I've been playing around a bunch with screen recordings lately (as you'll see in my next blog post), and I've noticed a pretty common problem: people leaving ClearType on while recording. ClearType is cool stuff, adding improved anti-aliasing on LCD displays. But the way it works is by taking advantage of the little sub-pixel strips of Red, Green, and Blue each LCD pixel is made of. This improves detail and readability. But, as you can see below, when you zoom in you get color fringing on that small text.
Those little color fringes make the video somewhat harder to encode, since they change with the position of the text. And they also look wrong when then video is played back on a non-LCD display, and really wrong on an oddball LCD display which has a different pattern of the colored strips.
ClearType Font Smoothing @ 100% Zoom
ClearType Font Smoothing @ 800% Zoom
Standard Font Smoothing @ 100% Zoom:
Standard Font Smoothing @ 800% Zoom:
When doing any screen captures, be it Camtasia or via a HDMI to SDI bridge like I used for my Expression Encoder 1.0 training, make sure you have ClearType off. In Vista, you do that via the Appearance Settings control panel's Effects button.
If you wind up with source video that has been recorded with ClearType on, turning on Chroma Search can help quality some by enabling the code to pick up on all hue/saturation changes on text as it moves around. I recommend using the "Full True Chroma" mode if using a tool based on the VC-1 Encoder SDK, like Expression Encoder 2.0.