Talk:720p

NBC Resolution

"NBC uses the tagline "the nation's finest high-definition standard" in advertising its 720p programming."

But the NBC website claims that all NBC HD broadcasts are in 1080i:

"NBC broadcasts HDTV in the 1080i format, which provides the highest possible resolution to our audience." [1]

Lee M 17:24, 12 Dec 2004 (UTC)

I see that the reference to NBC has now been changed to Fox. It's all a bit academic to me anyway because I'm in the UK... Lee M 17:08, 17 Dec 2004 (UTC)

which one is better 720p or 1080i? cheers

There is a consensus building that 720p is better for moving images, whereas 1080i is better for video with a lot of still or near-still footage. Thus, movies, nature, and drama content are better in 1080i, like on PBS-HD and NBC. Sports are better in 720p, like on ABC, Fox, and ESPN-HD. Obviously, 1080p60 would be the best of both worlds, but too bad, we can't have it. --Locarno 22:56, 9 Feb 2005 (UTC)

1080p60 just requires more efficient data compression. They'll get there eventually, and then they'll start working on even higher definition systems.
Interesting that the ATSC saw the two systems as content-specific, but the Networks, possibly for financial reasons, have each opted for just one. It'll be interesting to see what happens when Sky HD launches in the UK.... incidentally (or perhaps not) Britain will use 1080i25 and 720p50, meaning that despite having the same picture resolution as the US there'll still be frame-rate conversion issues to contend with. Not to mention the whole thorny question of up-and-down converting from PAL and NTSC.Lee M 02:50, 8 Mar 2005 (UTC)

Sorry, but what Locarno says is only true when comparing, say, 720p/60 with 1080i/30. If that is the case he should have stated so. If no refresh rates are specified one is forced to assume they are the same, in which case the opposite of what he wrote is true. Motion portrayal is smoother when using interlaced scanning, for a given refresh rate. 83.104.249.240 (talk) 05:25, 13 March 2008 (UTC)+-

No, that's not a sensible comparison because now you have 1080i at it's maximum temporal resolution against 720p with it's bandwidth cut in half for no stated reason. In a "which is better" comparison, you have to assume that both contenders are working at their maximum potential. Anyone who is interested in motion portrayal would use the maximum frame rate available for a given system, so 720p wold have the advantage of less line crawl on moving objects. Algr (talk) 15:11, 4 June 2008 (UTC)

I disagree with the first sentence. Such an assumption certainly cannot be made. The majority of 720p programming is in fact at 24 fps therefore there would be no reason to assume a higher frame rate. 83.104.249.240 (talk) 21:20, 22 June 2008 (UTC)

The majority of driving happens at maybe 24 mph, but you wouldn't assume that that is as fast as a car can go. Using 24 fps is an artistic choice for drama, no one is ever required to use it. News, game and talk shows are shot at 60 fps, and they add up very quickly, so I doubt that the majority of 720p programming is 24 fps. Algr (talk) 15:09, 24 June 2008 (UTC)

Whether that is the case or not is hardly relevant. My point was and remains the fact that unless explicitly stated I wouldn't automatically assume one frame rate for one resolution/scan mode combination and another for a different combination. The driving analogy is irrelevant. What does the average driving speed versus the maximum have to do with video refresh rates? I would make no assumption about either and would expect both to be explicitly stated. Similarly, going back a bit, why would I assume the same bandwidth unless it was explicitly stated? There are various other parameters to be considered and I would make no assumptions about any of them. Why should I? 83.104.249.240 (talk) 19:38, 19 September 2008 (UTC)

If you are making such assumptions then why assume that a "frame" contains two images taken at separate points in time? Who would expect that to happen if it wasn't explicitly stated?Algr (talk) 16:43, 20 September 2008 (UTC)

The point is that nothing should be assumed when making comparisons of this type, therefore all parameters need to be explicitly stated: number of active lines, scan mode and refresh rate. MegaPedant (talk) 02:14, 5 October 2008 (UTC)

That is what I was telling 83.104.249.240. His claim was based on some illogical assumptions about how video would be used. Algr (talk) 19:04, 5 October 2008 (UTC)

