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External Device Interfaces for DV Camcorders

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[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The WDM Video Capture filter exposes three interfaces for controlling a camcorder.

Label Value
IAMExtDevice The base interface for external device control.
IAMExtTransport Controls the VCR functions.
IAMTimecodeReader Reads timecode from the device.

 

Note

To use these interfaces with the MSDV camcorder driver, include the header file XPrtDefs.h in your project.

 

After you select a capture device and create an instance of the capture filter, query the filter for these interfaces. The following example declares a custom structure that holds the interface pointers, along with Boolean values that specify the availability of each interface:

struct _MyDevCap
{
    IAMExtDevice       *pDevice;
    IAMExtTransport    *pTransport;
    IAMTimecodeReader  *pTimecode;
    BOOL                bHasDevice;
    BOOL                bHasTransport;
    BOOL                bHasTimecode;
} MyDevCap;

HRESULT hr;
IBaseFilter *pDVCam;  // Pointer to the capture filter.

// Create an instance of the capture filter (not shown).

hr = pDVCam->QueryInterface(IID_IAMExtDevice, (void **)&MyDevCap.pDevice);
MyDevCap.bHasDevice = (SUCCEEDED(hr));

hr = pDVCam->QueryInterface(IID_IAMExtTransport, (void **)&MyDevCap.pTransport);
MyDevCap.bHasTransport = (SUCCEEDED(hr));

hr = pDVCam->QueryInterface(IID_IAMTimecodeReader, (void **)&MyDevCap.pTimecode);
MyDevCap.bHasTimecode = (SUCCEEDED(hr));

Controlling a DV Camcorder