[MEncoder-users] reencoding to time lapse

[Moritz Barsnick]

Moin Volker,

On Thu, Nov 22, 2007 at 13:15:32 +0100, Volker Poplawski wrote:

> My input video is 10fps - 25fps. By specifing -ofps 25 frames are inserted 
> (duplicated), so my output is not speed up.

No, the logic is irritating if you think of speedup, but correct in any
other case. "-ofps" tells mencoder that the output video shall be 25
FPS, _but still basically show the same footage_. That's why you see
your effect.

What does the trick is "-ofps 25 -noskip"!. :-)

But the other way around, if you want mencoder to re-interpret the
source as slower, and speed it up x2 while keeping the "real" frame
rate, you do need to skip, and you need to think the other way around:
"-fps 60 -ofps 30". (I don't quite the the factor x2 though.)

NB: Watch out for the sound! It's not being sped up.

HTH,
Moritz

(Time lapse is cool on webcam shots recorded by motion e.g. at 5fps.
Works nice on DVD at 25fps!)