As some of you may recall, every time I've posted a demo video to LAD, I've had to include a disclaimer excusing the poor quality due to a lack of functional screencasting tools.
Well, it took a couple of weeks of hair pulling and many, many hours of testing, but I finally arrived at a solution.
Get ffmpeg. Apply this patch to it:
Build it with vorbis and h264 support.
Then, start your favorite desktop environment. I use Xephyr for this.
Have jack running (at -r 48000)
Then run the following command:
ffmpeg -fflags +genpts+igndts -f x11grab -vsync 0 -r 30 -s 1920x1080 -i :${DISPLAY}.+0,0 -vcodec h264 -f jack -ac 2 -r:a 48000 -i screencast -acodec pcm_s16le -r:v 30 -vsync 2 -async 1 -map 0:0,1,0 -map 1:0 -preset ultrafast -qp 0 "$FILE"
Where DISPLAY is the number of your X11 display and FILE is the filename for the screencast. I use a .mkv extension for the matroska container.
Remember to connect the streams you want recorded to the 'screencast' JACK inputs!
With this setup I'm able to record a full 30 FPS @ 1080P with audio in perfect sync. Please share your results too. With some more evidence I might have a good case to get ffmpeg to accept my patch.
Enjoy!