Bitrate might be off by a factor of 8

[fanuch]

Love the readme.

Have been testing your code to see my own results and I noticed my file sizes export to about 1.35 MB.

I am not an expert in ffmpeg but I believe your bitrate needs to be multiplied by 8 to approximate what is actually intended.

e.g.

name	original size (MB)	bitrate kbit/s	final size (MB)	bitrate * 8 kbit/s	final size (MB)
file 1	90.1	497	1.35	3976	8.1
file 2	92.2	529	1.41	4232	8.5

Proposed solution

bitrate=$(( $(echo "scale=0; $targetSizeKilobytes/ $durationSeconds" | bc) * 8 ))

hopefully this helps :)