Ruby: SMPTE Converter

If you need to do any sort of screen capturing using FFMPEG, you might need this one day.

# http://ifhere.org/ffmpeg

# Example

# SMPTECodes.standard= :pal #=> :pal
# SMPTECodes.fps #=> 25.0

# t = "95:33:24.92" #=> "95:33:24.92" 
# t.to_frame #=> 8256118
# t.to_frame.to_smpte #=> "95:33:24.92" 
# t == t.to_frame.to_smpte #=> true

# SMPTECodes.standard= :ntsc #=> :ntsc
# SMPTECodes.fps #=> 29.97002997003

# t = "95:33:24.70" #=> "95:33:24.70" 
# t.to_frame #=> 10309831
# t.to_frame.to_smpte #=> "95:33:24.70" 
# t == t.to_frame.to_smpte #=> true


class SMPTECodes
  #http://en.wikipedia.org/wiki/SMPTE_timecode

  @@standard = :ntsc

  def self.standard
    @@standard
  end

  # Set the frequency standard, ie :ntsc, :pal, :dv
  def self.standard=(code)
    @@standard = code
  end

  def self.fps
    case self.standard
      when :ntsc: 30/1.001
      when :pal: 25.0
      when :dv: 30.0
    end
  end

  module String
    # Converts an SMPTE code into a frame number based upon the current FPS 
    def to_frame
      t = self.split(/:|\./).map {|i| i.to_i}
      while t.length < 4 do 
        t.insert 0, 0
      end
      # hours(?):Miutes:seconds.frames
      ((t[0]*(60*60*SMPTECodes.fps)) + 
      (t[1]*(60*SMPTECodes.fps)) + 
      (t[2] * SMPTECodes.fps) +  
      ( (t[3].to_f*(SMPTECodes.fps/100)).round)).round
    end
  end

  module Numeric
    # Converts an a frame number to an SMPTE string
    def to_smpte
      h, m = self.divmod(60 * 60* SMPTECodes.fps)
      m, s = m.divmod(60* SMPTECodes.fps)
      s, f = (s).divmod(SMPTECodes.fps)
      f = (f.round*(100.0/SMPTECodes.fps))

      if f >= 100
        s = s+1;
        f = 0;
      end

      "#{("%02d" % h.round)}:#{("%02d" % m.round)}:#{("%02d" % s.round)}.#{("%02d" % f.round)}" 
    end
  end
end

# Mixin the modules
String.send :include, SMPTECodes::String
Numeric.send :include, SMPTECodes::Numeric