Well actually, more like "all TVs are dumb and HDTVs shouldn't be but they are anyway." I had no idea about this and it's kind of funny to find out.
A discussion a couple of days ago about DPI detection (which is best summarised by this and this and I am not having this discussion again) made me remember a chain of other awful things about consumer displays and EDID and there not being enough gin in the world, and reading various bits of the internet and wikipedia seemed to indicate that almost everybody who's written about this has issues with either (a) technology or (b) English, so I might as well write something.
The first problem is unique (I hope) to 720p LCD TVs. 720p is an HD broadcast standard that's defined as having a resolution of 1280x720. A 720p TV is able to display that image without any downscaling. So, naively, you'd expect them to have 1280x720 displays. Now obviously I wouldn't bother mentioning this unless there was some kind of hilarious insanity involved, so you'll be entirely unsurprised when I tell you that most actually have 1366x768 displays. So your 720p content has to be upscaled to fill the screen anyway, but given that you'd have to do the same for displaying 720p content on a 1920x1080 device this isn't the worst thing ever in the world. No, it's more subtle than that.
EDID is a standard for a blob of data that allows a display device to express its capabilities to a video source in order to ensure that an appropriate mode is negotiated. It allows resolutions to be expressed in a bunch of ways - you can set a bunch of bits to indicate which standard modes you support (1366x768 is not one of these standard modes), you can express the standard timing resolution (the horizontal resolution divided by 8, followed by an aspect ratio) and you can express a detailed timing block (a full description of a supported resolution).
1366/8 = 170.75. Hm.
Ok, so 1366x768 can't be expressed in the standard timing resolution block. The closest you can provide for the horizontal resolution is either 1360 or 1368. You also can't supply a vertical resolution - all you can do is say that it's a 16:9 mode. For 1360, that ends up being 765. For 1368, that ends up being 769.
It's ok, though, because you can just put this in the detailed timing block, except it turns out that basically no TVs do, probably because the people making them are the ones who've taken all the gin.
So what we end up with is a bunch of hardware that people assume is 1280x720, but is actually 1366x768, except they're telling your computer that they're either 1360x765 or 1368x769. And you're probably running an OS that's doing sub-pixel anti-aliasing, which requires that the hardware be able to address the pixels directly which is obviously difficult if you think the screen is one size and actually it's another. Thankfully Linux takes care of you here, and this code makes everything ok. Phew, eh?
But ha ha, no, it's worse than that. And the rest applies to 1080p ones as well.
Back in the old days when TV signals were analogue and got turned into a picture by a bunch of magnets waving a beam of electrons about all over the place, it was impossible to guarantee that all TV sets were adjusted correctly and so you couldn't assume that the edges of a picture would actually be visible to the viewer. In order to put text on screen without risking bits of it being lost, you had to steer clear of the edges. Over time this became roughly standardised and the areas of the signal that weren't expected to be displayed were called overscan. Now, of course, we're in a mostly digital world and such things can be ignored, except that when digital TVs first appeared they were mostly used to watch analogue signals so still needed to overscan because otherwise you'd have the titles floating weirdly in the middle of the screen rather than towards the edges, and so because it's never possible to kill technology that's escaped into the wild we're stuck with it.
tl;dr - Your 1920x1080 TV takes a 1920x1080 signal, chops the edges off it and then stretches the rest to fit the screen because of decisions made in the 1930s.
So you plug your computer into a TV and even though you know what the resolution really is you still don't get to address the individual pixels. Even worse, the edges of your screen are missing.
The best thing about overscan is that it's not rigorously standardised - different broadcast bodies have different recommendations, but you're then still at the mercy of what your TV vendor decided to implement. So what usually happens is that graphics vendors have some way in their drivers to compensate for overscan, which involves you manually setting the degree of overscan that your TV provides. This works very simply - you take your 1920x1080 framebuffer and draw different sized black borders until the edge of your desktop lines up with the edge of your TV. The best bit about this is that while you're still scanning out a 1920x1080 mode, your desktop has now shrunk to something more like 1728x972 and your TV is then scaling it back up to 1920x1080. Once again, you lose.
