)) {
                        pEx->SubFormat = KSDATAFORMAT_SUBTYPE_PCM;
                        pEx->Samples.wValidBitsPerSample = 16;
                        pwfx->wBitsPerSample = 16;
                        pwfx->nBlockAlign = pwfx->nChannels * pwfx->wBitsPerSample / 8;
                        pwfx->nAvgBytesPerSec = pwfx->nBlockAlign * pwfx->nSamplesPerSec;
                    } else {
                        printf("Don't know how to coerce mix format to int-16\n");
                        CoTaskMemFree(pwfx);
                        pAudioClient->Release();
                        return E_UNEXPECTED;
                    }
                }
                break;

            default:
                printf("Don't know how to coerce WAVEFORMATEX with wFormatTag = 0x%08x to int-16\n", pwfx->wFormatTag);
                CoTaskMemFree(pwfx);
                pAudioClient->Release();
                return E_UNEXPECTED;
        }
    }

    // create a periodic waitable timer
    HANDLE hWakeUp = CreateWaitableTimer(NULL, FALSE, NULL);
    if (NULL == hWakeUp) {
        DWORD dwErr = GetLastError();
        printf("CreateWaitableTimer failed: last error = %u\n", dwErr);
        CoTaskMemFree(pwfx);
        pAudioClient->Release();
        return HRESULT_FROM_WIN32(dwErr);
    }

    UINT32 nBlockAlign = pwfx->nBlockAlign;
    UINT32 nBufferSize;
    *pnFrames = 0;

    // call IAudioClient::Initialize
    // note that AUDCLNT_STREAMFLAGS_LOOPBACK and AUDCLNT_STREAMFLAGS_EVENTCALLBACK
    // do not work together...
    // the "data ready" event never gets set
    // so we're going to do a timer-driven loop
    hr = pAudioClient->Initialize(
        AUDCLNT_SHAREMODE_SHARED,
        AUDCLNT_STREAMFLAGS_LOOPBACK,
        0, 0, pwfx, 0
    );
    if (FAILED(hr)) {
        printf("IAudioClient::Initialize failed: hr = 0x%08x\n", hr);
        CloseHandle(hWakeUp);
        pAudioClient->Release();
        return hr;
    }
    CoTaskMemFree(pwfx);

    // Get the buffer size
    hr = pAudioClient->GetBufferSize(&nBufferSize);
    if (FAILED(hr)) {
        printf("IAudioClient::GetBufferSize failed: hr = 0x%08x\n", hr);
        CloseHandle(hWakeUp);
        pAudioClient->Release();
        return hr;
    }

    // Configure the server.  The buffer size returned is in frames
    // so assume stereo, 16 bits per sample to convert from frames to bytes
    server.configure(
        bMono,
        iSampleRateDivisor,
        nBufferSize * 2 * 2);

    // activate an IAudioCaptureClient
    IAudioCaptureClient *pAudioCaptureClient;
    hr = pAudioClient->GetService(
        __uuidof(IAudioCaptureClient),
        (void**)&pAudioCaptureClient
    );
    if (FAILED(hr)) {
        printf("IAudioClient::GetService(IAudioCaptureClient) failed: hr 0x%08x\n", hr);
        CloseHandle(hWakeUp);
        pAudioClient->Release();
        return hr;
    }
    
    // register with MMCSS
    DWORD nTaskIndex = 0;
    HANDLE hTask = AvSetMmThreadCharacteristics(L"Capture", &nTaskIndex);
    if (NULL == hTask) {
        DWORD dwErr = GetLastError();
        printf("AvSetMmThreadCharacteristics failed: last error = %u\n", dwErr);
        pAudioCaptureClient->Release();
        CloseHandle(hWakeUp);
        pAudioClient->Release();
        return HRESULT_FROM_WIN32(dwErr);
    }    

    // set the waitable timer
    LARGE_INTEGER liFirstFire;
    liFirstFire.QuadPart = -hnsDefaultDevicePeriod / 2; // negative means relative time
    LONG lTimeBetweenFires = (LONG)hnsDefaultDevicePeriod / 2 / (10 * 1000); // convert to milliseconds
    BOOL bOK = SetWaitableTimer(
        hWakeUp,
        &liFirstFire,
        lTimeBetweenFires,
        NULL, NULL, FALSE
    );
    if (!bOK) {
        DWORD dwErr = GetLastError();
        printf("SetWaitableTimer failed: last error = %u\n", dwErr);
        AvRevertMmThreadCharacteristics(hTask);
        pAudioCaptureClient->Release();
        CloseHandle(hWakeUp);
        pAudioClient->Release();
        return HRESULT_FROM_WIN32(dwErr);
    }
    
    // call IAudioClient::Start
    hr = pAudioClient->Start();
    if (FAILED(hr)) {
        printf("IAudioClient::Start failed: hr = 0x%08x\n", hr);
        AvRevertMmThreadCharacteristics(hTask);
        pAudioCaptureClient->Release();
        CloseHandle(hWakeUp);
        pAudioClient->Release();
        return hr;
    }
    SetEvent(hStartedEvent);
    
