True HDTV on projectors.

[IndyKlipschFan]

I loved this article, and hope it helps others and sparks conversation too.

Have you heard this one yet from a projector salesman. "You don't want to buy THAT projectorit doesn't do TRUE HDTV." Well, certainly nobody would want to buy a projector that didn't do real HDTV, right? But they all claim to do HDTV. So what's the scoop?

It is easy to understand why the confusion exists. But it is also easy to sort it all out. First, let's start by defining HDTV. There are two common HDTV formats in use today, usually referred to as 1080i and 720p. The numbers refer to the number of horizontal lines in each frame of video (also known as "vertical resolution" since it is the number of horizontal lines as counted vertically from top to bottom of the screen). So in a 1080i signal, there are 1,080 lines per frame of video, and in a 720p signal there are 720 lines per frame.

The "i" and "p" indicate whether the signal is interlaced or progressive. In an interlaced signal, all of the even numbered lines are transmitted in one batch, followed by all of the odd numbered lines. (This is done to reduce transmission bandwidth.) In a progressive signal, all lines of the frame are transmitted at once in sequence. So with the interlaced 1080i signal, only 540 lines are recorded by the camera and transmitted at a time; they are then reassembled at the time of display. Meanwhile, with 720p, all 720 lines are recorded and transmitted in sequence.

Both of these signal formats maintain a 16:9 aspect ratio. That means the picture is 16 units in width for every 9 units in height. This is what has become known as the standard widescreen television formatall widescreen format TVs, plasmas, and projectors have a native 16:9 aspect ratio these days.

In order for an HDTV signal to maintain a 16:9 aspect ratio that matches the widescreen format, it needs to have 16 pixels on each line for every 9 lines of video in the frame. So a 1080i signal has 1920 pixels horizontally. That is why you will sometimes see the actual resolution of the 1080i format designated as 1920x1080. (If you divide 1920 by 16, then multiply the result by 9, you get 1080.)

Similarly, a 720p format signal has 1280 pixels on each line. So the physical resolution of the 720p format is often noted as 1280x720. (Once again, if you divide 1280 by 16, then multiply the result by 9, you get 720.)

So far, so good. Now.what is TRUE HDTV? This is where it gets confusing, because people use the term to mean different things. Some people think that the only real, legitimate HDTV format is 1080i because it has the highest physical resolution. So they refer to 1920x1080 as true HDTV. Others have been calling 1080i "full HDTV," presumably to distinguish it from the less full 1280x720.

Fans of the 720p format object to this. They point out that progressive scanning produces a cleaner, higher resolution signal when the subject is in fast motion. It has no deinterlacing fuzziness. And since the 1080i camera captures only 540 lines at a time, the actual resolution of 1080i when the subject is in motion is only 540 lines, not 1080. So many folks think 720p is better for rapid motion sports like football and soccer, while 1080i is better for, say, golf, where people are just basically standing around.

The fact is that both 1080i and 720p are great HDTV formats that look a lot better than standard television. Both formats are being broadcast by the major networks today, so your projector needs to be able to display both of them, and all projectors that are HDTV compatible do in fact display both of them.

So what does it mean to ask "does your projector display true HDTV?" Often what is really meant is, "does it need to re-scale the image?" In other words, does the video information coming in on the HDTV signal need to be either compressed or expanded to fit the physical resolution of the projector? In most cases, it does.

Any given projector has just one physical resolution, usually called the native resolution. Native resolution is the number of pixels actually available on the display. So an SVGA projector, for example, has display panels or chips with a native 800x600 pixel matrix. In order to display a 16:9 signal, it uses an active area of 800x450 on the display. So any HDTV signal that it gets, whether it is 1280x720 or 1920x1080, it must reformat (compress) that incoming signal into 800x450 before feeding it to its internal display. So no matter what, it cannot display any HDTV signal without compressing it, and losing a bit of image detail in the process.

This is true of standard XGA resolution projectors as well. They have a native resolution of 1024x768. In order to display a 16:9 image, they use an active portion of their display that is 1024x576, which is a 16:9 matrix. Therefore the HDTV signals, whether 1920x1080 or 1280x720, must be compressed to fit into a 1024x576 matrix before they are displayed.

Many new home theater projectors have native 1280x720 LCD panels or DLP chips. These are built expressly for the purpose of displaying HDTV 720p without needing to compress it or expand it. Some would say that projectors with the 1280x720 matrix are true HDTV projectors. However, some wouldn't, because when they get a 1080i signal these projectors still need to compress the 1920x1080 information into their native 1280x720 displays.

For the purist with unlimited funds, the only real, genuine HDTV projector is one with 1920x1080 internal resolution. These will display 1080i without any compression. There are a small handful of projectors on the market with this resolution, and at the moment they cost $20,000 and up. But these units need to reformat 720p signals, scaling them up to fit their native 1920x1080 displays. Technically, then, you could say that even these units are not true HDTV when it comes to 720p format.

