Quantcast KVCD: How to Calculate Required Bitrate? - digitalFAQ.com Forums [Archives]
  #1  
10-13-2004, 08:51 AM
pappukanghi pappukanghi is offline
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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
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  #2  
10-13-2004, 09:09 AM
kwag kwag is offline
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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
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10-13-2004, 09:09 AM
incredible incredible is offline
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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
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10-13-2004, 09:10 AM
kwag kwag is offline
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Beat ya Inc
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10-13-2004, 09:12 AM
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10-13-2004, 09:21 AM
pappukanghi pappukanghi is offline
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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
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10-13-2004, 10:06 AM
Boulder Boulder is offline
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(Media size in kilobytes * 8 / length in seconds) - audio bitrate = video bitrate ?
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10-13-2004, 10:59 AM
pappukanghi pappukanghi is offline
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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
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10-13-2004, 11:47 AM
Boulder Boulder is offline
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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.
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