@setlocal

@rem folder where ffmpeg.exe is located
@set FF=C:\ffmpeg
@set PATH=%FF%;%PATH%

@set filename=%1

@rem audio bitrate
@set ab=320

@set aproc2="pan=stereo|FL < FL+1.414FC+0.5BL+0.5SL+0.25LFE+0.125BR|FR < FR+1.414FC+0.5BR+0.5SR+0.25LFE+0.125BL,loudnorm=I=-12:TP=-1.5:LRA=11"


for /r %%i in (*.mkv) do (

	@ffmpeg.exe -hide_banner -v 32 -stats -y -i "%%i" -map 0:a -c:a ac3 -ac 2 -ar 48000 -ab 640k -filter:a %aproc2% -f matroska "%%~dpni [Stereo].mkv"
    @ffmpeg.exe -hide_banner -v 32 -stats -y -i "%%i" -i "%%~dpni [Stereo].mkv" -map 0:v -map 0:a -map 1:a -map 0:s? -c copy -f matroska "%%~ni [Stereo].mkv"

)

pause