The HDMI spec actually defines an extension block for EDID that indicates whether the display will overscan or not, but doesn't provide any way to work out how much it'll overscan. We haven't seen many of those in the wild. It's also possible to send an HDMI information frame that indicates whether or not the video source is expecting to be overscanned or not, but (a) we don't do that and (b) it'll probably be ignored even if we did, because who ever tests this stuff. The HDMI spec also says that the default behaviour for 1920x1080 (but not 1366x768) should be to assume overscan. Charming.
The best thing about all of this is that the same TV will often have different behaviour depending on whether you connect via DVI or HDMI, but some TVs will still overscan DVI. Some TVs have options in the menu to disable overscan and others don't. Some monitors will overscan if you feed them an HD resolution over HDMI, so if you have HD content and don't want to lose the edges then your hardware needs to scale it down and let the display scale it back up again. It's all awful. I recommend you drink until everything's already blurry and then none of this will matter.
Am I the only person getting overwhelmed by how awful and nonsensical everything's become? Companies, business practices, the government? All of it? I literally can't think of a single company or type of business or anything at all that I think is good. I like... books?
I mean why not just make a 1360 16:9 ratio television? Is it that much more difficult to make a perfectly complaint device?
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"SMOKEDOG42O taught me how to feel love, but fetus taught me how to make love." - Pablo Escobar
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Love is better than anger. Hope is better than fear. Optimism is better than despair. So let us be loving, hopeful and optimistic. And we’ll change the world.
Okay. Well, for starters, that's just dumb. In addition to how dumb that is, I have a question for you - how many girls have thrown themselves at you for your contributions to this topic?
the icon ownz all posted... From: SMOKEDOG42O | #006 literally can't think of a single company or type of business or anything at all that I think is good. I like... books? I just bought this ( http://www.amazon.com/Fall-Roman-Empire-Barbarians-ebook/dp/B000SEI0JQ ) for $2. I can get behind their business practices
Hm. Well met.
I was mostly referring to, for example, television manufacturers. If you know that these standards are in place, why not conform to them? It's actually more work to fudge around the edges and offer a product of lesser quality. I've started going to a local butcher for my steaks and beef because A) the quality is off the chain; B) they don't mess around - I get exactly what I want; and C) I'm one of those buy local nerds.
I have no idea how to use semi-colons.
I'm just going through a sea-change where I'm becoming more and more aware of how much time, money, intelligence, and effort is wasted in the bureaucratic process at every level, and how all of it passes down to us.
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"SMOKEDOG42O taught me how to feel love, but fetus taught me how to make love." - Pablo Escobar
From: SMOKEDOG42O | #006 I mean why not just make a 1360 16:9 ratio television? Is it that much more difficult to make a perfectly complaint device?
When you're engineering a device such as an HDTV, there are a ridiculous amount of factors that go into every little design decision. It's extremely rare to find a design that straight up improves a device with no drawbacks at all. Almost all of these decisions are made with the tradeoffs in mind. I am not a TV engineer, and I doubt the writer of the article is either, so we can't know what the reason for the design choices really was.
It's really easy to poke holes and criticize a design when you're only looking at one part of the whole (screen resolution in this case).
-- _foolmo_ 'Oh please, if foolmo made that analogy you'd think it was picture perfect' - Biolizard28
HDTVs are kind of a mess in a couple ways. we've got the resolution issues described above, we've got a minimum of 1 frame of input lag added because of various filters applied to every image before it gets displayed (usually 2-3 frames on most HDTVs) and no way to get around either of them. Both are unpleasant for enthusiasts but they don't get fixed because most people don't notice or care. Heck, most people I know are stretching 4:3 standard definition images to fill up the space on their widescreen, this other stuff won't matter to them at all.
