ShiZZZoN-
Hey, I apologize as the first equation i put on ehre was a little confusing but now i got 3 and these are simplified down perfect and here the are-
There are 3, one to find vid bitrate, one to find audio bitrate(if you like using high vid bitrate), and 3rd, to see how much room its gonna take up-
T = Time in seconds of vid clip
C = Cd size (this is ONLY for 80 min cds- 819,200 KB)
A = audio bitrate
X = vid bitrate

This is called the CatX equation
To find vid bitrate, here is equation-

TX = C - AT
EX.- your time is 4800 sec(90 min), you have an 80 min cd and want to put whole movie on it(cd= 819,200), your audio bitrate is- 128kbits, heres how to find it-

First you must remember, you must have ALL units the same.
So- 819,200 kb and 128 kbits are different. 128 kbits = 16 KB, now to figure out and substitute-

TX = C - AT=
4800x= 819,200 - (16)(4800)
4800x= 819,200 - 76,800
4800x= 742,400 kb
x= 154.666666667
This is your vid bitrate in KB, but tmgpenc displays it as kbits, so multiply this number by 8, and you get-
1237.333333333333
NOTE- NO MATTER WHAT YOU ARE FINDING, ALWAYS ROUND DOWN, EVEN IF IT WAS 1237.999, IT WOULD STILL BE 1237 BECAUSE YOU DONT WANT YOUR MOVIE LARGER THAN THE CD SIZE!

Next equation- calculate how big file will be or how many cds it will take-

C = TX + AT
Lets do same example-
C= (4800)(154.6667) + (16)(4800
C = 819,200 KB Perfect cd size (if you get over this, you will probably be using 2 cds. this is a very useful equation.)

Last, calculate your audio bitrate, lets do same example-

AT= C - TX
A(4800)= 819,200 - (4800)(154.6667)
A(4800)=76,800 KB
A=16 KB, tmpgenc displays it in kbits, so multiply 16 by 8 and you get- 128


so 3 revised equations are-
find vid bitrate- TX= C - AT
find file size- C= TX + AT
Find audio bitrate- AT= C - TX