Mp3 files encode their metadata (artist, song title, etc.) in ID3 tags.

Note: ID3v1 and ID3v2 are seperate tags formats.

This tag format is well documented at the site for the open source c/c++ id3lib library, which I strongly recommend over any other tag library.

MyID3 is a pure-Java library that can read & write ID3v1 and ID3v2 tags.

Although not yet version 1.0, MyID3 is working. I've tested it with a wide variety of mp3s.

It is Open Source; free as in freedom and free as in beer.

Full support for .m4a/.aac/.mpa files coming soon.

News: A MyID3 user has ported the previous version of the library to Android. Thanks, 砂井裏鍵(aka Romulus 仲明) !

Version 0.83 released December 3rd, 2008.

Binary: myid3.jar

Source: myid3-src.zip

Source distribution includes binary, source and this document. This project has three dependencies:

• Jakarta Regexp, and (tested up to version 5.2). Jakarta Regexp is available under the same license as MyID3: the ASF (Apache) License.
• Nanoxml, a lightweight XML parsing library. (tested up to version 5.2). Nanoxml is available under the zlib/libpng License. Note: Nanoxml is only neccesary if you use the included GUI test tool.
• I've recently open sourced the last dependency of this project, sharedlib.

MyID3 exposes two apis: a simplified interface, and a "raw" interface.

The Simple Interface hides the differences between the ID3v1 and ID3v2.

It maps values from both tags into a MusicMetadata object which has typed accessor methods for the following fields: Album, Artist, Comment, Compilation, Composer, Composer2, DurationSeconds, Genre, Producer, ProducerArtist, SongTitle, Year.

 
import org.cmc.music.myid3.*;
import org.cmc.music.common.MusicMetadata;

File src = ?;
MusicMetadataSet src_set = new MyID3().read(src); // read metadata

if (src_set == null) // perhaps no metadata
	...
	
Debug.debug("src_set", src_set); // dump all info.
Debug.debug("src_set", src_set.getArtist()); 

MusicMetadata metadata = src_set.getSimplified();
String artist = metadata.getArtist();  
String album = metadata.getAlbum();  
String song_title = metadata.getSongTitle(); 
Number track_number = metadata.getTrackNumber(); 

metadata.setArtist("Bob Marley");

File dst = ...
new MyID3().write(src, dst, src_set, metadata);  // write updated metadata

The Raw Interface exposes the differences between the ID3v1 and ID3v2, every frame, as well as the underlying bytes, etc.

 
import org.cmc.music.myid3.*;
import org.cmc.music.common.MusicMetadata;

File src = ?;
MusicMetadataSet src_set = new MyID3().read(src); // read metadata
String id3v1_artist = src_set.id3_v1_raw.values.getArtist();
String id3v2_artist = src_set.id3_v2_raw.values.getArtist();

byte id3v1_tag_bytes[] = src_set.id3_v1_raw.bytes; // tag bytes
byte id3v2_tag_bytes[] = src_set.id3_v2_raw.bytes; // tag bytes

Vector id3v2_frames = src_set.id3_v2_raw.frames; // 
if (id3v2_frames.size() > 1)
{
	MyID3v2Frame first_frame = (MyID3v2Frame) id3v2_frames
			.get(0);
	String frame_frame_id = first_frame.frame_id;
	byte frame_frame_bytes[] = first_frame.data_bytes;
}

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