For MP3 software Developers:

M3U files can hold MP3 files inside as an album file, called M3A

There is a file format used for Album files, ALBW 
This is free to extract files, but not free to create. 

Having M3A files do the same makes the format open and free to use by anyone.
M3A format does not attempt to re-invent the wheel, it uses existing M3U format known
to any mp3 software devlopers already, with a small addition.

Using the M3U file with file names listed as normal.
An additonal 2 entries are used
#EXTBYT: 
#EXTBIN: 

The size of the file to be inserted is preceeded by EXTBYT as follows

#EXTBYT:510000 
filename1.mp3 
#EXTBYT:702500 
filename2.mp3 

All file name entries are preceeded by #EXTBYT: values of each file 

Following all entries the actual files are inserted after
#EXTBIN: 

To be precise, #EXTBIN: plus CR+LF is the 0 offset for the first file.
All mp3 files are joined and inserted as is after that point.

To extract file from an M3A you have the file size of each file in #EXTBYT: size value. 
Each additional file #EXTBYT: is summed to find the end position of the preceeding
file to the one you wish to extract. 

Extracted files are created using filenames and #EXTBYT: as file size.

This means all files are added to M3A without modification and there is no tag in the M3A itself that can be modified corrupting the Album file. 

The player can still read m3a part to find the content. 

Addional m3u/m3a formating can add Album descriptions to it. 
#EXTINF:seconds, track- artist 
or 
#EXTALB: 
#EXTART: 
(These are existing m3u values that some mp3 players support already.)

JukeBox Decoder will currently create M3A files and view and extract mp3 files from M3A. 

JukeBox Decoder will treat the file as M3A playing same filenames of files listed in it, if those files already exist in the same folder as an M3A file just the same as a normal M3U, if there are no external copies it will then allow extraction of those tracks from the M3A.

The m3a file will play as one continuous mp3 if renamed to mp3.

There is a seperate stand alone program m3aExtract limited to view tracks in an M3A file and extract them in the case you dont have JukeBox Decoder installed.

Any programs can use the #EXTBIN: and #EXTBYT: to create Album files, read them and extract contents. 

Additonal optional entries are 
#EXTM3U 
#EXTM3A 
These simply indicate the other EXT entries are present or explicit naming of the content
and placed in the first line of the file.. 

Feel free to distribute this document.

www.mp3software.com.au/m3a-fmt.txt
© Copyright BirdCage Software © 2002-2003
The creator retains copyright to this document only and makes no other claims to m3a.