I am using Windows 7 64bit in bootcamp on my aging Macbook and while recently watching a movie using VLC I noticed slight tearing. It is noticeable when the scene changes and very noticeable in action scenes.
Thinking that perhaps the MKV format was the issue, I went into OSX (snow leopard) and played the same video with VLC again and video playback was smooth, very smooth.
So I am very unsure what the issue is.
Under OSX, I am using VLC version 2.1 64bit, and under Windows 7 64bit, I am running VLC version 2.2 32bit but I downloaded the latest 64bit version just in case and the result is the same.
As far as I know I haven't changed anything in OSX's VLC settings.
Checking the video driver for the "Mobile Intel 965 Express Chipset Family adapter" in Windows, it appears that I am using the latest version, 188.8.131.520
I've downloaded MPC-HC x64, recommended as an alternative to VLC, and the same problem there as well. So I guess then the problem is with the video drivers...