[NicolasB]

Introduction


I have hopes that this may become a "sticky" thread, or at least one that's referenced in a FAQ, as it covers issues that come up rather a lot. In particular I am getting very, very tired of people constantly claiming "You don't need a 1080p screen, as there won't be any 1080p around for years" without having any understanding of what they're talking about. Hopefully, while this post is tediously long it will at least finally lay that particular question to rest.

To be fair, people use the terms "1080i" and "1080p" to mean a lot of different things, and it is understandable that some might be confused. I think it might help to go back to first principles and discuss all the possible meanings of those terms before we try and come to any conclusions about what is or is not important.





The Basics

First, let's make sure we actually understand the difference between an "interlaced" signal and a "progressive" one. A video signal is a sequence of pictures. Each picture is made up of dots or "pixels", laid out in a rectangular grid pattern. In a progressive signal, you are given the first horizontal line of pixels, then lines 2, 3, 4, 5, 6, 7, and so on: each set of lines makes up a complete picture.

In an interlaced signal, you are given lines 1, 3, 5, 7, 9, etc. (all the odd-numbered lines); then there's a break; then you get all the even-numbered lines - 2, 4, 6, 8, etc.; then another break; then another set of odd lines; another set of even lines; and so on.

So, "progressive" means a sequence of complete pictures (known as "frames") while "interlaced" means a sequence of half-pictures (or "fields"), with alternate fields containing odd and even lines.

The "1080" part refers to the number of horizontal rows of pixels in each full picture. Either 1080i or 1080p is intended to be viewed on a display with a resolution of 1920x1080.




Signal Formats


Field/Frame Rate

Now, if we want to fully describe a video signal, we need more information than either "1080i" or "1080p" tells us. First, we need to know something about the signal frequency. 1080i, for example, might have 50 or 60 fields per second (which might or might not be equivalent to 25 or 30 frames per second - more on that in a moment). So, for example, "1080i/50" means we get 50 fields per second, or 50 half-frames per second.

"1080p/60" would mean we get 60 full 1920x1080 frames per second.


Film Or Video

Another piece of information we need to fully identify the signal is: was the original source of the images inherently progressive or inherently interlaced?

Suppose we're watching a movie on Sky HD. This will consist of a 1080i/50 signal. The way this was produced was:

- Start with a cinema film, which has 24 frames per second, and scan it in.

- Scale each each frame to a resolution of 1920x1080. (So you now have a sort-of 1080p/24 signal).

- Split each frame into two fields, the first containing the odd lines, and the second containing the even lines. (You've now effectively got a 1080i/48 signal).

- This is converted to 1080i/50 simply by playing it back faster - the same fields are in the signal, but they're coming at you more quickly.


If you need to convert a film to a 1080i/60 signal, then the process then is:

- Convert to 1080i/48 as above.

- Broadcast each four pairs of fields in this sequence:

Odd field 1
Even field 1
Odd field 2
Even field 2
Odd field 2 again
Even field 3
Odd field 3
Even field 4
Odd field 4
Even field 4 again.

An important point in either case is that, although the eventual signal is interlaced, the source material it was produced from was progressive. Each pair of odd and even fields come from what was originally the same single progressive frame - the odd lines and the even lines were photographed at the same moment in time.

But this isn't always true. If you're watching a football match on Sky Sports HD, then it may well have been filmed using a native 1080i TV/video camera. In other words, the actual pictures the camera takes are not 25 full-frame pictures per second - it is taking 50 pictures per second, but only recording half the lines in a full frame each time it does it.

Now, the odd and even fields in each pair do not come from the same original progressive frame, and were not taken at the same time.


Filtering

The final thing we need to know is whether there has been additional filtering (effectively downscaling) of the original source image. 1080i signals (indeed, all interlaced signals) were originally designed to be displayed on CRT devices, which are capable of displaying an interlaced signal directly: they display one line of the picture at a time, and they can actually display the lines in the order 1, 3, 5, 7, etc. If you're displaying 1080i on a system like this, and there is some feature in the picture that is exactly 1 vertical pixel wide (say, a bright dot on a black background), you will only see that dot thirty (or, in this country twenty five) times per second. This creates very visible and annoying flickering called "line twitter".

To prevent this, interlaced signals were (and often are) vertically filtered i.e. made more blurry, so the effective vertical resolution of 1080i drops to about 800 lines. This guaranteea that nothing is ever only one vertical pixel wide, but it also causea a loss of detail. Many actual 1080i transfers were also filtered horizontally, lowering the effective horizontal resolution from 1920 to about 1440.


Summary

So, to fully describe a video signal, we need to know:

1) Is it progressive or interlaced?

2) How many fields or frames per second does it contain?

3) Was the original source material progressive (film) or interlaced (video)?

4) If the signal (but not necessarily the source) is interlaced, has there been additional filtering of the source image to prevent line twitter?




Displays


We now have to worry about what we might or might not mean by describing a display as "1080p".


