How discernable is 1080p over 1080i ?

[JimPullan]

There are a multitude of 1080i HDTV's having been sold and now the introduction of the 1080p displays. With the advent of the 1080p capable Blu-Ray players, can the average consumer actually see a difference between a 1080p movie over the exact 1080i movie ? Will a 1080p experience be any more thrilling than the 1080i experience ?

Jim

[Deciazulado]

depends on several factors, Jim,

A: An image optimized (or video filtered) for interlaced display has a resolution equivalency or sharpness that can be down to approx. 70% (some call it the Kell factor) of a progressive image in a worst case scenario. (In other words, "It's all in the mastering!")

B: Your 1080i input display or player could either deinterlace correctly (weave) or "incorrectly" (bob) a progressive (film) image, and of course all 1080p displays and/or 1080p output players have to deinterlace interlaced (shot on HDTV video) images by some method, ranging from optimally (motion pixel adaptive, etc, etc), to the more common bob, that again, at worst, would give you 70% of the sharpness. (In other words, "It's all in the deinterlacing!")

Remember this reduction to 70% of 1080p can happen if the transfer is "suboptimal" and you have a 1080p player -> 1080p display; or if the transfer is "perfect" and at some point between the 1080 player and 1080 display there's a worst (bob) deinterlace occurring.*

So depending on those two factors, a 1080i vs 1080p path can vary from the 1080i being equivalent to about 768p, to looking equal to 1080p

(If you wanna play the laws of averages between the extremes of those two possibilities occurring :-P, that comes out to be about 900p, which in comparison to 1080p is: about the same difference between a 16:9 coded widescreen movie DVD and a 4:3 coded widescreen movie DVD).

Then:

C: Seating distance also affects perceived quality:

The eye finds an about 2000p image to be excellent at 0.8x screen width viewing distance from a 16:9 screen.

At 1x screen width sitting distance 1600p
At 1.25x screen width sitting distance 1250p
At 1.6x screen width sitting distance 1000p
At 2x screen width sitting distance 800p
At 2.5x screen width sitting distance 640p
At 3.2x screen width sitting distance 500p
At 4x screen width sitting distance 400p

(In other words, "It's all in how close you sit to the screen!")


D: You may also tolerate a less than excellent image (well, we accept average 35mm theatrical projection which is miles away from perfectly focused 70mm, etc ) For example, tho a 2000p image watched 9 feet from a 16:9 wide 12 feet diagonal screen will look outstanding, that doesn't mean a 1000p image will look bad, it'll look great still. (In other words, "It's all in what you think is good enough!")

E: A judiciously adjusted sharpness control with proper contrast and black level can do wonders to a slightly fuzzy image :-P (In other words nothing beats a correctly calibrated home theater!)

F: So in answer to your question: In some cases it might be more thrilling, (but if you have 1080i now don't worry about it and start enjoying your 6x times better than interlaced NTSC DVD video

G: I can't wait for Blu-ray





*(With both the transfer and the deinterlacing being bad occurring at the SAME time we would still end up with the same potential 70% of max, since what is happening on both process is just putting the same cap on the vertical resolution) (Well, one would hope!)

[JimPullan]

Thanks so much for the detailed explanation. It was certainly more than what I expected. You sure did your homework on this. Again, thanks!

Jim

[vick vega]

yeah, no doubt that was the easiest to understand explanation of 1080i vs. 1080p

[Cysquatch]

i just bought a 1080i 50" plasma and was wondering the exact same thing. Thanks so much for the explanation. 1080p would be awesome but I couldn't pass up the price of the plasma.

