1080i vs 1080p vs 720p

[Steve Mullen]

Originally Posted by Ken Ross

It's a lot more than just 'reality shows'. You can add to that most HD documentaries & theme shows (virtually everything on HDNet), nature shows (Discovery HD, National Geographic HD etc.), talk shows such as Leno, Leterman....I could go on.

Nope, interlaced HD is far from going away. I myself much prefer the look of reality that 60i brings to the screen. To my eyes there's nothing like looking at an HDTV and feeling as if you're looking through a window. Progressive just doesn't do that for me. Each to his own. :)

While you are correct that there is no 30p video being used for HDTV -- you are simply wrong about 60i. The best HD is 60p which is why FOX, ABC, DOD, and NASA use it. These folks care about perfect motion rendition which is why the use 60p. This is why the EBU recommended only 50p for Europe.

[Douglas Spotted Eagle]

Originally Posted by Steve Mullen

While you are correct that there is no 30p video being used for HDTV -- you are simply wrong about 60i. The best HD is 60p which is why FOX, ABC, DOD, and NASA use it. These folks care about perfect motion rendition which is why the use 60p. This is why the EBU recommended only 50p for Europe.

So you're saying Fox and ABC are broadcasting 60p?

[Ken Ross]

I'll disagree with you there Steve. I prefer the full 1920X1080i as opposed to the 720p programming. In fact, most people I've seen comment much prefer football programming on CBS & NBC as opposed to ABC or FOX. You may improve the issue of interlaced artifacts with 720p, but the fact is that with HD, interlaced artifacts are nowhere near as bad as they were with NTSC. Additionally, the vast majority of people simply don't see the difference in motion handling between events on FOX and similar events on CBS & NBC.

The big gain with 1920X1080i is the significantly greater detail. If you don't have a full rez HDTV, you can easily miss that. But to be perfectly honest, I can easily see the difference in detail & sharpness between FOX and CBS. The average show on CBS is significantly sharper than FOX.

By the way, most inside sources I've read have stated that the decision to use 720p was done more for economy than quality. 720p requires less bandwidth than 1080i. Viewer reaction is simply more favorable to 1080i than 720p and I'm sure it's the added sharpness that does it.

The big change will be when/if we ever get 1920X1080p....THAT will be the flat out best.

[Thomas Smet]

Originally Posted by Ken Ross

I'll disagree with you there Steve. I prefer the full 1920X1080i as opposed to the 720p programming. In fact, most people I've seen comment much prefer football programming on CBS & NBC as opposed to ABC or FOX. You may improve the issue of interlaced artifacts with 720p, but the fact is that with HD, interlaced artifacts are nowhere near as bad as they were with NTSC. Additionally, the vast majority of people simply don't see the difference in motion handling between events on FOX and similar events on CBS & NBC.

The big gain with 1920X1080i is the significantly greater detail. If you don't have a full rez HDTV, you can easily miss that. But to be perfectly honest, I can easily see the difference in detail & sharpness between FOX and CBS. The average show on CBS is significantly sharper than FOX.

By the way, most inside sources I've read have stated that the decision to use 720p was done more for economy than quality. 720p requires less bandwidth than 1080i. Viewer reaction is simply more favorable to 1080i than 720p and I'm sure it's the added sharpness that does it.

The big change will be when/if we ever get 1920X1080p....THAT will be the flat out best.

720p uses almost the same amount of bandwidth as 1080i. Yes 1280x720 is less but it has 60 frames so the bandwidth is also very high. In fact 1080i only uses 1/8th more bandwidth then a 720p stream. This does not make a huge savings.

I don't know how you can say 1080i football games look better. I guess that is your view of it. I recently watched two games one on ABC and one on NBC and I flipped back and forth between the two. The 1080i had a lot of compression artifacts in the grass while the 720p was almost perfect. The levels of detail were very close as well. 1080i may have a slight horizontal advantage of resolution but really to most people they look to have the same amount of detail. My wife even asked me the other day why ABC looks better then NBC. She could care less about this stuff so I have never told her before what the difference was. She however noticed right away that ABC had a cleaner artifact free image while all the other stations can fall apart easily. About the only thing that really does look better on 1080i are still graphics such as the score graphics. They don't even look better to me but slightly sharper. The 720p graphics look perfectly fine to me and in fact in motion graphic opening sequences with particles and flares and a lot of fast moving elements the 720p broadcast almost looked perfect with no artifacts at all.

