1080p vs. 720p Displays

I've long heard the argument that you cannot tell the difference between 720p and 1080p displays unless you have a large screen and/or you sit very close to the TV. That sounds reasonable enough. But there's one thing I've never heard addressed as part of this debate—the issue of scaling. If most high-definition channels are broadcast at 1080i, aren't there scaling issues if you're viewing it on a 720p TV? Obviously, the real-world impact depends on the incoming signal and where the scaling occurs (TV, receiver, cable box). What do you think? Is this a noticeable issue?

Chris Keczkemethy

Actually, I make this very point every time I talk about the difference between 720p and 1080p displays. It's true that you can't see any difference in detail if you're farther than a certain distance from a screen of given size, but scaling artifacts could be very visible. And you're exactly right that most HD channels are broadcast at 1080i (1920x1080), so they must be scaled to 1280x720 or 1366x768 (the actual resolution of some so-called "720p" TVs) if viewed on such a set. Of course, the opposite is true if you watch a 720p channel such as ABC, Fox, or ESPN on a 1080p display, so the signal is sometimes going to be scaled one way or the other no matter what the resolution of your display.

You are also entirely correct that the real-world impact depends on the incoming signal and the quality of the scaler that's doing the job. Nothing can be done about the quality of the incoming signal, but there are typically several devices in the signal chain that can scale the signal, and you can determine which one does the best job.

To see if the cable/satellite box, A/V receiver, or TV does the best job, start by setting the output resolution of the cable/satellite box to that of the display (720p or 1080i). Most cable/satellite boxes cannot output 1080p, so if you have a 1080p display, something else in the signal chain will have to deinterlace the signal. Also, be sure that overscanning is disabled in the display, because this can cause its own artifacts.

If the signal passes through an AVR, set it to pass-through mode, so it does no video processing. Then, select an HD channel that broadcasts at a resolution other than your display—that is, if your display is 1080p, select ABC, Fox, or ESPN; if it's 720p, select CBS, NBC, or another 1080i channel—and watch for a few minutes. If your cable/satellite box includes a DVR, record a few minutes of material so you can watch the same content in the next two tests.

Next, set the cable/satellite box to output the native resolution of whatever channel it's tuned to, which prevents it from doing any scaling. Set the AVR to output the same resolution as your display, which means it will do the scaling, and watch the same channel or, even better, the same recorded content as before. If you have a 1080p display, also watch a 1080i channel in this configuration to see how well the AVR deinterlaces 1080i.

Finally, set the cable/satellite box to output each channel's native resolution and the AVR to pass-through mode and watch the same two channels or clips as before. In this configuration, the TV is doing the scaling and, if necessary, the deinterlacing.

Of the three configurations, which one exhibits the fewest scaling artifacts? These artifacts can include softness and jaggies along well-defined diagonal edges. What about deinterlacing artifacts, such as jaggies and moiré distortion in areas of fine detail? Scrolling text, such as at the beginning of the Star Wars movies, will look jittery and jagged if the scaling is poor. Whichever configuration works best is the one you should use to watch TV.

If you have an A/V question, please send it to askhometheater@gmail.com.

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COMMENTS
mailiang's picture

I watch 720p and 1080i broadcasts on my 720p set and I have found little difference in the picture quality between them. Even 1080p on Blu-Ray looks stunning and I've yet to see any visible scaling artifacts. But like Scott said it's all about how well you set your devices up. In order to get the best results, it is always better to use just one part of your device chain to do the processing. The worst case is to have your set top box or BD/DVD player do some, and your AVR and or TV doing some. Personally, I have found that using the NATIVE mode on the DVR, cable or satellite receiver and using the 1080p or auto mode on the player, works best. Most artifacts show up due to double scaling, not necessarily because you are trying to scale a higher resolution to a lower one.

