From: Axel Kohlmeyer (
Date: Wed Feb 17 2010 - 21:24:14 CST

On Wed, 2010-02-17 at 18:20 -0800, Samuel Coulbourn Flores wrote:
> Hi Guys,
> I am making a move of ribosome motion. I have ~50 frames of its
> trajectory, and it's not easy for me to generate more than this. When
> I try to make a movie, it goes through the entire motion very quickly,
> then lingers on the last frame for the remaining time. Is there a way
> to slow down the motion? I could generate GIFs and then concatenate
> those using convert, but I wonder if there's an easier way within VMD.

actually, that is exactly what the VMD movie maker script does,
if you ask it to produce an animated GIF.

slowing down an mpeg movie is much more difficult. there are some
movie container formats (or sometimes inofficial extensions) where
custom frame rates can be set. but for mpegs generated with ppmtompeg,
the range is limited (and last time i checked, even that didn't work).

a simple way is to keep all files. and then change .par file
to include each file twice. that is often done in stop-motion
animation, to speed up the process, but that reduces your frame
rate to effectively 12fps.

a more sophisticated way would be to "clone" your system, e.g.
by only reading a .psf file as a second molecule and then loop over
the frames of the existing file and create more frames by interpolating
between existing frames. it is a bit tedious to script it, but
not too difficult either. specifically to avoid artefacts, one
would have to run pbc unwrap on the second of the two i
nterpolated frames and then undo the unwrap.

john, i've been pondering this idea for quite a while and
would be willing to add this to the moviemaker script, if
there was sufficient interest and no objections. the second
option would be to put this together with my trajectory
"denoising" tool into a separate package and then this would
be a two step process. cleaner, but requiring more storage.

> Thanks
> Sam

Dr. Axel Kohlmeyer
Institute for Computational Molecular Science
Temple University, Philadelphia PA, USA.