id3

package module
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 Go to latest Published: Mar 22, 2015 License: MIT Imports: 9 Imported by: 1

README

This library is in development, there's no release yet, don't use it yet.

The API isn't stable, it might eat your files, and I reserve the right to rewrite history.

Documentation

Overview

Package id3 implements a decoder and encoder for ID3 tags.

Nomenclature

ID3 uses nomenclature that might be counterintuitive to people not familiar with it. Because this library uses the same choice of words the following list of clarifications is included. 

tag: In ID3, tag means the entire set of metadata, not just one
     field of it.

frame: A frame describes a single piece of information, for example
       a song's title.

Supported versions

This library supports reading v2.3 and v2.4 tags, but only writing v2.4 tags.

The primary reason for not allowing writing older versions is that they cannot represent all data that is available with v2.4, and designing the API in a way that's both user friendly and able to reject data is not worth the trouble.

Automatic upgrading

The library's internal representation of tags matches that of v2.4. When tags with an older version are being read, they will be automatically converted to v2.4.

One consequence of this is that when you read a file with v2.3 tags and immediately save it, it will now be a file with valid v2.4 tags.

The upgrade process makes the following changes to the tags:

  • TYER, TDAT and TIME get replaced by TDRC
  • TORY gets replaced by TDOR
  • XDOR gets replaced by TDOR
  • The slash as a separator for multiple values gets replaced by null bytes

One special case is the TRDA frame because there is no way to automatically convert it to v2.4. The upgrade process will not directly delete the frame, so that you can manually upgrade it if desired, but it won't be written back to the file. The frame is rarely used and insignificant, so it's not a big loss.

Accessing and manipulating frames

There are two ways to access frames: Using provided getter and setter methods (there is one for every standard frame), and working directly with the underlying frames.

For frames that usually support multiple values, e.g. languages, there will be two different setters and getters: One that operates on slices and one that operates on single values. When getting a single value, it will return the first value from the underlying list. When setting a single value, it will overwrite the list with a single value.

Text frames and user text frames can be manipulated with the GetTextFrame* and SetTextFrame* class of functions. There are special methods for working with integers, slices and times. This class of functions expects the raw frame names (e.g. "TLEN"), with the special case of user text frames ("TXXX") where it expects a format of the kind "TXXX:The frame description" to address a specific user text frame.

Encodings

While ID3v2 allows a variety of encodings (ISO-8859-1, UTF-16 and in v2.4 also UTF-8), this library only supports writing UTF-8. When reading frames with different encodings, they will be converted to UTF-8.

The rationale behind this is that UTF-8 is the encoding assumed by most of the Go standard library, and that the other encodings have no realistic benefits over UTF-8.

Behaviour when encountering invalid data

There are two kinds of invalid data that can be encountered: Data that doesn't look like a valid frame, and data that is invalid in the context of its frame.

An example for the first case is a frame identifier that doesn't consist of only A-Z0-9. That usually happens when other programs wrote invalid data. One common case are wrongly encoded sizes, which will cause us to read random binary data.

An example for the second case is text that isn't valid according to the specified encoding.

In the first case, parsing of the entire tag will be aborted because it cannot be ensured that bad things won't happen.

In the second case only that specific frame will be dropped.

Unsupported frames

Unsupported frames, like extensions by Apple, will be left untouched, meaning that they will be read and written as raw byte slices. If you know how to handle them, you can write your own function to parse and modify the content. All unsupported frames will be of type UnsupportedFrame.

Index

Constants

View Source 
const TimeFormat = "2006-01-02T15:04:05"

Variables

View Source 
var FrameNames = map[FrameType]string{
	"AENC": "Audio encryption",
	"APIC": "Attached picture",
	"ASPI": "Audio seek point index",
	"COMM": "Comments",
	"COMR": "Commercial frame",

	"ENCR": "Encryption method registration",
	"EQU2": "Equalisation (2)",
	"ETCO": "Event timing codes",

	"GEOB": "General encapsulated object",
	"GRID": "Group identification registration",

