XvPortNotify - event generated when port attributes change
#include <X11/extensions/Xvlib.h>
     typedef union {
       int type;
       XvVideoNotifyEvent xvvideo;
       XvPortNotifyEvent xvport;
       long pad[24];
     } XvEvent;
     typedef struct {
       int type;
       unsigned long serial;
       Bool send_event;
       Display *display;
       XvPortID port_id;
       Time time;
       Atom attribute;
       long value;
     } XvPortNotifyEvent;
  - type
- Specifies the type of event: XvPortNotify.
- serial
- Number of the last request processed by the server.
- send_event
- True if the event was generated by a SendEvent request.
- display
- A pointer to the display the event was read from.
- port_id
- The port whose attribute has changed.
- attribute
- An atom specifying the attribute that changed.
- value
- The new value of the attribute.
XvPortNotify events are generated when a port attribute is set using the
  XvSetPortAttribute(3) function.
XvSetPortAttribute(3), XvGetPortAttribute(3),
  XvSelectPortNotify(3).