Ask HDBeat: How can I tell the difference between 1080i and 1080p
John, this is easily one of the most common questions we get. We have covered it before and, well, honestly we don't mind covering it again. This time around though we will break it down nice and easy for not only you but the hundreds that have the same question: How can you tell the difference between 1080i and 1080p? You probably can't.We are serious.They both have the same amount of data being displayed, but the 'i' stands for interlaced. You see, a interlaced picture displays the picture by showing the odd number of horizontal lines and then the even numbered ones on the screen at a rate of 1/30 of a second. The 'p' type stands for progressive that displays all the info at the same time. So is there a difference - yes; can you see it - probably not anymore.
The main reason you cannot tell comes from the type of HDTVs that are on the market these days. LCDs, DLPs, SXRD/DILA/LCoS, and plasmas are always a progressive type TV. Only CRTs can properly display an interlaced signal. The other type of displays will take that incoming interlaced signal and display it in a progressive type resolution like 720p or 1080p. There is of course a good amount of technical stuff behind that (see Deinterlacing and telecine) but we promised John and everyone else that we will keep it nice and easy.
[Thanks for the question John!]
Reader Comments (Page 1 of 1)
William C Bonner @ Jul 24th 2006 12:02PM
My latest Laptop (Fujitsu Lifebook P7120) has a 1280x768 LCD display, and appears to be interlaced.
I notice this if I'm displaying an image that has a pattern of alternating horizontal lines in light and dark colors, or if I'm scrolling a page of text quickly.
This was not somethign I noticed when I looked at the models in stores, and not somethign that I would have looked for on an LCD in general.
Has anyone run across this sort of thing.
Dan @ Jul 24th 2006 12:10PM
Why is it then that the sales flyers never advertise 1080i? The Besy Buy ads always have 720p splashed over everything. Also, the info I read from time to time explains 1080p as being a higher resolution somehow. Any info. appreciated.
Thanks.
Kevin @ Jul 24th 2006 12:21PM
It is my understanding that no Plasma or LCD tv can display 1080i because it is interlaced. The tv can certainly accept that signal, but it will only down convert it to the tv's native resolution (usually 720p or close).
It would seem to me that the major advantage of a 1080p television is not so much the better picture from 1080i to 1080p, but the fact that the plasma or lcd can display 1080 lines of resolution. It is the upgrade from 720p to 1080i that you are going to be able to see.
Granted, a lot of content on cable or satellite (ESPN HD for instance) outputs their shows in 720p. In this case, the picture wouldn't look any better as the 1080p tv would just upconvert the picture to 1080p. But for the stations that output in 1080i (no 1080p yet), your tv will be able to display the full 1080 lines of resolution by merely deinterlacing the signal. A 720p tv would take the 1080i signal and downgrade it to 720p thus losing the extra resolution.
Someone please correct me if I am wrong, but this is my understanding of the issue. I have never heard anyone state that the difference between 720p output and 1080i output is what makes 1080p so great. I currently own a 42" Westinghouse 1080p monitor and the picture is stunning.
HarperBrad @ Jul 24th 2006 2:33PM
Actually, you can tell the difference if the 1080i source is:
a) Truly interlaced (each field is temporally unique)
b) Full of horizontal motion
So, you can see the difference in a sports broadcast with text scrolling left to right on the bottom. Each field is really only 540 lines. This field is scaled up to 1080 lines (if you have a 1080p panel, otherwise, its probably 768 lines). The problem that shows up with scaling each field up to full screen is that the flat tops of the letters seem to bob up and down due to the 1/2 line offset between the field pairs. So you will see horizontal lines sort of shake at the tops.
A more sophisticate deinterlacing algorythm will combine several fields to a single frame. This eliminates the shimmer on horizontal lines, but usually gets it a little wrong for text scrolling sideways. Side-scrolling text is extremely hard to deinterlace. The main issue is that motion vectors can get confused with side-scrolling text. So errors will show up with the edges of the text in this case.
