XvQueryEncodings - Man Page

return list of encodings for an adaptor


#include <X11/extensions/Xvlib.h>

int XvQueryEncodings(Display *dpy, XvPortID port,
                     unsigned int *p_num_encodings,
                     XvEncodingInfo **pp_encoding_info);



Specifies the connection to the X server.


Specifies the port whose adaptor is to be queried for its list of encodings.


A pointer to where the number of encodings supported by the adaptor is written.


A pointer to where the list of returned encoding information is returned. XvEncodingInfo has the following structure:

    typedef struct {
      XvEncodingID encoding_id;
      char *name;
      unsigned long width;
      unsigned long height;
      XvRational rate;
      unsigned long num_encodings;
    } XvEncodingInfo;

Specifies the encoding-id of the encoding.  The encoding-id is used to identify an encoding when a port's encoding attribute is changed.


A pointer to a formatted string that identifies the encoding.  The string has the format "timing-signaltype".  For example "ntsc-composite".


The width and height, in pixels, of the decoded video image.


The field rate of the decoded video.

The XvRational structure is used to specify a fractional number. It has the following structure:

    typedef struct {
      int numerator;
      int denominator;
    } XvRational;

The numerator and denominator fields specify the appropriate parts of a fractional number.


XvQueryEncodings(3) returns encoding information about an adaptor.  Each encoding is described by the XvEncodingInfo structure described above.  The encodings are identified by an encoding-id, which can be used to set or get the encoding attribute of a port.

Return Values


Returned if XvQueryEncodings(3) completed successfully.


Returned if the Xv extension is unavailable.


Returned if XvQueryEncodings(3) failed to allocate memory to process the request.



Generated if the requested port does not exist.

See Also


Referenced By

Xv(3), XvFreeEncodingInfo(3).

libXv 1.0.12 X Version 11 libXv Functions