[MEncoder-users] Vbitrate not honored?

RC rcooley at spamcop.net
Sat Aug 26 17:06:06 CEST 2006

On Fri, 25 Aug 2006 11:21:50 +0200
Stefan Neufeind <mencoder at stefan-neufeind.de> wrote:

> It's only needed for WMV, or for other codecs as well?

There are just a few other files that can handle vfr (variable
frame-rate), but WMV is the only I've come across in my personal
experience.  So you're pretty safe if you just do it for WMVs.

> Using ofps was a general rule for automatically converting might not
> be a good idea - I guess - becuase that might leasd
>  to framerate-changes (and copying/dropping frames). Is that right?

It won't matter if you set an ofps (or not) on most material.  mencoder
doesn't support outputting vfr, anyhow.  

> Is there a way to determine the optimal fps to use? 

fps and ofps are very different, and you should be clear about which you
mean, as it will be a mess if you make that mistake.

You can detect the approximate frame-rate of WMV files by playing
through them (perhaps with "-speed 100 -nosound"), then dividing the
number of frames by the time.  From there, I would strongly suggest
rounding up to the next common frame-rate value (eg. 28.65 becomes
-ofps 30000/1001, 24.5 becomes -ofps 25, etc.).

Alternatively, it's been said that ffmpeg does a good job of detecting
the actual framerate of WMV files, so you might want to try using that
to get the proper value beforehand.

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