class Mp3Info
- License
-
Ruby
- Author
-
Guillaume Pierronnet (guillaume.pierronnet@gmail.com)
- Website
Constants
- BITRATE
- CHANNEL_MODE
- GENRES
- LAYER
- SAMPLERATE
- SAMPLES_PER_FRAME
- TAG1_SIZE
- TAG_MAPPING_2_2
map to fill the “universal” tag (#tag attribute) for id3v2.2
- TAG_MAPPING_2_3
for id3v2.3 and 2.4
- VERSION
Attributes
bitrate in kbps
channel mode => “Stereo”, “JStereo”, “Dual Channel” or “Single Channel”
error protection => true or false
the original filename unless used with a StringIO
Hash representing values in the MP3 frame header. Keys are one of the following:
-
:private (boolean)
-
:copyright (boolean)
-
:original (boolean)
-
:padding (boolean)
-
:error_protection (boolean)
-
:mode_extension (integer in the 0..3 range)
-
:emphasis (integer in the 0..3 range)
detailled explanation can be found here: www.mp3-tech.org/programmer/frame_header.html
layer = 1, 2, or 3
length in seconds as a Float
mpeg version = 1 or 2
samplerate in Hz
a sort of “universal” tag, regardless of the tag version, 1 or 2, with the same keys as @tag1 this tag has priority over @tag1 and @tag2 when writing the tag with close
id3v1 tag as a Hash. You can modify it, it will be written when calling “close” method.
id3v2 tag attribute as an ID3v2 object. You can modify it, it will be written when calling “close” method.
variable bitrate => true or false
Public Class Methods
Test the presence of an id3v1 tag in file or StringIO
filename_or_io
# File lib/mp3info.rb, line 162 def self.hastag1?(filename_or_io) if filename_or_io.is_a?(StringIO) io = filename_or_io io.rewind else io = File.new(filename_or_io, "rb") end hastag1 = false begin io.seek(-TAG1_SIZE, File::SEEK_END) hastag1 = io.read(3) == "TAG" ensure io.close if io.is_a?(File) end hastag1 end
Test the presence of an id3v2 tag in file or StringIO
filename_or_io
# File lib/mp3info.rb, line 181 def self.hastag2?(filename_or_io) if filename_or_io.is_a?(StringIO) io = filename_or_io io.rewind else io = File.new(filename_or_io,"rb") end hastag2 = false begin hastag2 = io.read(3) == "ID3" ensure io.close if io.is_a?(File) end hastag2 end
Instantiate Mp3Info object with name
filename
. options hash is used for ID3v2#new. Specify
:parse_tags => false to disable the processing of the tags (read and
write). Specify :parse_mp3 => false to disable processing of the mp3
# File lib/mp3info.rb, line 219 def initialize(filename_or_io, options = {}) warn("#{self.class}::new() does not take block; use #{self.class}::open() instead") if block_given? @filename_or_io = filename_or_io if @filename_or_io.nil? raise ArgumentError, "filename is nil" end options = {:parse_mp3 => true, :parse_tags => true}.update(options) @tag_parsing_enabled = options.delete(:parse_tags) @mp3_parsing_enabled = options.delete(:parse_mp3) @id3v2_options = options reload end
“block version” of ::new
# File lib/mp3info.rb, line 302 def self.open(*params) m = self.new(*params) ret = nil if block_given? begin ret = yield(m) ensure m.close end else ret = m end ret end
Remove id3v1 tag from filename
# File lib/mp3info.rb, line 200 def self.removetag1(filename) if self.hastag1?(filename) newsize = File.size(filename) - TAG1_SIZE File.open(filename, "rb+") { |f| f.truncate(newsize) } end end
Remove id3v2 tag from filename
# File lib/mp3info.rb, line 208 def self.removetag2(filename) self.open(filename) do |mp3| mp3.tag2.clear end end
Private Class Methods
returns the selected bit range (b, a) as a number NOTE: b > a if not, returns 0
# File lib/mp3info.rb, line 697 def self.bits(number, b, a) t = 0 b.downto(a) { |i| t += t + number[i] } t end
# File lib/mp3info.rb, line 495 def Mp3Info.get_frames_infos(head) # be sure we are in sync if ((head & 0xffe00000) != 0xffe00000) || # 11 bit MPEG frame sync ((head & 0x00060000) == 0x00060000) || # 2 bit layer type ((head & 0x0000f000) == 0x0000f000) || # 4 bit bitrate ((head & 0x0000f000) == 0x00000000) || # free format bitstream ((head & 0x00000c00) == 0x00000c00) || # 2 bit frequency ((head & 0xffff0000) == 0xfffe0000) raise Mp3InfoInternalError end mpeg_version = [2.5, nil, 2, 1][bits(head, 20,19)] layer = LAYER[bits(head, 18,17)] raise Mp3InfoInternalError if layer == nil || mpeg_version == nil bitrate = BITRATE[mpeg_version][layer-1][bits(head, 15,12)-1] samplerate = SAMPLERATE[mpeg_version][bits(head, 11,10)] padding = (head[9] == 1) if layer == 1 size = (12 * bitrate*1000.0 / samplerate + (padding ? 1 : 0))*4 else # layer 2 and 3 size = 144 * (bitrate*1000.0 / samplerate) + (padding ? 1 : 0) end size = size.to_i { :layer => layer, :bitrate => bitrate, :samplerate => samplerate, :mpeg_version => mpeg_version, :padding => padding, :size => size } end
Public Instance Methods