[Steve Mullen]

Originally Posted by Douglas Spotted Eagle

So you're saying Fox and ABC are broadcasting 60p?

Yes. And, all NASA and DOD is also 720p60. Obviously, NASA needs max temporal resolution with no interlace artifacts.

The EBU is going to push for only 50p once Sony gets it products to 1080p50. Sony are already shipping switchable 1080i and 1080p studio cameras.

That's why 3ClearVid is so important to Sony. The CMOS and EIP all run at 1080/60p. It's only the recording system that needs to be enhanced. First, comes "Full HD" AVCHD already speced at 1920x1080/60i at 24Mbps. This arrives in 2007. (Not speculation, I have the spec. from Japan.)

[Douglas Spotted Eagle]

Originally Posted by Steve Mullen

Yes. And, all NASA and DOD is also 720p60. Obviously, NASA needs max temporal resolution with no interlace artifacts.

The EBU is going to push for only 50p once Sony gets it products to 1080p50. Sony are already shipping switchable 1080i and 1080p studio cameras.

That's why 3ClearVid is so important to Sony. The CMOS and EIP all run at 1080/60p. It's only the recording system that needs to be enhanced. First, comes "Full HD" AVCHD already speced at 1920x1080/60i at 24Mbps. This arrives in 2007. (Not speculation, I have the spec. from Japan.)

Brian Kitchens, engineer for ABC Western Regional office: "If we're broadcasting 720p60, it's news to me."

[Steve Mullen]

Originally Posted by Thomas Smet

I don't know how you can say 1080i football games look better. I guess that is your view of it. I recently watched two games one on ABC and one on NBC and I flipped back and forth between the two. The 1080i had a lot of compression artifacts in the grass while the 720p was almost perfect. The levels of detail were very close as well. 1080i may have a slight horizontal advantage of resolution but really to most people they look to have the same amount of detail. My wife even asked me the other day why ABC looks better then NBC.

You've stated it very well! Compression artifacts on NBC and CBS as well as all the premium 1080i channels are horrible. And, certainly not worth the very slight increase in resolution of 1080i over 720p. Plus, we know more than 50% of HDTVs fail to deinterlace well -- so their vertical resolution is less than when viewing 720p. (So much for Full HD.)

Oh, yes -- DirecTV cuts 1920 to 1280 and so do some cable companies. Which means there's a good chance folks aren't really seeing any increased resoution with 1080.

Yes, studio cameras offer 1920, but everything shot with HDCAM -- which is the kind of stuff we shoot -- is 1440 verses 1280. That's a nearly invisible difference.

Moreover, 720p60 has room for 1 SD channel. There is no room in 1080i, yet may stations are adding one or even two SD sub-channels. So the desire for profits cuts 1080i quality.

[Steve Mullen]

Originally Posted by Douglas Spotted Eagle

Brian Kitchens, engineer for ABC Western Regional office "If we're broadcasting 720p60, it's news to me."

Leave it be Spot -- ABC has been 720p60 from day 1. As has FOX and ESPN1 and ESPN2.

"Good HDTV: It's More Than a Numbers Game

by Randy Hoffner
ABC Television Network

Since digital HDTV broadcasting began, we have heard a lot of discourse about the two HDTV scanning formats that are used by broadcasters: 1080i and 720P.

The other HDTV scanning format, 720P, is a progressively-scanned format. Each 720P line is made up of 1,280 pixels, and there are 720 lines in each frame. 720P is typically transmitted at about 60 full frames per second, as opposed to 1080i's 60 half-frames per second. This affords 720P some significant advantages in picture quality over 1080i, advantages such as improved motion rendition and freedom from interlace artifacts.

