I have to disagree a bit here. Your ascent looks good, but lowering the weight things go awry. You're moving the bar away from your body and bending your knees way too much way too soon. It looks like an awkward reverse squat, not a deadlift descent. As a rule, when lowering the weight, the bar should stay as close to the legs as possible, and you don't need to bend your knees until AFTER the bar passes them on the descent. Your current descent is putting significant stress on your spinal erectors, and with heavy weight could lead to injury.
Read Eric Cressey's "Mastering the Deadlift" series. It includes video of popular mistakes in form (including what you're doing) as well as a video in which Eric demonstrates perfect form. Eric pulls 650 at only 165lbs of bodyweight, so if you don't want to take my word for it, read his series, you'll be pulling properly in no time.