?

Log in

No account? Create an account
Previous Entry Share Next Entry
Graphing Networks
photogeek
crschmidt
Taking an idea and some motivation from a project of Jibbler's, I decided tonight that I would make graphs of the two channels I run PieSpy bots in. I learned some interesting things.

First of all, the mplayer documentation provides a command that segfaults on running. The command:

mencoder "mf://*.png" -mf fps=25 -o output10.avi -ovc divx4

Runs through, gets to a certain step - and dies. no more encoding. The fix wasn't too difficult, I just needed to specify some different options, but it made me scratch my head. I had to ask in #mplayer for what to do. However, they helped me out, with information about how the mencoder options work, so I was able to generate images after that. Command used was mencoder -oac copy -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=1000 mf://*.png -mf fps=$numFPS -o $outputfilename

I've learned that it's really easy to generate these things - just a few minutes of processing time, and I've turned the 1000+ png images of channel relationships into a video!

These videos show the network of #foaf over the last week or so.

https://netfiles.uiuc.edu/crschmid/www/foaf-fast.avi -- 30fps version -- 4.9 meg
This file is recommended if you have a play back device which can slow down output - you'll probably want to run it at about 1/3rd-1/5th speed.

https://netfiles.uiuc.edu/crschmid/www/foaf.avi -- 7 fps -- 11.13 meg
Recommended if you can't control the speed of your output. Larger file, because of the lower frames per second.

Next, I generated images for #drupal. These images are smaller, because the bot was offline for a couple days, and I didn't realize it. But they're still pretty nifty, and don't have the crazily strong link that #foaf seems to have generated between drumm, xavier and I.

https://netfiles.uiuc.edu/crschmid/www/drupal-slow.avi -- 7MB -- 7 fps
https://netfiles.uiuc.edu/crschmid/www/drupal-fast.avi -- 3.16 MB -- 30fps video.
Second one is good for people who can slow down playback, first is good for those who can't.

Current graphs for the channels in question are available at http://foaf.crschmidt.net/foaf/foaf-current.png and http://drupal.crschmidt.net/drupal/drupal-current.png .

  • 1
I don't get it. Why does slowing down the frame rate make the file bigger?

Probably the way I'm encoding it.

Keyframes are generated every x time units. As the video grows longer, the time units count grows higher - more key frames. The answer to this, of course, would be to bump the number of keyframes so that it's equal to the number of frames - that way, all the videos would be the same size.

However, I haven't figured out how to do that - my efforts have been foiled in every case.

If you have ideas as to how to make the video encoding less hungry or modify the number of keyframes used, feel free to share it.

  • 1