Screencasting technologies
Although all screencasting software ultimately produces a demo movie or a training tutorial, the process used to create them is different. And it is necessary to be aware of these differences in the technology used for creating screencasts in order to know what can be achieved and what cannot.
First, there are two different principles of dealing with images – interpolated screenshots and fluid movies. Historically interpolated screencasting is first and fluid screencasting is the more modern approach.
Interpolated screenshots
With interpolated programs, screenshots are taken at prespecified intervals of time, or at the occurrence of a particular event (mouse click, or pressing a keyboard key), or at pressing a specific key the screen is captured. The result is a bunch of static screenshots that are later linked to one another. The problem with this approach is that the movie looks rather artificial and sometimes, when the transition between two frames is not smooth, part of the actions that have happened on screen are lost (for instance, you do not see the mouse moving, you only see that a dialog box opens and you have to figure out how that has been accomplished). Needless to say, that this kind of screencasting programs is very clumsy in capturing rapid changes on screen. What is more, if your computer is a slow one, even normal mouse movements seem like slow motion.
Fluid Movies
The more modern approach to screencasting is recording fluid movies. This class of programs captures the output of the video- and sound adapters into a file that can later be played either with a movie player, or previewed in the screencasting application. Generally this approach requires a more powerful computer (especially if you need to make a longer movie), in comparison to the interpolated screencasting but the development of new codecs and the advent of more powerful hardware make it less a concern.