anchor.diff:  , dc1394Support ? false, libdc1394 ? null
   , x11grabSupport ? false, libXext ? null, libXfixes ? null
   , playSupport ? true, SDL ? null
  -, freetypeSupport ? true, freetype ? null
  +, freetypeSupport ? true, freetype ? null, fontconfig ? null
   }:
   
   assert speexSupport -> speex != null;
  
positive.code:     ++ stdenv.lib.optional dc1394Support libdc1394
      ++ stdenv.lib.optionals x11grabSupport [ libXext libXfixes ]
      ++ stdenv.lib.optional playSupport SDL
      ++ stdenv.lib.optional freetypeSupport freetype;
  
    enableParallelBuilding = true;
  
  
negative.code:     ++ stdenv.lib.optional dc1394Support "--enable-libdc1394"
      ++ stdenv.lib.optional x11grabSupport "--enable-x11grab"
      ++ stdenv.lib.optional playSupport "--enable-ffplay"
      ++ stdenv.lib.optional freetypeSupport "--enable-libfreetype --enable-fontconfig";
  
    buildInputs = [ pkgconfig lame yasm zlib bzip2 alsaLib texinfo perl ]
      ++ stdenv.lib.optional mp3Support lame
  