capControlCallback callback function
The capControlCallback function is the callback function used for precision control to begin and end streaming capture. The name capControlCallback is a placeholder for the application-supplied function name.
Handle to the capture window associated with the callback function.
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.
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.
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.
Minimum supported client
|Windows 2000 Professional [desktop apps only]|
Minimum supported server
|Windows 2000 Server [desktop apps only]|