I suspect the two of you are talking at crossed purposes. Rewinding back to the top of the page, Locarno answers the question "Which one is better, 720p or 1080i?" without mentioning the relative refresh rates of the two standards he's comparing. I think Algr assumed that he was comparing 720p/50 with 1080i/25 (say) because the bandwidth used by both is similar. I think 83.104.249.240 assumed that he was comparing 720p at any frame rate with 1080i at any frame rate. From those standpoints both make valid points. My pedantic point is that all three people were making assumptions, none of which can be taken for granted to be valid. It is only meaningful to compare different line standards and scan modes if the refresh rate is also specified because it simply can not be assumed. One thing that has to be considered is that 720p/24, 720p/25 and 720p/29.97 are seen by some programme originators as a cheap way of getting into HD as it uses about half the storage of 1080i at the same refresh rate. Now, this doesn't give the comparatively smooth motion portrayal that 720p/50, 720p/59.94, 1080i/25 or 1080i/29.97 do but smooth motion portrayal isn't necessarily what it being sought after by the production company whose inexpensive HDV camcorders don't do 720p at the higher frame rates. MegaPedant (talk) 01:07, 6 October 2008 (UTC)

Television resolution chart

How does one edit the Television resolution chart on this page? It contains incorrect references to "240i" and "288i" In fact, these are progressive, (240p) even when displayed on NTSC and PAL sets. Algr 05:01, 22 February 2006 (UTC)

Fox Revert

Fox uses 720p, but it is possible that some of their affiliates convert this to 1080i before broadcast. Many sets do a poor job with native 720p, and look much better if such a signal is converted to 1080i by something else first. Algr 05:49, 30 April 2006 (UTC)

citation needed?

Some U.S. broadcasters use 720p60 as their primary high-definition format; others use the 1080i standard.

We already have references showing that both 720p and 1080i are in use. Algr 07:05, 13 August 2006 (UTC)

What Algr says is certainly true, however I would say that the 720p material is almost entirely captured at 24 frames per second (or the NTSC-friendly 23.976 Hz variant). The small amount that isn't is almost certainly captured at 29.97 frames per second in the U.S. The assertion that Some U.S. broadcasters use 720p60 as their primary high definition format therefore does require citation. 83.104.249.240 (talk) 05:14, 13 March 2008 (UTC)

Interlace is misunderstood ...

These 2 sentences contain gross misunderstandings ...

Progressive scanning reduces the need to prevent flicker by filtering out fine details, so spatial resolution is much closer to 1080i than the number of scan lines would suggest.

and

The main tradeoff between the two is that 1080i may show more detail than 720p for a stationary shot of a subject at the expense of a lower effective refresh rate and the introduction of interlace artifacts during motion.

Interlace doesn't "filter out fine details". Some interlace systems may low-pass filter vertical detail (only) to a very slight degree, in order to eliminate interline twitter that occurs when the subject includes narrow horizontal stripes that approach the vertical field resolution. 1920 horizontal pixel resolution is definitely greater than 1280.

Interlace doesn't introduce artifacts during motion. Interlaced video is quite good at capturing and portraying motion. Interlace artifacts are only introduced when interlaced video is converted to progressive scan.

That is completely incorrect. Interlacing can introduce spatio-temporal aliasing (edge flicker, line crawl, etc) unless video is properly low-pass filtered in the vertical dimension. Interlacing samples space-time at half the rate of progressive scanning.

Don - both of us are guilty of not signing our posts. Clearly you know what you are talking about... but I don't completely agree with your statements. As you know, aliasing can occur when you digitally sample something that has information at a frequency greater than half the sampling frequency (the Nyquist frequency). Interlace has half of the vertical resolution per field, but the same vertical resolution per frame as progressive scan. If the picture being captured by the video camera contains information with a lot of detail, artifacts can occur. However there are many reasons why this is not normally a problem. The camera would have to be in focus on the object, otherwise the lack of focus serves as a low-pass filter. If the object or camera are in motion, the motion blur low-pass filters the detail. The accuracy of the lens and the sensor (CCD, CMOS) can low-pass filter the detail. In general, most scenes being shot don't have the type of image detail that causes visible artifacts. Very high-end cameras filter the vertical resolution in order to reduce interline twitter, but most cameras don't... it isn't necessary for most situations. Finally, I would have to say that interlacing samples space-time at the same rate of progressive scanning, to be fair. Space is sampled at half the quantization level at twice the frequency... but the trick of offsetting the samples between frames by on line (spatially) gives the eye a moving average of the detail and the motion. If the object is moving, your eye gets updated information at a better refresh rate. If the object isn't moving, your eye still gets all of the detail of the full frame (due to the way the human visual system works). I've got nothing against 720p... it's great stuff. Progressive scan has advantages over interlace, particularly when it comes to editing (like slow motion detail), or display on progressive scan displays (which are all the rage for TVs these days, plus they are a part of every PC). But interlace is a technique that works, even if it isn't well understood. Tvaughan1 23:52, 26 October 2006 (UTC)

