Free software for batch basic editing and down-sampling
I'm fairly certain you can do this with VLC 3.0+ or via the command line. 

https://wiki.videolan.org/VLC_HowTo/Transcode_multiple_videos/

This can be done using the transcode/streaming options via the file menu in the graphical app. You can set the in and out and select all te files to process, as well as the codec and container format.