Copyright (c) 2013, Mark VandenBrink. All rights reserved.

A pure Lisp implementation for reading MPEG-4 audio and MPEG-3 audio tags and audio information.

**Mostly complete.  Your mileage may vary. Most definitely, NOT portable.  Heavily dependent on Clozure CCL.**

Note: There a lot of good (some great) audio file resources out there.  Here are a few of them:

* [l-smash](http://code.google.com/p/l-smash/)
* [taglib](http://taglib.github.io/)
* [mplayer](http://www.mplayerhq.hu)
* [eyeD3](http://eyed3.nicfit.net/) 
* [The MP4 Book](http://www.amazon.com/gp/search?index=books&linkCode=qs&keywords=0130616214) I actually didn't order this until well into writing this code.   What a maroon.

Sample invocations and output:

````
(let (foo)
    (unwind-protect
        (setf foo (parse-mp4-file "01 Keep Yourself Alive.m4a"))
    (when foo (stream-close foo)))    ; make sure underlying open file is closed

	(mp4-tag:show-tags foo))
````

Yields:

```
01 Keep Yourself Alive.m4a
sample rate: 44100.0 Hz, # channels: 2, bits-per-sample: 16, max bit-rate: 314 Kbps, avg bit-rate: 256 Kbps, duration: 4:03
    album: Queen I
    album-artist: Queen
    artist: Queen
    compilation: no
    disk: (1 1)
    genre: 80 (Hard Rock)
    title: Keep Yourself Alive
    track: (1 11)
    year: 1973
```

The show-tags methods also have a "raw" capability.  Example:

```
(let (foo)
    (unwind-protect
        (setf foo (parse-mp3-file "Queen/At the BBC/06 Great King Rat.mp3"))
    (when foo (stream-close foo)))    ; make sure underlying open file is closed

	(mp3-tag:show-tags foo :raw t))
```

Yields:

```
Queen/At the BBC/06 Great King Rat.mp3: MPEG 1, Layer III, VBR, sample rate: 44,100 Hz, bit rate: 128 Kbps, duration: 5:60
Header: version/revision: 3/0, flags: 0x00: 0/0/0/0, size = 11,899 bytes; No extended header; No V21 tag
    Frames[9]:
        frame-text-info: flags: 0x0000: 0/0/0/0/0/0, offset: 0, version = 3, id: TIT2, len: 15, NIL, encoding = 0, info = <Great King Rat>
        frame-text-info: flags: 0x0000: 0/0/0/0/0/0, offset: 25, version = 3, id: TPE1, len: 6, NIL, encoding = 0, info = <Queen>
        frame-text-info: flags: 0x0000: 0/0/0/0/0/0, offset: 41, version = 3, id: TPE2, len: 6, NIL, encoding = 0, info = <Queen>
        frame-text-info: flags: 0x0000: 0/0/0/0/0/0, offset: 57, version = 3, id: TALB, len: 11, NIL, encoding = 0, info = <At the BBC>
        frame-text-info: flags: 0x0000: 0/0/0/0/0/0, offset: 78, version = 3, id: TRCK, len: 4, NIL, encoding = 0, info = <6/8>
        frame-text-info: flags: 0x0000: 0/0/0/0/0/0, offset: 92, version = 3, id: TPOS, len: 4, NIL, encoding = 0, info = <1/1>
        frame-text-info: flags: 0x0000: 0/0/0/0/0/0, offset: 106, version = 3, id: TYER, len: 5, NIL, encoding = 0, info = <1995>
        frame-text-info: flags: 0x0000: 0/0/0/0/0/0, offset: 121, version = 3, id: TCON, len: 5, NIL, encoding = 0, info = <(79)>
        frame-txxx: flags: 0x0000: 0/0/0/0/0/0, offset: 136, version = 3, id: TXXX, len: 33, NIL, <Tagging time/2013-08-08T16:38:38>
```