[martino]

You probably did not have a type 1 file if it had subtitles and they didn't get hardcoded to the video. It's always a good idea to first open the .avs script in your media player to check whether it works fine.

Why would AviSynth need to get copied or moved? You install it and that's it. Perhaps the instructions weren't clear enough, but with a bit of common sense you can deduce that if tool x is needed, and comes as an .exe installation package, it has to be installed before it can be used either by the user or program y. Anyway, I guess I'll have to amend it to make it clearer.

For troubleshooting please launch the script from the command prompt (Start -> Run -> cmd or Windows key + R and cmd) and paste in everything that it outputs into the window, as well as the .avs script that you used.

Lastly, this script is meant to provide good quality at acceptable speed... imo anyway. If you want it better, faster, slower, or worse you'll have to change it yourself. Google and x264 --help or --longhelp is your friend.