[PurpleAardvark]

Good exp. Just saw the price tag on that new 1080p 65" plasma $10,000. Since we are all such loyal BD fans here I know NYG is going to buy one for each of us at Christmas. 2 for me seeing how I don't get the free panny. Here is the link:

http://www.crutchfield.com/S-rV5QSx7...0&I=13365PX600

[welwynnick]

Originally Posted by Stephan.klose

I work in an electronics shop. We have well over a 100 TV's there. I tested most of them and switched between 1080i and p input. To the naked eye it's mostly indistinguishable

Could you qualify that by describing what sorts of TV you were testing. Were they 768 or 1080 line TVs? What material did you test with? Was it mastered interlaced or progressive? Was it distributed interlaced or progressive? Where you input 1080p, was that de-interlaced from a 1080i medium? In which case, was the source or display de-interlacer better? These are some of the issues that need to be considered in the 1080p question.

Nick

[DjLoudsound]

I used to work for a satellite company creating channels and monitoring Video and Audio quality and I can tell you that I can notice a difference from 1080p and 1080i. To the regular joe you will not see a difference. The only thing that might throw it away would be a little noise present on the 1080i image that would not be present on the 1080p image to the regular joe. Since the previous company I worked for only sends out 1080i you wouldnt see a difference unless you owned blu-ray.

[takezo]

Originally Posted by JimPullan

Thanks so much for the detailed explanation. It was certainly more than what I expected. You sure did your homework on this. Again, thanks!

Jim

Also note that 1080p tvs are at the moment, only availible from sizes 40" and Higher. Computer monitors are the exception. 16:9 computer monitors are geared for 1080p or 720p. If you plan to sit far from a PC monitor when you watch HD, then HD really is not going to matter.


With smaller HDTVs, its better to use 1080i. Although a properly encoded 720p hd video would suite it better. 1080p encoded videos look better at 1080i, due to the fact of downscaling. In short, the player must resize the video on the fly, which the quality is totaly based on the player's built in algorithm. By outputing 1080i, you player does nothing to moddify the video, it just telecines it which interlaces it. Your TV will scale it to fit the screen.

I have already tested it on the PS3. While PS3 is unable to scale BD-movies to 720p, it can however scale 1080p movie trailers you can download from PS3 store. At this moment the PS3 scaler adds softeness in the video at 720p, while un altered 1080i video seams cleaner and sharper.

Basicaly to avoid the variables of how good your player is at scaleing, just leave video as is.

[Zvi]

Originally Posted by Deciazulado

C: Seating distance also affects perceived quality:

The eye finds an about 2000p image to be excellent at 0.8x screen width viewing distance from a 16:9 screen.

Deci, can you clarify a little bit more on that? 0.8x? So, for m 61" Sammy I should be sitting less than 5 ft from it? I thought optimal distance was 8-9 ft for that screen with 1080p.

[Deciazulado]

Originally Posted by Deciazulado

C: Seating distance also affects perceived quality:

The eye finds an about 2000p image to be excellent at 0.8x screen width viewing distance from a 16:9 screen.

Originally Posted by Zvi

Deci, can you clarify a little bit more on that? 0.8x? So, for m 61" Sammy I should be sitting less than 5 ft from it? I thought optimal distance was 8-9 ft for that screen with 1080p.

mmm. I measure in PH (picture heights, because movies are projected at constant height and is the width that changes). THX TAP recommends 1.42 PH for the closest viewing distance (not to be confused with the bad front row seats where you damage your neck looking up!), while the minimum size you should be watching a film (the last row on a theater, the worst seat) should be at 3.61 PH. (See top left image of page 25 of this PDF document for a 450 square feet (approx. 14' x 33') 35mm state-of-the-art THX film dubbing stage)

For a 16:9 wide screen (1.78 wide), 1.42PH is 0.8 screen widths.

At that distance the eye could distinguish about 4000 pixels from top to bottom (4000p) under some circumstances, but those details would be at the very threshold of vision and probably not be seen more than half of the time.

With details twice as thick (only 2000 pixels, or "2000p"), that would be the practical limit with an image virtually indistinguishable from the 4000p one. (I'd say 4000p would look 5% better at that viewing distance, but for that improvement you'd need 400% the bandwidth or data!)