Output

First, we might be referring to the actual output of the screen - the image that we actually look at.

There are a few plasma panels from Hitachi and Toshiba which use a technology called ALIS and which are inherently interlaced - they display the odd lines and even lines of a display alternately, but never together. However these are a) fairly rare and b) crap, so we don't really have to worry about them.

CRT-based devices are also able to directly display interlaced images. Some of these are most emphatically not crap - high-end CRT projectors still produce images at least as good as the best digital projectors, and have done so for many years. But these too are fairly rare, and direct-view CRT televisions capable of displaying native 1080i are almost unknown in this country.

So, for practical purposes, any high definition display you are likely to be thinking about buying at the moment is inherently progressive, that is they display all the pixels in the picture at once. This applies regardless of whether it's plasma, LCD, LCOS (which includes DILA and SXRD), DLP, or even future technologies like SED and OLED.

Because all of these displays are inherently progressive it has become quite common to use the term "1080p screen" as shorthand for "screen with a resolution of 1920x1080".


Inputs

However, the output is not the whole story. We also have to worry about inputs. A screen that has a resolution lower than 1920x1080 might still be described as being "compatible with 1080i" or even "compatible with 1080p" if it is capable of accepting an input signal in 1080i or 1080p format and displaying an intelligible image derived from it.

Many 50" plasma screens, for example, have a resolution of 1366x768. Most so-called high-definition 42" plasmas have a resolution of 1024x768. But they are still able to accept a 1080i signal at the input. That signal is deinterlaced and then downscaled to the resolution of the screen.

A second possibility is that a screen may actually have a resolution of 1920x1080 (i.e. it is able to display 1080p images) but still not be able to accept a 1080p signal at its inputs. A startlingly large number of so-called 1080p displays work like this: the picture may be 1080p/60, but you can't feed it any kind of 1080p signal, only a 1080i one. (There are also screens that will accept a 1080p input over analogue - VGA or component - but not via a digital input).

Finally, even if a screen can accept a 1080p signal, you then have to ask what signal frequencies it can deal with. Can it accept 1080p/100? 1080p/75? 1080p/72? 1080p/60? 1080p/50? 1080p/48? 1080p/24? The fact it can accept some of these frequencies doesn't mean it can accept all of them, which becomes important when we think about deinterlacing - more on that in a moment.

There are some very odd devices out there. The Sharp Aquos LC45GD1E, for example, cannot accept a 1080p input at the media box. But if you bypass the media box you can pass 1080p/60 direct to the screen - but not 1080p/50. (Among other things this means the media box is converting 50Hz signals to 60Hz ones, which is very nasty ).


Deinterlacing

A full description of deinterlacing - that is, converting an interlaced signal into a progressive one - is outside the scope of this post. But there are a few important points to grasp.

- Because virtually all hi-def displays are inherently progressive, they are incapable of displaying 1080i actually as 1080i - somewhere along the line it must be converted to 1080p.

- On a fixed-pixel display (i.e. more or less anything except CRT) if you're displaying a picture full-screen then the picture that is eventually displayed has to be the same resolution as the device it is being displayed on. So, if you (for example) feed a 1080i image to a 1024x768 plasma, somewhere along the line the picture will have be to resized or "scaled" from 1920x1080 all the way down to 1024x768. And, before an interlaced image can be scaled it must first be deinterlaced.

- All non-CRT display devices therefore contain a built-in deinterlacer and scaler.

- Deinterlacing is actually a very difficult computational problem. If you know for certain that your original source image was progressive (e.g. it was shot on film) then weaving together each pair of fields into a single frame is simple. But how does the device know whether or not the source material was progressive?

And, if the original source material was inherently interlaced, how do you go about combining two half-pictures taken at different times into a single picture that is all shown at once?

The process of guessing whether the material was originally film or video and the process of doing video-type deinterlacing is really quite complex.

- So, the most important thing to understand about deinterlacing is that virtually all of the deinterlacers built into displays are not very good.

This can cause a wide variety of objectionable picture problems including loss of vertical resolution (so you end up watching something with only 540 lines of vertical resolution instead of 1080), "combing" (where the even rows of pixels seem to have been displaced sideways relative to the odd rows), "jaggies" (diagonal lines looking blocky and jagged rather than smooth), and jerky or irregular motion.



Sources

Now let's consider what types of HD source material are out there.


PCs

These will typically generate 1080p/60.


"Next gen" games consoles

The output from these remains somewhat uncertain, but there will certainly be 1080p/60 or 1080p/50 sometimes.


Video processors (sometimes inaccurately known as "scalers")

Because most built-in deinterlacers (and, to a lesser extent, most built-in scalers) are a bit crap, one important thing to think about when buying a hi-def display is whether or not you want to use some kind of external device to do the deinterlacing and scaling. If you do, then clearly it is very important for the display to accept a 1080p signal, otherwise there's no point in having an external deinterlacer.

