"Time for a quick refresher course on frame rate analysis based on feedback from the Digital Foundry forum (ie. "please explain the graphs"), combined with a debut outing for a new revised version of our frame detection tools.
The principal of frame rate detection is remarkably straightforward... in theory at least. With the Xbox 360 and PlayStation 3 (and indeed PC) giving us pure digital outputs to capture from, ascertaining how many times the output changes in any given second is a simple matter of counting unique frames from the 60Hz source. It honestly is as simple as that for a great many games. The only real skill required is making sure that the clips chosen do not include any static screens – loading screens, pause screens, that kind of thing. Because of the level of accuracy involved when you have 921,600 pixels to scan in a 720p capture, you can be remarkably precise in what is a unique frame and what isn't. Indeed, even a sample of 1280 pixels from a single line scan is usually enough to get an accurate result. It's rare to non-existent that what the eye perceives to be a static screen during gameplay actually is one."