XvQueryEncodings - return list of encodings for an adaptor
#include <X11/extensions/Xvlib.h>

 "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: .EX 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: .EX typedef struct { int numerator; int denominator; } XvRational; The numerator and denominator fields specify the appropriate parts of a fractional number.

XvQueryEncodings(__libmansuffix__) 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 if XvQueryEncodings(__libmansuffix__) completed successfully. Returned if the Xv extension is unavailable. Returned if XvQueryEncodings(__libmansuffix__) failed to allocate memory to process the request. Generated if the requested port does not exist.

XvFreeEncodingInfo(__libmansuffix__)