gistfile1.rb

module Paperclip
  # Creates short snippets of an mp3
  # SoX FTW! http://sox.sourceforge.net/sox.html
  class TrackPreview < Processor

    def initialize(file, options = {})
      super
      @file = file
      @current_format   = File.extname(@file.path)
      @basename         = File.basename(@file.path, @current_format)
    end

    def make
      output_file = Tempfile.new([@basename, @current_format].compact.join("."))
      output_file.binmode
      trim = "trim 10 30" # start at 10 seconds, duration 30 seconds.
      fade = "fade 2 30" # fade duration is 2 seconds, end fade-out at 30 seconds.
      begin
        success = Paperclip.run('sox', "-t mp3 #{File.expand_path(file.path)} -t mp3 #{File.expand_path(output_file.path)} #{trim} #{fade}")
      rescue PaperclipCommandLineError
        raise PaperclipError, "There was an error processing the clip for #{@basename}"
      end
      output_file
    end

  end
end