	"LINK": "Linked information",

	"MCDI": "Music CD identifier",
	"MLLT": "MPEG location lookup table",

	"OWNE": "Ownership frame",

	"PRIV": "Private frame",
	"PCNT": "Play counter",
	"POPM": "Popularimeter",
	"POSS": "Position synchronisation frame",

	"RBUF": "Recommended buffer size",
	"RVA2": "Relative volume adjustment (2)",
	"RVRB": "Reverb",

	"SEEK": "Seek frame",
	"SIGN": "Signature frame",
	"SYLT": "Synchronised lyric/text",
	"SYTC": "Synchronised tempo codes",

	"TALB": "Album/Movie/Show title",
	"TBPM": "BPM (beats per minute)",
	"TCOM": "Composer",
	"TCON": "Content type",
	"TCOP": "Copyright message",
	"TDEN": "Encoding time",
	"TDLY": "Playlist delay",
	"TDOR": "Original release time",
	"TDRC": "Recording time",
	"TDRL": "Release time",
	"TDTG": "Tagging time",
	"TENC": "Encoded by",
	"TEXT": "Lyricist/Text writer",
	"TFLT": "File type",
	"TIPL": "Involved people list",
	"TIT1": "Content group description",
	"TIT2": "Title/songname/content description",
	"TIT3": "Subtitle/Description refinement",
	"TKEY": "Initial key",
	"TLAN": "Language(s)",
	"TLEN": "Length",
	"TMCL": "Musician credits list",
	"TMED": "Media type",
	"TMOO": "Mood",
	"TOAL": "Original album/movie/show title",
	"TOFN": "Original filename",
	"TOLY": "Original lyricist(s)/text writer(s)",
	"TORY": "Original release year",
	"TOPE": "Original artist(s)/performer(s)",
	"TOWN": "File owner/licensee",
	"TPE1": "Lead performer(s)/Soloist(s)",
	"TPE2": "Band/orchestra/accompaniment",
	"TPE3": "Conductor/performer refinement",
	"TPE4": "Interpreted, remixed, or otherwise modified by",
	"TPOS": "Part of a set",
	"TPRO": "Produced notice",
	"TPUB": "Publisher",
	"TRCK": "Track number/Position in set",
	"TRSN": "Internet radio station name",
	"TRSO": "Internet radio station owner",
	"TSOA": "Album sort order",
	"TSOP": "Performer sort order",
	"TSOT": "Title sort order",
	"TSO2": "Album Artist sort order",
	"TSOC": "Composer sort oder",
	"TSRC": "ISRC (international standard recording code)",
	"TSSE": "Software/Hardware and settings used for encoding",
	"TSST": "Set subtitle",
	"TYER": "Year",
	"TXXX": "User defined text information frame",

	"UFID": "Unique file identifier",
	"USER": "Terms of use",
	"USLT": "Unsynchronised lyric/text transcription",

	"WCOM": "Commercial information",
	"WCOP": "Copyright/Legal information",
	"WOAF": "Official audio file webpage",
	"WOAR": "Official artist/performer webpage",
	"WOAS": "Official audio source webpage",
	"WORS": "Official Internet radio station homepage",
	"WPAY": "Payment",
	"WPUB": "Publishers official webpage",
	"WXXX": "User defined URL link frame",
}
View Source 
var Genres = []string{}/* 126 elements not displayed */
View Source 
var Magic = []byte("ID3")
View Source 
var PictureTypes = []string{
	"Other",
	"32x32 pixels 'file icon' (PNG only)",
	"Other file icon",
	"Cover (front)",
	"Cover (back)",
	"Leaflet page",
	"Media (e.g. label side of CD)",
	"Lead artist/lead performer/soloist",
	"Artist/performer",
	"Conductor",
	"Band/Orchestra",
	"Composer",
	"Lyricist/text writer",
	"Recording Location",
	"During recording",
	"During performance",
	"Movie/video screen capture",
	"A bright coloured fish",
	"Illustration",
	"Band/artist logotype",
	"Publisher/Studio logotype",
}

Functions

func Check 

func Check(r Peeker) (bool, error)

Check reports whether r looks like it starts with an ID3 tag.