It is difficult to work out who wrote what in the discussion above as only the last contribution is signed but it seems to me that both contributors are making assumptions without expressing them. Tvaughan1 is assuming the same frame rate between the two scanning modes, such as 1080i/25 and 1080p/25. The former refers to a system with 1080 lines of vertical resolution interlace scanned at 50 fields per second, giving a refresh rate of 25Hz. The latter refers to a system with the same number of lines of vertical resolution progressively scanned at 25 frames per second, also giving a refresh rate of 25Hz. This is the correct way of making comparisons between the two scanning modes, the result being that for static images the two modes give identical results whereas for moving pictures the progressively scanned system gives a better perception of vertical resolution at the expense of the quality of the motion portrayal, for a given refresh rate. The other contributor (Don?) is mistakenly assuming that moving from interlace scanning to progressive scanning necessarily involves doubling the frame rate. He is therefore comparing, say, 1080i/25 with 1080p/50 without explicitly stating so. This is an unfair comparison because the latter uses twice the bandwidth of the former and should naturally look better to the viewer—though I would say not better by a factor of two. 83.104.249.240 (talk) 05:01, 13 March 2008 (UTC)

I didn't continue to follow this thread, but you can find a discussion of the theory of interlacing in a paper I wrote for SIGGRAPH 199o. This discusses the mechanism of aliasing that can cause moving edges to flicker. Television engineers sometimes talk about the "Kell Factor" which is lower for interlaced video. http://www.mentallandscape.com/Papers_siggraph90.pdf DonPMitchell (talk) 01:12, 6 February 2010 (UTC)

720p vs. 1080i

Just a suggestion, but I think it would be better to have a separate article for 1080i vs. 720p, and on that page include a table of what broadcaster uses what standard. Maybe even a separate page for that, updating as each one goes along? It would take some clutter out of this article, and would probably make a more sensible link on the 1080i page. Uagent 10:41, 5 February 2007 (UTC)

In order to compare the quality of motion captured and displayed at 720p with 1080i the frame rate of each must be specified or the results are meaningless. This section as it stands doesn't make sense. Is the author comparing 1080i/30 with 720p/30 or with 720p/60, or even with the much more common 720p/24? 83.104.249.240 (talk) 03:47, 13 March 2008 (UTC)

768

Almost all LCD televisions in the 20"-40" range have resolutions of 1366x768. (Plasmas seem to be 1024x768, which is 4:3, but they have rectangular pixels.) Wouldn't this provide a worse image than an LCD with only 720 lines? With LCD computer monitors, you have to set your desktop resolution to the native resolution of your monitor or you'll get blurry images. Maybe because computer monitors deal with text, the problem is more pronounced on

Why does 720p even exist?

Does anyone know how this, or any of the other HD standard resolutions, came about? The number simply don't make sense to me. Can someone who really knows this stuff comment on my stream-of-conscious below?

The maximum theoretical resolution of NTSC is 525 lines, and of this 486 lines are visible. When they introduced DVDs, the obvious solution was to round this off to 480 lines, and provide the rest of the 525 "on the fly" in the players. So far, so good.

And then comes HDTV. This is where I get really confused. The painfully obvious selection for HDTV would be 480 x 2 = 960. This is very close to the existing 1080 standard, but because it's an even multiple it makes the scaling a whole lot simpler. So why isn't 1080 actually 960? Ok, so maybe you want a standard that can do both NTSC, PAL and SECAM, but that suggests you'd want to find a factor between 480 and 576, which suggests a number based on a multiple of 96... like 960.

The history section notes that the 720 was originally an analog system that was later converted to digital. OK, but how is it that they selected this format? I seem to recall the Japanese standard was something close to 1050 (which makes perfect sense given they used 525 at the time) so it seems like they simply selected this number "out of thin air". Does anyone know why it's 720 specifically?

