XvQueryEncodings(3)

Name
XvQueryEncodings - return list of encodings for an adaptor

Syntax
#include <X11/extensions/Xvlib.h>

XvQueryEncodings(dpy, port, p_num_encodings, pp_encoding_info)

register Display *dpy;
XvPortID port;
unsigned long *p_num_encodings;
XvEncodingInfo **pp_encoding_info;

Arguments

*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.

Description
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.

Returned Values

[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.

Diagnostics

[XvBadPort]
    Generated if the requested port does not exist.

See Also
XvFreeEncodingInfo(3)