If you want a reset button that remembers what the original factory settings are and reverts to them, that does not exist. However, you can manually update the settings back to the original values at any given time. To discover what the original values are, you have options:

* Look inside the .sdf database file in the download package. It's in the gs_GallerySetting table. Use a tool like the SQL Server Compact Toolbox to open the DB.
* Install a fresh copy of GSP and look at the settings.

I don't know what FFmpeg settings you would use for those conversions. You'll probably have better luck on a FFmpeg forum.