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Is there an advantage to HD displays for SD DVDs?


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#1 of 84 OFFLINE   Brad Russell

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Posted January 04 2007 - 09:43 AM

I’m in the demolition phase of a new home theater and need to begin thinking about the components. I think for at least the next 4-5 years we’ll only be watching SD DVDs and SDTV. Is there any advantage to having a projector with higher resolution than 480p? And at that resolution should I be looking for DVI or HDMI?

Thanks!

Brad

#2 of 84 OFFLINE   ChrisClearman

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Posted January 04 2007 - 09:52 AM

If you're building a new theatre certainly don't put anything less than a 720p projector in there. They can be had for ~$1k now.

And yes, they are a step up from a 480p projector. Even with Digital-SD (480i) content from a DVD player the projector will upconvert the image to 720p. Does it look as good as 720p source? No, but it've very close.

#3 of 84 OFFLINE   SethH

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Posted January 04 2007 - 09:52 AM

There is some advantage because, for instance, a 720p projector will scale all source data to its native resolution (720p). The quality of the processing in the display will determine how good this turns out, but it certainly should not come out worse than 480p.

If you do just run 480p, component would be more than adequate. I'd be a little surprised if you even found a 480p projector with an HDMI input.

720p projectors are relatively inexpensive these days, I don't think it would make too much sense to get anything less than 720p for front projection.

Also, what size screen do you plan to use? If you go too large 480p could look terrible.

#4 of 84 OFFLINE   Brad Russell

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Posted January 04 2007 - 10:29 AM

I was thinking the InFocus IN72 at 96-100" screen. But it sounds like I should look at a 720p projector. Now I've got to convince the wife about doubling the projector budget.

Thanks!

Brad

#5 of 84 OFFLINE   Jeff_CusBlues

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Posted January 04 2007 - 10:38 AM

Brad. Another way you will take advantage of the higher resolution is if you watch HD TV channels.

#6 of 84 OFFLINE   SethH

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Posted January 04 2007 - 09:56 PM

Brad. Another way you will take advantage of the higher resolution is if you watch HD TV channels.


. . . which you can pick up with a cheapo antenna in most locations.

#7 of 84 OFFLINE   Brad Russell

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Posted January 05 2007 - 02:52 AM

Don't you have to have a HD receiver?

#8 of 84 OFFLINE   Rhoq

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Posted January 05 2007 - 09:00 AM

Quote:
Originally Posted by Brad Russell
Don't you have to have a HD receiver?

Not for your HD locals.

#9 of 84 OFFLINE   SethH

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Posted January 05 2007 - 11:59 AM

Don't you have to have a HD receiver?


You have to have a digital tuner for locals. If there is not one built into your projector you'd need an external one. I picked mine up used for $50.

#10 of 84 OFFLINE   Parker Clack

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Posted January 05 2007 - 09:43 PM

A great little projector is the Mitsubishi HD 1000 that was recently reviewed by Ben Williams on the forum. It is native 720p and highly regarded by many people and best of all is only $995.

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#11 of 84 OFFLINE   ChrisWiggles

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Posted January 06 2007 - 06:24 AM

Absolutely, a very very significant benefit to an HD display. If you have an SD display you're going to have to sit extremely far away from it to reduce display structure visibility. Scaling up an SD image also provides significant benefits in terms of most fully resolving the content, assuming decent scaling.

#12 of 84 OFFLINE   Brad Russell

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Posted January 08 2007 - 08:04 AM

Thanks for all the info! I have been looking at the Mits HD100 or Optoma HD70 for my folks since they are already getting some HD broadcasts but wondered if I would benefit. Thanks again and to decide between the optoma or the mits!

Brad

#13 of 84 OFFLINE   Kevin C Brown

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Posted January 08 2007 - 12:46 PM

Quote:
Originally Posted by ChrisWiggles
Absolutely, a very very significant benefit to an HD display. If you have an SD display you're going to have to sit extremely far away from it to reduce display structure visibility. Scaling up an SD image also provides significant benefits in terms of most fully resolving the content, assuming decent scaling.

I have tested this, and it's not "very, very significant". Posted Image I agree with the first point about display structure visibility (SDE, etc). But I don't agree with the 2nd point. When you scale from 480p to anything else, you cannot create info (and resolution) that wasn't there to begin with. All you're doing is replacing less pixels with more pixels, but you aren't adding any additional information.

Maybe not so much anymore, but a lot of early HD displays did not display SD content as well as SD displays specifically due to problems with upscaling.
If it's not worth waiting until the last minute to do, then it's not worth doing.

