Module Mad

module Mad: sig .. end

Functions for decoding mp3 files using the libmad.

Author(s): Samuel Mimram

Exceptions

exception Mad_error of string

An error occured with libmad.

exception Read_error of string

An error occured while reading a file.

exception End_of_stream

The end of the mp3 stream was reached.

exception Openfile_error of string

Could not open a file.

exception Closefile_error of string

Could not close a file.

Decoding files

type mad_file

An mp3 file opened for decoding.

type mpeg_layer =

`\|`	`Layer_I`
`\|`	`Layer_II`
`\|`	`Layer_III`

type emphasis =

`\|`	`None`
`\|`	`MS_50_15`
`\|`	`CCITT_J_17`
`\|`	`Reserved`

type channel_mode =

`\|`	`Single_channel`
`\|`	`Dual_channel`
`\|`	`Joint_stereo`
`\|`	`Stereo`

type frame_format = {

	`layer : mpeg_layer;`
	`mode : channel_mode;`
	`emphasis : emphasis;`
	`bitrate : int;`
	`samplerate : int;`
	`channels : int;`
	`samples_per_channel : int;`
	`original : bool;`
	`copyright : bool;`
	`private_bit : bool;`

}

val openfile : string -> mad_file

Open an mp3 file.

Raises Openfile_error if an error occured while trying to open the file.

val openstream : (int -> string * int) -> mad_file

openstream read_func opens a stream where read_func n should be a function which returns n bytes of data or less, the second component of the result being the number of bytes to read in the fist component.

val skip_id3tags : read:(int -> string * int) -> seek:(int -> int) -> tell:(unit -> int) -> unit

Skip ID3 tags that may be present at the beginning of a stream. This function may be used to a mp3 file opened using openstream. ID3 tags are always skipped when using openfile.

seek is a callback to seek to an absolute position on the encoded data, and tell a callback to fetch the current position. read is the reading callback.

val close : mad_file -> unit

Close an mp3 file previously opened with openfile.

Raises Closefile_error if an error occured while trying to close the file.

val get_current_position : mad_file -> int

Get the current position (in bytes) of the decoder in the mp3 file which should have been opened with openfile.

type time_unit =

`\|`	`Hours`
`\|`	`Minutes`
`\|`	`Seconds`
`\|`	`Deciseconds`
`\|`	`Centiseconds`
`\|`	`Milliseconds`

val get_current_time : mad_file -> time_unit -> int

Get the current time position (in the given unit) of the decoder.

val decode_frame : mad_file -> string

Decode an mp3 frame. Returned data in interleaved when there are two channels, and mono data when there is only one.

val decode_frame_float : mad_file -> float array array

Decode an mp3 frame.

val skip_frame : mad_file -> unit

Skip one frame. The current time/position is updated but the frame is not decoded.

val get_frame_format : mad_file -> frame_format

val get_output_format : mad_file -> int * int * int

val duration : string -> float

Compute the duration of a file, in seconds. Never raises any exception, but returns 0. in case of error.