The bottom line is that all projectors are built to scale a wide variety of incoming signal formats into their one native display. They will all do standard television, they will all do DVD, and almost all of them will do HDTV 1080i and 720p as well. In addition, most of them will display a variety of computer resolutions, including SVGA, XGA, and so forth. Really, when it comes to HDTV, there are only two circumstances where scaling is not required: 720p for a projector with 1280x720 native resolution, and 1080i for a projector with 1920x1080 resolution. Other than for those two unique matches, scaling is always required no matter what.

So this whole issue about "true HDTV" misses the point. Even the cheapest low resolution projectors will display HDTV pictures that look better than any television you ever saw. The fact that you are seeing a compressed signal is quite beside the point. Scalers have gotten so good these days that even low resolution projectors deliver amazing HDTV quality for the money, even after the compression. So who cares if it isn't "true HDTV?"

The real question is how much are you willing to spend on a projector? Generally, the projectors with higher native resolutions tend to cost more than those of lower resolution. With higher resolution you get reduced pixelation, and usually a smoother, cleaner, more filmlike image. And you usually get these improvements, to varying degrees, on all video sources whether they be television, DVD or HDTV. Getting better image quality across the board is usually a more important key to your overall viewing satisfaction than the question of whether the HDTV image is scaled or not.

Yes, it is true that today's 1280x720 format projectors are indeed particularly impressive for 720p display. But the amount of 720p material you will view compared to everything else will probably be rather small unless your weekly video entertainment consists mainly of HD sports broadcasts from ABC, ESPN, and Fox. And meanwhile, 1080i can look spectacular on a 1280x720 projector, even though the 1080i signal is compressed and not "true" 1080i.

Therefore, next time a salesman says, "Don't buy that projector, it doesn't do true HDTV," think twice and don't take his word for it. That relatively inexpensive projector you are considering just might deliver the best possible HDTV picture for the money on the market.

http://www.projectorcentral.com/true_hdtv.htm

[capo72]

interesting read, thanx!

Jeremy

[IndyKlipschFan]

I am surprised only one post so far... Hmmmmmm

[Northshore]

I recently installed the Sony VPLHS51 HD projector. After reading this post I will read further into the fine print to see if I actually have a "true HD projector or simply a wannabe. Thanks Indy

[JJkizak]

I gave up trying to define true HD. The pr guy's have butchered things up so bad that now I call everything True HD. So if I broadcast some old 8mm films on a "True HD" channel does that mean they are HD quality? I think not. Brownie pictures? no. Super 8 film? no. Black $ white documentary still pictures 80 years old? No. Digital 16 x 9 camcorders? No. (HD cameras have twice the resolution). Still digital cameras set for 1900 x 1900? Yes. 16mm film? Sometimes yes. 35mm film? Yes. VHS tapes? No. DVD discs standard players? No. DVD discs up convert players? Getting close. Projectors? All the ones I have seen really sucked. Dim, low contrast, fuzzy. This includes professional models that cost thousands. What do I mean by Sucked? Go look at the projectors in a pro sports facility or resturant---they suck compared to High-Definition.

JJK

[WMcD]

I agree a lot of stuff is sold without explanation of what is going on. Certainly the set's native mode is very important and up until recently was not widely stated by manufacturers. This is not just a front projector issue.

OTOH, Sound and Vision has had several articles which do describe the issues. Some of it is native resolution; alignment-calibration; up converting algorthims; and what you're upverting from, i.e. what is the source.

At least some of the "problem" is just how poor a picture we had in the old days. VHS tape was well below NTSC standards. I suspect a lot of sets, even with a good off the air, got to NTSC standards. (Consider that you had to buy a Heathkit color TV to get a built in alignment generator! Long before VHS of course.)

Therefore, just about any improvement was impressive enough to distract consumers from making a studied examination of technical merits of the entire system. For example, a clean cable signal on a well aligned 4:3 rear projector was a good first step. You could enjoy it for half a decade while promised improvements were on the drawing board.

I have watched DVDs on a buddy's Samsung TI DLP rear projector. Actually the DVD format has only NTSC grade material, i.e. VGA resolution, which gets upverted to marginal HDTV of roughly 1200 x 700. Yet it looks spectacular. Digital cable is impressive too even though on that system the Samsung is not getting to 1920 x 1040 and the source is not either.

I wonder if just ED (sub HDTV) plasma sets were not a good buy. For most consumers, they were sufficent for the source material available which was not cutting edge. Maybe they still are for the same reasons.

In conclusion, it is easy for anyone to say a given set up is marginal compared to what is coming around the corner in a year or two. It is, though, a big improvement on what has gone before. Like they said about computers, you have to jump on the merry-go-round at some point.

Thanks for the heads up though. I'm holding off for another product cycle or two or three. OTOH, I WILL buy if the Cubs go to the World Series. This could take a few additional product cycles?

Best,

Gil

[j-malotky]

Nice points Indy. Formats can be a real pain in the butt. That is why I built a HTPC over the winter and drive my projector in its native mode and having the PC create the image using descalers and post proccesing. Takes some time to set up but you get stunning results.

JM

[dkp]

Great post Indy. Very informative-thanks for posting.

