HDTV Almanac - Oh Boy! A New iPad!

> things could get ugly as you stretch each pixel by 1.06 and two-thirds. <

I don't have time to respond to the entire article ATM, but two-thirds? ??? Where did that come from?

- Tim

Tim, 2,048 divided by 1,920 equals 1.066666666666667. That is the same as "1.06 and two thirds" though it would have been more precise to say "two-thirds of one hundredth". The risk of artifacts when making such a small scaling change is pretty large.

Alfred Poor
HDTV Almanac

Ah, thanks for the explanation, Alfred. I've never heard such a thing described that way. I'm pretty sure I would never have figured that one out on my own.

As for scaling the image up by 6.66...% just to be able to say you filled all the pixels, that seems a bit silly. Not just due to artifacts. If you use a resampling filter, they won't be that bad (even the poorest ones scale pretty well). Though if you use simple resizing, it will definitely get noticably crusty-looking. I just tried scaling some video stills up, using the poorest-quality and fastest (Hermite) filter. With 2M pixels, artifacts aren't even noticable on my 25" screen. On a 10" screen, you'd never be able to see them at all. But because the extra GPU overhead (and battery consumption) isn't justified, to fill that ~half inch (128 pixels = 2048-1920).

I'd suspect (hope) they'd simply run it 1:1. But if they didn't, the main downside would likely be battery life impact, not artifacts, unless their scaler was extremely poor.

- Tim

Alfred,

> The news for me is that the iPad finally can display full high-definition images without scaling. Granted, the panel still uses the same old 4:3 aspect ratio as your grandfather’s television set, <

Urg. Are we still on that old kick? The screens on tablets should be 16x9, because some of our content is 16x9? And a 4x3 panel is some-how "old-fashioned"? If the purpose of tablets was exclusively for video display of HD aspect-ratios, there might be some merit to that. However, they are also used extensively for reading materials (and other purposes). And based on all the PDFs I have, a 4x3 AR fits them vastly better in Portrait mode than 16x9. I know that because I have other tablets with narrower ARs (1280x800, e.g.), and the result is that when reading such content, there are huge wasted bands on top and bottom, which reduces the size of the (already small) text I'm trying to read.

But maybe we should have "HD" tablets with a 2.37 AR? That's what more than 80% of all the HD content I watch is in. After all, having any 'wasted' pixels on any screen is a crime, isn't it? So I guess such tablet screens should be 8" wide, and, oh, 3.38" high. Now THAT would be a lot of fun to use in portrait mode.

> Richard also points out that these smaller pixels mean less room for light to be transmitted (smaller aperture ratio) which translates to the need for a brighter backlight which in turn impacts battery life. He expresses his suspicion that the device has a larger battery to respond to this extra power draw, along with the additional power required for the new processor. <

I haven't had time to read Richard's material yet, but I can say that his suspicions are correct. I actually thought Apple made that pretty clear. They had to use twice as many LED backlights, and a more powerful GPU to move the bits around. The end result was a net 70% greater power usage profile. Since no one would have been happy with an iPad with a 6-hour battery life, Apple had to increase the battery capacity by a corresponding amount to compensate. Not surprisingly, they boosted it from ~ 25Wh to ~42 Wh. This maintained the previous 10 hour lifespan, but prevented them from making the new device even thinner and lighter than they may have otherwise preferred.

Even "magical" Apple devices can't violate the laws of Physics.

- Tim

Tim, I don't mean to imply that tablet screens should be 16:9; I'm only saying that if you do watch HD content on it (and I expect many people would want to), you're going to have 436 blank lines or about a third of the screen. That's going to bother a lot of people. (Be honest with me; how many homes have you been to where the image has been stretched vertically to eliminate letterboxing or pillaring? More than one is too many, and I've seen WAY more than too many.) And I'm not trying to pick on Apple; they were the ones that promoted the iPad2 as the ultimate movie viewing experience.

As for Apple defying the laws of physics, you and I know that they can't, but that doesn't seem to stop them from implying that they can.

Alfred

Alfred,

> I don't mean to imply that tablet screens should be 16:9; <

Thanks for the clarification. From your remark about "same old" and "like your grandfather" that was the implication I drew. From day one, Apple made a conscious decision that a 4x3 ratio was best for handling the entire range of activities such a portable device could be used for. Not simply be optimized for one specific use-case. There's not much point in harping on that, because it's obviously never going to change. And I think it was the right choice, though I realize not everyone will agree. (BTW, I don't own one, if that's the impression anyone is getting, though I do own many other tablets, from 5-12 inches. Perhaps the better screen will finally convince me to make the leap.)

OTOH, Apple now has the first and only device with so much resolution that it could function well as a two-page landscape display. (Though the upcoming 1920x1200 tablets from Asus and others will come close.) A two-page display for books, PDFs, and magazines would work really well... assuming the typeface wasn't so small that those of us with our grandfather's eyes (grin) could still read it.

> I'm only saying that if you do watch HD content on it (and I expect many people would want to), you're going to have 436 blank lines or about a third of the screen. That's going to bother a lot of people. <

I can't argue with you there. I'm sure it will. And to them I say, tough nuggies. Besides, those folks have carefully overlooked the fact that these tablets are touch devices, and thus require some screen real-estate for controls. Unless you like having your controls overlay and obliterate part of your image (which personally, I don't). To me, having more space than required for the image itself makes a lot of sense.

> (Be honest with me; how many homes have you been to where the image has been stretched vertically to eliminate letterboxing or pillaring? More than one is too many, and I've seen WAY more than too many.) <

Not too many, though I admit that it's still way more common than it should be. I think this is slowly starting to change a bit, as folks become better educated... and they're watching more scope content. Stretching 2.40 content up to 16x9 is something even the most adamant about "but my screen isn't full" would have a hard time stomaching. (Unless they also cropped off some of the sides of the image as well.)

> And I'm not trying to pick on Apple; they were the ones that promoted the iPad2 as the ultimate movie viewing experience. <

Well, I'd take issue with them on that point, because I don't think any 9.7" device would qualify in that category. I have a 12" 1280x800 Windows tablet that displays 720p HD just fine (w/o scaling, or 1080p with), and I suspect may even look better than the much smaller iPad, yet that too is far from an "ultimate experience".

> As for Apple defying the laws of physics, you and I know that they can't, but that doesn't seem to stop them from implying that they can. <

Absolutely. That was the reason for my comment. Their presentations and other materials are carefully constructed to give that impression.

- Tim

Oh, and while I'm no Apple fanboy, I don't think they're getting the credit they deserve in the media for what they have accomplished in one area. Assuming you believe that a 2048x1526 display is an achievement in itself, and of some value, which I do. As you pointed out, to provide that resulted in a 70% greater power usage than previous models. That's a lot. And they managed to provide that extra 70% power capacity without changing the size, the weight, or the price! That's a pretty amazing feat in and of itself, in my book.

Yet many in the media are writing it off as "pretty much the same old thing, except for a higher-rez screen". That overlooks the magnitude of what they did manage to pull off (essentially a 17-hour iPad2), which was really quite impressive (though not necessarily immediately obvious to all).

- Tim