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#14 of 84 OFFLINE   ChrisWiggles

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Posted January 08 2007 - 04:23 PM

Quote:
Originally Posted by Kevin C Brown
I have tested this, and it's not "very, very significant". Posted Image I agree with the first point about display structure visibility (SDE, etc). But I don't agree with the 2nd point. When you scale from 480p to anything else, you cannot create info (and resolution) that wasn't there to begin with. All you're doing is replacing less pixels with more pixels, but you aren't adding any additional information.

You are not adding information, but you are recovering the full information in the content. In that sense, you are indeed "adding information," but you are not adding information that isn't already there. This is often confusing for people to understand, because it is true that you cannot *add* information that is not present. However, the native sampling of the content itself belies the amount of information it actually contains, especially with video content that is usually sourced from high-definition masters then scaled down to SD resolutions. Each pixel that is represented in the data does not have any area to it, it is just a point on a grid lattice basically. We tend to think of pixels as being rectangles or squares with area that is all the same color, because that is what our displays show us, but this is misleading. But when video is sampled, those pixels don't have a size to them, they are just a sample. If you take a film image, you make samples across the image and that is coded digitally. The nature of real images though, is that most individual area-less points in an image are very related to the ones adjacent to them. We can call them continuous-tone images, because they aren't computer generated (say text for instance). When you have all these samples, there is significant continuity between the various samples. If we impose a rectangular area onto an area-less sample, we've introduced high-frequency noise into the content in the form of blocks which were not present in the real image. So if you take a 480p image, you have 720x480 sample locations, but if you then decide to display that as 720x480 rectangular pixels, you are actually not fully resolving everything that those 720x480 samples capture in the image because you are adding noise and actually reducing the effective resolution of everything that those samples represent. You are adding high frequency noise in the shape of hard boundaries between each rectangular display element. If you scale the image to a theoretically infinite resolution image, you much better recreate the original image in a more accurate way than just displaying at the native resolution of the content's sampling. This is not *adding* information, but it is recovering everything that can reasonably be recovered. Displaying at a native resolution does not achieve this. The reason that this provides benefits hinges on the fact that the images we are watching are continuous tone images, and not arbitrary images where pixels are not at all related to pixels nearby.

I have an excellent image that helps illustrate the above as well, but I can't post attachments in this forum, unfortunately.

#15 of 84 OFFLINE   Fredrik L

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Posted January 08 2007 - 11:56 PM

ChrisWiggles:

Great answer, I've always wondered about that too.

But, what happens in the opposite direction, when a movie in native 1080p-resolution is downsampled to a 720p projector? For exampel, does it look worse then when displaying an alternative 720p-native version of the same movie on a 720p projector?

#16 of 84 OFFLINE   Jeff Gatie

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Posted January 09 2007 - 12:45 AM

Quote:
This is not *adding* information, but it is recovering everything that can reasonably be recovered. Displaying at a native resolution does not achieve this. The reason that this provides benefits hinges on the fact that the images we are watching are continuous tone images, and not arbitrary images where pixels are not at all related to pixels nearby.


Bad word - "recovering". It makes it seem as if you are finding something that was lost. Scaling doesn't find something that was lost in the original SD transfer and magically recreate it. It can't do that. What scaling does is use an algorithm to estimate what was lost and fill it in to the best of the algorithm's ability. Some algorithms are good, some are downright awful, but not all are equal and not all really improve the picture.

A good example (in reverse) is to think back to the days of anamorphic DVD's displayed on 4:3 TV's. Some DVD players used sophisticated image analysis to scale down the anamorphic transfer to fit in the 4:3 display, using complex linear algebra techniques to detect edges, patterns, etc and weave them into a good picture, and some players took out every 4th line.

Not all scaling is alike and not all is beneficial.

PS:
Quote:
If you scale the image to a theoretically infinite resolution image, you much better recreate the original image in a more accurate way than just displaying at the native resolution of the content's sampling.

No algorithm can scale to an infinite resolution or even close. It would lead to mush after about 4 or 5 iterations and definitely would not be "more accurate". It is this type of thinking that makes the writers on CSI think a computer can take a low res traffic cam still and zoom onto the reflection from someone's eye glasses to suddenly get a 5 megapixel mug shot of someone's face. It can't be done.

#17 of 84 OFFLINE   Parker Clack

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Posted January 09 2007 - 02:06 AM

Chris:

What do you mean when you say you can't post an attachment? Do you have the image loaded on another server or would you need to upload it? If you need to upload it make sure you are using at leave the Standard Editor for posting/replying and you will be given an option to upload an attachment.

Parker

"I tried to get my medical records from the company but they say they

are confidential and can only be released to other insurance companies,

pharmaceutical​ reps, suppliers of medical equipment and for some

reason the RNC."
 


#18 of 84 OFFLINE   ChrisWiggles

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Posted January 09 2007 - 04:29 AM

Quote:
Originally Posted by Parker Clack
Chris:

What do you mean when you say you can't post an attachment? Do you have the image loaded on another server or would you need to upload it? If you need to upload it make sure you are using at leave the Standard Editor for posting/replying and you will be given an option to upload an attachment.

