@medjdoub45 the answer from @pleriche is of course an excellent one. I just replayed your video in slow motion and this is more than just a brightness issue between the two side. This looks more like a timing issue. This could be caused by a bad T-con board as well as bad cables. You need to tell us what exact make and model your TV is so we can help you out further. Also, unplug your TV and take lots of good pictures of the circuit boards. Post those with your question so we can see what you see. Use this guide [guide|21499] for that.