Convert audio files on an external hard drive into MP3 format on my desktop

convert-music.rb

require "fileutils"
require "open3"
require "pathname"
require "progressbar"

input_directory = "/Volumes/Artemis/Music"
output_directory = "/Users/soffes/Desktop/Music"
extensions = %w[wav aiff mp3 m4a]
target_extension = "mp3"

glob = File.join(input_directory, "**", "*.{#{extensions.join(",")}}")

# This can be pretty slow
puts "Gathering file list…"
files = Dir.glob(glob, File::FNM_CASEFOLD)

if files.empty?
  puts "No files found."
  exit 1
end

# Make output directory
FileUtils.mkdir_p(output_directory)

progressbar = ProgressBar.create(
  title: "Converting",
  format: "%t: |%B| %E %c/%C",
  total: files.count
)

files.each do |path|
  # Change the directory to be relative to our output directory instead
  output = File.join(output_directory, path.delete_prefix(input_directory))

  # Replace the extension with our target extension
  album_dir = File.dirname(output)
  output = File.join(album_dir, "#{File.basename(output, ".*")}.#{target_extension}")

  # Skip if we have already converted it
  next if File.exist?(output)

  # Make the directory for the album
  FileUtils.mkdir_p(album_dir)

  # Convert
  command = %(ffmpeg -i "#{path}" -b:a 320k "#{output}")
  Open3.capture3(command) # using this instead of `` suppresses the output

  progressbar.increment
end