Recording screencasts using ttyrec and ffmpeg

I'm preparing walk-through screencasts for workshop about virtualization so I needed easy way to produce console screencasts.

First, I found TTYShare which displays ttyrec files using flash, but I really wanted to copy/paste parts of commands and disliked flash plugin requirement.

It seems that I wasn't only one who wanted JavaScript client for ttyrec. jsttplay can produce screencasts like this one about OpenVZ using plain copy/paste friendly JavaScript within browser.

But, for some parts (like Debian installation under VirtualBox) I really needed movie capture. x11grab option from ffmpeg seemed easy enough to use:

ffmpeg -f x11grab -s 640x480 -r 10 -i :0.0 /tmp/screencast.avi
but getting right window size isn't something I want to do by hand. So, I wrote small perl script which extract window position and size using xwininfo and pass it to ffmpeg so I don't have to.