Stand-alone scaler/deinterlacers are often able to convert a 1080i-encoded movie back to the original 1080p/24 movie frames (or 1080p/25). You will therefore not get the best out of an external video processor unless the display can accept 1080p/24 and 1080p/25 as well as higher frequencies.


BluRay/HD-DVD

Movies in these disc formats are often advertised as "1080p". What that means is:

a) They're 1080p/24.

b) There hasn't been any twitter-supressing filtering applied. (By contrast, an awful lot of 1080i broadcast or D-Theatre material has been filtered).

So the film, as stored on the disc, is full-resolution 1080p/24. The actual output from current-generation players isn't 1080p/24, though - it's 1080i/60, with all the inherent deinterlacing problems that implies. (One would hope that the players released next year will actually output 1080p/24, or at least 1080i/48).




So, does 1080p matter?!


The answer, as you will have realised by now, is: "that depends what you mean by 1080p". If we make the question more specific, then maybe we can finally answer it!


Q: Is it worth having a screen that has a resolution of 1920x1080?

A: Yes, very much so. Any 1080i video signal requires a resolution of 1920x1080 to be displayed without loss of detail. This does not, of course, mean that all 1920x1080 displays will automatically look better than all lower-resolution screens - there is a lot more to picture quality than just resolution.

However, if there are no other differences between two displays except that one is 1080p-native (1920x1080), and the other is (say) 720p native (1280x720), and if you are sitting close enough to the screen, and if you're feeding them both a 1080i signal, which is being deinterlaced correctly, the 1080p display will look a great deal better than the lower-res one.

Let's just emphasise that one more time: you cannot watch 1080i without loss of detail unless you have a 1080p screen - 1080p output resolution, anyway.


Q: Are there any sources of 1080p material?

A: Yes, loads. Nearly all PCs. (Some downloadable video material is - I believe - in 1080p/60 format). Next gen games consoles. The next batch of BluRay and HD-DVD players (hopefully). And, which is particularly important, stand-alone video processors (scaler/deinterlacers).


Q: Do I need a screen which can accept a 1080p input signal?

A: Yes, if you want to use any of the devices mentioned in the previous answer.


Q: Will there be any actual TV programmes shot and broadcast as 1080p/50 or 1080/60?

A: Not for some time.


Q: At what frequencies does a screen need to accept a 1080p signal?

A: For use with a PC, 60Hz. For use with a console, 60Hz and possibly also 50. For best use with an external video processor, definitely both 50 and 60Hz and also some multiple of 24Hz (e.g. 24, 48, 72, 96).


Q: What do I need to check to see if my screen is "true" 1080p?

A: The following:

- What is the actual resolution of the display? (Is it 1920x1080?)

- Can it accept 1080p input or only 1080i?

- Can it accept 1080p over a digital input that supports HDCP? (HDMI always supports HDCP. DVI sometimes does but usually doesn't.)

- What frequencies of 1080p can it deal with?


Q: If my display is "HD Ready", am I covered for all eventualities?

A: No, definitely not. "HD Ready" means:

- The vertical resolution actually displayed must be at least 720 pixels (but the horizontal resolution can be absolutely anything!)

- It must be able to accept both 720p and 1080i signals.

- It must accept both signals at 50 or 60Hz.

- It must accept both both resolutions and frequencies on a digital input that supports HDCP.

Note that there's no reference to 1080p anywhere in that definition. To see whether or not that matters, read the rest of the post!


Edit (9/3/2008):

As this thread is still linked to in a FAQ, and especially as it has just been bumped back up to the top of the forum anyway, I should probably make two small additions:


1) Since this post was first composed, we've seen a lot more HD-DVD and Blu-Ray players hit the market. (And we're now seeing HD-DVD on it way out!). HD-DVD and Blu-Ray players now quite often have the ability to output a 1080p signal with a 24Hz refresh rate. At the time I originally composed this, the only way you could easily get 24 frames-per-second playback of hi-def movie material was by using a video processor to correctly deinterlace a 60Hz 1080i signal. Now, most higher-end hi-def disc players will produce 1080p/24, and the result of doing this (on a display that correctly supports it) will look a lot nicer than it will if you have to convert 1080i/60 to 1080p/60. The ability to accept a 1080p signal, and specifically to accept one at 24Hz, is therefore significantly more important now than it used to be.

In fact most "1080p" or "full HD" screens these days can now take a 1080p input at 50 or 60Hz; a smaller number can accept 24Hz input.

If you have to watch a BluRay of HD-DVD movie as 1080p/60 (and this is what nearly all TVs will do if you feed them a 1080i/60 signal, even if they recognise it as film) then you will get a "judder" effect on motion. What actually happens is that some of the original film frames are shown twice, while others are shown three times; this makes motion much less smooth.


