How do I calculate the final bitrate?

[egov]

Hi!
I have a 22min. movie 640x480, with 112kbis/sec stereo audio and I want to fit it on 700MB CD.
Now, I got a whole bunch of bitrate calculators (Adv. bitrate calculator, Equador bitrate calculator) but it seems too difficult for me to figure it out, because no one ask me for the video width and height. Ok, how the hell they would suggest a DIVX bitrate without even knowing the picture size? Do they tell me that 4000Kbit/sec is OK for both 640x480 and 120x90???

[Sciascia]

Yes, it is. Look at what you are asking for, bitrate which literally means rate of bits in a second. It doesn't matter what the data is, it is the amount of data and that is where the bitrate comes in.

[Phil Pugh]

Bit Rate calulators = A calculator

You have 22mins of video/audio to get onto a 700MB disc so...

22 mins = 1320 seconds

700MB = 700000000*8 bits = 56000000000 bits (I am taking 1Mb to be 1000000 bytes here - I know it's not strictly correct).

Now for the really difficult part!

Average bit rate of audio/video combined is 560000000/1320 which I make (using Windows Calulator) 4242.42kbps

Your audio is 112kbps so your video should be encoded at a lower rate than 4130kbps. Lets call it 4000kbps.

For more accurate numbers you should take off the overhead for whatever structures you are creating (e.g. DVD/SVCD/VCD file structures) and directory structures. But as a rule of thumb you now know what bitrate to use.