XvQueryEncodings

Section: libXv Functions (3)
Updated: libXv 1.0.5
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NAME

XvQueryEncodings - return list of encodings for an adaptor

SYNOPSIS

#include <X11/extensions/Xvlib.h>

int XvQueryEncodings(Display *dpy, XvPortID port,
                     unsigned int *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.

RETURN 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.