Grabbing a sequence of screen shots

Grabbing screen shots as a movie

You can use the VNC set of tools to grab a screen as a movie, to create canned demos of your application. The following commands worked for me:

• vncserver - this runs a "headless" X server. the first time you use it, you will be prompted to supply a password. The X server ID should be different from your normal one. So if your normal screen is cvplws86:0, the new one might be cvplws86:1, i.e.:

   vncserver :1 -geometry 1280x800

• vncviewer - this runs the "virtual" screen that connects to the headless server, in which you run your application in the normal way:

  vncviewer :1 &

  You will be prompted for the password set above.
• vncrec - use this to:
  • Start recording the session to a file:

        vncrec -record <file>

    Kill it to stop (unless there is a better way).
  • To view it:

        vncrec -play <file> &

  • You can pipe the output - so to convert it to e.g. png files:

        setenv VNCREC_MOVIE_CMD "xpmtoppm | pnmtopng -force > img_%05d.png"
        vncrec -movie <file>
    

    N.B. The -force option is sometimes needed to get mencoder to work properly.
  • Then to create an avi you could try:

        mencoder "mf://img_*.png" -mf fps=10:type=png -ovc lavc -lavcopts vcodec=msmpeg4v2:vqscale=1:vhq -o abc.avi

  vncrec -help for quick help; tar file if no executable.

• To finish the session, killing off the server kills off any other VNC tasks:

      vncserver -kill :1

See man pages and look on the web for more ideas.