Don't use copy-back, even my 7750 isn't fast enough for it sometimes. Set LAV to DXVA2, that should be the best option for you.
Go to Catalyst - Video, disable all the crap there or set to "take settings from the app". The only thing you need there is de-interlacing, set it to Vector Adaptive, tick Auto. Do the same with 3D. In other words, you have to set video driver to max speed.
Start playback, go window mode, press Ctrl+J, wait for 30 sec, make screenshot and post it here.
Burned by the Audio Inquisition