Quick fluctuations in some aspect of a signal such as amplitude or frequency resulting in a signal that is not stable and an output (video image or audio sound) that is not stable. Jitter is a common problem with CD players and other digital media. There are a number of “jitter reducing” components on the market which seek to eliminate most or all of the jitter in a digital signal. Jitter is caused most often by tiny fluctuations in disc size or spin rate compared to the constant clock speed (or problems with the clock itself, although this is not as often the culprit of jitter). Jitter results in distortion of the end product audio or video signal. Jitter is also common in video resulting in decreased picture quality or a slight shaking of the image on screen.