tag/README.md

# MP3/MP4/OGG/FLAC metadata parsing library
[![Build Status](https://travis-ci.org/dhowden/tag.svg?branch=master)](https://travis-ci.org/dhowden/tag)
[![GoDoc](https://godoc.org/github.com/dhowden/tag?status.svg)](https://godoc.org/github.com/dhowden/tag)

This package provides MP3 (ID3v1,2.{2,3,4}) and MP4 (ACC, M4A, ALAC), OGG and FLAC metadata detection, parsing and artwork extraction.

Detect and parse tag metadata from an `io.ReadSeeker` (i.e. an `*os.File`):

```go
m, err := tag.ReadFrom(f)
if err != nil {
	log.Fatal(err)
}
log.Print(m.Format()) // The detected format.
log.Print(m.Title())  // The title of the track (see Metadata interface for more details).
```

Parsed metadata is exported via a single interface (giving a consistent API for all supported metadata formats).

```go
// Metadata is an interface which is used to describe metadata retrieved by this package.
type Metadata interface {
	Format() Format
	FileType() FileType

	Title() string
	Album() string
	Artist() string
	AlbumArtist() string
	Composer() string
	Genre() string
	Year() int

	Track() (int, int) // Number, Total
	Disc() (int, int) // Number, Total

	Picture() *Picture // Artwork
	Lyrics() string

	Raw() map[string]interface{} // NB: raw tag names are not consistent across formats.
}
```

## Audio Data Checksum (SHA1)

This package also provides a metadata-invariant checksum for audio files: only the audio data is used to
construct the checksum.

[http://godoc.org/github.com/dhowden/tag#Sum](http://godoc.org/github.com/dhowden/tag#Sum)

## Tools

There are simple command-line tools which demonstrate basic tag extraction and summing:

    $ go get github.com/dhowden/tag/...
    $ cd $GOPATH/bin
    $ ./tag 11\ High\ Hopes.m4a
    Metadata Format: MP4
     Title: High Hopes
     Album: The Division Bell
     Artist: Pink Floyd
     Composer: Abbey Road Recording Studios/David Gilmour/Polly Samson
     Year: 1994
     Track: 11 of 11
     Disc: 1 of 1
     Picture: Picture{Ext: jpeg, MIMEType: image/jpeg, Type: , Description: , Data.Size: 606109}

    $ ./sum 11\ High\ Hopes.m4a
    2ae208c5f00a1f21f5fac9b7f6e0b8e52c06da29