What exactly is high-definition television? Stepping aside for the moment from what we define as high definition today, it has always been a system that has higher resolution than a current system.
A confusing example of what HDTV is may be found on a plaque on the side of the Alexandra Palace in London commemorating the inauguration of …the worlds first regular high-definition television service… Those who associate the development of what is called HDTV today might be surprised when they look at the date and see November, 1936. No, it isnt an error. It simply explains that in 1936 the 405-line electronic system was twice the definition of the mechanical systems previously in use. By definition it was higher.
In 1941, on this side of the ocean, when the 525-line system was first proposed by the NTSC as the standard for television broadcasting in the U.S., it, too, was hailed as high definition, given the considerable increase over previously used 343-line systems. Today, high-definition has a totally different meaning, with a pixel count just at or over one million being used as the dividing line between what is high definition and what is not. Within that we have transmission at 1280×720 and 1920×1080 in an assortment of frame rates and with interlaced or progressive scanning as outlined in the ATSC Table of 18 formats.
Confusing things to some degree, the actual resolution of the display doesnt always match the transmitted image, with things such as 1366×768 resolution being a popular pixel count for large-screen, flat-panel displays such as LCD and plasma. However, scalar chips and outboard processors take the incoming signal, no matter whether it is HD or not, and convert it to match the native resolution of the display. Indeed, with raster-scanned CRT displays on their way out, and different broadcast outlets using differing formats, scaling is becoming the norm.
Stepping into this stew of display technology and transmission formats, comes yet another format that is most definitely high definition, and very much in the public eye post-CEDIA EXPO:1080p displays. In reality they have been around for the past year or so, but for the first time this year there will be an abundance of 1080p capable LCD, LCoS (including D-ILA and SXRD) and DLP rear projectors, LCoS front projectors and both LCD and PDP direct-view products. Video products featuring 1080p will receive a significant amount of manufacturer and mainstream retail advertising support. For all of those reasons, it is likely to on the minds of customers this selling season, so it is a good idea to delve into some of the specifics of 1080p displays this month.
While a number of scientific, economic, marketing, and political issues contributed to the development and promulgation of a high-definition system to replace NTSC and PAL, one of the core issues was to have a video display system with more lines of resolution, rendering scan lines virtually invisible without sacrificing image quality. If you could combine more lines with more frames and display it all in a progressive-scanned picture, that would be the video equivalent of having your cake and eating it, too. When you distill it all down, that is what 1080p is all about.
One more piece of the puzzle is required, however. As is the case with most anything HD, there is more than one flavor of 1080p, and the difference is significant. It all has to do with how many frames per second are represented by the p. A reasonably common form is 1080/24p, meaning that there are 24 complete frames per second in the imagethe same rate as the decades-old frame rate for standard motion picture photography and reproduction. Thus, if you want to shoot on video in HD, and transfer later to film, 24p is a natural. Due to a variety of mathematical equations, 24p also represents a kind of lingua franca that makes it relatively simple to convert from 1080/24p to one of the 720p standards.
The ATSCs Table of 18, notes that there are four 1080p possibilities, but 1080/60p is not one of them. Thus, when you explain to a client that the display they are purchasing is 1080p, you may get some push back with a question along the lines of, You mean that set that isnt 1080p cant receive 1080/24p or 1080/30p programming? The answer is that yes it can, as scaling circuitry can convert the incoming 1080/24p, 1080/30p, or for that matter 1080/60i programming into the native rate of the display. To display any 1080p imaging, you need a 1920×1080 pixel array, most of the time. That is important to understand, as some 1080p products do have the full grid, while others achieve the 1080 display with a bit of technical artistry. For LCD direct view, LCD projection, LCoS projection and PDP products claiming 1080p, that is truly what you get. Displays in each of those categories are either available now, or will be some time before the end of the year.
The fun comes with the current DLP-based 1080p rear projectors. They absolutely show a 1080p image, but they do it based on a DMD device with a display capability of 960 column pairs and 540 row pairs (one black and one white row per pair), and an actual mirror-pixel count of 960×1080. Thanks to the use of an optical actuator that offsets the positioning of the DMD pixels in relation to the exit lens by half a pixel, persistence of vision in the brain glues the two sub-frames together into a seamless full 1080p frame.
Of course there will always be those who will no to accept anything less than a full 1920×1080 pixel count; dont be put off by DLP technology. A complete 1920×1080 array chip is in the works and a projector based on it was shown at CEDIA. Expect one-chip and three-chip front projectors, and later rear projectors with the full-count chips later this year into early 2006.
Exactly what can you watch in 1080/60p? On one level, using appropriate scaling, any incoming signal can be converted up to 1080/60p. However, if you want to view programming that was actually shot in 1080/60p, that can be difficult. Yes, 1920×1080/60p cameras are available. In fact, CBS has announced that it is buying a few of the cameras for its Television City facility in Los Angeles. All well and good, but at the moment the remainder of the infrastructure to support the full production process in 1080/60p is scarce to non-existent. If you are looking for programming originated in that format, dont hold your breath.
Even if the programming were available, theirs is the problem of getting it to a 1080/60p display. A look at Table of 18 shows that 1080/60p is not an option. That is because the current ATSC transmission system cannot accommodate 1080/60p using the current MPEG 2, MP/HL compression technique. A system change would require an upgrade or replacement of the ATSC tuners currently in use as well a change to the infrastructure for cable and satellite carriage of HD. No one is anxious to do this anytime soon. And while 1080/60p delivers a marketable and demonstrable benefit, it can confuse clients and prospects. Heres an easy way to play that out: Take a 42-inch-wide display and explain that an ED set has to be at least 10 feet back before the picture smoothes to remove resolution harshness. Change the ED display to an HD display and then that distance shrinks to something in the seven-foot range. Step all the way up to a 1080/60p display and you can have that same 42-inch-wide screen size, but not be put off by visible patterning at about five feet. These differences are based on prevalent formulas, but for either you or your clients, your mileage may vary. However, if you have all three classes of display on one wall in a deep enough viewing area, have the prospects simulate the original HDTV research by playing the same source on each of the screens, and then have them move a chair to where the image looks good for each display. That should make the case for 1080/60p every time. It is more a matter of making certain that after someone becomes a customer for a 1080/60p display that they understand exactly its limitations and possibilities.
If the 1080p story doesnt work, that still leaves open the easy-to-sell advantages of a conventional high-def display, so it isnt as though youve lost a sale to the competition, more that youve helped the customer make an intelligent and informed purchasing decision. No matter what the product, that is a winner every time.
Michael Heiss ([email protected]) is a technology and marketing consultant based in Los Angeles.