Waveform Capture: (2) Create a capture device object

You can create a capture device object by calling the DirectSoundCaptureCreate8 or DirectSoundFullDuplexCreate8 function. Both of these functions get a pointer to the IDirectSoundCapture8 interface.

The Lpcguid parameter of the directsoundcapturecreate or the Pcguidrenderdevice parameter of the DirectSoundFullDuplexCreate8 can be a GUID obtained by the enumeration, Or one of the following predefined GUIDs:

Guid	Description
Dsdevid_defaultcapture	The system's default sound capture device. You can also specify a device by passing a null pointer instead of a device GUID.
Dsdevid_defaultvoicecapture	The default sound communication device. Typically, this is a secondary device such as a USB headset with a microphone.

If there is currently no device driver, the call fails.

You can also use the CoCreateInstance function to create an object. This process is similar to creating a device object. The steps are as follows:

1. Initializing COM objects by calling the CoInitializeEx function at application startup

Code

HRESULT hr = CoInitializeEx(NULL, 0);
　　if (FAILED(hr))
　　{
　　　ErrorHandler(hr);　// Add error-handling here.
　　}

2. Create device objects by calling the CoCreateInstance method and the Idirectsound8::initialize method instead of using the DirectSoundCreate8 function

Code

LPDIRECTSOUND8 lpds;
　　hr = CoCreateInstance(&CLSID_DirectSound8,
　　　　　　　NULL,
　　　　　　　CLSCTX_INPROC_SERVER,
　　　　　　　IID_IDirectSound8,
　　　　　　　(LPVOID*) &lpds);
　　if (FAILED(hr))
　　{
　　　ErrorHandler(hr);　// Add error-handling here.
　　}

Clsid_directsound8 is the class identifier of the DirectSound driver object class, Iid_idirectsound8 is the interface identifier. The LPDS parameter receives a pointer to this interface.