int XvGetPortAttribute(Display *dpy, XvPortID port, Atom attribute, int p_value);
Specifies the connection to the X server.
Specifies the port, associated with the given display, for
which the attribute values are to be returned.
An atom that identifies the attribute to be queried by this
request. Control atoms are obtained using the XInternAtom
request with a string from the following table.
Pointer to the location where the attribute value is written on
returns the current value of the requested
port attribute in the integer pointed to by p_value.
The attribute is identified using an Atom that equates to the attribute name.
The XInternAtom request can be used with one of the strings
below to return a matching Atom.