2) Another change to the market since I first composed this is that "upscaling DVD players" are much more common than they used to be. Generally speaking, the way these players are marketed is a con; the salesman will try to convince you that it somehow converts a standard-definition image into a high-definition one. It doesn't. Actually it does the same thing as your hi-def TV already does: if you're watching something that is originally in standard definition (such as a DVD) and the picture is filling the screen (as opposed to being displayed in a tiny little box in the middle) then it has been upscaled: that's all upscaling means, blowing up the picture till it fills the whole screen. However, sometimes DVD players will do a better job of deinterlacing and scaling than the equivalent circuitry inside the television, and the picture quality will therefore be a bit better if you let the player do the processing and feed a progressive signal to the TV at the native resolution of the screen.

If you plan to use an upscaling DVD player, as with a stand-alone video processor. then it is important that the screen is able to accept a progressive signal at its native resolution, otherwise you won't get the full benefit from the external scaling because the TV will be doing additional processing. If, therefore, you have a 1920x1080 display, and you want to use it with an upscaling player, it is important that it be able to accept a 1080p input signal.

Thanks for the time and effort you put into this post. I've just got some keen pricing on a Panasonic PH50PX600 with 5 year guarantee, and was considering dipping in. In my eyes, true 1080p screens will be the norm for Xmas 2007, and for Xmas 2006 all they will help to do is drive down the price point of current 1080i screens.

However, this forum gives a clear message about the quality of SD viewing on 1080p screens - it can be poor. And until my household has some kind of HD feed for regular tv, I struggle to see the need.

Plus, I want a plasma now, and cant keep on waiting.

[neilmcl]

Good post Nic, well written.

[Pecker]

Cheers, a great resource.

The only thing not really covered is the difference in perceivable PQ when moving from 720p to 1080p. However, this is understandable for many reasons. For one, this can be quite a subjective judgement. Secondly, there are not a lot of side-by-side comparisons available.

It would be nice to have some screen shots of 1080p vs 720p projectors to see what all this means in the real world.

Unfortunately, there will be very few people out there who have both a 720p and a 1080p projector.

Steve W

[NicolasB]

Originally Posted by sixluckynumbers

However, this forum gives a clear message about the quality of SD viewing on 1080p screens - it can be poor.

It's not so much that watching on a SD 1080p screen is poor, it's that watching SD on a large screen tends to be poor, and that really, when all's said and done, competing technologies still don't actually look as good as CRT does (in my opinion). The fact that (say) a plasma screen isn't 1080p doesn't in any way improve its ability to display SD. A 1080p plasma of the same size would look just as good. (Or just as bad!)

[Pecker]

I think a bigger issue is comparison.

If you watch (say) 20% of your material in HD, you may find yourself not enjoying SD.

If the format wars continue on disc, and Sky's/the BBC's output remains minimal, that might mean us being disappointed in most of the things we watch.

Steve W

[Cyril]

I guess what most people who haven't bought a HD screen yet want to know is it worth paying extra for a 1080p over a 720p?

I would say YES if you

a) have the money
b) watch or intend to watch a lot more 1080p content than SD
c) have a screen size about 50" or more or you sit very close to the screen
d) use the screen for computer use a lot

It's a tough choice if you are somewhere in-between those requirements.

I went for a Fujitsu 720p plasma instead of the Pioneer 50" 1080p as

a) it was 63"
b) not much more expensive and better bang for the buck IMHO
c) I watch about 50% SD material
d) resolution is only one of many factors affecting picture quality - the Fujitsu 58 and 51 series are only 720p but produce outstanding results for the price IMHO.


For purely selfish reasons I hope everybody goes out and buys 1080p screens so that Fujitsu will be forced to bring out a high-end 1080p plasma sooner and at a lower cost

[NicolasB]

If you're likely to watch only SD then (IMO) you'll probably still be better off buying a good conventional CRT television even now. They're on their way out, but that's not because other technologies are better, it's because people in this country care far more about a TV being thin than they care about the picture quality.

As a semi-aside, I was setting up my girlfriend's PC today, and tried playing a 720p video clip on it. I'd previously watched the same clip on my own machine, which is hooked up to a Dell 2405FPW - quite respectable 24" LCD monitor (widescreen, 1920x1200). My girlfriend's PC uses a 17" CRT monitor that must be 6 or 7 years old, and the model came out about 11 years ago. I expected that the clip might look better on the CRT screen, but I was staggered by quite how much better it looked - astonishing difference in terms of colour accuracy. Clearly the 2405FPW doesn't exactly represent the pinnacle of LCD TV technology(!) but I think people often forget just how good CRT actually is compared to competing tech, and are consequently dissappointed when they buy a huge, expensive, non-CRT screen.

If you are going to buy a large-screen TV then personally I think you're better off not scaling SD pictures up to full screen. A widescreen PAL DVD, for example, could be scaled to 1024x576 and then shown letterboxed. Unfortunately very few (if any) displays allow you to do that: you can only do it if you use either an external video processor or a Home Theatre PC.

[NicolasB]

Originally Posted by Cyril

I guess what most people who haven't bought a HD screen yet want to know is it worth paying extra for a 1080p over a 720p?

