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Au Japon : LA UHDTV

8 juin 2004


La télévision haute définition qui connaît un succès important aux USA, se voit depuis de plus en plus présente dans le paysage audiovisuel Japonais.

Aussi pour proposer une offre complémentaire à la HDTV, la chaîne nationale japonaise NHK pousse les limites de cette même HDTV en proposant une version revue et corrigée la UHDTV.
Ce nouveau système qui se base sur des spécificités incroyables (ci-dessous) présente selon ses créateurs (des ingénieurs et chercheurs japonais) un très gros avantage : l'œil humain ne peut pas différencier les images réelles et celles diffusées par la UHDTV.

Spécifications :
UHDTV : 7,680 x 4,320 pixels soit 4000 lignes
HDTV : 2 Millions Pixels 1000 lignes

Qui dit nouvelle norme dit nouveaux appareils, or aujourd'hui alors que la HDTV n'est que trop peu connue dans le monde, on se demande quel sera l'avenir de ce standard

Les informations cites sont issues d'un article paru dans le Herald Tribune :

High-definition television may be just beginning to catch on, but researchers at the Japanese national broadcaster NHK are already working on a successor. The format, called Ultra High Definition Video, or UHDV, has a resolution 16 times greater than plain-old HDTV, and its stated goal is to achieve a level of sensory immersion that approximates actually being there. At a picture size of 7,680 by 4,320 pixels - that works out to 32 million pixels - UHDV's resolution trounces even high-end digital still cameras. HDTV, by comparison, has about two million pixels, and normal TV about 200,000 (and only 480 lines of horizontal resolution, versus 4,000 with UHDV).

Add to that UHDV's beefed-up refresh rate of 60 frames a second (twice that of conventional video), projected onto a screen with a diagonal measurement of 11.4 meters, or 450 inches, along with more than 20 channels of audio, and you've got an impressive home theater on your hands.

Of course, UHDV's current dimensions make it impractical for most homes. The NHK researchers are investigating how to squeeze all those pixels onto smaller screens.

But the project aims to do more than just make home entertainment more realistic. The UHDV standard may someday find applications in museums, hospitals, shopping malls or other places where a keener representation of detail might be desirable.

All of that is a long way off, however, because the standard is still in the early stages of development. UHDV "will take many years," said Fumio Okano, a researcher with the network. But NHK is familiar with long-term projects: It began developing the HDTV standard in 1964, and the first high-definition content arrived only in 1982.

The pixel count of UHDV may be impressive, but as anyone who has tried to watch TV on a sunny beach knows, pixels are not the whole picture. "Resolution is only one of the key measurements," said John Lowry of Lowry Digital Images, a California company that digitizes films at the highest possible quality for archival purposes. Perhaps even more important than pixels, he said, is the dynamic range of an image, which is measured in terms of contrast ratio.

The eye can perceive contrasts between the brightest white and the darkest black of roughly 100,000 to 1, whereas today's best projectors can only muster levels of about 4,000 to 1.

To achieve truly realistic images, Lowry said, "the blacks have to be really black, while still seeing the glint off a diamond."

So while current projection technology cannot meet the demands of UHDV, the standard excels in other crucial areas, for example breadth of view. While both UHDV and HDTV use the widescreen 16:9 aspect ratio (standard TV uses 4:3), HDTV offers only a 30-degree field of view horizontally, whereas UHDV's screen size expands this to about 100 degrees, said Okano, who said his research indicated that this angle was where "immersive sensation" peaks.

In developing UHDV, NHK has also focused on sound. The standard calls for 22.2 sound: 10 speakers at ear level, 9 above and 3 below, with another two for low-frequency effects. It is a setup that is well beyond the level of the multichannel systems currently in vogue, like the 5.1 surround system.

That adds up to a lot of data. In a test, an 18-minute UHDV video gobbled up 3.5 terabytes of storage, equivalent to about 750 DVDs.

NHK is still years from having to worry about how to sell UHDV to consumers. Perhaps the format will always be out of reach for most, but there is always hope: While it took 40 years, HDTV eventually gained a foothold.

"I applaud them," Lowry said of NHK. "They are reaching off into what a lot of people might call never-never land at the moment. But why not?"



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