Types

type Comment 

type Comment struct {
	Language    string
	Description string
	Text        string
}

type CommentFrame 

type CommentFrame struct {
	FrameHeader
	Language    string
	Description string
	Text        string
}

func (CommentFrame) Encode 

func (f CommentFrame) Encode() []byte

func (CommentFrame) Size 

func (f CommentFrame) Size() int

func (CommentFrame) Value 

func (f CommentFrame) Value() string

type Decoder 

type Decoder struct {
	// contains filtered or unexported fields
}

func NewDecoder 

func NewDecoder(r io.Reader) *Decoder

func (*Decoder) Parse 

func (d *Decoder) Parse() (*Tag, error)

Parse parses a tag.

Parse will always return a valid tag. In the case of an error, the tag will be empty.

If Parse successfully parsed a tag, the reader will be positioned immediately after the tag, which usually is directly before audio data. If there wasn't a valid tag, however, the position of the reader is undefined. If you're not sure if your reader starts with a tag at all, consider using Check first.

Parse cannot be called if either ParseHeader or ParseFrame have been called for the current tag.

func (*Decoder) ParseFrame 

func (d *Decoder) ParseFrame() (Frame, error)

ParseFrame reads the next ID3 frame. When it reaches padding, it will read and discard all of it and return io.EOF. This should set the reader immediately before the audio data.

ParseHeader must be called before calling ParseFrame.

func (*Decoder) ParseHeader 

func (d *Decoder) ParseHeader() (Header, error)

ParseHeader parses only the ID3 header.

type Encoder 

type Encoder struct {

	// The amount of padding that will be added after the last frame.
	Padding int
	// contains filtered or unexported fields
}

func NewEncoder 

func NewEncoder(w io.Writer) *Encoder

func (*Encoder) WriteFrame 

func (e *Encoder) WriteFrame(f Frame) error

func (*Encoder) WriteHeader 

func (e *Encoder) WriteHeader(size int) error

func (*Encoder) WritePadding 

func (e *Encoder) WritePadding() error

func (*Encoder) WriteTag 

func (e *Encoder) WriteTag(t *Tag) error

type Encoding 

type Encoding byte

func (Encoding) String 

func (e Encoding) String() string

type Frame 

type Frame interface {
	ID() FrameType // TODO consider renaming to Type()
	Header() FrameHeader
	Value() string
	Encode() []byte
	Size() int
}

type FrameFlags 

type FrameFlags uint16

func (FrameFlags) Compressed 

func (f FrameFlags) Compressed() bool

func (FrameFlags) Encrypted 

func (f FrameFlags) Encrypted() bool

func (FrameFlags) Grouped 

func (f FrameFlags) Grouped() bool

func (FrameFlags) PreserveFileAlteration 

func (f FrameFlags) PreserveFileAlteration() bool

func (FrameFlags) PreserveTagAlteration 

func (f FrameFlags) PreserveTagAlteration() bool

func (FrameFlags) ReadOnly 

func (f FrameFlags) ReadOnly() bool

type FrameHeader 

type FrameHeader struct {
	// contains filtered or unexported fields
}

func (FrameHeader) Header 

func (h FrameHeader) Header() FrameHeader

func (FrameHeader) ID 

func (f FrameHeader) ID() FrameType

type FrameType 

type FrameType string

func (FrameType) String 

func (f FrameType) String() string

type FramesMap 

type FramesMap map[FrameType][]Frame

func (FramesMap) Size 

func (fm FramesMap) Size() int
type Header struct {
	Version Version
	Flags   HeaderFlags
	Size    int // The size of the tag (exluding the size of the header)
}

type HeaderFlags 

type HeaderFlags byte

func (HeaderFlags) Experimental 

func (f HeaderFlags) Experimental() bool

func (HeaderFlags) ExtendedHeader 

func (f HeaderFlags) ExtendedHeader() bool

func (HeaderFlags) UndefinedSet 

func (f HeaderFlags) UndefinedSet() bool

func (HeaderFlags) Unsynchronisation 

func (f HeaderFlags) Unsynchronisation() bool

type InvalidFrameHeaderError 

type InvalidFrameHeaderError struct {
	Bytes struct {
		ID    [4]byte
		Size  [4]byte
		Flags [2]byte
	}
}