this method returns the “audio-only” data boundaries of the file, i.e. content stripped form tags. Useful to compare 2 files with the same audio content but with differents tags. Returned value is an array
- position_in_the_file, length_of_the_data
# File lib/mp3info.rb, line 354 def audio_content pos = 0 length = @io_size if hastag1? length -= TAG1_SIZE end if hastag2? pos = @tag2.io_position length -= @tag2.io_position end [pos, length] end
Flush pending modifications to tags and close the file not used when source IO is a StringIO
# File lib/mp3info.rb, line 374 def close puts "close" if $DEBUG return unless @io_is_a_file if !@tag_parsing_enabled return end if @tag != @tag_orig puts "@tag has changed" if $DEBUG # @tag1 has precedence over @tag if @tag1 == @tag1_orig @tag.each do |k, v| @tag1[k] = v end end # ruby-mp3info can only write v2.3 tags TAG_MAPPING_2_3.each do |key, tag2_name| @tag2.delete(TAG_MAPPING_2_2[key]) @tag2[tag2_name] = @tag[key] if @tag[key] end end if @tag1 != @tag1_orig puts "@tag1 has changed" if $DEBUG raise(Mp3InfoError, "file is not writable") unless File.writable?(@filename_or_io) #@tag1_orig.update(@tag1) @tag1_orig = @tag1.dup File.open(@filename_or_io, 'rb+') do |file| if @tag1_orig.empty? newsize = @io_size - TAG1_SIZE file.truncate(newsize) else file.seek(-TAG1_SIZE, File::SEEK_END) t = file.read(3) if t != 'TAG' #append new tag file.seek(0, File::SEEK_END) file.write('TAG') end str = [ @tag1_orig["title"]||"", @tag1_orig["artist"]||"", @tag1_orig["album"]||"", ((@tag1_orig["year"] != 0) ? ("%04d" % @tag1_orig["year"].to_i) : "\0\0\0\0"), @tag1_orig["comments"]||"", 0, @tag1_orig["tracknum"]||0, @tag1_orig["genre"]||255 ].pack("Z30Z30Z30Z4Z28CCC") file.write(str) end end end if @tag2.changed? puts "@tag2 has changed" if $DEBUG raise(Mp3InfoError, "file is not writable") unless File.writable?(@filename_or_io) tempfile_name = nil File.open(@filename_or_io, 'rb+') do |file| #if tag2 already exists, seek to end of it if @tag2.parsed? file.seek(@tag2.io_position) end # if @io.read(3) == "ID3" # version_maj, version_min, flags = @io.read(3).unpack("CCB4") # unsync, ext_header, experimental, footer = (0..3).collect { |i| flags[i].chr == '1' } # tag2_len = @io.get_syncsafe # @io.seek(@io.get_syncsafe - 4, IO::SEEK_CUR) if ext_header # @io.seek(tag2_len, IO::SEEK_CUR) # end tempfile_name = @filename_or_io + ".tmp" File.open(tempfile_name, "wb") do |tempfile| unless @tag2.empty? tempfile.write(@tag2.to_bin) end bufsiz = file.stat.blksize || 4096 while buf = file.read(bufsiz) tempfile.write(buf) end end end File.rename(tempfile_name, @filename_or_io) end end
iterates over each mpeg frame over the file, allowing you to write some
funny things, like an mpeg lossless cutter, or frame counter, or whatever
you like ;) frame
is a hash with the following keys: :layer,
:bitrate, :samplerate, :mpeg_version, :padding and :size (in bytes)
# File lib/mp3info.rb, line 481 def each_frame @io.seek(@first_frame_pos, File::SEEK_SET) loop do head = @io.read(4).unpack("N").first frame = Mp3Info.get_frames_infos(head) @io.seek(frame[:size] -4, File::SEEK_CUR) yield frame #puts "frame #{frame_count} len #{frame[:length]} br #{frame[:bitrate]} @io.pos #{@io.pos}" break if @io.eof? end end
close and reopen the file, i.e. commit changes to disk and reload it (only works with “true” files, not StringIO ones)
# File lib/mp3info.rb, line 463 def flush return unless @io_is_a_file close reload end
return the length in seconds of one frame
# File lib/mp3info.rb, line 368 def frame_length SAMPLES_PER_FRAME[@layer][@mpeg_version] / Float(@samplerate) end
Does the file has an id3v1 tag?
