@echo off
setlocal enabledelayedexpansion

REM Set input and output folders
set "input=.\mov_backup"
set "output=.\mov"

REM Loop through all .dat files
for %%F in ("%input%\*.dat") do (
    set "filename=%%~nF"
    ffmpeg -i "%%F" -c:v mpeg4 -q:v 2 -c:a mp3 -q:a 2 -f avi "%output%\!filename!.avi"
)

REM Rename all .avi files to .dat
for %%A in ("%output%\*.avi") do (
    ren "%%A" "%%~nA.dat"
)

echo Done.
pause