Running Two Instances of a Program Simultaneously

[dodle]

I am using ffmpeg to capture my screen. Though i am having a problem with audio syncronisation:

ffmpeg -f x11grab -r 30 -s 1280x800 -i :0.0 -f alsa -i hw:0,0 -sameq -vcodec libxvid -acodec libmp3lame -ab 128k -ar 44100 -ac 1 test.avi

One site I read suggested recording audio and video separately, so I tried this:

ffmpeg -f x11grab -r 30 -s 1280x800 -i :0.0 -sameq -vcodec libxvid video.avi & \
ffmpeg -f alsa -i hw:0,0 -acodec libmp3lame -ab 128k -ar 44100 -ac 1 audio.mp3

But only the audio is recored while an empty "video.avi" is created. How can I create two instances of ffmpeg running at the same time?


----- SEMI-SOLVED -----

I figured out how to use nohup in order to successfully run the first intance of ffmpeg in the background:

: nohup ffmpeg -f x11grab -r 30 -s 1280x800 -i :0.0 -vcodec libxvid video.avi & \
ffmpeg -f alsa -i hw:0,0 -acodec libmp3lame -ab 128k -ar 44100 -ac 1 audio.mp3

The problem now is how to kill the first process along with the second.


----- SOLVED -----

The PID of the first instance of ffmpeg can be placed in a variable using $!, then just kill that process ID when the second instance is finished:

nohup ffmpeg -f x11grab -r 30 -s 1280x800 -i :0.0 -vcodec libxvid video.avi &
P1=$!
ffmpeg -f alsa -i hw:0,0 -acodec libmp3lame -ab 128k -ar 44100 -ac 1 audio.mp3

kill $P1