The advocates of 1080i HDTV support their cause with a flurry of numbers: 1080 lines, 1920 pixels per line, 2 million pixels per frame. The numbers, however, don't tell the whole story. If we multiply 1920 pixels per line times 1080 lines, we find that each 1080i frame is composed of about two million pixels. 1080i advocates are quick to point out that a 720P frame, at 1280 pixels by 720 lines, is composed of about one million pixels. They usually fail to mention that during the time that 1080i has constructed a single frame of two million pixels, about 1/30 second, 720P has constructed two complete frames, which is also about two million pixels. In fact, if the horizontal pixel count of 1080i is reduced to 1440, as is done in some encoders to reduce the volume of artifacts generated when compressing 1080i, the 1080i pixel count per second is less than that of 720P.

Another parameter 1080i advocates use to advance their cause is resolution. Resolution is the ability to preserve the separate components of fine detail in a picture, so that they may be discerned by the viewer. But picture quality is not dependent on resolution alone. Numerous studies of perceived picture quality reveal that it is dependent on brightness, color reproduction, contrast, and resolution. Color reproduction is identical in all HDTV scanning formats, and may thus be disregarded as a factor. A typical study assigns the following weights to brightness, contrast, and resolution:

Contrast 64%

Resolution 21%

Brightness 15%

Resolution, then, is only a factor, and not the largest factor, in the determination of the subjective quality of a television picture.

Television pictures move, so when we consider resolution, dynamic resolution is typically a more important factor than static resolution. Similarly, a moving 1080i picture may have its vertical resolution reduced to around 540 lines. Thus, the real vertical resolution of a 1080i picture dynamically varies between the limits of almost 1080 lines and almost 540 lines, depending on the degree and speed of motion. This resolution degeneration in interlaced scanning has been well known for many years, and its degree is quantified by application of the interlace factor, which effectively specifies dynamic vertical resolution as a percentage of the total number of lines in an interlaced frame. Progressive scanning does not have this problem, and the dynamic vertical resolution of a 720P picture is very close to 720 lines under any conditions of motion.

Results of testing done by the Japanese broadcaster NHK in the early 1980's indicate that picture quality achieved with interlacing is nearly equivalent to that achieved from progressive scanning with only 60 percent of the number of scanning lines, which is an interlace factor of 0.60. This finding agrees with the 1967 study, and also with another study that was published back in 1958. What this means to the HDTV viewer is that the vertical resolution of any HDTV pictures that have a vertical motion component is better in 720P than in 1080i. Based on the above findings, progressively-scanned images equivalent to the observed dynamic vertical resolution of 1080i may be achieved using only 648 lines. If we want to play a numbers game, 720P has better dynamic vertical resolution than 1080i by 72 lines.

Horizontal motion also causes artifacts when interlaced scanning is used. Depending on its speed, horizontal motion in interlaced scanning generates distortions that range from serrated edges, through blurriness, to double images in the extreme case.

But wait, there's more! The resolution impairments of interlace, plus the fact that progressive scanning affords far better motion rendition than interlaced scanning, make it apparent that a football game, for example, would be much more enjoyable in 720P than in 1080i. Add to this its freedom from other well-known interlace artifacts such as visibility of scanning lines, line crawl, and flickering aliases, and it quickly becomes clear that 720P is equal to, if not better than, 1080i in the representation of real-world, moving television images.

We have seen that interlaced scanning was born as a compromise to conserve analog bandwidth; a compromise that results in picture impairments and artifacts. A DTV broadcast is limited not by analog bandwidth but by digital bandwidth: the critical limitation is on the number of digital bits per second that may be transmitted. In order to broadcast DTV pictures, their bit rate must be aggressively reduced by digital compression to fit within the broadcast channel or pipeline that is available. The digital bits representing HDTV pictures must be compressed by a ratio that averages around 70 to 1 in order to fit into the 19 megabit-per-second DTV transmission channel. This creates a "funnel effect": for each 70 bits that enter the funnel's large end, only a single bit passes through the small end of the funnel into the transmission channel. Digital compression technology is improving rapidly, but it has been consistently observed that 720P HDTV pictures may be compressed much more aggressively than 1080i pictures before they become visually unacceptable. In fact, compression of 1080i pictures routinely generates visible artifacts, particularly when the pictures contain fast motion or fades to or from black. These artifacts cause the picture to degenerate into a blocky, fuzzy, mosaic, that may be observed frequently in 1080i broadcasts. The stress level to the HDTV broadcast system caused by bit rate reduction is much lower for 720P, and blockiness artifacts are seldom observed in 720P broadcast pictures. It may be expected that 720P will always lead 1080i in compressibility and freedom from compression artifacts, because progressive scanning is by its nature superior in the area of motion estimation. This gives it a "coding gain" relative to interlaced scanning, and the result will always be delivery of the same picture quality at a lower bit rate.