# File lib/mp3info.rb, line 335 def hastag1? !@tag1.empty? end
Does the file has an id3v2 tag?
# File lib/mp3info.rb, line 340 def hastag2? @tag2.parsed? end
Does the file has an id3v1 or v2 tag?
# File lib/mp3info.rb, line 330 def hastag? hastag1? || hastag2? end
reload (or load for the first time) the file from disk
# File lib/mp3info.rb, line 233 def reload @header = {} if @filename_or_io.is_a?(StringIO) || @filename_or_io.is_a?(IO) @io_is_a_file = false @io = @filename_or_io @io_size = @io.size @filename = nil else @io_is_a_file = true @io = File.new(@filename_or_io, "rb") @io_size = @io.stat.size @filename = @filename_or_io end if @io_size == 0 raise(Mp3InfoError, "empty file or IO") end @io.extend(Mp3FileMethods) @tag1 = @tag = @tag1_orig = @tag_orig = {} @tag1.extend(HashKeys) @tag2 = ID3v2.new(@id3v2_options) begin if @tag_parsing_enabled parse_tags @tag1_orig = @tag1.dup if hastag1? @tag = @tag1.dup end if hastag2? @tag = {} # creation of a sort of "universal" tag, regardless of the tag version tag2_mapping = @tag2.version =~ /^2\.2/ ? TAG_MAPPING_2_2 : TAG_MAPPING_2_3 tag2_mapping.each do |key, tag2_name| tag_value = (@tag2[tag2_name].is_a?(Array) ? @tag2[tag2_name].first : @tag2[tag2_name]) next unless tag_value @tag[key] = tag_value.is_a?(Array) ? tag_value.first : tag_value if %w{year tracknum}.include?(key) @tag[key] = tag_value.to_i end # this is a special case with id3v2.2, which uses # old fashionned id3v1 genres if tag2_name == "TCO" && tag_value =~ /^\((\d+)\)$/ @tag["genre_s"] = GENRES[$1.to_i] end end end @tag.extend(HashKeys) @tag_orig = @tag.dup end if @mp3_parsing_enabled parse_mp3 end ensure if @io_is_a_file @io.close end end end
Remove id3v1 from mp3
# File lib/mp3info.rb, line 318 def removetag1 @tag1.clear self end
Remove id3v2 from mp3
# File lib/mp3info.rb, line 324 def removetag2 @tag2.clear self end
write to another filename at close()
# File lib/mp3info.rb, line 345 def rename(new_filename) raise(Mp3InfoError, "cannot rename an IO") unless @io_is_a_file @filename = new_filename end
inspect inside Mp3Info
# File lib/mp3info.rb, line 470 def to_s s = "MPEG #{@mpeg_version} Layer #{@layer} #{@vbr ? "VBR" : "CBR"} #{@bitrate} Kbps #{@channel_mode} #{@samplerate} Hz length #{@length} sec. header #{@header.inspect} " s << "tag1: "+@tag1.to_hash.inspect+"\n" if hastag1? s << "tag2: "+@tag2.to_inspect_hash.inspect+"\n" if hastag2? s end
Private Instance Methods
reads through @io from current pos until it finds a valid MPEG header returns the MPEG header as FixNum
# File lib/mp3info.rb, line 583 def find_next_frame # @io will now be sitting at the best guess for where the MPEG frame is. # It should be at byte 0 when there's no id3v2 tag. # It should be at the end of the id3v2 tag or the zero padding if there # is a id3v2 tag. #dummyproof = @io.stat.size - @io.pos => WAS TOO MUCH dummyproof = [ @io_size - @io.pos, 2000000 ].min dummyproof.times do |i| if @io.getbyte == 0xff data = @io.read(3) raise(Mp3InfoError, "end of file reached") if @io.eof? head = 0xff000000 + (data.getbyte(0) << 16) + (data.getbyte(1) << 8) + data.getbyte(2) begin Mp3Info.get_frames_infos(head) return head rescue Mp3InfoInternalError @io.seek(-3, IO::SEEK_CUR) end end end if @io.eof? raise Mp3InfoError, "cannot find a valid frame: got EOF" else raise Mp3InfoError, "cannot find a valid frame after reading #{dummyproof} bytes" end end
# File lib/mp3info.rb, line 611 def frame_scan(frame_limit = nil) frame_count = bitrate_sum = 0 each_frame do |frame| bitrate_sum += frame[:bitrate] frame_count += 1 break if frame_limit && (frame_count >= frame_limit) end average_bitrate = bitrate_sum/frame_count.to_f length = (frame_count-1) * frame_length [average_bitrate, length] end
gets id3v1 tag information from @io assumes @io is pointing to char after “TAG” id