And how was it that this selection of two incompatible standards has managed to survive to this day? It's one thing to pick a lower resolution standard for an analog system, but since everything went digital the cost of the extra resolution is pretty small. Why didn't it get eliminated somewhere along the line? Or, if the article is correct and the resolution of 720p is actually as good as 1080i, then how is it that 1080i survived? How did we end up in this ridiculous situation of having two standards that don't even have a common multiple?

Maury (talk) 21:57, 9 January 2008 (UTC)

I'm not sure about the exact numbers, but it takes about the same analog bandwidth to transmit 720p as 1080i:

720x1280x60=55,296,000

1080x1920x30=62,208,000

In the early '90s the computer industry experimented with interlaced computer displays, and consumers absolutely hated them, so they wanted to make sure that progressive displays were standard. For things like reading text on a screen, a 720p CRT would look much better then 1080i. Algr (talk) 00:07, 26 February 2008 (UTC)

The above assumes that the 720p signal runs at twice the frame rate as the 1080i signal—in this case 60Hz and 30Hz, respectively. However, that is by no means universally the case. 720p/24 is in fact much more common.

I believe that a vertical resolution of 1080 pixels is derived from the number of active lines used by the NHK 1125-line analogue HiVision system. The 1080-line standard was designed with interlace in mind, and with progressive scanning as an option. The 720-line standard was designed only for progressive scanning from the outset and the 33% reduction in line count was felt to give a similar perception of vertical resolution as the 1080-line interlaced standard, at a given refresh rate. Ideally both standards would have the same number of horizontal pixels because interlace has no effect on horizontal resoluton but to maintain an aspect ratio of 16:9 with square pixels means that the 720-line standard needs 1280 of them while the 1080-line standard needs 1920. So, while it can be argued that 720p gives a similar perception of vertical resolution to 1080i at the same frame rate, 1080i has potentially a significantly higher horizontal resolution. I say "potentially" because 1920 pixels of horizontal resolution are not often achieved in practice. Until quite recently HD television cameras had CCDs with only 1440 (rectangular) pixels horizontally. The most common HD videotape recording formats (HDV, DVCPro-HD and HDCAM) down-sample each line and record only 1440 anamorphic samples. In the case of DVCPro-HD working at 1080i/29.97 it actually records only 1280 samples per line, levelling the playing field a little, but not fully because at 720p/24 it records only 960 samples per line. The only two videotape formats in common use that record the full horizontal resolution of 1920 samples per line are HD-D5 and HDCAM SR. Then again, in order to save bandwidth broadcasters often reduce the horizontal resolution of the 1080i signal to 1440 anamorphic pixels when coding it up for transmission. How many people have 1920×1080 resolution television display, anyway? I know the number is growing but most displays branded "HD Ready" have only around 1360×760 pixels. Even if you've paid the huge premium and invested in a real 1920×1080 display are you sure you're getting 1:1 pixel mapping, and can you see the difference anyway? It really is a minefield. 83.104.249.240 (talk) 04:36, 13 March 2008 (UTC)

720p and 1080i were proposed at about the same time, in response to the analog HD format developed in Japan. The television industry backed the interlaced format, because it was a familiar trick for them. The computer industry was afraid that interlacing would become comoditized and begin to appear on computer monitors, where it has very poor properties (text and lines flicker). Furthermore, the effective resolution of 1080i is not really much better than 720p, because interlaced video has to be veritically filters to avoid 30Hz flicker and other motion and aliasing artifacts. DonPMitchell (talk) 02:58, 22 May 2011 (UTC)

720p vs 1080p - Screen Size

If a TV's size is only, let's say, 1366 by 768 pixels, is there a noticeable difference between 720p and 1080p on a screen of this size?--Just James ^T/C 14:45, 3 June 2008 (UTC)

Because 720 and 768 are so close, there is a fair amount of loss when images are scaled - every 15 lines in the signal has to be stretched into 16 lines on the display, resulting in a lot of detail falling between the cracks. A true 720p set would look much better, given a 720p signal. The 1080p signal would suffer less from this effect, but would not look as good as a hypothetical 1366 by 768 image. (Such as if the set were being used as a computer monitor.) Algr (talk) 15:21, 4 June 2008 (UTC)

BBC

"The BBC is one of the EBU members transmitting in HDTV. It has not yet made a final decision on picture scanning format."