We saw previously that the real vertical resolution of 720P pictures is better than that of 1080i pictures. It is also true that the additional horizontal resolution that 1080i boasts cannot be displayed on any currently available consumer HDTV display of any technology. Fortunately for the viewer, it is not necessary to the enjoyment of HDTV. An instructive illustration is the much-admired digital cinema, where micromirror projectors are used to project theatrical features onto screens that may be 50 feet or more wide. The horizontal resolution capability of these projectors is 1280 pixels, the same as that of 720P, and we have not heard anyone complain that digital cinema has inadequate horizontal resolution.

All these advanced displays are inherently scanned progressively, and 720P may be displayed on all of them without the potentially image-degrading de-interlacing step.

AND MORE:

"What production format does FSN (FOX) HD use?
FSN HD broadcasts games in the 720p format. The 720p format presents a picture with 720 vertical pixels and 1280 horizontal pixels. The 'p' stands for progressive scanning, which takes 60 sharp, complete pictures per second, producing spectacular moving images. In fact, because of its ability to render ultra-sharp pictures of subjects in fast motion, 720p provides excellent resolution for HD sports programming.

AND MORE:

"ESPN HD, launched March 30th, 2003 is a high-definition simulcast of the cable television network ESPN, both owned by Disney that broadcasts 24 hours a day, 7 days a week. It uses the 720p standard because the progressive 'p' nature of that signal is thought by some to be better for the fast fluid motion seen in sports."


AND MORE:

The European Broadcasting Union (EBU) recommends to its members to use 720p50 for emission with the possibility of 1080i50 on a programme-by-programme choice and 1080p50 as a future option. Sveriges television in Sweden broadcasts in 720p50.

Case closed.

[Ken Hodson]

Archaic, is archaic. Should Sony make an only interlace Blue-ray? Why not? Why is all digital media inherently progressive? Hmm.
I don't see any modern TV of quality being interlaced, so why?
Film is progressive. Digital is progressive, so lets convert it to interlaced? Please, help my logic.
Are PC's digital output interlaced? Why?
Is my LCD monitor interlaced?
Is my Plasma interlaced?
Is my projector interlaced?
What single part of the future is interlaced?(besides bandwidth starved HDTV)
Tell me how to buy interlaced, please!!
Who's content is derived from all sources including film(progressive).
Everyone is buying progressive. Why is the capture cams so slow on the realization? Huh? Of course, marketing!!!!

[Ken Ross]

Originally Posted by Brett Sherman

Actually I'm pretty sure National Geographic does 30P. They shoot on Varicam and deliver 30P for US. I know someone who works there. My guess is the Discovery is the same. Just because it is delivered in 1080i doesn't mean it was shot in 1080i. You can show a progressive scan image on an interlaced format (just not the other way around) To me 60i looks too live. But that's an aesthetic opinion of which there are many.

I think it's not necessarily progressive that you don't like, but less temporal detail of a 30P image. 60P will replace 60i at some point. Which will give the same window effect, but not have the problems that interlaced introduces.

Brett, in actuality both Discovery HD & NG HD use both 30p and 60i. Some shows are shot one way and others another way. But it's very easy to tell which is which while watching. However, I certainly do prefer the look of 60i...to me it's the greatest window effect on TV.

Since I haven't seen 60p, I'll reserve judgement on that. I'm sure it's a very subjective thing.

[Alex Leith]

At the same resolution 60p would presumably look even MORE realistic than 60i, given that interlace only gives you half the vertical resolution every 60th whereas progressive gives you the full raster.

