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Module Mad

module Mad: sig .. end

Functions for decoding mp3 files using the libmad.

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.

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.

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.