http://forum.doom9.org/archive/index.php/t-37204.html
http://avisynth.org.ru/docs/english/...s/autocrop.htm
http://doom10.org/index.php?topic=1255.0
Please check those. I really want to contribute to your project.
Did you think about the Extracting the subtitle files with the output? Like, encode the video file and select the subtitle files on the .mkv and extract them to the output folder too? Maybe a subtitle convertor intergration would be nice. I haven't seen that anywhere yet.