For you CE forks, The TechZone explains Digital Signal Processing.
It happens that many people have no idea what Digital Signal Processing means, although they hear more and more often these words, today. Considering the name, Digital Signal Processing, people are lead towards thinking that this procedure deals with digital signals. No; Digital Signal Processing is a method of improving the quality of the analog signals, only. Indeed, the naming used is rather improper, because it relates to all types of digital processing, only that the methods, and the techniques used in DSP deal only with signals that are analog in nature.
In the digital signals case, we can only compress, encrypt, and translate them to other digital formats; these (different) procedures do not require any DSP techniques. Using the DSP name when referring to digital signals causes confusion. Read more over The Tech Zone.