anchor.diff:        ;
   
       buildInputs = [ pkgconfig lame yasm zlib bzip2 SDL ]
  +      ++ [ perl ] # for install-man target
         ++ optional mp3Support lame
         ++ optional speexSupport speex
         ++ optional theoraSupport libtheora
  
positive.code: { stdenv, fetchurl, pkgconfig, yasm, bzip2, zlib
  , mp3Support    ? true,   lame      ? null
  , speexSupport  ? true,   speex     ? null
  , theoraSupport ? true,   libtheora ? null
  
negative.code:       "--enable-avplay"
        "--enable-shared"
        "--enable-runtime-cpudetect"
        "--cc=cc"
      ]
        ++ optionals enableGPL [ "--enable-gpl" "--enable-swscale" ]
        ++ optional mp3Support "--enable-libmp3lame"
  