20.3.2 Parser Objects

Parser objects (returned by createparser()) have the following methods:

addcallback( type, func, arg)

Adds a callback for the parser. The parser has callbacks for eight different types of data in the digital audio data stream. Constants for these types are defined at the cd module level (see above). The callback is called as follows:

func(arg, type,
data)

, where arg is the user supplied argument, type is the particular type of callback, and data is the data returned for this type of callback. The type of the data depends on the type of callback as follows:

Type	Value
`audio`	String which can be passed unmodified to `al.writesamps()`.
`pnum`	Integer giving the program (track) number.
`index`	Integer giving the index number.
`ptime`	Tuple consisting of the program time in minutes, seconds, and frames.
`atime`	Tuple consisting of the absolute time in minutes, seconds, and frames.
`catalog`	String of 13 characters, giving the catalog number of the CD.
`ident`	String of 12 characters, giving the ISRC identification number of the recording. The string consists of two characters country code, three characters owner code, two characters giving the year, and five characters giving a serial number.
`control`	Integer giving the control bits from the CD subcode data

deleteparser( )

Deletes the parser and frees the memory it was using. The object should not be used after this call. This call is done automatically when the last reference to the object is removed.

parseframe( frame)

Parses one or more frames of digital audio data from a CD such as returned by readda(). It determines which subcodes are present in the data. If these subcodes have changed since the last frame, then parseframe() executes a callback of the appropriate type passing to it the subcode data found in the frame. Unlike the C function, more than one frame of digital audio data can be passed to this method.

removecallback( type)

Removes the callback for the given type.

resetparser( )

Resets the fields of the parser used for tracking subcodes to an initial state. resetparser() should be called after the disc has been changed.

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