XvQueryExtension − return version and release of extension #include<X11/extensions/Xvlib.h> , unsigned int *int XvQueryExtension(Display *dpy , unsigned int *p_revision , unsigned int *p_request_base , unsigned int *p_event_base ); unsigned int *p_error_base dpy Specifies the connection to the X server. p_version Pointer to where the current version number of the Xv video extension is written. p_revision Pointer to where the revision number of the Xv video extension is written. p_request_base Pointer to where the extension major request number is returned p_event_base Pointer to where the extension event base is returned p_error_base Pointer to where the extension error base is returned returns the version and release numbers for the Xv video extension currently loaded on the system. The extension major request number, event base, and error base are also returned. [Success] Returned if completed successfully. [XvBadExtension] Returned if the Xv video extension is not available for the named display.