1080p content skips all of this issue by having no fields, just full size frames. Some 1080i content is really 1080p content that sends half the lines at a time. In other words, the fields are not temporally unique. This sort of content is extremely easy to deinterlace to a 1/2 frame rate 1080p.
Hope this helps. I'm actively solving some of these problems in the industry.
Tyler @ Jul 24th 2006 7:44PM
If anybody could help me:
With a 1080i CRT HDTV, how good will a 1080p source (say a movie on Blu-ray or HD-DVD)look compared to a 720p or 1080p display?
jim @ Jul 24th 2006 8:08PM
I can't believe someone posted that you probably CAN'T tell the difference! A better answer would be it depends on if your display renders 1080p natively or not. If you have an old rear projection HDTV CRT unit - it probably only displays 1080i but if you have a newer LCOS or other HDTV made in the last year it might display 1080p.
If you can tell the difference between 480i and 480p (and you can) you can probably tell the difference between 1080i and 1080p - the question is does your TV display 1080p.
The person who responded saying you can't tell the difference could probably say the same thing about HDTV and regular OTA standard definition - if you are viewing on a 20" TV you probably can't or if you downgrade the picture from 1080i broadcast to standard broadcast because that is all your old tv set is capable of - then no, you can't tell the difference - but you can't because of the TV set not because the human eye is not discerning enough to tell the difference.
I think the original writer is the type to say - when we were young we had a 13" black and white TV and only got 3 channels and that is more than enough!
Mark W @ Jul 24th 2006 8:23PM
This conversation kills me. "Kevin" above hit the nail on the head- most HDTVs sold today are natively 720p and will scale a 1080i picture down to 720p. The main reason you want a 1080p set is because the native resolution of that set is 1080p- it will upscale 720p, not downscale 1080i or 1080p.
If you have a 1080p set, not a 720p set the accepts 1080i input, you CAN tell the difference.
dinther @ Jul 24th 2006 8:44PM
Thank you for the article and all the comments. Now I am even more confused. Can't we all go back to a 21" crt and composite video?
Donn @ Jul 24th 2006 10:18PM
I know many people that can't tell the difference between 480p (standard progressive scan DVD) and 720p. I think the truth is that if you can't tell the difference, you wouldn't want one anyway. I for one, want a 1080p LCD or DLP so I can display 1920 x 1200 from my computer, as well as have th best possible HD resolution. I realize the only supposed source at the moment is Blue-Ray, which I don't intend on being a guinea pig for. But within a year or so, according to trend, this whole argument will be moot because there will be a new improved capability that far exceeds 1080p. I for one am happy to be at the early downslope of the new product curve, after all the current noise abates and the next big thing is on the horizon.
Joe @ Jul 24th 2006 10:21PM
To say that you cannot tell the difference between 1080i and 1080p, although bold, is wrong. It all depends on the viewing distance. The closer to the screen, plasma, DLP RPTV, etc., the more likely you will notice the small artifacts inherant in an interlaced signal. At any decent viewing distance, though (1-1/2 times the screen height is a good place to start) you would be hard pressed to see the difference in 1080p vs. 1080i and at that point would obtain an outstanding picture (when compared to 1080i) with a 720p set.
James Matthews @ Jul 24th 2006 11:13PM
Clearly an article written for shock value to generate more traffic. Fine. I'll bite.
The truth is, if a display DOES have actual 1080P capability with 1920x1080 (or higher) resolution, and your source material is actually 1080P, then it will indeed look better than any interlaced signal using the same hardware.
Jim above said it first...
"If you can tell the difference between 480i and 480p..."
And he's right.
This is due to de-interlacing methods, none of which are ideal. Both will display some degree of image degradation.
A. De-interlacing by combining 2 or more fields. This is garbage. You're taking two separate moments in time and trying to re-splice them - it doesn't look right, especially in high motion scenes. Lotsa tearing, and even if you introduce algorithms to reduce the effect, it's still not representative of how that moment in time actually appeared.
B. De-interlacing using Field Doubling. This is basically using half the resolution of the source image and doubling it to eliminate the flicker. Sucktacular.