I would say YES if you

a) have the money
b) watch or intend to watch a lot more 1080p content than SD
c) have a screen size about 50" or more or you sit very close to the screen
d) use the screen for computer use a lot

I didn't discuss that very much, because my main aim was simply to clarify what is actually meant by "1080p" and "1080i". But yes, that is an important question.

Point C is worth emphasising very strongly, I think. Unless you are sitting close or the screen is large, the human eye simply cannot resolve enough detail to be able to detect the difference between 720p and 1080p.

For example, if you have a 42" screen then, at a distance of 8.2 feet, 1280x720 (720p) is the maximum amount of detail someone with typical eyesight will be able to see. So 1080p only becomes useful if either your screen size is significantly larger than 42", or your viewing distance is significantly less than 8 feet. (Or both). The optimum screen size for a 1080p screen viewed from 8.5 feet away is 65".

For some more info about viewing distances and screen sizes, check out an earlier thread of mine: Optimum screen size/viewing distance

[Cyril]

Originally Posted by NicolasB

As a semi-aside, I was setting up my girlfriend's PC today, and tried playing a 720p video clip on it. I'd previously watched the same clip on my own machine, which is hooked up to a Dell 2405FPW - quite respectable 24" LCD monitor (widescreen, 1920x1200). My girlfriend's PC uses a 17" CRT monitor that must be 6 or 7 years old, and the model came out about 11 years ago. I expected that the clip might look better on the CRT screen, but I was staggered by quite how much better it looked - astonishing difference in terms of colour accuracy. Clearly the 2405FPW doesn't exactly represent the pinnacle of LCD TV technology(!) but I think people often forget just how good CRT actually is compared to competing tech, and are consequently dissappointed when they buy a huge, expensive, non-CRT screen.

Which is why I went for the Fujitsu 51 series plasma as it gives a more CRT like picture than any LCD I have seen.

Colour accuracy and what I think is called 'high dynamic range' are as or maybe more important than resolution in terms of perceived image quality in my eyes.

[Welwynnick]

Well, this panders to one of my favourite hobby horses, so a sticky it is!

Thanks, Nicholas.

Nick

[MAW]

1 more thing, Nick, apart from congratulations on shedding some light on a muddy issue. Overscan. 99% of consumer devices do it. 1080p displays are no exception. For PC and VP use, it is vital to ensure your 1080p dsplay can be pixel mapped at 1080p inputs. That will currently limit you to about 5 screens I know of, not all of which are yet released. Perhaps a definitive list of these dislpays would be useful in this thread. May I start the running with the fortcoming Panasonic commercial plasmas, the PF series, and the Pioneer 5000. There is a Tosh LCD, model number someone else will know. Any more, anyone, which genuinely do not overscan, or have enough adjustment built in?

[BENN0]

The Sony X2000 and W2000 series have a user selectable option for 1:1 pixelmapping over HDMI.

Re 1080i vs. 1080p: If your source is a 1080p24 signal (HD-DVD or BluRay movie) that gets converted by the player to 1080i60, all the original picture information is still in the converted 1080i60 signal right?
So if your display can do a decent job of deinterlacing (and reverse 3:2 pulldown) you will have lost no picture information and the resulting picture would be the same as if the display was directly fed a 1080p24 signal?

[NicolasB]

Originally Posted by BENN0

Re 1080i vs. 1080p: If your source is a 1080p24 signal (HD-DVD or BluRay movie) that gets converted by the player to 1080i60, all the original picture information is still in the converted 1080i60 signal right?
So if your display can do a decent job of deinterlacing (and reverse 3:2 pulldown) you will have lost no picture information and the resulting picture would be the same as if the display was directly fed a 1080p24 signal?

Unfortunately the "if your display can do a decent job of deinterlacing" part is a very large "if". Many displays do not recognise 3:2 pulldown correctly on 1080i; and, even if a particular screen does, there's no guarantee that it will deinterlace to 1080p/24. It may well display it as 1080p/60 instead.

Also don't forget about movies on Sky HD - they're 1080i/50 rather than 1080i/60, and that is much harder to deinterlace correctly.

[Sonic67]

For me £1000 blue ray drives and £600 to Sky for a drive and subscription isn't going to happen. Besides I think Sky dishes are down market and I don't want to invest in a HD DVD technology that might turn out to be another betamax. It's not even guaranteed either format will take off. Some have felt that HD DVD isn't sufficiently better than DVD as DVD was over VHS. Obviously is money is no object then fine spend away. It's your money and you can spend it how you wish (as can anyone else).

http://www.practical-home-theater-gu...080p-hdtv.html

"It is true that these sets are capable of producing spectacular results with ultra sharp images, but please take note that it is extremely unlikely that you will be able to see any difference in image quality between a 720p display and a 1080i signal displayed on a 1080p HDTV set - in particular, because of the limitations associated with the 1080i format already detailed earlier on.

Surely, you will not perceive any difference in image detail between 720p and 1080i/p HDTV material on the smaller sets from 10-feet away. You need to sit closer and feed your 1080p HDTV set with a good quality HD source to possibly start to see any difference.

