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4/8/2010

Some cameras can produce a still image separate from the capture stream, and often the still image is of higher quality than the images produced by the capture stream. The camera may have a button that acts as a hardware trigger, or it may support software triggering. A camera that supports still images will expose a still image pin, which is pin category PIN_CATEGORY_STILL (see Pin Property Set).

To trigger the still pin, use the IAMVideoControl::SetModemethod when the graph is running, as shown in the following code.

Copy Code 
pControl->Run(); // Run the graph.
IAMVideoControl *pAMVidControl = NULL;
hr = pCap->QueryInterface(IID_IAMVideoControl,
(void**)&pAMVidControl);
if (SUCCEEDED(hr))
{
	// Find the still pin.
	IPin *pPin = 0;
	hr = pBuild->FindPin(pCap, PINDIR_OUTPUT,
&PIN_CATEGORY_STILL, 0,
		FALSE, 0, &pPin);
	if (SUCCEEDED(hr))
	{
		hr = pAMVidControl->SetMode(pPin,
VideoControlFlag_Trigger);
		pPin->Release();
}
	pAMVidControl->Release();
}

Query the capture filter for an IAMVideoControl interface. If the interface is supported, get a pointer to the still pin's IPin Interfaceby calling the ICaptureGraphBuilder2::FindPinmethod, as shown in the previous example.

Note:
Depending on the camera, you might need to render the capture pin (PIN_CATEGORY_CAPTURE) before the still pin will connect.

See Also