# File lib/mp3info.rb, line 557 def gettag1 @tag1_parsed = true %w{title artist album}.each do |tag| v = @io.read(30).unpack("A*").first @tag1[tag] = Mp3Info::EncodingHelper.convert_from_iso_8859_1(v) end year_t = @io.read(4).to_i @tag1["year"] = year_t unless year_t == 0 comments = @io.read(30) if comments.getbyte(-2) == 0 @tag1["tracknum"] = comments.getbyte(-1).to_i comments.chop! #remove the last char end comment = comments.unpack("A*").first @tag1["comments"] = Mp3Info::EncodingHelper.convert_from_iso_8859_1(comment) @tag1["genre"] = @io.getbyte @tag1["genre_s"] = GENRES[@tag1["genre"]] || "" # clear empty tags @tag1.delete_if { |k, v| v.respond_to?(:empty?) && v.empty? } @tag1.delete("genre") if @tag1["genre"] == 255 @tag1.delete("tracknum") if @tag1["tracknum"] == 0 end
# File lib/mp3info.rb, line 624 def parse_mp3 ### extracts MPEG info from MPEG header and stores it in the hash @mpeg ### head (fixnum) = valid 4 byte MPEG header found = false head = nil 5.times do head = find_next_frame() @first_frame_pos = @io.pos - 4 current_frame = Mp3Info.get_frames_infos(head) @mpeg_version = current_frame[:mpeg_version] @layer = current_frame[:layer] @header[:error_protection] = head[16] == 0 ? true : false @bitrate = current_frame[:bitrate] @samplerate = current_frame[:samplerate] @header[:padding] = current_frame[:padding] @header[:private] = head[8] == 0 ? true : false @channel_mode = CHANNEL_MODE[@channel_num = Mp3Info.bits(head, 7,6)] @header[:mode_extension] = Mp3Info.bits(head, 5,4) @header[:copyright] = (head[3] == 1 ? true : false) @header[:original] = (head[2] == 1 ? true : false) @header[:emphasis] = Mp3Info.bits(head, 1,0) @vbr = false found = true break end raise(Mp3InfoError, "Cannot find good frame") unless found seek = @mpeg_version == 1 ? (@channel_num == 3 ? 17 : 32) : (@channel_num == 3 ? 9 : 17) @io.seek(seek, IO::SEEK_CUR) vbr_head = @io.read(4) if vbr_head == "Xing" puts "Xing header (VBR) detected" if $DEBUG flags = @io.get32bits stream_size = frame_count = 0 flags[1] == 1 and frame_count = @io.get32bits flags[2] == 1 and stream_size = @io.get32bits puts "#{frame_count} frames" if $DEBUG raise(Mp3InfoError, "bad VBR header") if frame_count.zero? # currently this just skips the TOC entries if they're found @io.seek(100, IO::SEEK_CUR) if flags[0] == 1 #@vbr_quality = @io.get32bits if flags[3] == 1 samples_per_frame = SAMPLES_PER_FRAME[@layer][@mpeg_version] @length = frame_count * samples_per_frame / Float(@samplerate) @bitrate = (((stream_size/frame_count)*@samplerate)/144) / 1024 @vbr = true else # for cbr, calculate duration with the given bitrate stream_size = @io_size - (hastag1? ? TAG1_SIZE : 0) - (@tag2.io_position || 0) @length = ((stream_size << 3)/1000.0)/@bitrate # read the first 100 frames and decide if the mp3 is vbr and needs full scan begin bitrate = frame_scan(100).first if @bitrate != bitrate @vbr = true @bitrate, @length = frame_scan end rescue Mp3InfoInternalError end end end