Tips : how to make a video

[admin]

Gephi doesn't include a tool for recording videos yet, but I give you my way to make the videos you watch in Vimeo.

I'm on Ubuntu, but it should work well on all Linux. You need the 2 following softwares (available in Ubuntu repositories) :

• recordmydesktop
• mencoder

On Windows and Mac OSX, use Jing

Once installed, just start recordmydesktop (set quality to the maximum), display Gephi on your screen and do you stuff, and stop recordmydesktop. The video is encoded in Ogg Theora and could be a large file. You may keep your movie now, but I had some little problems in my own videos : recordmydesktop recorded the whole desktop, but I just needed the Gephi window, I had to cut off the video before the end, and in order to publish on the Web, I needed a smaller file size.

So we use mencoder to re-encode our ogg theora file to a mpeg-4 file. This is the command I use to keep the best quality possible :

First pass:

Code: Select all

mencoder input.ogg -vf crop=1680:998:0:0 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=3152:v4mv:mbd=2:trell:v4mv:cbp:last_pred=3:predia=3:dia=4:vmax_b_frames=2:vb_strategy=1:precmp=3:cmp=3:subcmp=3:preme=3:qns=2:vpass=1 -oac mp3lame -o output.avi -endpos 00:05:12

And pass two is the same, except that we specify vpass=2:

Code: Select all

mencoder input.ogg -vf crop=1680:998:0:0 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=3152:v4mv:mbd=2:trell:v4mv:cbp:last_pred=3:predia=3:dia=4:vmax_b_frames=2:vb_strategy=1:precmp=3:cmp=3:subcmp=3:preme=3:qns=2:vpass=2 -oac mp3lame -o output.avi -endpos 00:05:12

Hints :

• -vf crop=w:l:x:y delete unwanted areas
• -ovc lavc video codec
• -lavcopts ... options for lavc (see readme for details)
• -oac mp3lame audio codec
• -endpos hh:mm:ss cut off the video

It takes roughly 2 hours to re-encode a 5-minute video, but we gain a lot in file size, passing from 200MB to 30MB !

Reference: http://www.mplayerhq.hu/DOCS/HTML/en/me ... codec.html

Example on Advanced features demo