So again, in practical terms at approx. 1.5 PH (0.8 screen width for a 16:9 display) the eye finds an about 2000p image to be excellent.

With 1000p at that distance the image would be very good.

2000p would be equivalent to 70mm while 1000p would be the equivalent of 35mm


61" 16:9 Sammy screen is 30" x 53". Sitting at 9 feet (108") the numbers would be (assuming no overscan):

1.37 movies at 3.6PH (or 2.6 screen widths)
1.78 HDTV at 3.6PH (or 2 screen widths)
1.85 movies at 3.7PH (or 2 screen widths)
2.39 movies at 4.8PH (or 2 screen widths)

As you can see those viewing distances are like watching a film in the last row of a theater. That would make 35mm film (or 1000p) look as sharp as 70mm film, but of course then the field of view is 4 times as small as the one you get by sitting in the middle or the front on the theater, where you experience the unique telepresence that only Cinema with its 35mm (and 70mm) film could give until now.





If I sit on the last row of a theater, I feel like I'm watching through a small window, called TV. Or DVD.





61" 16:9 Sammy screen is 30" x 53". Sitting at 5 feet (60") the numbers would be:

1.37 movies at 2PH (or 1.45 screen widths)
1.78 HDTV at 2PH (or 1.13 screen widths)
1.85 movies at 2.1PH (or 1.13 screen widths)
2.39 movies at 2.7PH (or 1.13 screen widths)


(Remember that all movies screen image heights should be the same, but since the display is only 1.78 wide, wider films than that get shrunk)

[Zvi]

Thanks Deci. That's some complicated calcs right there, but quite interesting

[i want HD movies]

The other thing to consider is that most 1080i tv's are actually 1300 x 720. for the non technically oriented simply 720p is all 720 lines, whereas 1080i is only 540 at any given time meaning all 720p sets are technically 1080i also.

on a set that is 1920 x 1080, there will be little discernability between 1080i and 1080p since the tv, assuming it does a decent job, will simply be deinterlacing the full resolution. Very few sets ever fit this category though as most tv's which do 1920 x 1080 are already 'p' capable. The only exception that I can readiy think of is the first Sharp 45" LCD we carried that ony did 1080i.

[Mikeblu]

Originally Posted by Deciazulado

C: Seating distance also affects perceived quality:

The eye finds an about 2000p image to be excellent at 0.8x screen width viewing distance from a 16:9 screen.

At 1x screen width sitting distance 1600p
At 1.25x screen width sitting distance 1250p
At 1.6x screen width sitting distance 1000p
At 2x screen width sitting distance 800p
At 2.5x screen width sitting distance 640p
At 3.2x screen width sitting distance 500p
At 4x screen width sitting distance 400p

(In other words, "It's all in how close you sit to the screen!")

I never really thought that cos IMO when you sit further away the image sort of blends (espeicialy with lo PQ) which looks more natural IMO. This only really counts to low PQ sets like the PSP though.

[prerich]

Originally Posted by Deciazulado

depends on several factors, Jim,

A: An image optimized (or video filtered) for interlaced display has a resolution equivalency or sharpness that can be down to approx. 70% (some call it the Kell factor) of a progressive image in a worst case scenario. (In other words, "It's all in the mastering!")

B: Your 1080i input display or player could either deinterlace correctly (weave) or "incorrectly" (bob) a progressive (film) image, and of course all 1080p displays and/or 1080p output players have to deinterlace interlaced (shot on HDTV video) images by some method, ranging from optimally (motion pixel adaptive, etc, etc), to the more common bob, that again, at worst, would give you 70% of the sharpness. (In other words, "It's all in the deinterlacing!")

