The following command converts all AVI files in a directory to H264 480p using ffmpeg :
FOR /F "tokens=*" %G IN ('dir /b *.avi') DO ffmpeg -i "%G" -codec:v libx264 -preset slow -b:v 500k -maxrate 500k -bufsize 1000k -vf scale=-1:480 -threads 0 -codec:a aac -b:a 128k "%~nG.mp4"