1080p Displays: In Search of Applications
October 5, 2005
If you have attended any recent tradeshow featuring displays or paid attention to the display press, you will have seen and heard about 1080p displays. You will no doubt remember that in the early days of HDTV, which we might call the "CRT days," one of the pearls of conventional wisdom was that a consumer display capable of resolving 1920 x 1080 HDTV images was not available. That wisdom was accurate then, but the display picture, so to speak, has changed markedly since then.
We are now moving well into the advanced display era. CRTs are rapidly vanishing from showroom floors to yield space to LCDs, plasma panels and rear projection displays. A shopper can almost hear the thud of falling flat panel prices over the past year or so, and careful listening will reveal the sound of display manufacturers scrambling to replace lost revenue. One way is to offer 1080p displays.
The realities of the advanced display marketplace today have brought about developments on both ends of the resolution spectrum. As prices for HD flat panels drop, fewer extended-definition flat panels are being offered. We are hearing a great deal about 1080p displays, which are becoming available in a variety of sizes and technologies. Looking at some recent information on advanced display sales, we can get a snapshot of the 1080p display landscape. Sixteen 1080p flat panels in sizes ranging from 37 to 65 inches are reportedly becoming available this year. It is reported that panels 45 inches and larger will be priced prohibitively, but smaller units will carry attractive price tags.
More than 35 models of 1080p rear-projection TVs using technologies that include liquid crystal on silicon and digital light projection are reportedly becoming available this year. No 1080p LCD rear-projection sets are expected this year, even though LCD is the top-selling microdisplay technology in the current rear-projection marketplace. This is likely because manufacturers are still working on reducing a 1920 x 1080 LCD die to an appropriate size. We may expect this state of affairs to be rectified in 2006. It is further expected that large 1080p plasma panels will become available later this year.
NOWHERE TO GO
Now that manufacturers have 1080p displays to sell, one of their problems is a lack of 1080p programming to display. It is, in fact, reported that only two manufacturers will offer 1080p inputs on their displays, and these will be VGA inputs. The VGA interface will accommodate computers, but no DVD player or set-top box is expected to VGA outputs. The crop of 1080p displays will take in 720p, 1080i or SD television formats, which must be converted and/or de-interlaced. The astute observer knows that this provides an opportunity to degrade images.
No one yet knows how the HD-DVD/Blu-ray battle will come out, but it is known that the first generation of both formats will have 720p or 1080i outputs, but not 1080p.
We well know that the ATSC broadcast standard can accommodate 1080/24p and 1080/30p, but not 1080/60p. There does not currently seem to be any movement toward producing equipment that can record or transmit 1080/30p. We well know that much television post production is done in the 1080/24p scanning format, with source material being obtained by the transfer of 24 fps film to video or direct 1080/24p video capture.
Although 1080/24p is included in the ATSC standard, 24p video is not typically, if ever, used. Such material is converted either to 720p/60 or 1080i/30 with the addition of 3:2 pulldown before being broadcast, so we are back to upconversion in the receiver before it can be displayed as 1080/60p in the home.
There is a 1920 x 1080 studio/field video camera capable of 4:4:4 RGB output at 1080/60p, but no mention is made of any device that might be used to record or edit the images. The data sheets indicate that it is also capable of HD-SDI outputs at 1080/24p and 1080/30p, as well as 720/60p and 1080/30i.
It is, at this juncture, impossible to successfully compress 1080/60p to fit into a 6 MHz U.S. television channel using the MPEG-2 compression tools available to us. It is, in fact, quite difficult to successfully compress some 1080/30i material to fit into a 6 MHz television channel using these tools.
We have learned that European HDTV broadcasting will very likely use MPEG-4 AVC compression, as the Europeans have the advantage of beginning with a "blank sheet of paper" when they initiate HDTV service in the near future. It is difficult to conceive of the U.S. ATSC broadcast standard being changed to make use of MPEG-4 compression, since this would disenfranchise the owners of all the MPEG-2 DTV receivers in the field.
Even with the announced coding gains provided by MPEG-4 over MPEG-2, it would seem to be difficult at best to successfully code 1080/50p into even a 7 or 8 MHz European television channel, even using MPEG-4. In fact, as you have read in this publication and elsewhere, the European Broadcasting Union is recommending broadcasting HDTV at 720/50p.
What 1080/60p native signals are available for display on these visually stunning 1080/60p displays? We are told that the PlayStation 3 console will have a 1080p output with games released on Blu-ray discs. We are also told that there are 1080p movie trailers available on the Internet. But wait! These started life as 24fps film, so are they really 60fps?
In sum, the resolution capabilities of advanced displays have caught up to the resolution of the 1920 x 1080/60p HD scanning format, but it will be a while before there is much native 1080/60p material available for viewing.