Class: Mp3Info

Inherits:
Object
  • Object
show all
Defined in:
lib/mp3info.rb,
lib/mp3info/extension_modules.rb

Defined Under Namespace

Modules: HashKeys, Mp3FileMethods

Constant Summary collapse

VERSION = 
"0.6.11"
LAYER = 
[ nil, 3, 2, 1]
BITRATE = 
{
  1 => 
  [
    [32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448],
    [32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384],
    [32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320] ],
  2 => 
  [
    [32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256],
    [8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160],
    [8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160]
  ],
  2.5 => 
  [
    [32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256],
    [8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160],
    [8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160]
  ]
}
SAMPLERATE = 
{
  1 => [ 44100, 48000, 32000 ],
  2 => [ 22050, 24000, 16000 ],
  2.5 => [ 11025, 12000, 8000 ]
}
CHANNEL_MODE = 
[ "Stereo", "JStereo", "Dual Channel", "Single Channel"]
GENRES = 
[
"Blues", "Classic Rock", "Country", "Dance", "Disco", "Funk",
"Grunge", "Hip-Hop", "Jazz", "Metal", "New Age", "Oldies",
"Other", "Pop", "R&B", "Rap", "Reggae", "Rock",
"Techno", "Industrial", "Alternative", "Ska", "Death Metal", "Pranks",
"Soundtrack", "Euro-Techno", "Ambient", "Trip-Hop", "Vocal", "Jazz+Funk",
"Fusion", "Trance", "Classical", "Instrumental", "Acid", "House",
"Game", "Sound Clip", "Gospel", "Noise", "AlternRock", "Bass",
"Soul", "Punk", "Space", "Meditative", "Instrumental Pop", "Instrumental Rock",
"Ethnic", "Gothic", "Darkwave", "Techno-Industrial", "Electronic", "Pop-Folk",
"Eurodance", "Dream", "Southern Rock", "Comedy", "Cult", "Gangsta",
"Top 40", "Christian Rap", "Pop/Funk", "Jungle", "Native American", "Cabaret",
"New Wave", "Psychadelic", "Rave", "Showtunes", "Trailer", "Lo-Fi",
"Tribal", "Acid Punk", "Acid Jazz", "Polka", "Retro", "Musical",
"Rock & Roll", "Hard Rock", "Folk", "Folk/Rock", "National Folk", "Swing",
"Fast-Fusion", "Bebob", "Latin", "Revival", "Celtic", "Bluegrass", "Avantgarde",
"Gothic Rock", "Progressive Rock", "Psychedelic Rock", "Symphonic Rock", "Slow Rock", "Big Band",
"Chorus", "Easy Listening", "Acoustic", "Humour", "Speech", "Chanson",
"Opera", "Chamber Music", "Sonata", "Symphony", "Booty Bass", "Primus",
"Porn Groove", "Satire", "Slow Jam", "Club", "Tango", "Samba",
"Folklore", "Ballad", "Power Ballad", "Rhythmic Soul", "Freestyle", "Duet",
"Punk Rock", "Drum Solo", "A capella", "Euro-House", "Dance Hall",
"Goa", "Drum & Bass", "Club House", "Hardcore", "Terror",
"Indie", "BritPop", "NegerPunk", "Polsk Punk", "Beat",
"Christian Gangsta", "Heavy Metal", "Black Metal", "Crossover", "Contemporary C",
"Christian Rock", "Merengue", "Salsa", "Thrash Metal", "Anime", "JPop",
"SynthPop" ]
TAG1_SIZE = 
128
TAG_MAPPING_2_2 =

map to fill the “universal” tag (#tag attribute) for id3v2.2

{ 
  "title"    => "TT2",
  "artist"   => "TP2", 
  "album"    => "TAL",
  "year"     => "TYE",
  "tracknum" => "TRK",
  "comments" => "COM",
  "genre_s"  => "TCO"
}
TAG_MAPPING_2_3 =

for id3v2.3 and 2.4

{ 
  "title"    => "TIT2",
  "artist"   => "TPE1", 
  "album"    => "TALB",
  "year"     => "TYER",
  "tracknum" => "TRCK",
  "comments" => "COMM",
  "genre_s"  => "TCON"
}
SAMPLES_PER_FRAME =

www.codeproject.com/audio/MPEGAudioInfo.asp

[
  nil,
  {1=>384, 2=>384, 2.5=>384},    # Layer I   
  {1=>1152, 2=>1152, 2.5=>1152}, # Layer II
  {1=>1152, 2=>576, 2.5=>576}    # Layer III
]

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(filename, options = {}) ⇒ Mp3Info

Instantiate Mp3Info object with name filename. options hash is used for ID3v2#new. You can specify :parse_tags => false to disable the processing of the tags (read and write).



