anchor.diff:  , mp3Support ? true, lame ? null
   , speexSupport ? true, speex ? null
   , theoraSupport ? true, libtheora ? null
  -, vorbisSupport ? true, libvorbis ? null
  +, vorbisSupport ? false, libvorbis ? null
   , vpxSupport ? false, libvpx ? null
   , x264Support ? true, x264 ? null
  -, xvidSupport ? true, xvidcore ? null
  +, xvidSupport ? false, xvidcore ? null
   , faacSupport ? false, faac ? null
   }:
   
  
positive.code:     ++ stdenv.lib.optional xvidSupport xvidcore
      ++ stdenv.lib.optional faacSupport faac;
  
    crossAttrs = {
      dontSetConfigureCross = true;
      configureFlags = configureFlags ++ [
  
negative.code: assert xvidSupport -> xvidcore != null;
  
  stdenv.mkDerivation rec {
    name = "ffmpeg-0.8";
    
    src = fetchurl {
      url = "http://www.ffmpeg.org/releases/${name}.tar.bz2";
      sha256 = "03zwwc1qs117pfjk9r071fbx4al3j0c85j97dgwqc0wp2z1zs9iy";
    };
    
    # `--enable-gpl' (as well as the `postproc' and `swscale') mean that
  