ffmpeg \\ -i main.avi\\ -i mini.avi\\ -filter_complex "[0:v:0][0:a:0][1:v:0][1:a:0]concat=n=2:v=1:a=1[outv][outa]; \\ [0:v:1][0:a:0][1:v:1][1:a:0]concat=n=2:v=1:a=1
