how to loop avi files in ffmpeg (Debian 7)

[Koze]

I am using Debian 7 with ffmpeg-dmo-1.0.10 installed within root folder. Within root I have also another folder which contains 2 .avi files (W1.avi and W22.avi)
I am using following command to stream W1.avi file:

ffmpeg -i '/root/folder2/W1.avi' -acodec aac -vcodec libx264 -s 640x480 -preset medium -strict experimental -f flv rtmp://live.xyz.tv/app/a9085ebcedxxxxxxx83

and all works great.

Now I would like to add second file named W22.avi and make them both loop all the time.

So what I have done, I created list.txt file with following content:

file 'W1.avi'
file 'W22.avi'

and placed this list.txt file within folder2

and then I tried to use following commend:

ffmpeg -f concat -i '/root/folder2/list.txt' -acodec aac -vcodec libx264 -s 640x480 -preset medium -strict experimental -f flv rtmp://live.xyz.tv/app/a9085ebcedxxxxxxx83

After running above command I am getting following error:

Unknown input format: 'concat'

Can you kindly guide me what I am doing wrong? Or maybe there is another way to get what I need?

Thank you in advance,