As already indicated, the quality of the source material you are viewing is very important. With most of today HD broadcasts, you will be hard pressed to see a difference in picture quality when you compare the image on current 720p sets versus the latest 1080p HDTV models.

You would need to go really big for the extra image resolution to make any difference - but then keep in mind that at present, true 1080p HDTV material is almost non-existent. What's more, none of the major networks has announced 1080p broadcasts - and it is unlikely that they will make such a move in the near future considering the bandwidth requirements."

[dazed & confuse]

Thanks Nicolas, what a great summary.

Withregard to viewing distance, I sit approx 12' from my 42" wall mounted Plasma. I've just ordered the Pioneer PDP-507XD, which is not 1080p.
Would there be much benefit from upgrading to 1080p on that size TV at that distance.
Once again great posts.......

[NicolasB]

Originally Posted by dazed & confuse

Thanks Nicolas, what a great summary.

Withregard to viewing distance, I sit approx 12' from my 42" wall mounted Plasma. I've just ordered the Pioneer PDP-507XD, which is not 1080p.
Would there be much benefit from upgrading to 1080p on that size TV at that distance.
Once again great posts.......

On the subject of screen sizes and viewing distances, I suggest you consult an earlier thread of mine:

Optimum screen size/viewing distance

It rambles a bit but there is some (I think) useful info in there. Try out the spreadsheet it links to.

The short answer is that, for a 42" screen, 720p and 1080p are indistinguishable at a distance of slightly over 8 feet for a person with normal eyesight. At 12 feet with a 42" screen there's no virtually no point even in having 720p: there will be almost no visible difference between 720p and standard definition. (That assumes both are displayed correctly. Many HD screens f*ck up SD to the point where, on the same screen, there is a visible difference between SD and HD. But that's not because the HD looks better, it's because the SD looks worse.)

At a distance of 12 feet, the optimum screen size for 720p is 62". The optimum screen size for 1080p is 92".

[Phill1978]

^ true, which means for people with 26" screens it may look crisper but unless your running 60" + then 720p will deliver the same effect. in essence its a high end format for serious home theater installs but again with tiny living rooms in uk there isnt going to be a massive difference to justify the outlay until the format is fully here and now.

[NicolasB]

Originally Posted by Sinelanguage

sure there is but at full 1080p ?

All of the sources I mentioned (Sky HD movies, BluRay and HD-DVD) are already full 1080p, and will never be anything else. On the discs the movie is recorded as 1080p/24 which is output as 1080i/60. Given suitable deinterlacing one can reconstruct the original film frames. For Sky HD movies the signal is 1080i/50, which can be reconstructed into 1080p/25. Non-film content on Sky HD (e.g. football) will be mostly 1080i - there will be little, if any, native 720p. Regardless of whether the signal is 1080i or 1080p, unless you have a 1920x1080 screen, you are losing a lot of the potential detail.

If any of this is news to you, please go back and actually read the first post in the thread! I know it's tiresomely long but the reason for its existence is precisely to clear up questions like this!

Originally Posted by sinelanguage

but unless your running 60" + then 720p will deliver the same effect.

Not really. If we assume a perfectly reasonable viewing distance of eight feet, then 1080p will look better than 720p on any screen larger than 42".

[NicolasB]

Originally Posted by Sonic67

For me £1000 blue ray drives and £600 to Sky for a drive and subscription isn't going to happen.

It's safe to assume prices will come down pretty quickly, just as they did with Sky+ and DVD players.

Originally Posted by Sonic67

Besides I think Sky dishes are down market

Downmarket and too expensive?

Originally Posted by Sonic67

and I don't want to invest in a HD DVD technology that might turn out to be another betamax. It's not even guaranteed either format will take off.

I think it's safe to assume at least one will. My prediction is that it will go the same way as writeable DVD: eventually all players will support both disc formats.

Originally Posted by Sonic67

Some have felt that HD DVD isn't sufficiently better than DVD as DVD was over VHS.

Some have also felt that the Earth is flat and that unicorns really exist. Possibly the people who feel this about HD-DVD weren't viewing them on 1920x1080 screens.

Originally Posted by Sonic67

http://www.practical-home-theater-gu...080p-hdtv.html

There are some dangerous inaccuracies in there.

"It is true that these sets are capable of producing spectacular results with ultra sharp images, but please take note that it is extremely unlikely that you will be able to see any difference in image quality between a 720p display and a 1080i signal displayed on a 1080p HDTV set - in particular, because of the limitations associated with the 1080i format already detailed earlier on.

Rubbish.

Surely, you will not perceive any difference in image detail between 720p and 1080i/p HDTV material on the smaller sets from 10-feet away. You need to sit closer and feed your 1080p HDTV set with a good quality HD source to possibly start to see any difference.

Depends entirely on the size of the screen. Besides, is viewing from 8 or 9 feet really such a hardship?

