ltmmCaptureCtrl.CaptureDIB is slow on Vista

Some customers have experienced speed problems with ltmmCaptureCtrl.CaptureDIB in Vista.  The exact same code will execute almost instantaneously on XP machines but on Vista it will take 1-2 seconds.  This is because Vista takes longer to build the DirectShow graphs and there's not much we can do about that.

Internally, CaptureDIB builds a capture graph, runs it, waits for a still image, stops the graph, rebuilds the preview graph, and runs it.  Therefore each time you call CaptureDIB you must stop and reconstruct two graphs.

As an alternative, you can call StartCapture(ltmmcapture_Mode_Still) which will bulid the capture graph.  Then, each time you want to capture a DIB, call GetStillDIB which will allow the graph to continue running unlike the behavior of CaptureDIB.

Whenever you close the application or change any settings (capture device, filters on the main graph, etc.) you should call StopCapture and then StartCapture again if necessary.