description, seek=true, duration=30, need-clock-sync=true
seek, name=Backward-seek, playback_time="min(5.0, (duration/4))", rate=1.0, start=0.0, flags=accurate+flush
seek, name=Backward-seek, playback_time="min(10.0, 2*(duration/4))", rate=1.0, start="min(5.0, duration/4)", flags=accurate+flush
seek, name=Backward-seek, playback_time="min(15.0, 3*(duration/4))", rate=1.0, start="min(10.0, 2*(duration/4))", flags=accurate+flush
stop, playback_time="min(15.0, 3*(duration/4))"