As already indicated, the quality of the source material you are viewing is very important. With most of today HD broadcasts, you will be hard pressed to see a difference in picture quality when you compare the image on current 720p sets versus the latest 1080p HDTV models.

Rubbish.

You would need to go really big for the extra image resolution to make any difference

Again, this depends strongly on viewing distance.

but then keep in mind that at present, true 1080p HDTV material is almost non-existent.

Rubbish. See much of the first post in this thread for more details.

What's more, none of the major networks has announced 1080p broadcasts - and it is unlikely that they will make such a move in the near future considering the bandwidth requirements."

True, but totally irrelevant - and demonstrating why it is totally irrelevant was my primary motivation for starting this thread in the first place.

[Sonic67]

You might rubbish his site but he seems to have a reasonable electronics background.

http://www.practical-home-theater-gu...this-site.html

By profession, I am a Telecoms Engineer with specialization in digital switching and Telecoms fraud management systems.

The trigger was an assignment to design a low-distortion MOSFET power audio amp; that's over 20 years ago!

Oh and Sky 'downmarket and expensive'. Well I think the dish doesn't look good (My house is covered in white painted rendering, it would really stand out) but I think the HD Sky + box is expensive. Two different things.

You're obviously an intelligent guy. I thought you'd be capable of better arguements.

[Phill1978]

^ agree, but it would seem he has floated down from the heavens not to discuss the virtues of 1080P but to tell us outright that we MUST have it


this is still a discussion forum you cannot escape that

[neilmcl]

Originally Posted by Sinelanguage

^ agree, but it would seem he has floated down from the heavens not to discuss the virtues of 1080P but to tell us outright that we MUST have it


this is still a discussion forum you cannot escape that

Actually I thought this was a sticky thread outlining a number of Facts, which you can take or leave. It was never meant as a discussion thread. If you don't agree with the OP then your more than welcome to start your own thread on the subject.

[Phill1978]

ok then delete all posts other than his






the guys write up as ive mentioned three times now is exellent and i appreciate it i found the article interesting but his attitude sucks

[Sonic67]

The info on 1080p are facts.
Whether it's worth the expense of buying one is debatable.

This question is very difficult to answer because not all displays are equal.

If you buy a 1080p display today it will almost certainly be an LCD, and I agree entirely with NicholasB's comments about the astonishing difference in colour accuracy between CRT and LCD displays. Similarly I recently compared the same HD material side by side (Jools Holland on BBC HD Preview) on Toshiba's 42WLT66 1920 x 1080p LCD with Panasonic's 42PX60 1024 x 768p plasma. It seemed to me that the plasma offered a richer more detailed picture than the LCD despite its lower pixel count.

My view is that at the moment - leaving aside a few high-end displays that deliver both - consumers are faced with a choice between picture quality and screen resolution.

I found the comments on ALiS displays surprising. Sure, they have their drawbacks - the low horizontal resolution and the full scanline field offset compared with the CRT's half-line - but being able to display 1080i natively and so avoid the pitfalls of deinterlacing is a significant advantage.

[NicolasB]

Originally Posted by Quickbeam

If you buy a 1080p display today it will almost certainly be an LCD

Generally, yes. There are some exceptions. There is the Pioneer PDP-5000EX, which is a (currently very expensive!) plasma. There are some other 1080p plasmas on their way, including a 65" one from Panasonic, but they aren't available in the UK yet.

There are also LCD projectors and LCD rear-projection devices, which have slightly different characteristics from direct-view LCD panels.

And there are LCOS devices (what Sony calls "SXRD" and JVC calls "DILA" - are we overdosing on abbreviations, yet? ). LCOS is based on LCD, but its operation is sufficiently different in practice that I think it's worth referring to "LCOS" and "LCD" as separate technologies. LCOS generally avoids, or at least reduces, many of the issues associated with conventional LCD - better colour accuracy, faster response time (hence, smoother motion and a lack of motion-blur), darker blacks, and almost no "screen door effect" - no dark gaps between pixels.

In america there are also a number of 1080p DLP rear-projection screens (and I think one or two 1080p DLP front projectors). As far as I know none of these are available in the UK yet.

Originally Posted by Quickbeam

I found the comments on ALiS displays surprising. Sure, they have their drawbacks - the low horizontal resolution and the full scanline field offset compared with the CRT's half-line - but being able to display 1080i natively and so avoid the pitfalls of deinterlacing is a significant advantage.

I think the word "natively" is a little bit misleading, there. ALIS panels typically have a resolution of 1024x1024. (Some of the newer ones are 1024x1080). A 1080i image (especially one produced from something like a BluRay or HD-DVD disc) has a resolution of 1920x1080. If you display that on an ALIS panel you are losing almost half of your horizontal resolution. That is not insignificant. All right, there doesn't necessarily have to be scaling in the vertical direction, but the downscaling in the horizontal direction is more severe than on most other "hi-def" devices.

ALIS panels also tend not to have particularly impressive image quality. They're usually very bright (which is good) but with poor contrast ratios - black comes out as washed-out grey.

