[MEncoder-users] Frame Rate and file Size

[Peter Hartshorn]

On Sat, 26 Feb 2005 11:18 am, bruno agostini wrote:
> I have a strange problem I quite don't understand here. I want to make a
> divx with 2000 jpg. So I use the following command:
>
> mencoder  mf://*.jpg -mf w=512:h=256:fps=30:type=jpg -ofps 30 -nosound
> -ovc lavc -lavcopts vcodec=msmpeg4v2:vbitrate=500 -o movie.avi
>
> Then I get a 5 MB movie of 67 sec and I am happy with that. But I also
> want to make a version at 5 fps (it is a scientific movie so that I want
> to have a slow version to see details without having to settle the speed
> on the player everytime). So I use:

Why not just make a copy of the 30 fps movie (cp movie.avi movie_5fps.avi) and 
then use avifix (from transcode?) to set the framerate to 5 in the avi header
(avifix -i movie_5fps.avi -f 5)

>
> mencoder  mf://*.jpg -mf w=512:h=256:fps=5:type=jpg -ofps 5 -nosound
> -ovc lavc -lavcopts vcodec=msmpeg4v2:vbitrate=500 -o movie.avi
>
> I have the same number of frame (2000), the same effective bitrate (I
> checked), only the fps (i.e. the movie is now 400 sec) has changed, but
> I get a 25 MB movie! But there is the same amount of information to
> encode in the second case isn't it? So why should the file size be
> different?
>
> thanks for your help!
>
>
>
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