Manpages - XvQueryEncodings.3

XvQueryEncodings - 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);

dpy

Specifies the connection to the X server.

port

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

p_num_encodings

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

pp_encoding_info

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;

encoding_id

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

name

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

width,height

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

rate

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.

[Success]

Returned if *XvQueryEncodings*(3) completed successfully.

[XvBadExtension]

Returned if the Xv extension is unavailable.

[XvBadAlloc]

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

[XvBadPort]

Generated if the requested port does not exist.

*XvFreeEncodingInfo*(3)