C. Combo of A and B and what have you... No good. Temporal distortion affects all interlaced video, and it's just not natural to the eye. The more you try to reduce the effect, the more resolution you lose.
The original authors are incorrect, or at least they are sloppy and vague in their declarations.
jim @ Jul 24th 2006 11:14PM
This is wrong on so many levels it is hard to know where to begin.
OK - let's start with the source -
1.
a. if the source is 1080i - then no 1080p capable sets won't improve the picture much.
b. if the source is 1080p - then a 1080p capable set can make a big difference depending on the size of the display
2.
a. Display size matters - the larger the set the more quality matters. A 19" screen from RadioShak competes with a top of the line 19" Sony - but when you get to 60"-100" the better the quality the set - the better it shows both the good and the bad.
3.
a. Transfer quality matters - just because a film was made recently doesn't mean it was transfered to disc well - Look at 5th element - superbit - made about a decade ago but transferred pretty well - then look at one of the Star Wars -episode 1 Phantom Menace - total crap except for CGI moments. That is not to say that older films won't benefit from 1080p - it is just a relatively recent comparison with plenty of moments for analysis.
4.
a. Televison sets/projectors need to be calibrated. If you go to Circuit City or some take it out of the box and plug it in place you can't be sure what looks good and what doesn't. Some places tweak the TV that gives them the most profit so people will buy that set - others are lazy and it is the luck of the draw which one looks best out of the box.
b. Go to a home theater specialty store - you can see what they look like tweaked - and you can haggle them down to the same price as the mass consumer stores.
I would like to suggest you post your questions where more knowledgeable people might respond than the author who removed too many factors in the equation. I'd suggest hometheatrespot and avsforum.
Benjamin J. Higginbotham @ Jul 24th 2006 11:16PM
Not sure I agree with the original article. 1080/60i content (it's 60 fields per second or 30 frames per second) will have all the standard problems of interlacing. The brodcast industry has been dealing with interlacing for years. Whip pans will tear a bit, freeze frames need to have field removal (depending on the speed of the scene), and diagonal lines will render jagged (interlacing is one of many factors there). With a progressive signal 1080/30p for example, all frames are rendered at the same time so most if not all of these issues go away.
Will a general consumer be able to tell the difference? probably not, but it also depends on the source and display they have. Most consumers have a hard time telling the difference of a 480p and 1080p signal on their home HDTVs (show the same people a 480p/1080p signal on calibrated screens and they may be able to tell).
It's not just lines of resolution that make up a picture. In the long term the progressive nature of 1080p will help to really push the quality of the video forward. There's a lot more data to work with there.
Matt Burns @ Jul 24th 2006 11:33PM
Hi Jim. How are you? Not very good and it looks like you have a problem with my post. I am glad that you wrote in with your response to it but I'm sorry to say...I have to disagree with a bunch of what you said. Well, let me qualify that a bit. A good amount of what you indicated is in fact great points but have little to nothing to do with the original question. But we will get to that in a bit.
Your point number 1 -
Take a Blu-ray player and it hook up to a 1080p display with both component and HDMI. Can you tell the difference? Probably not. The HDMI is presenting the HDTV with the true 1080p signal where the component is only doing 1080i. They will both look about the same. Is there a difference, sure, but not a noticeable one Size will only matter if it is a CRT display. Remember only a CRT can display a 1080i signal properly. Oh and I did do research for this...that fact found here.
http://en.wikipedia.org/wiki/Interlaced
Your point number two -
Size has little to do with interlaced and progressive but the type of display technology does. See the end of 'your point number 1.' 1080i and 1080p are both the same resolution, they just display that data in different ways.
Your point number 3 -
You are right bud. Transfer quality does matter a lot, but this does not apply to the original question.
Your point number 4 -
Once again you are right. Calibration is very important and if you are a regular reader...and I think you are...then you know we have covered this a lot the last few weeks, but once again, not much to do with the original question man.
