convert mp4 to mp3

mp4tomp3.bat

@echo off
setlocal
set FFMPEG=ffmpeg.exe
set LAME=lame.exe
set touch=touch.exe

if "%1"=="" echo usage: mp4tomp3 {directory} && goto err
if not exist %1 echo %1: Not found. && goto err

pushd %1
  if not %errorlevel%==0 echo pushd failed. && goto err

  for %%F in (*.mp4) do (
    echo "%%~nF"
    if not exist %FFMPEG% echo No ffmpeg. && goto err

    %FFMPEG% -y -i "%%~nF.mp4" -vn -acodec pcm_s16le -ac 2 -ar 44100 "%%~nF.wav"
    if not %errorlevel%==0 echo ffmpeg failed. && goto err

    if exist %LAME% (
      %LAME% -V2 --priority 0 "%%~nF.wav" "%%~nF.mp3"
      if not %errorlevel%==0 echo lame failed. && goto err

      del /f/q "%%~nF.wav"
      if exist %touch% %touch% -r "%%~nF.mp4" "%%~nF.mp3"
    )
  )
popd
exit /b 0

:err
exit /b 255