capControlCallback
The capControlCallback
function is the callback function used for precision control to begin and end
streaming capture. The capControlCallback callback function is a
placeholder for the application-supplied function name.
LRESULT CALLBACK capControlCallback(
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HWND hWnd, |
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int nState |
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); |
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Parameters
hWnd
Handle of the
capture window associated with the callback function.
nState
Current state
of the capture operation. The CONTROLCALLBACK_PREROLL value is sent initially
to enable prerolling of the video sources and to return control to the capture
application at the exact moment recording is to begin. The
CONTROLCALLBACK_CAPTURING value is sent once per captured frame to indicate
that streaming capture is in progress and to enable the application to end
capture.
Return Values
When nState
is set to CONTROLCALLBACK_PREROLL, this callback function must return TRUE to
start capture or FALSE to abort it. When nState is set to
CONTROLCALLBACK_CAPTURING, this callback function must return TRUE to continue
capture or FALSE to end it.
Remarks
The first
message sent to the callback procedure sets the nState parameter to
CONTROLCALLBACK_PREROLL after allocating all buffers and all other capture
preparations are complete.