-
-
Save sgastudio/f39d8966aa3879332ad3e2ab20179d80 to your computer and use it in GitHub Desktop.
An ID3 tag reader implemented in pure Lua. Supports ID3v1 tags and a subset of ID3v2 tags.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| --- A simple module to read ID3 tags from MP3 files. | |
| -- Supports ID3v1 tags and a (meaningful) subset of ID3v2 tags. | |
| -- @class module | |
| -- @name id3 | |
| -- @author Michal Kottman | |
| -- @copyright 2011, released under MIT license | |
| local id3 = {} | |
| local function textFrame(name) | |
| return function (reader, info, frameSize) | |
| local encoding = reader.readByte() | |
| info[name] = reader.readStr(frameSize - 1) | |
| end | |
| end | |
| -- only decode these ID3v2 frames | |
| local frameDecoders = { | |
| COMM = function (reader, info, frameSize) | |
| local encoding = reader.readByte() | |
| local language = reader.readStr(4) | |
| info.comment = reader.readStr(frameSize - 5) | |
| end, | |
| TALB = textFrame 'album', | |
| TBPM = textFrame 'bpm', | |
| TENC = textFrame 'encoder', | |
| TLEN = textFrame 'length', | |
| TIT2 = textFrame 'title', | |
| TPE1 = textFrame 'artist', | |
| TRCK = textFrame 'track', | |
| TYER = textFrame 'year', | |
| } | |
| local function unpad(str) | |
| return (str:gsub('[%s%z]+$', '')) | |
| end | |
| function isbitset(x, p) | |
| local b = 2 ^ (p - 1) | |
| return x % (b + b) >= b | |
| end | |
| --- Read ID3 tags from MP3 file. First tries ID3v2 tags, then ID3v1 and returns those | |
| -- which are found first. Returns the following tags (if they are contained in the file): | |
| -- <ul><li>title</li><li>artist</li><li>album</li><li>year</li><li>comment</li></ul> | |
| -- @name readtags | |
| -- @param file Either string (filename) or a file object opened by io.open() | |
| -- @return Table containing the metadata from ID3 tag, or nil. | |
| function id3.readtags(file) | |
| if type(file) == 'string' then | |
| file = assert(io.open(file, 'rb')) | |
| elseif type(file) ~= 'userdata' then | |
| error('Expecting file or filename as #1, not '..type(file), 2) | |
| end | |
| local position = file:seek() | |
| local function decodeID3v2(reader) | |
| local info = {} | |
| local rb = reader.readByte | |
| local version = reader.readInt(2) | |
| local flags = rb() | |
| local size = reader.readInt(4, 128) | |
| if isbitset(flags, 7) then | |
| local mult = version >= 0x0400 and 128 or 256 | |
| local extendedSize = reader.readInt(4, mult) | |
| local extendedFlags = reader.readInt(2) | |
| local padding = reader.readInt(4) | |
| reader.skip(extendedSize - 10) | |
| end | |
| while reader.position() < size + 3 do | |
| local frameID = reader.readStr(4) | |
| local frameSize = reader.readInt(4) | |
| local frameFlags = reader.readInt(2) | |
| if frameDecoders[frameID] then | |
| frameDecoders[frameID](reader, info, frameSize) | |
| else | |
| reader.skip(frameSize) | |
| end | |
| end | |
| file:seek('set', position) | |
| return info | |
| end | |
| local function decodeID3v1(reader) | |
| local info = {} | |
| info.title = reader.readStr(30) | |
| info.artist = reader.readStr(30) | |
| info.album = reader.readStr(30) | |
| info.year = reader.readStr(4) | |
| info.comment = reader.readStr(28) | |
| local zero = reader.readByte() | |
| local track = reader.readByte() | |
| local genre = reader.readByte() | |
| if zero == 0 then | |
| info.track = track | |
| info.genre = genre | |
| else | |
| info.comment = unpad(info.comment .. string.char(zero, track, genre)) | |
| end | |
| file:seek('end', -128 - 227) | |
| local hdr = reader.readStr(4) | |
| if hdr == "TAG+" then | |
| info.title = unpad(info.title .. reader.readStr(60)) | |
| info.artist = unpad(info.artist .. reader.readStr(60)) | |
| info.album = unpad(info.album .. reader.readStr(60)) | |
| -- some other tags omitted | |
| end | |
| file:seek('set', position) | |
| return info | |
| end | |
| local function readByte() | |
| local byte = assert(file:read(1), 'Could not read byte.') | |
| return string.byte(byte) | |
| end | |
| local reader = { | |
| readStr = function(len) | |
| local str = assert(file:read(len), 'Could not read '..len..'-byte string.') | |
| return unpad(str) | |
| end, | |
| readByte = readByte, | |
| readInt = function(size, mult) | |
| mult = mult or 256 | |
| local n = readByte() | |
| for i=2, size do | |
| n = n*mult + readByte() | |
| end | |
| return n | |
| end, | |
| position = function() return file:seek() end, | |
| skip = function(offset) file:seek('cur', offset) end | |
| } | |
| -- try ID3v2 | |
| file:seek('set', 0) | |
| local header = file:read(3) | |
| if header == "ID3" then | |
| return decodeID3v2(reader) | |
| end | |
| -- try ID3v1 | |
| file:seek('end', -128) | |
| header = file:read(3) | |
| if header == "TAG" then | |
| return decodeID3v1(reader) | |
| end | |
| end | |
| if not ... then | |
| -- debug if not called by 'require' as module | |
| require 'pl.pretty'.dump(id3.readtags('song.mp3')) | |
| else | |
| return id3 | |
| end |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment