138 lines
3.8 KiB
Go
138 lines
3.8 KiB
Go
// Copyright 2015, David Howden
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// Package tag provides MP3 (ID3: v1, 2.2, 2.3 and 2.4), MP4, FLAC and OGG metadata detection,
|
|
// parsing and artwork extraction.
|
|
//
|
|
// Detect and parse tag metadata from an io.ReadSeeker (i.e. an *os.File):
|
|
// 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).
|
|
package tag
|
|
|
|
import (
|
|
"errors"
|
|
"fmt"
|
|
"io"
|
|
"os"
|
|
)
|
|
|
|
// ErrNoTagsFound is the error returned by ReadFrom when the metadata format
|
|
// cannot be identified.
|
|
var ErrNoTagsFound = errors.New("no tags found")
|
|
|
|
// ReadFrom detects and parses audio file metadata tags (currently supports ID3v1,2.{2,3,4}, MP4, FLAC/OGG).
|
|
// Returns non-nil error if the format of the given data could not be determined, or if there was a problem
|
|
// parsing the data.
|
|
func ReadFrom(r io.ReadSeeker) (Metadata, error) {
|
|
b, err := readBytes(r, 11)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
_, err = r.Seek(-11, os.SEEK_CUR)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("could not seek back to original position: %v", err)
|
|
}
|
|
|
|
switch {
|
|
case string(b[0:4]) == "fLaC":
|
|
return ReadFLACTags(r)
|
|
|
|
case string(b[0:4]) == "OggS":
|
|
return ReadOGGTags(r)
|
|
|
|
case string(b[4:11]) == "ftypM4A":
|
|
return ReadAtoms(r)
|
|
|
|
case string(b[0:3]) == "ID3":
|
|
return ReadID3v2Tags(r)
|
|
}
|
|
|
|
m, err := ReadID3v1Tags(r)
|
|
if err != nil {
|
|
if err == ErrNotID3v1 {
|
|
err = ErrNoTagsFound
|
|
}
|
|
return nil, err
|
|
}
|
|
return m, nil
|
|
}
|
|
|
|
// Format is an enumeration of metadata types supported by this package.
|
|
type Format string
|
|
|
|
// Supported tag formats.
|
|
const (
|
|
ID3v1 Format = "ID3v1" // ID3v1 tag format.
|
|
ID3v2_2 = "ID3v2.2" // ID3v2.2 tag format.
|
|
ID3v2_3 = "ID3v2.3" // ID3v2.3 tag format (most common).
|
|
ID3v2_4 = "ID3v2.4" // ID3v2.4 tag format.
|
|
MP4 = "MP4" // MP4 tag (atom) format.
|
|
VORBIS = "VORBIS" // Vorbis Comment tag format.
|
|
)
|
|
|
|
// FileType is an enumeration of the audio file types supported by this package, in particular
|
|
// there are audio file types which share metadata formats, and this type is used to distinguish
|
|
// between them.
|
|
type FileType string
|
|
|
|
// Supported file types.
|
|
const (
|
|
MP3 FileType = "MP3" // MP3 file
|
|
AAC = "AAC" // M4A file (MP4)
|
|
ALAC = "ALAC" // Apple Lossless file FIXME: actually detect this
|
|
FLAC = "FLAC" // FLAC file
|
|
OGG = "OGG" // OGG file
|
|
)
|
|
|
|
// Metadata is an interface which is used to describe metadata retrieved by this package.
|
|
type Metadata interface {
|
|
// Format returns the metadata Format used to encode the data.
|
|
Format() Format
|
|
|
|
// FileType returns the file type of the audio file.
|
|
FileType() FileType
|
|
|
|
// Title returns the title of the track.
|
|
Title() string
|
|
|
|
// Album returns the album name of the track.
|
|
Album() string
|
|
|
|
// Artist returns the artist name of the track.
|
|
Artist() string
|
|
|
|
// AlbumArtist returns the album artist name of the track.
|
|
AlbumArtist() string
|
|
|
|
// Composer returns the composer of the track.
|
|
Composer() string
|
|
|
|
// Year returns the year of the track.
|
|
Year() int
|
|
|
|
// Genre returns the genre of the track.
|
|
Genre() string
|
|
|
|
// Track returns the track number and total tracks, or zero values if unavailable.
|
|
Track() (int, int)
|
|
|
|
// Disc returns the disc number and total discs, or zero values if unavailable.
|
|
Disc() (int, int)
|
|
|
|
// Picture returns a picture, or nil if not available.
|
|
Picture() *Picture
|
|
|
|
// Lyrics returns the lyrics, or an empty string if unavailable.
|
|
Lyrics() string
|
|
|
|
// Raw returns the raw mapping of retrieved tag names and associated values.
|
|
// NB: tag/atom names are not standardised between formats.
|
|
Raw() map[string]interface{}
|
|
}
|