afQuery, afQueryLong, afQueryDouble, afQueryPointer - query the capabilities of
the Audio File Library
#include <audiofile.h>
AUpvlist afQuery (int querytype, int arg1, int arg2, int arg3, int arg4);
long afQueryLong (int querytype, int arg1, int arg2, int arg3, int arg4);
double afQueryDouble (int querytype, int arg1, int arg2, int arg3,
int arg4);
void *afQueryPointer (int querytype, int arg1, int arg2, int arg3,
int arg4);
querytype can be one of the following:
• AF_QUERYTYPE_FILEFMT
• AF_QUERYTYPE_INST
• AF_QUERYTYPE_INSTPARAM
• AF_QUERYTYPE_COMPRESSION
• AF_QUERYTYPE_COMPRESSIONPARAM
• AF_QUERYTYPE_MISC
• AF_QUERYTYPE_MARK
• AF_QUERYTYPE_LOOP
arg1, arg2, arg3, and arg4 are integer
selectors whose meaning depends upon querytype.
Upon success, afQuery will return a non-null AUpvlist value. Upon failure,
afQuery will return null while afQueryLong and afQueryDouble will return -1
and afQueryPointer will return null.
Pointers representing character strings are owned by the Audio
File Library and must not be freed; all other pointer values must be freed
by the caller.
For AF_QUERYTYPE_FILEFMT, the following selectors are valid values for
arg1:
AF_QUERY_LABEL
Request a short label string for the format (e.g.,
"aiff").
AF_QUERY_NAME
Request a short name for the format (e.g., "MS RIFF
WAVE").
AF_QUERY_DESC
Request a descriptive name for the format (e.g.,
"Audio Interchange File Format").
AF_QUERY_IMPLEMENTED
Request a boolean value indicating whether the format is
implemented for reading and writing in the Audio File Library.
AF_QUERY_ID_COUNT
Request the total number of formats implemented.
AF_QUERY_IDS
Request an integer array of the id token values of all
implemented file formats.
AF_QUERY_COMPRESSION_TYPES
Used with the selector AF_QUERY_VALUE_COUNT in
arg2, this will return a long integer containing the number of
compression schemes available for use within the format specified in
arg3. Used with selector AF_QUERY_VALUES, it returns a pointer to an
integer array containing the compression id values of the compression schemes
supported by the format specified in arg3.
AF_QUERY_SAMPLE_FORMATS
Used with the selector AF_QUERY_DEFAULT in arg2,
this will return the default sample format for the file format specified in
arg3.
AF_QUERY_SAMPLE_SIZES
Used with selector AF_QUERY_DEFAULT in arg2, this
will return the default sample width for the file format specified in
arg3.
For AF_QUERYTYPE_INST, the following selectors are valid for
arg1:
AF_QUERY_SUPPORTED
Request a boolean value indicating whether the file
format in arg2 supports instruments.
AF_QUERY_MAX_NUMBER
Request an integer value indicating the maximum number of
instruments supported by the file format in arg2.
For AF_QUERYTYPE_INSTPARAM, the following selectors are valid for
arg1:
AF_QUERY_SUPPORTED
Request a boolean value indicating whether the file
format in arg2 supports instrument parameters.
AF_QUERY_ID_COUNT
Request an integer value indicating the number of
instrument parameters supported by the file format in arg2.
AF_QUERY_IDS
Request an integer array containing the instrument
parameter values for the file format in arg2.
AF_QUERY_TYPE
For the file format in arg2, request the type of
the instrument parameter in arg3.
AF_QUERY_NAME
For the file format in arg2, request the name of
the instrument parameter in arg3.
AF_QUERY_DEFAULT
For the file format in arg2, request the default
value of the instrument parameter in arg3.
afQuery can produce the following errors:
AF_BAD_QUERYTYPE
The query type is unsupported.
AF_BAD_QUERY
The arguments to the query are bad.
Michael Pruett <michael@68k.org>
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