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# File 'lib/mp3info.rb', line 196

def initialize(filename, options = {})
  warn("#{self.class}::new() does not take block; use #{self.class}::open() instead") if block_given?
  @filename = filename
  @tag_parsing_enabled = options.delete(:parse_tags)
  if @tag_parsing_enabled == nil
    @tag_parsing_enabled = true
  end
  @id3v2_options = options
  reload
end

Instance Attribute Details

#bitrate ⇒ Object (readonly)

bitrate in kbps



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# File 'lib/mp3info.rb', line 119

def bitrate
  @bitrate
end

#channel_mode ⇒ Object (readonly)

channel mode => “Stereo”, “JStereo”, “Dual Channel” or “Single Channel”



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# File 'lib/mp3info.rb', line 125

def channel_mode
  @channel_mode
end

#error_protection ⇒ Object (readonly)

error protection => true or false



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# File 'lib/mp3info.rb', line 145

def error_protection
  @error_protection
end

#filename ⇒ Object (readonly)

the original filename



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# File 'lib/mp3info.rb', line 160

def filename
  @filename
end

#header ⇒ Object (readonly)

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



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# File 'lib/mp3info.rb', line 139

def header
  @header
end

#layer ⇒ Object (readonly)

layer = 1, 2, or 3



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# File 'lib/mp3info.rb', line 116

def layer
  @layer
end

#length ⇒ Object (readonly)

length in seconds as a Float



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# File 'lib/mp3info.rb', line 142

def length
  @length
end

#mpeg_version ⇒ Object (readonly)

mpeg version = 1 or 2



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# File 'lib/mp3info.rb', line 113

def mpeg_version
  @mpeg_version
end

#samplerate ⇒ Object (readonly)

samplerate in Hz



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# File 'lib/mp3info.rb', line 122

def samplerate
  @samplerate
end

#tag ⇒ Object (readonly)

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



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# File 'lib/mp3info.rb', line 149

def tag
  @tag
end

#tag1 ⇒ Object

id3v1 tag as a Hash. You can modify it, it will be written when calling “close” method.



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# File 'lib/mp3info.rb', line 153

def tag1
  @tag1
end

#tag2 ⇒ Object

id3v2 tag attribute as an ID3v2 object. You can modify it, it will be written when calling “close” method.



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# File 'lib/mp3info.rb', line 157

def tag2
  @tag2
end

#vbr ⇒ Object (readonly)

variable bitrate => true or false



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# File 'lib/mp3info.rb', line 128

def vbr
  @vbr
end

Class Method Details

.hastag1?(filename) ⇒ Boolean

Test the presence of an id3v1 tag in file filename

Returns:

  • (Boolean) 


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# File 'lib/mp3info.rb', line 163

def self.hastag1?(filename)
  File.open(filename) { |f|
    f.seek(-TAG1_SIZE, File::SEEK_END)
    f.read(3) == "TAG"
  }
end

.hastag2?(filename) ⇒ Boolean

Test the presence of an id3v2 tag in file filename

Returns:

  • (Boolean) 


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# File 'lib/mp3info.rb', line 171

def self.hastag2?(filename)
  File.open(filename) { |f|
    f.read(3) == "ID3"
  }
end

.open(*params) ⇒ Object

“block version” of Mp3Info::new()



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# File 'lib/mp3info.rb', line 360

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

.removetag1(filename) ⇒ Object

Remove id3v1 tag from filename



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# File 'lib/mp3info.rb', line 178

def self.removetag1(filename)
  if self.hastag1?(filename)
    newsize = File.size(filename) - TAG1_SIZE
    File.open(filename, "rb+") { |f| f.truncate(newsize) }
  end
end

.removetag2(filename) ⇒ Object

Remove id3v2 tag from filename



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# File 'lib/mp3info.rb', line 186

def self.removetag2(filename)
  self.open(filename) do |mp3|
    mp3.tag2.clear
  end
end

Instance Method Details

#audio_content ⇒ Object

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 


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# File 'lib/mp3info.rb', line 411

def audio_content
  pos = 0
  length = File.size(@filename)
  if hastag1?
    length -= TAG1_SIZE
  end
  if hastag2?
    pos = @tag2.io_position
    length -= @tag2.io_position
  end
  [pos, length]
end

