.TH XvQueryEncodings 3 "libXv 1.0.12" "X Version 11" "libXv Functions"
.SH NAME
XvQueryEncodings \- return list of encodings for an adaptor
.\"
.SH SYNOPSIS
.B #include <X11/extensions/Xvlib.h>
.sp
.nf
.BI "int XvQueryEncodings(Display *" dpy ", XvPortID " port ","
.BI "                     unsigned int *" p_num_encodings ","
.BI "                     XvEncodingInfo **" pp_encoding_info ");"
.fi
.SH ARGUMENTS
.\"
.IP \fIdpy\fR 8
Specifies the connection to the X server.
.IP \fIport\fR 8
Specifies the port whose adaptor is to be queried for its list of encodings.
.IP \fIp_num_encodings\fR 8
A pointer to where the number of encodings supported
by the adaptor is written.
.IP \fIpp_encoding_info\fR 8
A pointer to where the list of returned encoding information is returned.
XvEncodingInfo has the following structure:
.EX

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

.EE
.IP \fIencoding_id\fR 8
Specifies the encoding-id of the encoding.  The encoding-id is used to
identify an encoding when a port's encoding attribute is changed.
.IP \fIname\fR 8
A pointer to a formatted string that identifies the encoding.  The string
has the format "\fItiming\fR-\fIsignaltype\fR".  For example "ntsc-composite".
.IP \fIwidth,height\fR 8
The width and height, in pixels, of the decoded video image.
.IP \fIrate\fR 8
The field rate of the decoded video.
.PP
The XvRational structure is used to specify a fractional number.
It has the following structure:
.EX

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

.EE
The \fInumerator\fP and \fIdenominator\fP fields specify the
appropriate parts of a fractional number.
.\"
.SH DESCRIPTION
.BR 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.
.SH RETURN VALUES
.IP [Success] 8
Returned if
.BR XvQueryEncodings (3)
completed successfully.
.IP [XvBadExtension] 8
Returned if the Xv extension is unavailable.
.IP [XvBadAlloc] 8
Returned if
.BR XvQueryEncodings (3)
failed to allocate memory to process the request.
.SH DIAGNOSTICS
.IP [XvBadPort] 8
Generated if the requested port does not exist.
.\"
.SH SEE ALSO
.\"
.BR XvFreeEncodingInfo (3)