I use FFmpeg for making video screen capture from Xvfb display.
Currently I invoke it with:
ffmpeg -y -r 15 -g 600 -s 1280x1024x24 -f x11grab -i :100 -vcodec libx264 /tmp/video.mov
As I record video from about 5 Xvfb sessions my CPU usage is very high and there are lags because of it. Also memory usage is about 300 MB for each of ffmpeg processes.
Which parameters for ffmpeg should I use to minimize computer resources usage (particularly CPU and memory) when making video screen capture?