seek, name=Backward-seek, playback_time="min(5.0, (duration/4))", rate=1.0, start=0.0
seek, name=Backward-seek, playback_time="min(10.0, 2*(duration/4))", rate=1.0, start="min(5.0, duration/4)"
seek, name=Backward-seek, playback_time="min(15.0, 3*(duration/4))", rate=1.0, start="min(10.0, 2*(duration/4))", stop="min(15.0, 3*(duration/4))"