func (InvalidFrameHeaderError) Error 

func (err InvalidFrameHeaderError) Error() string

type InvalidTagHeaderError 

type InvalidTagHeaderError struct {
	Magic []byte
}

func (InvalidTagHeaderError) Error 

func (err InvalidTagHeaderError) Error() string

type MusicCDIdentifierFrame 

type MusicCDIdentifierFrame struct {
	FrameHeader
	TOC []byte
}

func (MusicCDIdentifierFrame) Encode 

func (f MusicCDIdentifierFrame) Encode() []byte

func (MusicCDIdentifierFrame) Size 

func (f MusicCDIdentifierFrame) Size() int

func (MusicCDIdentifierFrame) Value 

func (f MusicCDIdentifierFrame) Value() string

type Peeker 

type Peeker interface {
	Peek(n int) ([]byte, error)
}

type PictureFrame 

type PictureFrame struct {
	FrameHeader
	MIMEType    string
	PictureType PictureType
	Description string
	Data        []byte
}

func (PictureFrame) Encode 

func (f PictureFrame) Encode() []byte

func (PictureFrame) Size 

func (f PictureFrame) Size() int

func (PictureFrame) Value 

func (f PictureFrame) Value() string

type PictureType 

type PictureType byte

func (PictureType) String 

func (p PictureType) String() string

type PrivateFrame 

type PrivateFrame struct {
	FrameHeader
	Owner []byte
	Data  []byte
}

func (PrivateFrame) Encode 

func (f PrivateFrame) Encode() []byte

func (PrivateFrame) Size 

func (f PrivateFrame) Size() int

func (PrivateFrame) Value 

func (f PrivateFrame) Value() string

type Tag 

type Tag struct {
	Flags  HeaderFlags
	Frames FramesMap
}

func NewTag 

func NewTag() *Tag

NewTag returns an empty tag.

func (*Tag) Album 

func (t *Tag) Album() string

func (*Tag) AlbumSortOrder 

func (t *Tag) AlbumSortOrder() string

func (*Tag) Artist 

func (t *Tag) Artist() string

func (*Tag) Artists 

func (t *Tag) Artists() []string

func (*Tag) BPM 

func (t *Tag) BPM() int

func (*Tag) Band 

func (t *Tag) Band() string

func (*Tag) Clear 

func (t *Tag) Clear()

Clear removes all tags from the file.

func (*Tag) Comments 

func (t *Tag) Comments() []Comment

func (*Tag) Composer 

func (t *Tag) Composer() string

func (*Tag) Composers 

func (t *Tag) Composers() []string

func (*Tag) Conductor 

func (t *Tag) Conductor() string

func (*Tag) EncodingTime 

func (t *Tag) EncodingTime() time.Time

func (*Tag) GetTextFrame 

func (t *Tag) GetTextFrame(name FrameType) string

GetTextFrame returns the text frame specified by name.

To access user text frames, specify the name like "TXXX:The description".

func (*Tag) GetTextFrameNumber 

func (t *Tag) GetTextFrameNumber(name FrameType) int

func (*Tag) GetTextFrameSlice 

func (t *Tag) GetTextFrameSlice(name FrameType) []string

func (*Tag) GetTextFrameTime 

func (t *Tag) GetTextFrameTime(name FrameType) time.Time

func (*Tag) HasFrame 

func (t *Tag) HasFrame(name FrameType) bool

func (*Tag) ISRC 

func (t *Tag) ISRC() string

func (*Tag) Language 

func (t *Tag) Language() string

func (*Tag) Languages 

func (t *Tag) Languages() []string

func (*Tag) Length 

func (t *Tag) Length() time.Duration

func (*Tag) Mood 

func (t *Tag) Mood() string

func (*Tag) OriginalArtist 

func (t *Tag) OriginalArtist() string

func (*Tag) OriginalArtists 

func (t *Tag) OriginalArtists() []string

func (*Tag) OriginalFilename 

func (t *Tag) OriginalFilename() string

func (*Tag) OriginalReleaseTime 

func (t *Tag) OriginalReleaseTime() time.Time

func (*Tag) Owner 

func (t *Tag) Owner() string

func (*Tag) PerformerSortOrder 

func (t *Tag) PerformerSortOrder() string

func (*Tag) PlaylistDelay 

func (t *Tag) PlaylistDelay() time.Duration

func (*Tag) Publisher 

func (t *Tag) Publisher() string

func (*Tag) RecordingTime 

func (t *Tag) RecordingTime() time.Time

func (*Tag) RemoveFrames 

func (t *Tag) RemoveFrames(name FrameType)

