ffmpeg options syntax:
ffmpeg [options for 1st input] -i firstinput.file [options for 2nd input] -i secondinput.file [options for 1st output] firstoutput.file [options for 2nd output] secondoutput.file

Lossless screen caputure on Linux: (ffmpeg needs to be compiled with --enable-libfaac --enable-libx264 --enable-x11grab)
ffmpeg -f x11grab -r 15 -s 1280x800 -i :0.0 -f alsa -i hw:0 -c:a libvorbis -b:a 128k -c:v libx264 -crf 0 -preset ultrafast capture.mkv