ffmpeg is a powerful tool and it can do the work of capturing Linux desktop video very well. ffmpeg is a very fast video and audio converter that can also grab from a live audio/video source. ffmpeg can grab X11 input and create a video file such as mp4 at specific fps with the specific resolution.
$ ffmpeg -f x11grab -s 1280x1024 -r 25 -i :0.0+0,0 out.mp4
Options used here:
For more usage of
ffmpeg, please check ffmpeg manual.