anchor.diff:      ++ optional libpngSupport libpng
       ++ optional libjpegSupport libjpeg
       ++ optional bs2bSupport libbs2b
  +    ++ optional v4lSupport libv4l
       ++ (with darwin.apple_sdk.frameworks; optionals stdenv.isDarwin [ Cocoa OpenGL ])
       ;
   
  
positive.code: , jackaudioSupport ? false, libjack2 ? null
  , pulseSupport ? config.pulseaudio or false, libpulseaudio ? null
  , bs2bSupport ? false, libbs2b ? null
  # For screenshots
  , libpngSupport ? true, libpng ? null
  , libjpegSupport ? true, libjpeg ? null
  
negative.code:     (if x264Support then "--enable-x264 --disable-x264-lavc" else "--disable-x264 --enable-x264-lavc")
      (if jackaudioSupport then "" else "--disable-jack")
      (if pulseSupport then "--enable-pulse" else "--disable-pulse")
      (if v4lSupport then "--enable-v4l2 --enable-tv-v4l2" else "--disable-v4l2 --disable-tv-v4l2")
      "--disable-xanim"
      "--disable-ivtv"
      "--disable-xvid --disable-xvid-lavc"
  