720p60 and 1080i30 give you approximately the same number of "fresh" pixels each second.

I know the BBC are suggesting producing in 1080p25 and 1080i50 depending on the nature of the show.

Personally I don't think "i" has too much life left, given that television audiences are getting smaller, and major broadcasters are likely to switch distribution increasingly towards on-demand, internet based distribution, and that most HD flat panel televisions can't even display interlaced pictures without deinterlacing them first anyway!

[Douglas Spotted Eagle]

"i" has a *lot* of life left. A lot of life. It's not going anywhere soon. Psf will be more likely to take its place, as the two can work well together.
But either way, with all the broadcast support in place for a while to come, "I" broadcasts will be with us. Web is but a *very* small destination for watching content, and until televisions and computers converge more conveniently, they'll be separate.
I wish that wasn't so, but it is...
Acquiring in 'i' might not have such a future left, however...

[Steve Mullen]

Originally Posted by Brett Sherman

Actually I'm pretty sure National Geographic does 30P. They shoot on Varicam and deliver 30P for US. I know someone who works there. My guess is the Discovery is the same. Just because it is delivered in 1080i doesn't mean it was shot in 1080i.

I'm not sure where this idea of ANYONE using 30p for broadcast. They don't! It would look horrible. Which is why FOX gave up the idea of going DTV using 480p30.

This idea even appeared in a Panasonic PR. I caught the error. He is their reply:

`We queried Craig Piligian, and indeed he clarified what's in the story, to wit:'


"We used to shoot Chopper with the Varicams at 720p/60. Since the Varicam is a variable frame rate camera, it was more than we needed in that respect, but it did not shoot 1080i.

When Panasonic came out with the HDX900, we found it to be the perfect combination of a great HD picture
at an affordable price. Since we deliver a 1080i master, we decided to shoot at 1080i to avoid converting and maintain a clean path.

We are now shooting at 1080i/60 with the HDX900 and are very pleased with the picture quality, ease of use, and affordability."

`So, eagle eye, you're right on the money! All the best, P.'

--------


"Since I haven't seen 60p, I'll reserve judgement on that. I'm sure it's a very subjective thing."

If you watch ABC, ESPN, and FOX -- you have only been watching 60p.

-----------------

There are only two ATSC formats used in the USA and their proper designations are:

1080/60i or 1080i60 -- there is no such thing as 1080i30.

720/60p or 720p60

24fps movies are sent with 2-3 pulldown for both 1080/60i and 720/60p.

Some are thinking of transmitting film at 1080/24p as it will fit in a 6MHz channel. This would support displays than can use 24p, 48p, or 72p.

---------------

The BBC is not going to use 1080p25 for live video -- only for movies that are 25p. Live will be 1080i50 until it can go to 1080p50.

----------------

DSE seems to have removed my quotes from ABC, ESPN, and FOX that confirmed their use of 720p60.

[Tony Tremble]

what has I vs P got to do with V1 vs XH-A1?

Steve you are very quick to tell other people to stay on topic. Perhaps you should take a piece of your own advice.

Thanks

TT

[Alex Leith]

Originally Posted by Steve Mullen

The BBC is not going to use 1080p25 for live video -- only for movies that are 25p. Live will be 1080i50 until it can go to 1080p50.

That's not entirely true. Whilst delivery is still going to be 1080i50 the BBC are recommending that any programming that would benefit from a film "look" are acquired as 25p.

More programming in the UK is p25 (25psf) than i50. Films, dramas, soaps, documentaries, sitcoms, even gameshows.

Originally Posted by Douglas Spotted Eagle

Web is but a *very* small destination for watching content, and until televisions and computers converge more conveniently, they'll be separate.

You're right, but I don't think computers and televisions will merge 'cause we use them in different contexts. However, content delivery systems are already merging, and the technology that plays downloaded content on your TV (like Apple TV, etc) is going to quickly become much easier (and more integrated) into home entertainment systems.

We spend more time on the internet than watching TV each week, and broadcasters want to find new ways of getting our attention because they want the revenues.

(sorry Tony - this is still off topic... but I just can't help myself)!