[MPlayer-users] Bitrates and File Size

Joonas Koivunen rzei at mbnet.fi
Mon Aug 25 21:33:18 CEST 2003

On Monday 25 August 2003 21:51, Ethan John wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> Hi all,

> (New to the list) I've been ripping movies from DVD with MEncoder for
Please, don't reply to other threads to write to the list. Just select writing 
a new message instead of replying to older thread. (ofc when you aren't 
continuing the thread.) it's rather rude and will make some ppl miss your 

> Why don't the bitrate numbers match the file size numbers?
AFAIK this is explained in encoding-tips.txt, check it again.

> with an expected file size of 685 MB, but the file is only 600 MB. How
> is this possible? aren't mpeg4 movies constant bit rate unless you
> specify otherwise?
Afaik CBR isn't possible.. I might be wrong.. Either way, IMHO and AFAIK it'd 
be stupid.

> But in practice, this number is too small -- it yields files in the
> 600-650 MB range.
IMHO  you should target 700MB.

> Right now, I calculate bitrate based on trial and error from the past
> -- typically something like:
> (bits for 725 MB file) / (seconds in movie)
Hint: use 3 pass technique. mencoder will tell you a suggested bitrate.

> i.e., I calculate the video bitrate based upon wanting a 725 MB movie
> of _just_ video. This typically yields file sizes between 660 and 700
> MB.
If mencoder outputs a file much less (as in more than 3MB) smaller than you 
had expected, check out divx2pass.log, calc quantizer avg. If it's 2 or very 
close to 2, you shouldn't be scaling down that much. If it's less than 2 you 
really should limit it.. But there's in the docs about this too. Or if you 
are fine with the current video resolution, give more bits to the audio side.

> (I have a million more questions, but I'll try to keep it to one a day
> for a while. =- )

> ethan john

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