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View Full Version : How to calculate TMPGenc bit rate (CBR)

Chumboy
26th October 2002, 15:26
does anyone know the math formula for setting the CBR value in TMPGenc?

how do i calculate what bitrate to set?
Kenwood
26th October 2002, 18:23
In my case in use streamprocessing in DVD Decrypter.
Will rip the Movie, English 6 ch. Audio & 1 subtitle.
Then I will start Bitrate Viewer and press on the 'calc' (=calculator button) top right corner.
Default on 4.7GB DVD.
Movielenght -> example 111 mins.
Subtitle: 1
Encoder quality: Lever to right = max.
Image quality: Lever to right = max.
Then above in right corner the bitrate will show.
I always lower it down to a nice round figure.
Example: 4338 wil be 4300.
This calculator has never let me down, movie will always fit on a standard DVD (4.7 GB).
Best regards,

Kenwood

P.s. I always use automatic VBR for encoding en then set the average bitrate with the button 'Setting' right next to it !
ulfschack
29th October 2002, 15:01
Yes, that's a way, but he asked for "the formula". Heres my "own":

[(4.7*1024^3)-audio_MB*1024^2]*8/(movieLengthMinutes*60*1000)= [bitrate in thousands-of-bits-per-second]

Most (at least CCE and TmpgEnc) dont use 1024 as base when saying kbps, but rather 1000. Hence the thousands-of-bits-per-second.

I just finished encoding "a bugs life" this morning. Using the above yielded a bitrate of 6000, which I then promptly used. End result was 3.82 GB. Backward calculating gave me that I according to the formula had used a bitrate of 5977 k[1000]bps ... close enough (off by .4%).

I think that subs are small enough too vanish in the errormargins of the rough 4.7GB and the variance of TmpgEnc's CBR encoding (not using all 32 of them of course :) ).

cheers
Steelfanatic
1st November 2002, 02:18
Originally posted by Chumboy
does anyone know the math formula for setting the CBR value in TMPGenc?

how do i calculate what bitrate to set?

Chum, I just use TMPGEnc Plus, note the "Plus version" which uses a "wizard type interface" that takes care of the sizing for you and does 3:2 pulldown automatically, I prefer the ease of use over CCE. (my opinion please no flame war).:D