Parker

I don't know, actually. Maybe it was just late last night but the "manage attachments button" wasn't anywhere. I looked, it's usually right there down below by the options, and I look now and now it's there again! Anywho, the image is now attached. Strange. At least I'm not hearing voices... Posted Image

The attached image is from Poynton. It's a little funny because I made it a GIF, the jpeg was too big in size, but you get the idea.


#19 of 84 OFFLINE   ChrisWiggles

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Posted January 09 2007 - 04:38 AM

Quote:
Originally Posted by Jeff Gatie
Bad word - "recovering". It makes it seem as if you are finding something that was lost. Scaling doesn't find something that was lost in the original SD transfer and magically recreate it. It can't do that. What scaling does is use an algorithm to estimate what was lost and fill it in to the best of the algorithm's ability. Some algorithms are good, some are downright awful, but not all are equal and not all really improve the picture.

A good example (in reverse) is to think back to the days of anamorphic DVD's displayed on 4:3 TV's. Some DVD players used sophisticated image analysis to scale down the anamorphic transfer to fit in the 4:3 display, using complex linear algebra techniques to detect edges, patterns, etc and weave them into a good picture, and some players took out every 4th line.

Not all scaling is alike and not all is beneficial.

I disagree, quite strongly. Recover is I think the best way to think about it. You are correct, you are not adding information beyond what is contained in the native samples, but you are extracting everything possible from those samples and reducing noise artifacts in the image. In this way, scaling actually does recreate better what was in the original image, given the samples that are in the content. You are correct, it is not magic at all, rather it's basic image theory.

If you want to compare, take a view of a native 480p DVD at native 480p. Now view that at say 960p or 1080p. The level of detail present is increased, and the image looks FAR superior. This is not *adding* in NEW information, it is merely better recovering the information in the content itself by scaling which is a method very similar to a gaussian blur that is shown in the image I just attached. To be clear, it also is no replacement whatsoever for native content that is higher in resolution. You will not be able to get native 480p content at 1080p to look like native 1080p content for instance.

All of this, of course, assumes decent scaling. Perhaps that is a dangerous assumption, and in many cases unfortunately it is a poor assumption, but good quality scaling is available today very widely, which is a very good thing.

Quote:
No algorithm can scale to an infinite resolution or even close. It would lead to mush after about 4 or 5 interations and definitely would not be "more accurate". It is this type of thinking that makes the writers on CSI think a computer can take a low res traffic cam still and zoom onto the reflection from someone's eye glasses to suddenly get a 5 megapixel mug shot of someone's face. It can't be done.

You are confusing scaling with zooming in on an image. If you did need to zoom in on an image, by far the best way to do this would be to scale to a much higher resolution first. Otherwise, you're just going to be blowing up all the added HF noise laid over the image by the rectangular pixel boundaries. Scaling to a theoretically infinite resolution always is the best way to view any image. This does not have bearing on trying to zoom in on an image, you are still limited by the resolution of the content at hand. I can't be any more clear about this, which is why I said previously that you are not *adding* NEW information. But you are reducing noise (a great deal) and thus much better rendering the image as represented by a particular grid of samples. This is why scaling *any* image at *any* resolution to a theoretically infinite resolution for viewing at an infinite resolution resolves the maximum from that image that can realistically be possibly achieved.

#20 of 84 OFFLINE   ChrisWiggles

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Posted January 09 2007 - 04:43 AM

Quote:
Originally Posted by Fredrik L
ChrisWiggles:

Great answer, I've always wondered about that too.

But, what happens in the opposite direction, when a movie in native 1080p-resolution is downsampled to a 720p projector? For exampel, does it look worse then when displaying an alternative 720p-native version of the same movie on a 720p projector?

This is a good question. It depends. If you're downscaling, a lot is going to depend on the quality of the scaling. There are theoretical reasons why going from a 1080p and scaling down to 720p can actually look better, but in reality with a not too minor limitation of 720p at the display and 1080p and the content you can get things like aliasing problems and other things. Presumably, native 720p content would avoid these problems, but that is not always the case. Just as a for instance, there are HD-DVD trailers that are available at 1080p and 720p. However, the 720p do not appear to be scaled down in the best way and the content itself has aliasing in it. So 1080p scaled in my system looks better at 720p than this particular 720p content does. We also have to be clear that in my example, we're taking a DVD resolution and blowing it up a LOT. The difference between 720p and 1080p is less. In the former example, it is much more akin to going towards going to that "theoretically infinite" resolution, whereas moving between 720p and 1080p are relatively smaller changes in resolution and that is much more difficult to do because you'll get all those aliasing issues into play.


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