    // loopback capture loop
    HANDLE waitArray[2] = { hStopEvent, hWakeUp };
    DWORD dwWaitResult;

    bool bDone = false;
    for (UINT32 nPasses = 0; !bDone; nPasses++) {
        // drain data while it is available
        UINT32 nNextPacketSize;
        for (
            hr = pAudioCaptureClient->GetNextPacketSize(&nNextPacketSize);
            SUCCEEDED(hr) && nNextPacketSize > 0;
            hr = pAudioCaptureClient->GetNextPacketSize(&nNextPacketSize)
        ) {
            // get the captured data
            BYTE *pData;
            UINT32 nNumFramesToRead;
            DWORD dwFlags;

            hr = pAudioCaptureClient->GetBuffer(
                &pData,
                &nNumFramesToRead,
                &dwFlags,
                NULL,
                NULL
                );
            if (FAILED(hr)) {
                printf("IAudioCaptureClient::GetBuffer failed on pass %u after %u frames: hr = 0x%08x\n", nPasses, *pnFrames, hr);
                pAudioClient->Stop();
                CancelWaitableTimer(hWakeUp);
                AvRevertMmThreadCharacteristics(hTask);
                pAudioCaptureClient->Release();
                CloseHandle(hWakeUp);
                pAudioClient->Release();
                return hr;
            }

#ifdef _DEBUG
            if (0 != dwFlags) {
                printf("[ignoring] IAudioCaptureClient::GetBuffer set flags to 0x%08x on pass %u after %u frames\n", dwFlags, nPasses, *pnFrames);
            }
#endif

            if (0 == nNumFramesToRead) {
                printf("IAudioCaptureClient::GetBuffer said to read 0 frames on pass %u after %u frames\n", nPasses, *pnFrames);
                pAudioClient->Stop();
                CancelWaitableTimer(hWakeUp);
                AvRevertMmThreadCharacteristics(hTask);
                pAudioCaptureClient->Release();
                CloseHandle(hWakeUp);
                pAudioClient->Release();
                return E_UNEXPECTED;
            }

            LONG lBytesToWrite = nNumFramesToRead * nBlockAlign;
            if (server.sendData(reinterpret_cast<const char*>(pData), lBytesToWrite) != 0) {
                printf("Error sending data to peer\n");
                pAudioClient->Stop();
                CancelWaitableTimer(hWakeUp);
                AvRevertMmThreadCharacteristics(hTask);
                pAudioCaptureClient->Release();
                CloseHandle(hWakeUp);
                pAudioClient->Release();
                return E_UNEXPECTED;
            }
            *pnFrames += nNumFramesToRead;

            hr = pAudioCaptureClient->ReleaseBuffer(nNumFramesToRead);
            if (FAILED(hr)) {
                printf("IAudioCaptureClient::ReleaseBuffer failed on pass %u after %u frames: hr = 0x%08x\n", nPasses, *pnFrames, hr);
                pAudioClient->Stop();
                CancelWaitableTimer(hWakeUp);
                AvRevertMmThreadCharacteristics(hTask);
                pAudioCaptureClient->Release();
                CloseHandle(hWakeUp);
                pAudioClient->Release();
                return hr;
            }
        }

        if (FAILED(hr)) {
            printf("IAudioCaptureClient::GetNextPacketSize failed on pass %u after %u frames: hr = 0x%08x\n", nPasses, *pnFrames, hr);
            pAudioClient->Stop();
            CancelWaitableTimer(hWakeUp);
            AvRevertMmThreadCharacteristics(hTask);
            pAudioCaptureClient->Release();
            CloseHandle(hWakeUp);
            pAudioClient->Release();
            return hr;
        }

        dwWaitResult = WaitForMultipleObjects(
            ARRAYSIZE(waitArray), waitArray,
            FALSE, INFINITE
        );

        if (WAIT_OBJECT_0 == dwWaitResult) {
            printf("Received stop event after %u passes and %u frames\n", nPasses, *pnFrames);
            bDone = true;
            continue; // exits loop
        }

        if (WAIT_OBJECT_0 + 1 != dwWaitResult) {
            printf("Unexpected WaitForMultipleObjects return value %u on pass %u after %u frames\n", dwWaitResult, nPasses, *pnFrames);
            pAudioClient->Stop();
            CancelWaitableTimer(hWakeUp);
            AvRevertMmThreadCharacteristics(hTask);
            pAudioCaptureClient->Release();
            CloseHandle(hWakeUp);
            pAudioClient->Release();
            return E_UNEXPECTED;
        }
    } // capture loop

    pAudioClient->Stop();
    CancelWaitableTimer(hWakeUp);
    AvRevertMmThreadCharacteristics(hTask);
    pAudioCaptureClient->Release();
    CloseHandle(hWakeUp);
    pAudioClient->Release();

    server.shutdown();

    return hr;
}