Remember this reduction to 70% of 1080p can happen if the transfer is "suboptimal" and you have a 1080p player -> 1080p display; or if the transfer is "perfect" and at some point between the 1080 player and 1080 display there's a worst (bob) deinterlace occurring.*

So depending on those two factors, a 1080i vs 1080p path can vary from the 1080i being equivalent to about 768p, to looking equal to 1080p

(If you wanna play the laws of averages between the extremes of those two possibilities occurring :-P, that comes out to be about 900p, which in comparison to 1080p is: about the same difference between a 16:9 coded widescreen movie DVD and a 4:3 coded widescreen movie DVD).

Then:

C: Seating distance also affects perceived quality:

The eye finds an about 2000p image to be excellent at 0.8x screen width viewing distance from a 16:9 screen.

At 1x screen width sitting distance 1600p
At 1.25x screen width sitting distance 1250p
At 1.6x screen width sitting distance 1000p
At 2x screen width sitting distance 800p
At 2.5x screen width sitting distance 640p
At 3.2x screen width sitting distance 500p
At 4x screen width sitting distance 400p

(In other words, "It's all in how close you sit to the screen!")


D: You may also tolerate a less than excellent image (well, we accept average 35mm theatrical projection which is miles away from perfectly focused 70mm, etc ) For example, tho a 2000p image watched 9 feet from a 16:9 wide 12 feet diagonal screen will look outstanding, that doesn't mean a 1000p image will look bad, it'll look great still. (In other words, "It's all in what you think is good enough!")

E: A judiciously adjusted sharpness control with proper contrast and black level can do wonders to a slightly fuzzy image :-P (In other words nothing beats a correctly calibrated home theater!)

F: So in answer to your question: In some cases it might be more thrilling, (but if you have 1080i now don't worry about it and start enjoying your 6x times better than interlaced NTSC DVD video

G: I can't wait for Blu-ray





*(With both the transfer and the deinterlacing being bad occurring at the SAME time we would still end up with the same potential 70% of max, since what is happening on both process is just putting the same cap on the vertical resolution) (Well, one would hope!)

Excellent post!

[Blumovie]

The question is in the title!

Thanks,

[BallsHD]

let's say you have two tvs: a 720p tv and a 1080i tv. if you set the resolution settings on both tvs to 1080i, is there any difference in PQ or sharpness or any of that jazz? thanks for posting in advance.

[Deciazulado]

When you say 1080i TV, you mean a true interlaced TV like a 1080i CRT or you mean a 1080 LCD (which display everything as 1080p) but only accepts a 1080i signal but not a 1080p signal?

I'll assume the later.

A 720 x 1280 display has a max. of 720 x 1280 pixels if it deinterlaces the 1080i correctly

It would have a max. of 540 x 1280 if it deinterlaces the 1080i with the cheapest method. That would be equivalent to about 624 x 1108 square pixels

A 1080 x 1920 display has a max. of 1080 x 1920 pixels if it deinterlaces the 1080i correctly

It would have a max. of 540 x 1920 if it deinterlaces the 1080i with the cheapest method. That would be equivalent to about 764 x 1358 square pixels


So depending on the deinterlacing chips on the displays they could go from both looking very similar, to the 1080 LCD looking up to 3 times as good.


another thread

[i want HD movies]

lol. that about sums it up. Maybe to put it simpler...
Depends...lol

If it is a 720/1080i set (I am assuming non-crt tube): the pixel count will be the same, usually 1368 x 768 whether it is a plasma or LCD panel.

If it is a True-HD, Full HD or 1080P set (all the same just depends on the company wording) then the pixel count will be 1920 x 1080, or double the 720/1080i set.

So it depends.

Also, as was said, depends on the quality of the set. For instance a Pioneer Elite at 720p looks better than some no name brand 1080P LCD set just due to the quality of the processing. Whereas a Sony XBR3 1080P LCD looks much better than, say, a HP plasma at 720P.

[Stuie]

I have a Panasonic TH-42PX60B, any ideas on whether that processes the 1080i signal properly or not and is it a good tv?