Ubuntu 14.04

ffmpeg -y -f alsa -ac 2 -i pulse -f x11grab -r 30 -s 1920×1080 -i :0.0 -vcodec libx264 -pix_fmt yuv420p -crf 22 -acodec libmp3lame -ar 44100 -ab 126k -threads 3 ~/Skrivebord/screencast.mp4

Fedora 23, screengrab 720p no audio. bitrate 1200k

ffmpeg -video_size 1280×720 -framerate 30 -f x11grab -i :1+3840,200 -vcodec libx264 -b:v 1200k -threads 3 output3.mp4

Windows Screen Recording

ffmpeg.exe -f gdigrab -i desktop -framerate 25 -video_size 1366×768 -vcodec libx264 babe2.mkv