VMD-L Mailing List

From: Axel Kohlmeyer (akohlmey_at_cmm.chem.upenn.edu)
Date: Thu Apr 17 2008 - 16:23:34 CDT

On Thu, 17 Apr 2008, Anthony Ivetac wrote:

anthony,

AI> I am using the VMD Movie Maker plug-in with VMD 1.8.6 to generate MPG movies
AI> of simulation trajectories. Behind the scenes, the TCL script uses PPMTOMPEG
AI> to stitch the individual PPM images into an MPG file and I am wondering
AI> which settings in the PPMTOMPEG parameter file (.par) can be toggled to
AI> achieve better quality movies (presumably at the expense of compression)? I

john is a much better expert on this, so i guess he can give you
a more detailed answer, but from my limited experience there are
three things you could consider:

- mpeg-1 compression has its limitations, you can use a different
  tool (mjpegtools, mencoder) to do an mpeg-2 or mpeg-4 compression.
  just keep the intermediate images and run the new compressor manually.
- smooth images before compressing them. also try to reduce sharp
  contrasts in color and brightness as they create more artefacts.
- render larger images. some movie players can do a smoothed
  downscaling. this would come at a high computational and data or
  memory (storage) cost, though.

cheers,
   axel.

AI> find that, with the default settings, the output MPG movie is rather
AI> 'grainy'.

AI>
AI> Many thanks!
AI> 

-- 
=======================================================================
Axel Kohlmeyer   akohlmey_at_cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
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If you make something idiot-proof, the universe creates a better idiot.