The MCIWNDM_VALIDATEMEDIA message updates the starting and ending locations of the content, the current position in the content, and the trackbar according to the current time format. You can send this message explicitly or by using the MCIWndValidateMedia macro.
MCIWNDM_VALIDATEMEDIA
wParam = 0;
lParam = 0;
This message does not return a value.
Typically, you should not need to use this macro; however, if your application changes the time format of a device without using MCIWnd; the starting and ending locations of the content, as well as the trackbar, continue to use the old format. You can use this macro to update these values.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in vfw.h.
MCIWnd Window Class Overview, MCIWnd Messages, MCIWndValidateMedia