XvUngrabPort man page
XvUngrabPort — release port grabbed for video operation
int XvUngrabPort(Display *dpy, XvPortID port, Time time);
Specifies the connection to the X server.
Specifies the port to be released. If the port had not been previously grabbed, the request is ignored.
Specifies the request timestamp.
releases a grabbed port. If time specifies a time before the last XvGrabPort(3) was executed, the request is ignored.
Returned if XvUngrabPort(3) completed successfully.
Returned if the Xv extension is unavailable.
Returned if XvUngrabPort(3) failed to allocate memory to process the request.
Generated if the requested port does not exist.