How to make a 3d movie with ffmpeg

how to combine two seperate videos into one left-right video

1. Convert both movies to png still images
   1. ffmpeg -r 20 -i test01-left.avi -r 20 -s 640x480 frames-l/%09d.png
   2. ffmpeg -r 20 -i test01-rigth.avi -r 20 -s 640x480 frames-r/%09d.png

1. Putting still images side by side, using imagemagick's montage command

  a=1 
  while [ $a -lt 2416 ]  
  do 
     b=`printf "%09d" $a` 
     montage frames-l/$b.png  frames-r/$b.png -geometry 320x240+0+0 frames/$b.jpg 
     let a++
  done

1. Convert images to avi
   1. ffmpeg -i %03d.jpg -acodec copy -vcodec copy -f avi outputfile.avi