On top of that there are a number of questions about how ALIS devices deal with progressive-scan input. No one has ever nailed this issue down to my satisfaction (so if anyone actually works for Toshiba or Hitachi and is able to clear this up once and for all, please do!); but, as far as I am aware, any given pixel on an ALIS panel physically cannot be updated more than 30 times a second. That means that if you feed it a 720p high-definition signal, the image will actually have to be downscaled from 1280x720p to 1024x512p, before being line-doubled to 1024x1024i. That means you're losing a lot of resolution - more than you would lose on a 1024x768 screen, let alone one that is native 720p or higher.

To be fair, we won't be seeing very much 720p material in the UK - most of what's on Sky HD is 1080i.

It's also not clear how an ALIS screen would handle a standard-definition PAL progressive-scan signal (from a DVD player that does its own deinterlacing, or from a Sky HD box). It's possible that it needs to downscale the image from 576 lines to 512 in order to display it - in other words, you're actually losing resolution even with some standard-definition signals.

And of course, given a 1080p input, the best an ALIS screen will be able to do is downscale each frame from 1920x1080 to 1024x512. That, combined with the fact that they typically can't be fed a native 1024x1024i signal, sharply reduces the usefulness of an external video processor.

All in all, I think one should be cautious about ALIS. Its advantages are not as clear cut as they may initially appear.

<snip> there are a number of questions about how ALIS devices deal with progressive-scan input. No one has ever nailed this issue down to my satisfaction (so if anyone actually works for Toshiba or Hitachi and is able to clear this up once and for all, please do!)

I don't work for Hitachi but some time ago a forum member posted an email reply from Hitachi which explained how ALiS panels deal with a 576i input. I don't have the link, but to summarise, they do what any scaler does when upscaling to 1080i: 1) deinterlace to 576p; 2) upscale to 1080p; 3) reinterlace to 1080i. Where applicable, they will also crop to 1024i. It seems a reasonable assumption then that when fed a progressive scan input an ALiS panel's scaler skips stage 1 and moves straight on to stage 2, ultimately displaying progressive input in an interlaced format. As ALiS panels are inherently interlaced displays I'm not sure what else they could do.

I apologise if I have taken this thread off topic. I haven't seen enough of the other display types you mentioned to have a definite opinion of them, but LCoS displays are very highly regarded among both experts and the few people lucky enough to own one. Nor am I sure of the merits of ALiS panels versus a good quality 1024 x 768p plasma, but I do like the fact that they can display the full vertical resolution of 1080i. Is 1024 x 768p 'true' high definition though? In my opinion it's not, however good it looks. Is 1080p direct view LCD true HD? I don't think it is either unfortunately. I look forward to seeing what the much-hyped LED backlighting brings to LCD displays, along with the other technologies such as SED and OLED when they finally materialise.

[NicolasB]

Originally Posted by Quickbeam

I don't work for Hitachi but some time ago a forum member posted an email reply from Hitachi which explained how ALiS panels deal with a 576i input. I don't have the link, but to summarise, they do what any scaler does when upscaling to 1080i: 1) deinterlace to 576p; 2) upscale to 1080p; 3) reinterlace to 1080i. Where applicable, they will also crop to 1024i. It seems a reasonable assumption then that when fed a progressive scan input an ALiS panel's scaler skips stage 1 and moves straight on to stage 2, ultimately displaying progressive input in an interlaced format. As ALiS panels are inherently interlaced displays I'm not sure what else they could do.

I don't know if that is a reasonable assumption. A 576i signal is the equivalent of 25 full frames per second. Internally it could be deinterlaced to 576p/25 (although that would cause combing if the original source were not progressive); 576p/25 can be scaled to 1024p/25, which can be interlaced to 1024i/50. But a PAL progressive-scan signal is not 576p/25, it's 576p/50. The only way to apply your suggested approach would be to throw away half of the frames! If the original source image was progressive, you might get away with that, but if the original source was video rather than film, the effect of that would be horrendous. I think it's more likely that 576p is downscaled to 512p, then line-doubled. Even if there is some ingenious way of dealing with 576p, there's still the problem of 720p.

Originally Posted by Quickbeam

Is 1024 x 768p 'true' high definition though? In my opinion it's not, however good it looks.

In my opinion also no. It irritates me a great deal that the official "HD Ready" standard doesn't insist on a minimum horizontal resolution as well as a vertical one.

[AngelEyes]

Nic,

Thanks for this, it really helped clarify a few things for me.

Having read this thread in its entirety I can't see why anyone would take offence at anything you have written...

I am currently looking at getting a Sony Pearl 1080p SXRD. As far as I can tell it can play back 1080p 50/60. I am weighing up whether to get a video processor or to use an HTPC to route my SD sources. They would both probably cost the same assuming I get some half decent hardware in the PC. This is a bit of a woolly question but will the video processor do a noticably better job with SD material than a PC?

Thanks,

Adam