windows下使用CoreAudio采集音频

最近看obs的音频采集，发现它在采集音频时用到了两个方法：默认音频设备时采用CoreAudio、指定音频设备时采用DirectShow

对windows下的CoreAudio技术不是太熟，于是就认真学了一下。

参考微软官方文档：https://docs.microsoft.com/zh-cn/windows/desktop/CoreAudio/capturing-a-stream

//-----------------------------------------------------------
// Record an audio stream from the default audio capture
// device. The RecordAudioStream function allocates a shared
// buffer big enough to hold one second of PCM audio data.
// The function uses this buffer to stream data from the
// capture device. The main loop runs every 1/2 second.
//-----------------------------------------------------------
#include 
#include 
#include 
#include 
#include 
#include 
// REFERENCE_TIME time units per second and per millisecond
#define REFTIMES_PER_SEC  10000000
#define REFTIMES_PER_MILLISEC  10000

#define EXIT_ON_ERROR(hres)  \
              if (FAILED(hres)) { goto Exit; }
#define SAFE_RELEASE(punk)  \
              if ((punk) != NULL)  \
                { (punk)->Release(); (punk) = NULL; }

const CLSID CLSID_MMDeviceEnumerator = __uuidof(MMDeviceEnumerator);
const IID IID_IMMDeviceEnumerator = __uuidof(IMMDeviceEnumerator);
const IID IID_IAudioClient = __uuidof(IAudioClient);
const IID IID_IAudioCaptureClient = __uuidof(IAudioCaptureClient);

HRESULT RecordAudioStream()
{
	HRESULT hr;
	REFERENCE_TIME hnsRequestedDuration = REFTIMES_PER_SEC;
	REFERENCE_TIME hnsActualDuration;
	UINT32 bufferFrameCount;
	UINT32 numFramesAvailable;
	IMMDeviceEnumerator *pEnumerator = NULL;
	IMMDevice *pDevice = NULL;
	IAudioClient *pAudioClient = NULL;
	IAudioCaptureClient *pCaptureClient = NULL;
	WAVEFORMATEX *pwfx = NULL;
	UINT32 packetLength = 0;
	BOOL bDone = FALSE;
	BYTE *pData;
	DWORD flags;
	hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);
	hr = CoCreateInstance(CLSID_MMDeviceEnumerator, NULL,CLSCTX_ALL, IID_IMMDeviceEnumerator,(void**)&pEnumerator);
	EXIT_ON_ERROR(hr)
	hr = pEnumerator->GetDefaultAudioEndpoint(eCapture, eConsole, &pDevice);
	EXIT_ON_ERROR(hr)
	hr = pDevice->Activate(IID_IAudioClient, CLSCTX_ALL,NULL, (void**)&pAudioClient);
	EXIT_ON_ERROR(hr)
    hr = pAudioClient->GetMixFormat(&pwfx);
	EXIT_ON_ERROR(hr)
	hr = pAudioClient->Initialize(AUDCLNT_SHAREMODE_SHARED,0,hnsRequestedDuration,0,pwfx,NULL);
	EXIT_ON_ERROR(hr)
	// Get the size of the allocated buffer.
	hr = pAudioClient->GetBufferSize(&bufferFrameCount);
	EXIT_ON_ERROR(hr)
	hr = pAudioClient->GetService(IID_IAudioCaptureClient,(void**)&pCaptureClient);
	EXIT_ON_ERROR(hr)
	// Notify the audio sink which format to use.
	//hr = pMySink->SetFormat(pwfx);
	EXIT_ON_ERROR(hr)
	// Calculate the actual duration of the allocated buffer.
	hnsActualDuration = (double)REFTIMES_PER_SEC *bufferFrameCount / pwfx->nSamplesPerSec;
	hr = pAudioClient->Start();  // Start recording.
	EXIT_ON_ERROR(hr)
	// Each loop fills about half of the shared buffer.
	while (bDone == FALSE)
	{
		// Sleep for half the buffer duration.
		Sleep(hnsActualDuration / REFTIMES_PER_MILLISEC / 2);
		hr = pCaptureClient->GetNextPacketSize(&packetLength);
		EXIT_ON_ERROR(hr)
		while (packetLength != 0)
		{
			// Get the available data in the shared buffer.
			hr = pCaptureClient->GetBuffer(&pData,&numFramesAvailable,&flags, NULL, NULL);
			EXIT_ON_ERROR(hr)
			if (flags & AUDCLNT_BUFFERFLAGS_SILENT)
			{
				pData = NULL;  // Tell CopyData to write silence.
			}
			// Copy the available capture data to the audio sink.
			//hr = pMySink->CopyData(
			//	pData, numFramesAvailable, &bDone);
			printf("size=%d\n", numFramesAvailable);
			EXIT_ON_ERROR(hr)
			hr = pCaptureClient->ReleaseBuffer(numFramesAvailable);
			EXIT_ON_ERROR(hr)
			hr = pCaptureClient->GetNextPacketSize(&packetLength);
			EXIT_ON_ERROR(hr)
		}
	}
	hr = pAudioClient->Stop();  // Stop recording.
	EXIT_ON_ERROR(hr)

Exit:
	CoTaskMemFree(pwfx);
	SAFE_RELEASE(pEnumerator)
	SAFE_RELEASE(pDevice)
	SAFE_RELEASE(pAudioClient)
	SAFE_RELEASE(pCaptureClient)
	return hr;
}

int main()
{
	RecordAudioStream();
	return 0;
}