def retime_by_framerate(have, want)
      ratio = want.fps.to_f / have.fps.to_f
      have.subtitles.each do |subtitle|
        subtitle[:start] *= ratio
        subtitle[:end] *= ratio
      end
    end
def retime_by_framerate(have, want)
      ratio = want.fps.to_f / have.fps.to_f
      have.subtitles.each do |subtitle|
        subtitle[:start] *= ratio
        subtitle[:end] *= ratio
      end
    end
Rescales timecodes based on two differing framerates.

 @param have [Have] the subtitles we {Have}
 @param want [Want] the subtitles we {Want}