Copy tags from OGG or MP3 files to FLAC files. Matching files are found by patterns containing their track number. Optionally rename files.

copytags.rb

#! /usr/bin/ruby1.9.3 -w

require 'optparse'
require 'taglib'

FIELDS = %w( ALBUM ARTIST CDDB DATE GENRE DISCNUMBER TITLE TRACKNUMBER )

$dry_run = false
$tag = true
$rename = false
$quiet = false
$verbose = false
$help = false

def main
  opts = OptionParser.new
  opts.banner = "Usage: #{opts.program_name} [options] from_pattern to_pattern"

  opts.on('-n', '--dry-run', "Don't run any commands, just print them") {
    $dry_run = true
  }
  opts.on('-t', '--tag', "copy tags from matching files (default)") {
    $tag = true
  }
  opts.on('-T', '--no-tag', "do not copy tags from matching files") {
    $tag = false
  }
  opts.on('-r', '--rename', "rename from matching files") {
    $rename = true
  }
  opts.on('-R', '--no-rename', "do not rename from matching files (default)") {
    $rename = false
  }
  opts.on('-q', '--quiet', "Display less information") {
    $quiet = true
  }
  opts.on('-v', '--verbose', "Display extra information") {
    $verbose = true
  }
  opts.on('-h', '--help', "Show this message") {
    $help = true
  }

  args = opts.parse(ARGV)
  from_pattern, to_pattern = args

  if $help || from_pattern.nil? || to_pattern.nil?
    puts opts.help
    puts
    puts "Examples"
    puts "    # Copy tags from 1.Track.ogg to 1.Track.flac"
    puts "    #{opts.program_name} '%.1d.*.ogg' '%.1d.*.flac'"
    puts
    puts "    # Copy tags from 01.Track.ogg to 01.Track.flac"
    puts "    #{opts.program_name} '%.2d.*.ogg' '%.2d.*.flac'"
    puts
    puts "    # Assuming 1.Song.ogg, rename 1.Track.flac to 1.Song.flac"
    puts "    #{opts.program_name} -rT '%.1d.*.ogg' '%.1d.*.flac'"

    exit 0
  end

  (1..100).each do |track|
    from_file = match_pattern(from_pattern, track) or next
    to_file   = match_pattern(to_pattern, track) or next

    if $tag
      copy_tags(from_file, to_file)
    end
    if $rename
      rename_file(to_file, from_file)
    end
  end
end

def match_pattern(pat, track)
  candidate = pat.gsub(/([\[\]])/, '\\\\\1') % track
  matches = Dir[candidate]
  raise "Multiple matches for \"#{candidate}\"" if matches.size > 1
  matches.first
end


def copy_tags(from_file, to_file)
  puts "Copying tags from #{from_file} to #{to_file}" unless $quiet
  from_fields = read_fields(from_file)
  puts "  Tags: #{from_fields.inspect}" if $verbose
  write_fields(to_file, from_fields) unless $dry_run
end

def read_fields(file)
  case File.extname(file)
  when '.ogg', '.OGG'
  TagLib::Ogg::Vorbis::File.open(file, false) do |f|
    field_map = f.tag.field_list_map
    FIELDS.each_with_object({}) do |field, fields|
      value = field_map[field]
      fields[field] = value.first if value && FIELDS.include?(field)
    end
  end
  when '.mp3', '.MP3'
  TagLib::MPEG::File.open(file, false) do |f|
    tag = f.id3v2_tag
    FIELDS.each_with_object({}) do |fld, flds|
      m = fld.downcase
      flds[fld] = tag.public_send(m) if tag.respond_to?(m)
    end
  end
  else
    raise ArgumentError, "Cannot extract tags from #{file}"
  end
end

def write_fields(file, fields)
  TagLib::FLAC::File.open(file, false) do |f|
    tag = f.xiph_comment
    fields.each do |key, value|
      tag.add_field(key, value)
    end
    f.save
  end
end

def rename_file(new_path, old_path)
  ext      = File.extname(new_path)
  new_dir  = File.dirname(new_path)
  old_name = File.basename(old_path, '.*')
  path = File.join(new_dir, "#{old_name}#{ext}").sub(/^\.\//, '')
  unless path == new_path
    puts "Renaming #{File.basename(new_path)} -> #{File.basename(path)}" unless $quiet
    File.rename(new_path, path) unless $dry_run
  end
end

main