KVCD: How to calculate required bitrate?
 

Hi,
I am new to this forum, but not so new to KVCD(started a month ago). I have had excellent results with converting my recorded programs to KVCD format and my collection is growing day by day!
I use mencoder under Linux to encode the recordings (I use MythTV for recording purposes). I use windows for burning CD's only. I will stop using windows the day K3B ( a cd/dvd burning software under Linux) becomes mature enough to burn VCD's / Video DVD's.

Sorry for all this mumbo jumbo, I have one problem in my perfect setup(barring the disk burning issue) and that is calculation of Bitrate. I need this because almost always I overshoot or undershoot the required size (80 min VCD - i dunno the MB's - Can you please tell the size in MB's too that can fit in 80 min CD?).

Can anybody guide me in doing so? I want to write a small script/program under Linux that will be used in my encoding scripts.

Thanks in advance.
PK

Hi pappukanghi,

Download "CalcuMatic" from this forum.
That will give you the approximate size for just about every size media :)
It's a Windows app, btw.

-kwag

You can use "Calcumatic" for Bitratecalculation
http://www.kvcd.net/downloads/CalcuMatic.exe

or "bitratecalculator"
http://home.arcor.de/packshot/bitratecalculator.exe
in case of multiple "individual" Streams on DVD-R

Beat ya Inc :mrgreen:

:hihi:

Thanks to all of you for the suggestions. I had seen about calcumatic already.

But I need the formulas to write script/program myself so that my existing scripts (under Linux) which know movie duration, should be able to calculate bitrate too.

And yes, I have come to know that 80min=795Mb approx.

Thanks again,
PK

(Media size in kilobytes * 8 / length in seconds) - audio bitrate = video bitrate ?

Boulder
Is it that simple? I compared this calculation with what calcumatic gave me for a generic movie of 60 minutes.
(I calculated assuming 800Mb for 80 minutes and 1 Mb = 1000 Kbytes, I don't know if CD manufacturers take 1000 or 1024 for Kilo or Mega calculations)

Avg. bitrates came out to be:
Calculated acc. to your formula - 1649.78
Calcumatic(no mux overhead): 1692.4
Calcumatic(VCD/SVCD mux overhead): 1669.7
Calcumatic(DVD mux overhead): 1635.6


If I am wrong in my calculations, can you please rectify the mistake?

Thanks again
PK

You'll have to include some overhead calculations for the media size. For example, I've noticed that you can safely assume that a DVD is 4350MB (no need to subtract overhead anymore). Can't help you more with that but I recall that FitCD is quite accurate so you could use its output to determine a muxing overhead for VCD/SVCD.