Talk:720p

message: "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." 
:Lee M 17:24, 12 Dec 2004 (UTC)
replies: text: 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)
replies: text:  Neither. The two standards exist because each is better suited to different purposes, and the technology of the time wasn't good enough to provide what was actually desired - IE full rate 1080p. Instead we have the twin compromises of 720p and 1080i, the former better for high motion material where the effective display would otherwise be a rather weird 1920x540 and suffer interfield motion artefacts, and the latter better for bringing out finer details in low motion video and 24-frame filmed material (and avoids the need for HDTVs to have an initially rather expensive scan doubling framebuffer to prevent flicker, despite otherwise only having half the ideal framerate). If one was automatically "better" than the other in all situations, why would both standards have been enshrined? It's a waste of time and effort, doing something like that for no reason. 80.189.129.216 (talk) 23:56, 23 January 2018 (UTC)

text: 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)
replies: text: 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)
replies: text: 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)
replies: text:  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)
replies: text: 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)
replies: text:  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)
replies: text:  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)
replies: text:  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)
replies: text:  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)
replies: text:  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)
replies: text:  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)
thread_title:  NBC Resolution 

message: 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)
thread_title:  Television resolution chart 

message: 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)
thread_title:  Fox Revert

message: 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)
replies: text: 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)
thread_title: citation needed?

message: 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)
replies: text: 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)
replies: text: 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)
thread_title:  Interlace is misunderstood ... 

message: 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)
thread_title: 720p vs. 1080i

message: 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)
replies: text: 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)
replies: text: In practice, though, there's still some overscan anyway. EG a lot of supposed 1080p sets stretch out the centre 1856x1044 or so pixels to fill their 1920x1080 (for why, I'm not sure, maybe it's to compensate in case SD material is carelessly upscaled without the ragged edges being cropped off? It's a figure I've run across a handful of times with different devices, usually when they've glitched out and think that a PC input is actually broadcast material, and you lose the edges of the image, which is very inconvenient if it happens to be your OS desktop), and we can assume HDready 720p or 768p sets do the same. So we have 1044 lines being crammed down, or approx 696 lines stretched out, to 768. In any case, the amount of upscaling is small enough that it doesn't significantly affect clarity, and the downscaling only loses about a quarter of the total transmitted. The difference between the two will depend on the quality of the built-in scaler; a poor one will end up smearing 720p material (and you'll probably end up hunting out the Service Mode codes in order to enforce 1:1 scaling for that mode, same as I had to in order to make PC 1920x1080 modes work correctly), but give a decent impression of 1080-line (maybe with some interlace artefacts for 1080i), but a good one should give an only slightly softer image for 720p vs 1080i/p, and deinterlace 1080i intelligently too. 80.189.129.216 (talk) 22:59, 23 January 2018 (UTC)
thread_title: 720p vs 1080p - Screen Size

message: 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)
replies: text: Depends on the content. Mypal125 (talk) 22:35, 3 April 2016 (UTC)
replies: text: To whit: Uncompressed RGB, including usual blanking, is 1782mbit (4:2:0 YUV without blanking is 1188mbit, if my maths are correct). At the other extreme, the 25fps version used by the BBC on the iPlayer VOD site runs around 3mbit; probably if that was compressed with 2-pass VBR instead of a realtime CBR encoder it might average more like 2.5mbit. The upper limit of Blu-ray material (and HD video cameras) is somewhere around 21~24mbit. Most compressed cases (which I assume is what you're after) will be some arbitrary figure in-between those latter rates. 80.189.129.216 (talk) 22:46, 23 January 2018 (UTC)
thread_title:  Bitrate 

message: "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)
thread_title:  what does this mean? 

message: 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)
thread_title:  Objection to comment in opening paragraph 

message: 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 () 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)
replies: text: It's irrelevant in the case of 720p (or 1080p, 2160p... etc), as it's not interlaced. There are no fields, or perhaps more accurately every field is also a frame. Each 1/60th (or 1/59.94th) of a second, you get a full block of 720 lines, and each new block completely replaces the immediately previous one, instead of weaving inbetween them. Thus although the NTSC rate (60hz mono or 60/1.001hz colour) still holds sway for compatibility's sake, it's now the frame rate, not the field rate as it was previously. Of course, for 1080i, the distinction is still important, but this is an article about 720p ;) 80.189.129.216 (talk) 22:38, 23 January 2018 (UTC)
thread_title:  Frames v Fields 

message: 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)
thread_title:  720p is not frequently used in Europe? 

message: :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)
replies: text: It does, however, make interframe smoothing/motion blurring a bit easier, potentially improves the overall resolution (depending on how IVTC was performed before), and gets rid of the problem of deinterlacing/detelecine-ing glitches (back-forth jitter, excessive combing, etc) and bleed through between fields, which can make 3:2 pulldown even uglier than it already is. Also, I expect there's probably the option of using the "repeat frame"/IVTC flags as per DVD, both economising on bandwidth and allowing suitably intelligent displays (e.g. 120hz panels) to re-time a series of 60hz frames sent as (1)-R-(2)-R-R-(3)-R-(4)-R-R (etc) to a jitter free 24hz stream, without the additional complication of having to reconstruct the picture from individual fields that can come in four different arrangements. Effectively, the only image data being transmitted is the 24 full frames every second, same as with 25/50hz, just with a bunch of repeat flags inserted. However, it still loses out in terms of resolution, and if your hardware is sophisticated enough and transmission of good enough technical quality it should be able to reconstruct 60i into 24p just as well as 60p to 24p, just with twice as many pixels... 80.189.129.216 (talk) 22:22, 23 January 2018 (UTC)
thread_title:  Incorrect about 3:2 pulldown? 

message: 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)
replies: text: What? Are you feeling OK? 80.189.129.216 (talk) 20:23, 23 January 2018 (UTC)
thread_title:  Interlacing 

message: 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)
thread_title:  1080x720? 3:2 aspect? Rec 601 spec? eh?