anchor.diff:  , vdpauSupport ? true, libvdpau ? null
   , faacSupport ? false, faac ? null
   , dc1394Support ? false, libdc1394 ? null
  +, x11grabSupport ? false, libXext ? null, libXfixes ? null
   }:
   
   assert speexSupport -> speex != null;
  
positive.code: assert xvidSupport -> xvidcore != null;
  assert vdpauSupport -> libvdpau != null;
  assert faacSupport -> faac != null;
  
  stdenv.mkDerivation rec {
    name = "ffmpeg-1.0";
  
negative.code:     ++ stdenv.lib.optional xvidSupport "--enable-libxvid"
      ++ stdenv.lib.optional vdpauSupport "--enable-vdpau"
      ++ stdenv.lib.optional faacSupport "--enable-libfaac --enable-nonfree"
      ++ stdenv.lib.optional dc1394Support "--enable-libdc1394"
      ++ stdenv.lib.optional x11grabSupport "--enable-x11grab";
  
    buildInputs = [ pkgconfig lame yasm zlib bzip2 ]
      ++ stdenv.lib.optional mp3Support lame
  