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The reader is already an expert in signal processing, although possibly unaware of it. We are all remarkably complex signal processing systems, adaptively processing intricate audio and video signals every moment of our lives. While awake we input intricate signals from our environment, extract highlevel representations of information carried by these signals, make decisions based on this information, record some of the information for later recall and processing, and produce new signals to change our environment in real time | Digital Signal Processing A Computer Science Perspective Jonathan Y. Stein Copyright 2000 John Wiley Sons Inc. Print ISBN 0-471-29546-9 Online ISBN 0-471-20059-X Introductions Thereader is already an expert in signal processing although possibly unaware of it. We are ail remarkably complex signal processing systems adaptively processing intricate audio and video signals every moment of our lives. While awake we input intricate signals from our environment extract high-level representations of information carried by these signals make decisions based on this information record some of the information for later recall and processing and produce new signals to change our environment in real time. Even while sleeping although most of the input has been removed we unconsciously continue the processing off-line- we reintroduce recently input signals in order to correlate them with previously stored signals decide which signals should be stored for long periods of time and generally perfect our signal processing performance. Due to this signal processing we are extremely good at understanding speech and immediately reacting based on what has been said. We scarcely think about our ability to recognize faces and greet or avoid their owners. We take our proficiency at reading handwriting for granted except when admiring the pharmacist s even greater competency when presented with a physician s scrawl. It is therefore extremely frustrating to discover how difficult it is to design artificial devices that can perform as well. After decades of research devices that can understand unconstrained human speech are still extremely primitive and even speech synthesis is still to be considered a nontrivial problem. Machine recognition of human faces is possible only in severely restricted environments and even our limited capabilities are not yet commonplace due to being prohibitively expensive. While optical character recognition of high quality printed fonts has been perfected .