Ian

yachtmandu's picture

everything depends on the source material - what you feed the beast. the kuro is a 720p set that you can feed anything to and it makes your knees quiver...the panasonic 1080p set the other hand needs specific instructions from the blu-ray player to present it's best. in either situation...1080i is the least desirable...unless it's a BBC production...like planet earth...so here's the deal: stop counting pixels...and enjoy the show.

waski's picture

yatchmandu I don't know about which kuro you have but my pioneer kuro is a full 1080p display. You may want to check the back,it might be built in china ;-). I don't understand this, we are almost at the end of 2011 and we have people on this web site with 720p displays!!!come on people,get with the program!!

mailiang's picture

Certain non Elite models, such as the highly rated 2008 PDP-428XG Kruo, were 720p. What you don't understand is that although resolution is the most touted specification, it's the least important when it comes to picture quality. According to the Imaging Science Foundation, a consulting group for consumer electronic manufacturers, whom also train professional video calibrators, the most important facet of picture quality is contrast ratio, the second most important is color saturation, and the third most important is color accuracy. Resolution comes in fourth. Although 720p sets are slowly disappearing, it's mostly due to lower pricing, which makes the 1080p models more affordable. Many of the older, more expensive 720p sets can still match or even beat some of the latest 1080p displays in over all picture quality.

Ian

docrings's picture

People still think my older Pioneer PDP-503CMX 50" plasma is gorgeous, which is 768pixels high. No artifact of scaling from Blu-Ray players or from cable 1080i (both over component). It's calibrated for contrast, greyscale and color output... and looks heavenly still, even after 10 years.

Of course, it's been relegated to the basement, and not the "go-to" set, but it still does its job superbly, and no one is the wiser that its not 1080p.

Cheers,
Doc Rings

Funny, the Pioneer website still has this set listed for $15,500... LOL.
http://www.pioneerelectronics.com/PUSA/Professional/Plasma/PDP-503CMX

albert26's picture

Of ,course a Blueray player has a much better picture,,why are some of us still living in the past , Doc Rings & his great Harmony remote,,strictly an Amateur.. P means Progressive 720 or 1080 ,it scans horizontily & vertically,,better & faster picture
And you cannot adjust Native reseloution unless you have DirecTV!!!
I liked the ISF
comments,,completly true,,Yes ESPN & ABC boardcast 720p, Ill take that over 1080i,if your'e Panel is properly Calibrated ,its simply
better.Also VUDU is probably the best video streaming out there with choices of what you may want for content,, its 75% of 1080p.
find that with Netflix???and you can choose Dolby DTS Master or True Audio,theres your'e biggest difference of what a Blueray can do for you,Oppo or Panasonic ,,good luck Kids
Brian www.Floridahometheatersplus.com

mailiang's picture

I agree, technically speaking, that due to De-interlacing, 720p should render a better picture then 1080i. However, there is no real evidence that 720p offers better PQ then 1080i on most broadcast images. Many artifacts and HD anomalies are created by overly compressed video signals which can occur anywhere in the broadcast chain, this includes video transfers, broadcast bandwidth limitations, and the actual service provider, (ie: cable, satellite, Fios....) I have found that on the Audio/Video forums I participate in, many of those who have cable prefer the PQ when setting their top boxes to 1080i even if their set is 720p. Like I posted earlier, native works best on my DTV system since both my PDP's and LCD TV's do the best job when it comes to scaling. As far as Blu-Ray is concerned, it can't be beat when it comes to picture quality, even with 720p TV's. This is mainly due to it's incredible data storage capability, which offers the best visual resolution (the measurement of the smallest detail that can be viewed on a TV) of any format I have ever seen.

Ian

albert26's picture

Ian ,,its nice to listen to a smart person,outhere,
are you in the business,,know Bob Fucci,
Regards
Brian

mailiang's picture

Brian, I was formally the regional sales manager for the Boomer Mcloud car audio franchise here in the North East. Many of our stores specialized in car and home theater custom installations. I began my career as an actor many years ago, and also worked as a Television Production Assistant in LA back in the 80's.

Regards,
Ian

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