anchor.diff:  , meson
   , ninja
   
  -, ffmpeg
  +, ffmpeg_3
   , glib
   , gst-plugins-base
   , gstreamer
  
positive.code:   ];
  
    buildInputs = [
      ffmpeg
      glib
      gst-plugins-base
      gstreamer
  
negative.code:   postUnpack = /* gst-libav vendors outdated ffmpeg sources */ ''
      pushd $srcRoot/gst-libs/ext/
        rm -rfv libav/
        tar -xf ${ffmpeg_3.src}
        mv -v ffmpeg-*/ libav/
      popd
    '';
  