func (*Tag) Sanitize 

func (t *Tag) Sanitize()

Sanitize will remove all frames that aren't valid. Check the documentation of (*Tag).Validate() to see what "valid" means.

func (*Tag) SetAlbum 

func (t *Tag) SetAlbum(album string)

func (*Tag) SetAlbumSortOrder 

func (t *Tag) SetAlbumSortOrder(s string)

func (*Tag) SetArtist 

func (t *Tag) SetArtist(artist string)

func (*Tag) SetArtists 

func (t *Tag) SetArtists(artists []string)

func (*Tag) SetBPM 

func (t *Tag) SetBPM(bpm int)

func (*Tag) SetBand 

func (t *Tag) SetBand(band string)

func (*Tag) SetComments 

func (t *Tag) SetComments(comments []Comment)

func (*Tag) SetComposer 

func (t *Tag) SetComposer(composer string)

func (*Tag) SetComposers 

func (t *Tag) SetComposers(composers []string)

func (*Tag) SetConductor 

func (t *Tag) SetConductor(name string)

func (*Tag) SetEncodingTime 

func (t *Tag) SetEncodingTime(et time.Time)

func (*Tag) SetISRC 

func (t *Tag) SetISRC(isrc string)

func (*Tag) SetLanguage 

func (t *Tag) SetLanguage(lang string)

func (*Tag) SetLanguages 

func (t *Tag) SetLanguages(langs []string)

func (*Tag) SetLength 

func (t *Tag) SetLength(d time.Duration)

func (*Tag) SetMood 

func (t *Tag) SetMood(mood string)

func (*Tag) SetOriginalArtist 

func (t *Tag) SetOriginalArtist(name string)

func (*Tag) SetOriginalArtists 

func (t *Tag) SetOriginalArtists(names []string)

func (*Tag) SetOriginalFilename 

func (t *Tag) SetOriginalFilename(name string)

func (*Tag) SetOriginalReleaseTime 

func (t *Tag) SetOriginalReleaseTime(rt time.Time)

func (*Tag) SetOwner 

func (t *Tag) SetOwner(owner string)

func (*Tag) SetPerformerSortOrder 

func (t *Tag) SetPerformerSortOrder(s string)

func (*Tag) SetPlaylistDelay 

func (t *Tag) SetPlaylistDelay(d time.Duration)

func (*Tag) SetPublisher 

func (t *Tag) SetPublisher(publisher string)

func (*Tag) SetRecordingTime 

func (t *Tag) SetRecordingTime(rt time.Time)

func (*Tag) SetStationName 

func (t *Tag) SetStationName(name string)

func (*Tag) SetStationOwner 

func (t *Tag) SetStationOwner(owner string)

func (*Tag) SetTextFrame 

func (t *Tag) SetTextFrame(name FrameType, value string)

func (*Tag) SetTextFrameNumber 

func (t *Tag) SetTextFrameNumber(name FrameType, value int)

func (*Tag) SetTextFrameSlice 

func (t *Tag) SetTextFrameSlice(name FrameType, value []string)

func (*Tag) SetTextFrameTime 

func (t *Tag) SetTextFrameTime(name FrameType, value time.Time)

func (*Tag) SetTitle 

func (t *Tag) SetTitle(title string)

func (*Tag) SetTitleSortOrder 

func (t *Tag) SetTitleSortOrder(s string)

func (*Tag) StationName 

func (t *Tag) StationName() string

func (*Tag) StationOwner 

func (t *Tag) StationOwner() string

func (*Tag) Title 

func (t *Tag) Title() string

func (*Tag) TitleSortOrder 

func (t *Tag) TitleSortOrder() string

func (*Tag) UserTextFrames 

func (t *Tag) UserTextFrames() []UserTextInformationFrame

UserTextFrames returns all TXXX frames.

func (*Tag) Validate 

func (t *Tag) Validate() error

Validate checks whether the tags are conforming to the specification.

