encoding sintel source images is not that hard, you have to find how many digits they have 00000001.png becomes 000%05d.png
here is an example that should work, it outputs a file with realy high quality
ffmpeg -f image2 -i "000%05d.png" -r 23.976 -vcodec libx264 -preset slow -crf 22 out.mkv
downloading the sintel source files are as easy as
apt-get install aria2c
aria2c -Z -P http://media.xiph.org/sintel/sintel-4k-png16/[00000001-00021312].png
