ffmpeg vsync drop

#!/bin/bash
#
# Input is two .flv movies, each of which may have missing video frames.
# Output is a merged .mp4 (side-by-side).
#

ffmpeg -v debug -y -i $1 -i $2 -filter_complex "
 [0:0] pad='max(240,iw):max(180,ih):0:0', scale='240:180', pad='480:180:240:0' [left];
 [1:0] pad='max(240,iw):max(180,ih):0:0', scale='240:180' [right];
 [left] [right] overlay [out0];
 [0:1] [1:1] amerge [out1]" \
-codec:a  libfaac  -ar  44100 \
-codec:v libx264 -preset medium -vsync drop \
-map [out0] -map [out1] $3