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;
  assert x11grabSupport -> libXext != null && libXfixes != null;
  
  stdenv.mkDerivation rec {
    name = "ffmpeg-0.11.1";
  
negative.code:     ++ stdenv.lib.optional xvidSupport xvidcore
      ++ stdenv.lib.optional vdpauSupport libvdpau
      ++ stdenv.lib.optional faacSupport faac
      ++ stdenv.lib.optional dc1394Support libdc1394;
  
    enableParallelBuilding = true;
      
  