[FFmpeg-user] calculating size of encoded video

[Carlo Bongiovanni]

Hi All,

I am using ffmpeg to convert big files (>2GB) in short ones and to
download them.

I would like that, when I download, I choose the size of the encoded
file, and this gives the exact parameters to ffmpeg to encode the file
correctly.

I made a test for calculating bitrate and size by using the formula:
	
(Size - (Audio x Length )) / Length = Video bitrate

from (http://www.videohelp.com/calc.htm) but it is not working on my case.

I'm using the following command to do the encoding:

C:\Shell\ffmpeg\bin>ffmpeg.exe -i D:\XXX.mov -s 320x240 -r 30000/1001
-b:a 200k -bt 240k -vcodec libx264 -acodec libmp3lame -ac 2 -ar 48000
-ab 128k ../output.mp4
	
can anybody suggest me what should I do or what should I study to
solve this issue?

p.s. I also tried using -ps command (preferred size) but it didn't
work in my case.

thanks for any help
kind regards
carlo