anchor.diff:  { alsaSupport ? true, xvSupport ? true, theoraSupport ? true, cacaSupport ? true
   , xineramaSupport ? true, randrSupport ? true, dvdnavSupport ? true
  -, stdenv, fetchurl, x11, freetype, fontconfig, zlib
  +, stdenv, fetchurl, x11, freetype, fontconfig, zlib, ffmpeg
   , alsaLib ? null, libXv ? null, libtheora ? null, libcaca ? null
   , libXinerama ? null, libXrandr ? null, libdvdnav ? null
   , cdparanoia ? null, cddaSupport ? true
  
positive.code: in  
  
  stdenv.mkDerivation rec {
    name = "MPlayer-1.0-pre20101227";
  
    src = fetchurl {
      url = http://nixos.org/tarballs/mplayer-snapshot-20101227.tar.bz2;
      sha256 = "0q9rvjz3byvs0qlnb9jbnw3qs6c3vdcqaqxm1rnql8kqic442hv2";
    };
  
    buildInputs =
      [ freetype zlib pkgconfig ]
      ++ stdenv.lib.optional x11Support [ libX11 libXext mesa ]
      ++ stdenv.lib.optional alsaSupport alsaLib
      ++ stdenv.lib.optional xvSupport libXv
  
negative.code: 
    buildNativeInputs = [ yasm ];
  
    preConfigure = ''
      tar xf ${ffmpeg.src}
      mv ffmpeg* ffmpeg
    '';
  
    configureFlags = ''
      ${if cacaSupport then "--enable-caca" else "--disable-caca"}
      ${if dvdnavSupport then "--enable-dvdnav --enable-dvdread --disable-dvdread-internal" else ""}
  