ID3

ID3 is a metadata container most often used in conjunction with the MP3 audio file format. It allows information such as the title, artist, album, track number, and other information about the file to be stored in the file itself. ID3 is a metadata container most often used in conjunction with the MP3 audio file format. It allows information such as the title, artist, album, track number, and other information about the file to be stored in the file itself. ID3 is also specified by Apple as a timed metadata in HTTP Live Streaming, carried as a PID in the main transport stream or in separate audio TS. There are two unrelated versions of ID3: ID3v1 and ID3v2. ID3v1 takes the form of a 128-byte segment at the end of an MP3 file containing a fixed set of data fields. ID3v1.1 is a slight modification which adds a 'track number' field at the expense of a slight shortening of the 'comment' field. ID3v2 is structurally very different from ID3v1, consisting of an extensible set of 'frames' located at the start of the file, each with a frame identifier (a three- or four-byte string) and one piece of data. 83 types of frames are declared in the ID3v2.4 specification, and applications can also define their own types. There are standard frames for containing cover art, BPM, copyright and license, lyrics, and arbitrary text and URL data, as well as other things. Three versions of ID3v2 have been documented, each of which has extended the frame definitions. ID3 is a de facto standard for metadata in MP3 files; no standardization body was involved in its creation nor has such an organization given it a formal approval status. It competes with the APE tag in this arena. Lyrics3v1 and Lyrics3v2 were tag standards implemented before ID3v2, for adding lyrics to mp3 files. The difference with ID3v2 is that Lyrics3 is always on the end of a MP3 file, after the ID3v1 tag. The MP3 standard did not include a method for storing file metadata. In 1996 Eric Kemp had the idea to add a small chunk of data to the audio file, thus solving the problem. The method, now known as ID3v1, quickly became the de facto standard for storing metadata in MP3s. The ID3v1 tag occupies 128 bytes, beginning with the string TAG 128 bytes from the end of the file. The tag was placed at the end of the file to maintain compatibility with older media players. Some players would play a small burst of static when they read the tag, but most ignored it, and almost all modern players will correctly skip it. This tag allows 30 bytes each for the title, artist, album, and a 'comment', four bytes for the year, and a byte to identify the genre of the song from a predefined list of 80 values (Winamp later extended this list to 148 values). One improvement to ID3v1 was made by Michael Mutschler in 1997. Since the comment field was too small to write anything useful, he decided to trim it by two bytes and use those two bytes to store the track number. Such tags are referred to as ID3v1.1. Strings are either space- or zero-padded. Unset string entries are filled using an empty string. ID3v1 is 128 bytes long.