Oh and about your little note at the end of your post...those are great sites that I visit almost everyday and agree with you, they are very knowledgeable, but I will hold strong to this. Most consumers will not be able to tell the difference between 1080i and 1080p.
jim @ Jul 25th 2006 1:04AM
You are entitled to disagree but I have to say your article really left me feeling like I had been debriefed by the President's "experts".
Rebuttal number 1 – Once again your response brings out the limited “black and white” nature of your response – the quality of the transport medium effects the quality of the playback. SIZE is not just a matter of CRT technology – look at any plasma/led display – they have different response times – (ghosting for fast action films – which someone else mentioned – very important to many viewers) they have different resolution – not all screens are capable of 1080p. And please don’t site Wikpedia as credible source – that would be comparable to using Snapple caps IMHO. 1080p is not even available on all of the displays being released this year so please don’t let anyone assume that all displays show 1080p natively. In my opinion, I just scratched the surface of some of many points (many I neglected) that needed to be reviewed to answer this question. I felt your response had the depth of a one paragraph explanation as to why there is turmoil in the middle-east.
Rebuttal number 2 – see above.
Rebuttal number 3 – transfer quality might give an untrained viewer the illusion that 1080p and 1080i are of equal quality – if they were watching Gladiator on a 1080i screen and the original Fast Times at Ridgemont High on the 1080p they might have a difficult time concluding that one technology is superior to another.
Rebuttal number 4- see above – covered in 3 why it makes a difference.
As to your summation – I believe people who are 60 years and older are less likely to care about video quality as well as mouth-breathers who can’t understand the point of letterbox video and surround sound. I do believe that anyone who cares or takes the time to compare can quickly discern the difference.
Poisoncandy @ Jul 25th 2006 2:05AM
Unless you are running Crt, most people have 720p and some people have 1080p.
I sell tv's for a living, and I will tell you that you can see a difference in the picture quality of 1080p mostly with monitors 50" and above. Most customers don't see much difference in the smaller lcd models 37-40". The picture source in our store is running off of comcast cable set at 720p and our most popular set (when in stock) is the samsung dlp hls5087 1080p set. I have not had a single customer not identify the difference between 720 and 1080 even with the 720p source. Ask the wife which is the better picture, 1080p every time....ohh, almost forgot, their is a difference in contrast ratio on the 1080 sets (10,000 vs. 2500).
Kevin @ Jul 25th 2006 9:04AM
I wonder whether all the people taking such offense to the notion that you might not be able to tell the difference between 1080i and 1080p actually have a 1080p display and/or have seen the difference for themselves. Yes you should be able to tell the difference in theory, but in reality, you might not be able to. In fact, one of the first reviews of Bluray that I read stated that the reviewer could not tell the difference. I think the size of the tv is what may be the deciding factor.
This arguement can go back and forth forever, but no one is going to know for sure until everyone sees for themselves. I still feel that the most noticeable benefit of 1080p flat panel displays is the added lines of resolution from 720 to 1080. You are certainly more likely to notice this than the difference between 1080i and 1080p.
If HDBeat would be so kind as to donate a Bluray player to me, I will test it on my 1080p tv and report my findings. :)
Dick @ Jul 25th 2006 9:42AM
Jim, I have enjoyed reading your responses; however, I take exception to your statement that "people 60 years or older are less likely to care about video quality." The fact is we have been living with drastic changes in video and audio technology for 60 or more years. We are the innovators of most of what you see and hear today. I don't know how old you are but chances are you probably do not know what it is like to be 60. We are healty, active, and control most of the wealth. We are also very knowledgeable and up-to-speed with the latest developments in audio and visual technologies. Remember also that, if you are involved with sales, we are the ones most likely to be able to afford to purchase your top0of-the-line items. Manufacturers, wholesalers, and retailers should be very concerned about how the baby boomers feel about their products, and you should too.
HarperBrad @ Jul 25th 2006 2:39PM
Its in the source!
