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A Better Image

Various enhancements to current TV quality are expected over the next few years and consumers will have to choose whether the expense is worth the improvement. A recent workshop in Auckland looked at the prospects for enhanced television and related improvements. Various enhanced TV scenarios have been put forward as intermediate steps before high-definition TV (HDTV).

The greatest technical challenge is to increase the picture resolution for better image quality, and reduce picture interference. These enhancements are possible using the same transmission format and channel as current systems, and methods have been developed independently by Japanese and European teams. However these systems are still under development and, unless they become a commercial reality within a couple of years, the market is likely to wait for digital HDTV.

The issue with the greatest controversy, and yet the most widespread acceptance, is that of wide screen TV, where the width-to-height ratio of the television picture is 16:9, comparable to a movie screen. This format is more suited to our field of vision than the current 4:3 screens. While such sets are popular in Japan, there are a number of issues to be settled, such as the question of compatibility between the different source pictures for transmission and display.

Ghost cancellation technology, which removes ghost images caused by signal interference, is under development. An active ghost cancellation system should be available in all receivers within a couple of years.

Digital HDTV is likely to appear in the near future, as the US is planning to "simulcast" programmes using digital HDTV signals and the original NTSC broadcast transmission standard for older sets. Apart from the Japanese analog-based system, it is likely that HDTV will be implemented exclusively in digital format. Techniques for digital transmission of video, especially within current TV channel bandwidths are under active investigation in Europe and the US.

Digital HDTV will also encourage the introduction of a hierarchy of digital systems, with stepped improvements in TV image quality starting with a minimum transmission and enhancing the image with a series of additional information. The improvements from enhanced TV and HDTV will only be significant on proportionately larger screens, requiring a 40-inch screen for enhanced TV and even larger screens for HDTV.

Pay TV providers, even here in New Zealand, are likely to take up digital TV quickly, as a digital decoder can be incorporated in the descrambling unit. Other countries may move more directly or quickly to digital TV if they have the resources in the broadcast industry, as there is no doubt that the future of TV will be digitally based.

Analysis of the different enhancement techniques is usually performed using subjective tests, with a number of viewers comparing video sequences processed by the different methods. In Canterbury University's Electrical and Electronic Engineering Department, we have developed a system which enables us to simulate different enhancement algorithms and make comparisons in an objective and qualitative way.

This system has been applied to a variety of previous enhanced TV proposals, comparing them with the standard PAL system used in New Zealand. We hope to assess the most recent proposals from Europe and Japan over the next year, providing further, independent information for decisions in these countries and for the future of television in this country.

Dr Chris Carey-Smith, Electrical and Electronic Engineering Department, University of Canterbury