WM_CAP_SET_CALLBACK_YIELD
The
WM_CAP_SET_CALLBACK_YIELD message sets a callback function in the application.
AVICap calls this procedure when the capture window yields during streaming
capture. You can send this message explicitly or by using the capSetCallbackOnYield macro.
WM_CAP_SET_CALLBACK_YIELD
wParam = (WPARAM) 0;
lParam = (LPARAM) (LPVOID) (fpProc);
Parameters
fpProc
Address of
the yield callback function. Specify NULL for this parameter to disable a
previously installed yield callback function.
Return Values
Returns TRUE
if successful or FALSE if streaming capture or a single-frame capture session
is in progress.
Remarks
Applications
can optionally set a yield callback function. The yield callback function is
called at least once for each video frame captured during streaming capture. If
a yield callback function is installed, it will be called regardless of the state
of the fYield member of the CAPTUREPARMS structure.
If the yield
callback function is used, it must be installed before starting the capture
session and it must remain enabled for the duration of the session. It can be
disabled after streaming capture ends.
Applications
typically perform some type of message processing in the callback function
consisting of a PeekMessage,
TranslateMessage,
DispatchMessage
loop, as in the message loop of a WinMain function. The yield callback function must also
filter and remove messages that can cause reentrancy problems.
An
application typically returns TRUE in the yield procedure to continue streaming
capture. If a yield callback function returns FALSE, the capture window stops
the capture process.
See Also