TABLE OF CONTENTS There is hardly any field in engineering that does not benefit from the techniques of digital signal processing. In the realm of image processing, audio processing, digital communication, neural networks, pattern recognition, biomedical applications, astronomy, and in countless other applications we find digital signal processing playing an important role of processing data that produces meaningful results.
In this Appendix, three digital filtering applications are presented: image processing, audio processing, and filter testing. The image processing application features edge enhancement, smoothing, sharpening, inverting, and edge detection operation on a digital image stored as a bitmap file. The audio processing application detects the presence of a specific frequency in a stream of audio data acquired through devices such as the sound card in a PC. The frequency detection is a common application in telephony, where dial tones and dialing digits are transmitted as predefined frequencies over the telephone line. Transfer of data over the telephone requires digital filter applications that detect the presence of these frequencies in the audio signals. The filter test program is a simple tool to analyze poles and zeros of IIR filters.
The applications are being developed using the Perl/Tk modules. The intent is to present short and simple programs that demonstrate the use of digital filtering.
Images are captured as points in space, each with a certain level of intensity with reference to certain spatial coordinates and stored in computer memory as numbers reflecting the relative strength. Storing images in color requires more information...