I think the BBC has decided on 1080i50, as have all other UK broadcasters. I do not have a source for this, but I don't see a source to say it is wrong either. --Iain (talk) 19:38, 1 September 2008 (UTC)

In Europe the channels are larger then in the US - 7-8 MZ each. With this and H.264, and the slower refresh rate, I don't see why they keep going with half measures. Why not 1080/50p? Several cameras that can do this already exist. (The Red One for example.) Algr (talk) 18:48, 2 September 2008 (UTC)

720p and 1080i were already defined as broadcast standards when HD started in Europe. Many people would have already had the TVs for those standards, and there would have been negligible benefit of going down that route. Bandwidth is limited (especially terrestrial), and film based material, for example, has no benefit of being broadcast at 50p. Even though there would have been benefits in sports broadcasting, it would not have been economical for such a drastic change in infrastructure with added expense of bandwidth.--Iain (talk) 21:04, 3 September 2008 (UTC)

As far as I know the BBC hasn't made an announcement of any decision but all the HD work I've been involved with in the UK has invariably been 1080i/25. The BBC's HD delivery format was until recently HDCAM (which doesn't even support 720p) with multichannel sound having to be Dolby E encoded due to the format only supporting four regular PCM audio tracks. Their future delivery format will be the much superior but significantly more expensive HDCAM SR format. Algr: sorry to disappoint you, but in Europe at least, HD isn't about quality. It's driven by the equipment manufacturers and it's solely and cynically about separating (mostly gullible) customers from their money. A lot of these people have, in the last five years, already upgraded their television receivers from standard definition 4:3 to standard definition 16:9, then the early adopters of HD bought 1366 x 768 so-called "HD Ready" branded equipment which they are now being encouraged to ditch in favour of "true HD". Meanwhile it's virtually impossible to buy a CRT, whether for domestic or professional use, but the replacement display technologies are all markedly inferior. Meanwhile the digital replacement for analogue broadcasting is sacrificing quality for quantity. In the UK the only SD channel that makes any attempt at maintaining technical quality and which uses a data rate that's consistently over 4Mb/s is BBC ONE. Viewed on a CRT, digital BBC ONE flagship programmes such as Strictly Come Dancing and Doctor Who can look absolutely cracking, but they are the exception, not the rule. Everything else is poor by comparison. The situation in the US may well be different - I have no recent experience. I was last there in 1996, working at the Olympic Games in Atlanta and my opinion after watching several hours of television in my hotel room is that it was dreadful, both technically and in terms of its production values. I do hope it has improved in the intervening 12 years. MegaPedant (talk) 23:33, 9 October 2008 (UTC)

Bitrate

What is the bitrate of 720p? Do you need 5 megabit to stream it? —Preceding unsigned comment added by 83.108.232.65 (talk) 21:37, 24 March 2009 (UTC)

Depends on the content. Mypal125 (talk) 22:35, 3 April 2016 (UTC)

what does this mean?

"Unlike NTSC, the ATSC standards do allow for a true 1080p broadcast leaving this battle almost lost on both sides."

If the ATSC standards do allow for a true 1080p why is the battle lost on that side? Confusing. —Preceding unsigned comment added by 66.46.84.66 (talk) 19:45, 8 July 2009 (UTC)

Objection to comment in opening paragraph

I dont know why the following is allowed on the first paragraph or anywhere in Wikipedia, because it is quite simply incorrect:

"so spatial resolution (sharpness)" FIXED by SadxPandaxFace

This implies that spatial resolution and sharpness is equivalent, and are not. I am going to change it to say "so sharpness is much closer to 1080i". 62.244.190.66 (talk) 11:32, 11 December 2009 (UTC)

Frames v Fields

It seems this article frequently and erroneously uses the word "frames" where it should be using the word "fields". It is my understanding that NTSC standard is 30 or 29.97 FRAMES per second, but 60 or 59.94 FIELDS per second. Each frame consists of two fields, each consisting of half the number of horizontal lines that make up the full frame. Even the first referenced URL in the article ([2]) notes that this is the case. Unless there is evidence to the contrary, can we have all erroneous instances in this article corrected? --Ds093 (talk) 15:10, 1 January 2010 (UTC)

What is 720p when aspect ratio is not 16:9?

