inigo \
-blank 49 \
clip2.dv in=100 \
-track \
clip1.dv out=99 \
-transition \
mix start=0 end=1 in=49 out=50 a_track=1 b_track=0 \
-transition \
mix:1 in=51 out=99 a_track=1 b_track=0 \
$*