David

[Griffinator]

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On 5/4/2005 5:26:07 PM IndyKlipschFan wrote:

I am surprised only one post so far... Hmmmmmm

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As a dealer of a variety of projectors from the absolute lowest rez 640x480 to the outlandishly expensive 1080i 9" CRT monstrosities, I'm just sitting back and smiling at the truth finally being spoken by someone other than me...

The people that crow about "true HDTV" would absolutely drop dead if they found out that most rear-projection TV's have native rezzes of around 720x480, and that even the RP DLP's are right around 1024x768. Why is this not an issue with RPTV's? Because it's a lot easier to go peruse RP's, because everyone has them on display, and most dealers have HD signals fed into them, so you can see for yourself what they look like. The dealer doesn't have to talk about "true HD" when the customer is awestruck at the picture they're viewing.

Forward projectors, OTOH, are a completely different animal. You don't often have a dealer available that is equipped to let you compare several different forward projectors in the same room, on the same screen, etc. So you have to rely on specifications - often times specifications that really don't mean squat except for the guy who needs to do a Powerpoint presentation with his projector and needs to know what rez to set the display output at before he disconnects it from his CRT or LCD monitor...

There are a lot of people out there that are really snobby about native resolution specs. I'd be willing to wager large money that they've never actually previewed multiple projectors in the same room to ascertain the visual differences between, say, 1024x576, 1280x720, 1366x768, and 1920x1080 native rez. Sure, when you get down to 853x480 you start seeing the telltale EDTV artifacting, but you're absolutely right - the scaling technology, even onboard (never mind outboard scalers that are capable of all manner of astounding resampling work) will easily fool your eye from 10 feet away at 80 inch display size.

Does this mean that those spectacular 7, 8, or 9 inch theater-grade CRT projectors aren't worth it? Hell no. If you've got the dosh, you'll never see a more astounding picture at any size than one of these. But don't think for a minute that you can't get great quality projection for under $4K, because it's simply not true.

[scott0527]

Do you guys know what's up with the HDTV offered by cable companies. I haven't pad much attention in the last few years, but I recall a lot of talk in the past about it not being true HDTV. It looks good from my chair.

[tkot]

great post!!!

and now a question??

as stated before is it better to scale to the native res of the display? or just get close and let the internal scaler do the rest??

the reason i ask is that, in my case, my sony projectors native res is 1366 by 768. but in the book it says to set your computers

output res to xga (1024 by 768)

the new mac(duel g5 2.7 gig) that i just bought has the nvidia 6800 ultra ddl card that lets me scale to any res.

should i set it to 1366 by 768 or 1024 by 768 ??

any thoughts??

griff??

thanks,

jay

[Griffinator]

If the Sony projector will accept a 1366x768 input, then by all means, do that. You'll have to check with Sony as to whether that's possible.

[IndyKlipschFan]

Griff.. And others.

Great post, and also why I wanted to open up this dialoge too.

I am looking at two projectors pretty seriously just because I have seen them both pretty close side by side and on different screens / same screen. Comcast HD/Cable too.

Both DLP's and 7 color wheel

Infocus 7205 HD2+ chip..New mustang 1280 x 720

Infocus 7210 DC3 From Texas Instuments 1280 x 720

In a tottaly dark room (everyone else) seems to love the Grey screens...I think for dark movies, yes... They look very impressive. In sporting events, for me again, (personal opinion) so far they look..ok too Dark. I love the brilliant colors, incredible pictures, more than subdude colors and the utmost darks of darks and or blackest of blacks. I am not talking un natural or the oversaturation colors.

A lord of the rings or any typical space movie Verses...say The NBA, Football, etc., in HD I want all of them both to look fantastic!

Any thoughts on these projectors? The prices have fallen dramatically the last 2 years too. Your right, in the 3000 - 6000 range your getting an incredible projector these days..

Grey or White Matte screens. LOL

[j-malotky]

Indy

I have found that Grey screens look more colorful with brighter bulbs, say in the 2000 lumen range. Both those projectors are 1100 lumens and is probably why they look too dark on average viewing.

I use a grey screen and found the colors are slightly off when looking through the filters on a test DVD. But since the Greyscale is dead on, or even better than dead on with the super high contrast ratios, the picture is very - very impressive.

JM

[Istari]

I think that Fred Klipsch ought to buy these and put them in the Klipsch museum. I doubt that they could find a better specimen. I bet Fred is just too damn tight though. I really believe he couldn't care less about audio, he's just in it for the big bucks...

[tkot]

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On 5/5/2005 7:38:10 PM Istari wrote:

I think that Fred Klipsch ought to buy these and put them in the Klipsch museum. I doubt that they could find a better specimen. I bet Fred is just too damn tight though. I really believe he couldn't care less about audio, he's just in it for the big bucks...

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?

jay

[KungFuNat]

it comes down to native rez period, if its not 1280x720 or more, then there its just ED.. now for DVDs thats one thing, but for HDTV its another story.

BUT, i have seen some projectors with fantastic scaling ability, and you can get about 90% of the picture quality without a full 1280x720 native rez.. quite frankly, even most HDTV broadcasts are so far below the the optimum quality that you could get out of 720p, you might not even notice the difference with a lower rez.

i say, if you like what you see, go with it.. damn the specs