#close ⇒ Object

Flush pending modifications to tags and close the file



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# File 'lib/mp3info.rb', line 425

def close
  puts "close" if $DEBUG
  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)
    #@tag1_orig.update(@tag1)
    @tag1_orig = @tag1.dup
    File.open(@filename, 'rb+') do |file|
      if @tag1_orig.empty?
        newsize = file.stat.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)
    tempfile_name = nil
    File.open(@filename, 'rb+') do |file|
	#if tag2 already exists, seek to end of it
	if @tag2.parsed?
 file.seek(@tag2.io_position)
	end
#      if @file.read(3) == "ID3"
#        version_maj, version_min, flags = @file.read(3).unpack("CCB4")
#        unsync, ext_header, experimental, footer = (0..3).collect { |i| flags[i].chr == '1' }
#	tag2_len = @file.get_syncsafe
#        @file.seek(@file.get_syncsafe - 4, IO::SEEK_CUR) if ext_header
#	@file.seek(tag2_len, IO::SEEK_CUR)
#      end
	tempfile_name = @filename + ".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)
  end
end

#flush ⇒ Object

close and reopen the file, i.e. commit changes to disk and reload it



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# File 'lib/mp3info.rb', line 513

def flush
  close
  reload
end

#get_frames_infos(head) ⇒ Object

Raises:



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# File 'lib/mp3info.rb', line 338

def 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
  { :layer => layer,
    :bitrate => BITRATE[mpeg_version][layer-1][bits(head, 15,12)-1],
    :samplerate => SAMPLERATE[mpeg_version][bits(head, 11,10)],
    :mpeg_version => mpeg_version,
    :padding => (head[9] == 1) }
end

#hastag1? ⇒ Boolean

Does the file has an id3v1 tag?

Returns:

  • (Boolean) 


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# File 'lib/mp3info.rb', line 393

def hastag1?
  !@tag1.empty?
end

#hastag2? ⇒ Boolean

Does the file has an id3v2 tag?

Returns:

  • (Boolean) 


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# File 'lib/mp3info.rb', line 398

def hastag2?
  @tag2.parsed?
end

#hastag? ⇒ Boolean

Does the file has an id3v1 or v2 tag?

Returns:

  • (Boolean) 


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# File 'lib/mp3info.rb', line 388

def hastag?
  hastag1? || hastag2?
end

#reload ⇒ Object

reload (or load for the first time) the file from disk

Raises:



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# File 'lib/mp3info.rb', line 208

def reload
  raise(Mp3InfoError, "empty file") unless File.size?(@filename)

  @header = {}
  
  @file = File.new(filename, "rb")
  @file.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


    ### 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 = @file.pos - 4
      current_frame = 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 = bits(head, 7,6)]
	@header[:mode_extension] = bits(head, 5,4)
	@header[:copyright] = (head[3] == 1 ? true : false)
	@header[:original] = (head[2] == 1 ? true : false)
	@header[:emphasis] = 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)

    @file.seek(seek, IO::SEEK_CUR)
    
    vbr_head = @file.read(4)
    if vbr_head == "Xing"
	puts "Xing header (VBR) detected" if $DEBUG
	flags = @file.get32bits
	stream_size = frame_count = 0
	flags[1] == 1 and frame_count = @file.get32bits
	flags[2] == 1 and stream_size = @file.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
	@file.seek(100, IO::SEEK_CUR) if flags[0] == 1
	#@vbr_quality = @file.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) >> 10
	@vbr = true
    else
	# for cbr, calculate duration with the given bitrate
	stream_size = @file.stat.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, length = frame_scan(100)
        if @bitrate != bitrate
          @vbr = true
          @bitrate, @length = frame_scan
        end
      rescue Mp3InfoInternalError
      end
	if @tag2["TLEN"]
 # but if another duration is given and it isn't close (within 5%)
 #  assume the mp3 is vbr and go with the given duration
 tlen = (@tag2["TLEN"].is_a?(Array) ? @tag2["TLEN"].last : @tag2["TLEN"]).to_i/1000
 percent_diff = ((@length.to_i-tlen)/tlen.to_f)
 if percent_diff.abs > 0.05
   # without the xing header, this is the best guess without reading
   # every single frame
   @vbr = true
   @length = @tag2["TLEN"].to_i/1000
   @bitrate = (stream_size / @bitrate) >> 10
 end
	end
    end
  ensure
    @file.close
  end
end

#removetag1 ⇒ Object

Remove id3v1 from mp3



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# File 'lib/mp3info.rb', line 376

def removetag1
  @tag1.clear
  self
end

#removetag2 ⇒ Object

Remove id3v2 from mp3



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# File 'lib/mp3info.rb', line 382

def removetag2
  @tag2.clear
  self
end

#rename(new_filename) ⇒ Object

write to another filename at close()



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# File 'lib/mp3info.rb', line 403

def rename(new_filename)
  @filename = new_filename
end

#to_s ⇒ Object

inspect inside Mp3Info



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# File 'lib/mp3info.rb', line 519

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.inspect+"\n" if hastag1?
  s << "tag2: "+@tag2.inspect+"\n" if hastag2?
  s
end