record using ffmpeg

rec.sh

#!/bin/sh

INFO=$(xwininfo -frame)

WIN_GEO=$(echo $INFO | grep -oEe 'geometry [0-9]+x[0-9]+' |\
    grep -oEe '[0-9]+x[0-9]+')
WIN_XY=$(echo $INFO | grep -oEe 'Corners:\s+\+[0-9]+\+[0-9]+' |\
    grep -oEe '[0-9]+\+[0-9]+' | sed -e 's/+/,/' )

ffmpeg -f x11grab -y -r 15 -s $WIN_GEO -i :0.0+$WIN_XY -vcodec ffv1 -sameq -f alsa -ac 2\
    -i pulse -acodec ac3 -threads 2 $1.avi

thanks, man, this really helped me a lot.