mp3hash 0.0.1

Music file hasher

# mp3hash

Hashes music files ignoring meta-data.

Useful to detect the same song in different tagged files.

# Use

Similarly to `sha1sum` or `md5sum`, it takes one or more files and returns the hashes, in this way:

$ ./mp3hash *.mp3
6611bc5b01a2fc6a6386a871e8c51f86e1f12b33 13_Hotel-California-(Gipsy-Kings).mp3
6611bc5b01a2fc6a6386a871e8c51f86e1f12b33 14_Hotel-California-(Gipsy-Kings).mp3

It returns the same hash number, even though the tags are different, and so their regular hashes:

$ sha1sum *.mp3
6a1d5f8317add10e205ae30174630b47645fb5b4 13_Hotel-California-(Gipsy-Kings).mp3
c28d6976114d31df3366d9935eb0bedd36cf1f0b 14_Hotel-California-(Gipsy-Kings).mp3

The hash it's made strictly using the music data in the file, by calculating the tags sizes and
omitting them.

The default hashing algorithm is `sha-1`, but any algorithm can be used as long it's supported by
the Python's `hashlib` module. A complete list of all available hashing algorithms can be obtained
by calling the program with the `--list-algorithms`.

$ ./mp3hash --list-algorithms
md5
sha1
sha224
sha256
sha384
sha512

./mp3hash --algorithm md5
ac0fdd89454528d3fbdb19942a2e6653 13_Hotel-California-(Gipsy-Kings).mp3
ac0fdd89454528d3fbdb19942a2e6653 14_Hotel-California-(Gipsy-Kings).mp3

# Install

It doesn't have any dependences besides `python2.6+` so you should be able to run the script
straight.

# Technical details

Supported and ignored meta-data tags are: id3v1, id3v2 both in their simple and indexed forms


## About id3v1

- id3v1 is 128 bytes at the end of the file starting with 'TAG'
- id3v1 extended is 227 bytes before regular id3v1 tag starting with 'TAG+'

total size: 128 + (227 if extended)

## About id3v2

- id3v2 header have the following fields alog the 10 first bytes in the file
- byte 5 holds flags. 6th bit indicates extended tag
- bytes 6-10 are the tag size (not counting header)

- id3v2 extended has a 10 bytes header after the regular id3v2
- bytes 1-4 are the tag size (not counting header nor padding)
- bytes 5-6 holds some flags. Leftmost bit indicates CRC presence
- bytes 6-10 are the tag padding size (extra blank size within tag)

total size: 10 + tagsize + (10 + etagsize + padding if extended)

Based on id3v1 wikipedia docs: http://en.wikipedia.org/wiki/ID3
Based on id3v2 docs: http://www.id3.org/id3v2.3.0