Digital Television Image Enhancement

John P. Rossi

Television image enhancement has long been accomplished by using analog circuits to operate on the analog television signal and thereby emphasize both horizontal and vertical transitions. Now it is feasible to perform comparable image enhancement by digital techniques operating in real time on a pulse-code-modulated NTSC television signal. Several algorithms have been developed to generate vertical and horizontal video details from PCM NTSC television signals encoded at a 10.7-MHz rate (three times the color subcarrier frequency) and at a 14.3-MHz rate (four time the subcarrier frequency). Practical design concepts are presented to implement digital image enhancers. In addition to ensuring the stability, accuracy and reliability that are the usual advantages of digital systems, digital image enhancement will enable video processing techniques to be used that can actually be performed best by digital means. In particular, more nearly optimum coring or “crispening” circuits will be possible and the detail signals will be easily programmable, which may permit automatic adaptive enhancement.

Print ISSN
Published
1975-07
Content type
Original Research
DOI
10.5594/J13339