GNU|Linux
$ wget http://www.youtube.com/watch?v=dQw4w9WgXcQ -qO- | sed -n "/fmt_url_map/{s/[\'\"\|]/ /g;p}" | sed -n '/^fmt_url_map/,/videoplayback/p' | sed -e :a -e '$q;N;5,$D;ba' | tr -d ' ' | sed -e 's/\(.*\),\(.\)\{1,3\}/\1/' | wget -i - -O surprise.flv