Question

I have a Rails application where people can use an in browser sound editor to create wav files and upload them to the server.

I use Paperclip for handling the sound file upload.

I would like to be able to convert the wav file to an mp3, but keep both files.

I have read about Paperclip processors, but I’m not sure how to use them to get both files instead of just converting to mp3 only.

Answer 1

Ok, this probably isn’t optimal but it works pretty well. I ended up adding another attachment to my Sound class for the mp3, and added a before_validation filter to hook into it. In addition, since I had some existing wav attachments, I created a reconvert_to_mp3 method to handle the migrating of the existing records.

has_attached_file :mp3,
  :storage => :s3,
  :s3_credentials => "#{RAILS_ROOT}/config/s3.yml",
  :path => "sounds/:id/:style.:extension"

before_validation :convert_to_mp3

def reconvert_to_mp3
  wavfile = Tempfile.new(".wav")
  wavfile.binmode

  open(wav.url) do |f|
    wavfile << f.read
  end

  wavfile.close

  convert_tempfile(wavfile)
end

def convert_to_mp3
  tempfile = wav.queued_for_write[:original]

  unless tempfile.nil?
    convert_tempfile(tempfile)
  end
end

def convert_tempfile(tempfile)
  dst = Tempfile.new(".mp3")

  cmd_args = [File.expand_path(tempfile.path), File.expand_path(dst.path)]
  system("lame", *cmd_args)

  dst.binmode
  io = StringIO.new(dst.read)
  dst.close

  io.original_filename = "sound.mp3"
  io.content_type = "audio/mpeg"

  self.mp3 = io
end