I can tell you that lots depends on what source your 1080i or 1080p is made out of. Specifically, are the fields/frames temporally unique? Much 1080i/1080p content is pretty crappy. Its already been through at least one upsampling step in its life. No wonder you can say that 1080i and 1080p looks equally bad. But really good 1080i that takes advantage of 1080i will look worse on a 1080p output. And really good 1080p content will look better than 1080i. Much 1080i content is broken in one way or another. Perhaps it is not truly 60 fields per second. Perhaps it was 480i upscaled. Maybe it is decimated 1080p source?
Some of the best source material we use for testing deinterlacing is computer generated. Scrolling or spinning text, swinging pendulums, bouncing balls and the like. White on black, with each field temporally unique. These are really tough problems to take on for 1080p output. You _will_ see problems instantly in deinterlacing with this sort of content. Problems that are also present but less obvious in more traditional content.
--Harperbrad
Hajjie Belfon @ Aug 1st 2006 9:49AM
Hello guys , let me say first both matt and jim are very knowledgable i'am a small fish in a big pool of so called experts on digital resolution. Well let's start,try this out guys get a 720p 42 inch plasma and a 42 inch 1080p plasma and watch a regular hd broadcast (if you get a chance try jay leno on nbc recorded and broadcasted in hd) and watch the picture both at a distance of 8ft and you will see a disturbing fact. I wont say what as yet you guys will see it . Something funny i tested then calibrated then reset a 60 inch sony sxrd pushing a true 1080 lines of resoultion watching Chicken Little at the same time watching samsungs 61 inch 1080p dlp set only kicking out a wobulation (940 lines on top one another) Off both a samsung blu-ray player and totally disgusted at sony for selling this set for 4599.99 sams 3399.99. point being it's not just the scale of the resolution but how the techonolgy is conjuncted with other aspects of the set
Hajjie Belfon @ Aug 1st 2006 10:15AM
harperbrad is absolutely correct hd broadcast of 1080i looks like crap!!!! on any 1080p set it's kind of the same as watching 480p on a 720p enabled set . You will be so ready to take the set back to the store (which usually happens lol). Basics- it will do only what it can do. upconvert, downconvert still is not true. other than a blu-ray player you wont see much of a difference unless the source kicks out the correct resoultion for the display intended. If the swith to high-def broadcasting would have been done yaers ago like intended we would not be in a lagging actual broadcast capabilites versus techonolgy capabilites of display sets. This is going to be such a on going set-back that the display makers thrive on get the newest the best but braodcast will never catch up so will we ever really be getting what we pay for? lol somebody tell me please
Jordan @ Aug 6th 2006 9:54PM
Matt -
Can most "consumers" tell the difference between a Honda suspension and an Acura suspension? Maybe not, but the people reading Autoblog can.
Maybe most "consumers" cannot tell the difference between 1080i and 1080p, but I think most of your readers can, which might be why they feel disenfranchised and are arguing about it.
If you walk into your local big box electronics store, I would bet a small fortune that over 90% of the consumers couldn't tell the difference. But is there a difference? Yep, and I'd bet that a lot of the people reading this blog can tell that difference.
I think that's what the fuss is about. If someone came to me and asked, I'm probably going to tell them that they won't notice a difference, though there is a slight one.
In short, I agree with your post, and understand what you're getting at. I can also understand why these people are arguing, it's like passing by someone looking at Bose speakers who are stating that they are the best speakers in the world, when I know that they are not even worth half of their price. It's hard not to argue when you yourself can tell the difference.. ;)
jimmy @ Sep 8th 2006 11:37AM
I HAVE A HD TV WITH 1080i MY QUESTION IS CAN I PLAY THE NEW BLU-RAY DVD,S THROUGH THE NEW PLAYSTATION 3 BECAUSE IT SAYS IT ONLY PLAYS ON 1080p AND IF NO CAN I GET SOMETHING TO CONVERT 1080i TO 1080p
oscar g. @ Oct 18th 2006 6:11PM
You really can't tell. I have a Sony 60" HD LCD, with a cable card. I sit and watch hd channels; play xbox 360; all day and remember the picture, then watch and compare to 1080p blue-ray player, can't tell the difference. Same size tv. Not much difference. All up to the consumer. I thought about selling my 1080i tv for a 1080p tv, but for what.