Get the event/alarm subscription parameters.
BOOL NET_DVR_GetAlarmSubscribe( LONG lAlarmHandle, char *pData, DWORD dwDataLen );
[IN] Value returned by NET_DVR_SetupAlarmChan_V50
[OUT] Pointer to data buffer, see details in XML_SubscribeEvent
[IN] Size of data buffer, unit: byte, it cannot be 0.
Return TRUE for success, and return FALSE for failure.
If FALSE is returned, you can call NET_DVR_GetLastError to get the error code.