Do you want a software to capture your screen as a movie? For tutorial or games record? Vokoscreen is the answer. It is perfect for me. In ubuntu based linux, it comes as a program that easily install. Just do this :
#sudo apt-get install vokoscreen
Run the program and you can record as you like. The result format video that available for vokoscreen is avi and mkv. Of course I choose mkv, which is smaller in size than avi.
If you need in mp4 format, convert it with ffmpeg.
ffmpeg -i file.mkv fileoutput.mp4