How do you define 720p when the aspect ratio of the videos are not 16:9? Alot of movies uses e.g. 2.35:1 and in my experience these films usually have a definition of 1280x544. So it's not really the height of the signal that is constant in 720p, it's actually the width. So why don't we call it 1280p then, which would be the correct width in every video. And what would the definition be if the aspect ratio is 4:3? 1280x960, or 960x720? Cachinnus (talk) 03:11, 7 November 2010 (UTC)

720p is not frequently used in Europe?

This article says »720p is not frequently used in Europe.« but in the German Wikipedia we can read, that »ARTE HD Deutschland, Das Erste HD, Eins Festival HD, ZDF HD, ORF 1 HD, ORF 2 HD, HD suisse, SVT, NRK, DR und YLE« are using 720p. So this information is definitly false. —Preceding unsigned comment added by 95.115.238.66 (talk) 17:02, 4 April 2011 (UTC)

Incorrect about 3:2 pulldown?

A 720p60 (720p at 60Hz) video has advantage over 480i and 1080i60 (29.97/30 frame/s, 59.94/60 Hz) in that it comparably reduces the number of 3:2 artifacts introduced during transfer from 24 frame/s film.

I don't think that's true. There will be just as much "judder" - caused by repeated fields/frames - on 720p60 as 480i60 or 1080i60. David (talk) 14:21, 2 March 2013 (UTC)

720p60 CVT-RB

I am looking for some information for possible use in improving this article (assuming I can find a reliable source)

Background: unless I am mistaken, the specifications for 720p60 CEA-861 video are:
1280 × 720 Resolution
59.940 Hz Refresh
44.955 kHz Vertical
74.176 MHz Horizontal

What I cannot find are the specifications for 720p60 CVT-RB (reduced blanking) video.

CVT-RB is a VESA standard (Coordinated Video Timings, VESA-2003-9).

ESA-2003-9 is available at ftp://ftp.cis.nctu.edu.tw/pub/csie/Software/X11/private/VeSaSpEcS/VESA_Document_Center_Monitor_Interface/CVTv1_1.pdf (despite the "Microsoft Word" in the URL, it is a PDF document).

It has some formulas, but does not specifically list timings for 720p60 CVT-RB. Does anyone know where to find the timing for 720p60 CVT-RB? --Guy Macon (talk) 14:30, 10 March 2013 (UTC)

(Sound of Crickets...) --Guy Macon (talk) 08:16, 17 March 2013 (UTC)

Notes 1. = not 60 FPS

According to my calculater 60 * 1000/1001 = 59.94005994005994005994005994006

59.940059 940059 940059 940059 940059 ... (the number with whitespaces between blocks)

59.940059 940059 94 (number on the page)

59.940059 940059 94940059 940059 94940059 940059 94 (extended period)

The number on the page is not the same as the calculator outputs. Either the formular or the value is wrong

So the number should be 59.940059 - the underlined part is the part that repeats. (No clue how to put the line over the text.) — Preceding unsigned comment added by 77.23.100.19 (talk) 12:13, 19 September 2016 (UTC)

Interlacing

720 is like webTV. 30fps at and interlace at a "SPECIFIC" 120khs refresh rate. Well I could go on about Sytax and Vizio but some people care about 30fps or 60fps. Interesting talk though. — Preceding unsigned comment added by 2602:301:7751:160:DD52:A7BA:E943:107C (talk) 18:18, 28 March 2017 (UTC)

1080x720? 3:2 aspect? Rec 601 spec? eh?

OK, let's see... in a great many years, I've never seen the 1080x720 resolution mentioned anywhere before, nor any TV standard that has a 3:2 aspect ratio. Rec 601, at least as far as I knew, and indeed as far as the directly linked WP article is concerned, is an early 80s format that long pre-dates any serious attempt at establishing HD standards, and only defines 525- and 625-line interlaced SDTV modes. No 720p or indeed 1080i/p of any kind, and no horizontal resolutions wider than 768 pixels.

Is there any kind of veracity behind this oddity, or is it just some random misguided wikignome's wild imagining that can be safely deleted? I'm feeling strongly inclined to Be Bold with it. 80.189.129.216 (talk) 20:22, 23 January 2018 (UTC)