SET outfilename=%cd%\webemka.webm
ffmpeg.exe -i %infilename% -y -ss %start% -t %length% %cd%\output.wav
ffmpeg.exe -i %cd%\output.wav -acodec opus -frame_duration 60 -b:a %audio%k -ac 2 -dtx 1 -map 0:a %outfilename%
call :getFilesize %outfilename%
echo file size is %fileSize%
SET /A bitrate=((8*(10240*1024-%fileSize%))/%length%)/1024