Converts one or more AVI files given or found recursively under given paths or current directory to mp4 format using ffmpeg
Useful to be able to stream videos to devices like smart TVs that may otherwise not understand the codecs used in the original format
Names the generated files the same except with the '.avi' extension replaced with '.mp4'
Skips files which already have a corresponding adjacent '.mp4' file present to be able to resume partial directory conversions, and also removes partially complete files for consistency using bash trapping