This entails two checks: Whether only frames that are covered by the specification are present and whether all values are within valid ranges.

It is well possible that reading existing files will result in invalid tags.

Calling Save() will not automatically validate the tags and will happily write invalid tags.

Assuming that the original file was valid and that only the getter/setter methods were used the generated tags should always be valid.

type TextInformationFrame 

type TextInformationFrame struct {
	FrameHeader
	Text string
}

func (TextInformationFrame) Encode 

func (f TextInformationFrame) Encode() []byte

func (TextInformationFrame) Size 

func (f TextInformationFrame) Size() int

func (TextInformationFrame) Value 

func (f TextInformationFrame) Value() string

type URLLinkFrame 

type URLLinkFrame struct {
	FrameHeader
	URL string
}

func (URLLinkFrame) Encode 

func (f URLLinkFrame) Encode() []byte

func (URLLinkFrame) Size 

func (f URLLinkFrame) Size() int

func (URLLinkFrame) Value 

func (f URLLinkFrame) Value() string

type UnimplementedFeatureError 

type UnimplementedFeatureError struct {
	Feature string
}

func (UnimplementedFeatureError) Error 

func (err UnimplementedFeatureError) Error() string

type UniqueFileIdentifierFrame 

type UniqueFileIdentifierFrame struct {
	FrameHeader
	Owner      string
	Identifier []byte
}

func (UniqueFileIdentifierFrame) Encode 

func (f UniqueFileIdentifierFrame) Encode() []byte

func (UniqueFileIdentifierFrame) Size 

func (f UniqueFileIdentifierFrame) Size() int

func (UniqueFileIdentifierFrame) Value 

func (f UniqueFileIdentifierFrame) Value() string

type UnsupportedFrame 

type UnsupportedFrame struct {
	FrameHeader
	Data []byte
}

func (UnsupportedFrame) Encode 

func (f UnsupportedFrame) Encode() []byte

func (UnsupportedFrame) Size 

func (f UnsupportedFrame) Size() int

func (UnsupportedFrame) Value 

func (f UnsupportedFrame) Value() string

type UnsupportedVersionError 

type UnsupportedVersionError struct {
	Version Version
}

func (UnsupportedVersionError) Error 

func (err UnsupportedVersionError) Error() string

type UnsynchronisedLyricsFrame 

type UnsynchronisedLyricsFrame struct {
	FrameHeader
	Language    string
	Description string
	Lyrics      string
}

func (UnsynchronisedLyricsFrame) Encode 

func (f UnsynchronisedLyricsFrame) Encode() []byte

func (UnsynchronisedLyricsFrame) Size 

func (f UnsynchronisedLyricsFrame) Size() int

func (UnsynchronisedLyricsFrame) Value 

func (f UnsynchronisedLyricsFrame) Value() string

type UserDefinedURLLinkFrame 

type UserDefinedURLLinkFrame struct {
	FrameHeader
	Description string
	URL         string
}

func (UserDefinedURLLinkFrame) Encode 

func (f UserDefinedURLLinkFrame) Encode() []byte

func (UserDefinedURLLinkFrame) Size 

func (f UserDefinedURLLinkFrame) Size() int

func (UserDefinedURLLinkFrame) Value 

func (f UserDefinedURLLinkFrame) Value() string

type UserTextInformationFrame 

type UserTextInformationFrame struct {
	FrameHeader
	Description string
	Text        string
}

func (UserTextInformationFrame) Encode 

func (f UserTextInformationFrame) Encode() []byte

func (UserTextInformationFrame) Size 

func (f UserTextInformationFrame) Size() int

func (UserTextInformationFrame) Value 

func (f UserTextInformationFrame) Value() string

type Version 

type Version int16

func (Version) String 

func (v Version) String() string

Source Files

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Directories

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