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HDTV

The original impetus for HDTV came from wide-screen movies. Soon after wide-screen was introduced, movie producers discovered that individuals seated in the first few rows enjoyed a level of participation in the action not possible with conventional movies. Evidently, having the screen occupy a great field of view (especially peripherally) significantly increases the sense of "being there".

Early in the 1980s, movie producers were offered a high-definition television system developed by Sony and NHK in the late 70s. This system (called NHK Hi-vision) and its variants are capable of producing images having essentially the same detail as 35 mm film. With these systems, a scene could be recorded, played and edited immediately, and then transferred to film. As a consequence, many of the intermediate delays in conventional film production were eliminated. The new medium also offered a number of possibilities for special effects not possible in conventional film production.

Following the introduction of HDTV to the film industry, interest began to build in developing an HDTV system for commercial broadcasting. Such a system would have roughly double the number of vertical lines and horizontal lines when compared to conventional systems.

Now, the most significant problem faced with HDTV is exactly the same problem faced with color TV in 1954. There are approximately 600 million television sets in the world and approximately 70% of them are color TVs. An important and critical consideration is whether the new HDTV standard should be compatible with the existing color TV standards, supplant the existing standards, or be simultaneously broadcast with the existing standards (with the understanding that the existing standards would be faded out over time).

There is precedence for both compatibility and simultaneous broadcast. In 1957, the US chose compatibility when developing the color TV standard. Although there were some minor carrier interference problems due to the additional chrominance signal - to a large extent, both monochrome and color TVs could read the same signal.

As a example of simultaneous broadcast, consider Britain. Monochrome broadcast began in Britain in 1936 with a 405 line standard. In 1967, the 625 line PAL color standard was introduced. The color and monochrome standards then operated in parallel for fifty years. In 1986, when the 405 line service was terminated, so few 405 line monochrome monitors remained that it was seriously considered that Parliament simply purchase 625 line monitors for the remaining 405 line users, as that was considerably cheaper than maintaining the 405 line service. (This amusing idea did not happen however, due to possible political repercussions!)

new investment.

Thus, the goals of HDTV are:



 
next up previous
Next: Basic ideas for HDTV Up: Future Directions for Multimedia Previous: Further Reading
Dave Marshall
11/5/1999