anchor.diff:  , x11grabExtlib ? false, libXext ? null, libXfixes ? null # X11 grabbing (legacy)
   , x264 ? null # H.264/AVC encoder
   , x265 ? null # H.265/HEVC encoder
  -, xavs ? null # AVS encoder
  +#, xavs ? null # AVS encoder
   , xvidcore ? null # Xvid encoder, native encoder exists
  -, zeromq4 ? null # Message passing
  +#, zeromq4 ? null # Message passing
   , zlib ? null
   #, zvbi ? null # Teletext support
   /*
  
positive.code:     (mkFlag (x11grabExtlib && gplLicensing) "0.5" "x11grab")
      (mkFlag (x264 != null && gplLicensing) "0.5" "libx264")
      (mkFlag (disDarwinFix (x265 != null && gplLicensing)) "2.2" "libx265")
      (mkFlag (disDarwinFix (xavs != null && gplLicensing)) "0.7" "libxavs")
      (mkFlag (xvidcore != null && gplLicensing) "0.5" "libxvid")
      (mkFlag (zeromq4 != null) "2.0" "libzmq")
      (mkFlag (zlib != null) "0.5" "zlib")
      #(mkFlag (zvbi != null && gplLicensing) "2.1" "libzvbi")
      /*
  
negative.code: 
    buildInputs = [
      bzip2 celt fontconfig freetype fribidi gnutls ladspaH lame libass libbluray
      libbs2b /* libcaca */ libdc1394 libogg libopus libtheora libvdpau libvorbis
      libwebp libX11 libxcb libXext libXfixes libXv lzma SDL soxr speex x264
      xvidcore /* zeromq4 */ zlib
    ] ++ optional (disDarwinFix sambaExtlib) samba
      ++ optional openglExtlib mesa
      ++ optionals x11grabExtlib [ libXext libXfixes ]
      ++ optionals nonfreeLicensing [ faac faad2 fdk_aac openssl ]
      ++ optionals (!isDarwin) [
        frei0r /* game-music-emu gsm jack2 */ libmodplug libssh libvpx /* openal */
        openjpeg_1 pulseaudio rtmpdump vid-stab wavpack x265 /* xavs */
    ] ++ optional (!isDarwin && !isCygwin) libva
      ++ optionals isLinux [ alsaLib libraw1394 /* v4l_utils */ ];
  
    # Build qt-faststart executable
    buildPhase = optional (qt-faststartProgram && (reqMin "0.9")) ''make tools/qt-faststart'';
  