I've got several 1080p movies, they all have a bitrate of roughly 20Mbps, and stereo audio. They all play perfectly in mediaplayer-classic but, in Quicktime and iTunes, they are extremely choppy in both audio and video. Quicktime's move inspector shows them as playing at 6-12fps when they're encoded at 24fps.
I've tried everything I can find to do to fix it. I've tried enabling and disabling directx, directdraw, and direct3D acceleration in every combination possible (from quicktime). None of that fixed it. I've tried adjusting the audio settings in quicktime. I've tried turning off all of itunes' unnecessary features (Genius, sharing, wireless sync, etc.). And I've updated my graphics drivers to the latest version. All to the same result.
My hardware should be more than sufficient to play these videos, my raspberry pi can play them and that thing can't touch my computer. I've got a Phenom II x4 955 BE CPU, an XFX r6770 1gb GPU, 16GB DDR3 Ram, and a 5400RPM WD Green 1TB HDD. The computer is running Windows 7 64-bit. I'm using itunes version 220.127.116.11. and quicktime 7.7.3.
Anyone got any ideas as to why it would be doing this and maybe how to fix it? I would like to be able to play all my media from one place if at all possible.