The weird thing is they make non-commercial HDTVs that don't have these bizarre issues. I know a lot of airports have them for sure. The fighting game community used to recommend you try and find some of those if you could, when they were just realizing that most TVs were lagging a couple frames over CRTs.
When you're engineering a device such as an HDTV, there are a ridiculous amount of factors that go into every little design decision. It's extremely rare to find a design that straight up improves a device with no drawbacks at all. Almost all of these decisions are made with the tradeoffs in mind. I am not a TV engineer, and I doubt the writer of the article is either, so we can't know what the reason for the design choices really was.
Someone mentioned something about this in the comments below.
Matthew almost certainly already knows this, as he's steeped in the many and various ways that consumer electronics manufacturers try and do things on the cheap, but for everyone else:
1366x768 comes from a quirk of at least one method for manufacturing LCD panels. At one stage in manufacture, they're made as a big sheet of pixels, much, much larger than you want as screens. This is then cut into individual screens, first by cutting into vertical chunks, then cutting the line of screens into single screens.
The trick comes in when you're cutting - defects tend to cluster in individual spots on the screen. Any finished screen with too many defects is a failure and has to be discarded. So, vertically, you want to cut into as small a number of sizes as possible, and cut horizontal chunks avoiding any defects.
There are no common 720 high 4:3 screen sizes - 960x720 is unusual. Lots of people still want 1024x768 4:3 screens for various applications. You may be seeing why 1366x768 is popular at this point - you can now cut your lots by 768 stage into a mix of 1024x768 4:3 and 1366x768 16:9 screens, and can therefore get more usable screens from the same vertical cut.
Plus, TV is all about samples of an idealised continuous function, not pixels, and we have well-understood "perfect" algorithms for scaling 1280x720 samples to 1366x768 samples, such that lighting up an LCD pixel will reproduce the "same" continuous function whether you're lighting up 1280x720 pixels, or 1366x768 pixels, or even 1920x1080 pixels. This is not so good for computers, which are pixel based, not sample based.
Foolmo, I always think of you as a gruff, kind of rude, foolish, moronic brony. And I tend to forget that you're also really knowledgable about tech and how it works. I'd like to apologize for that.
tl;dr: Good point.
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"SMOKEDOG42O taught me how to feel love, but fetus taught me how to make love." - Pablo Escobar
The biggest overkill backwards compatibility thing, in my completely obnoxious opinion, is the 59.94 Hz drop frame timing thing.
Modern HDTV standards specify the expected 24, 25, 30, 50 and 60 Hz vertical refresh modes for progressive content (and interlaced at 50 and 60 Hz). They also add (for 24, 30 and 60 Hz) the option to multiply the vertical refresh by 1000 / 1001, to get 23.97 Hz, 29.97 Hz and 59.94 Hz.
Why do this? Back in the days of monochrome sets, 60 Hz regions used a genuine 60 Hz signal. When NTSC was designed, the chroma subcarrier was found to result in objectionable beat patterns on monochrome sets; the only way to fix this while staying within a 6 MHz channel bandwidth was to slightly reduce the frame rate, such that older sets (designed to lock to 60 Hz) would still lock to it, but would no longer interpret the chroma subcarrier as beat patterns in the picture.
Why keep it in HD standards? In theory, it means that if you are downscaling your HD content to SD, and then putting it into a monochrome TV set that's unaware of NTSC chroma encoding, you won't get the beat pattern. Colour-aware sets, even if they're monochrome (so virtually all designs since the 60s, and many 1950s designs) won't give the beat pattern at 60 Hz. But, we get to suffer the complications of drop frame, so that if you connect your HD source to a 1940s or 1950s TV, you won't see a beat pattern.
From: OmarsComin | #016 Lots of people still want 1024x768 4:3 screens for various applications. You may be seeing why 1366x768 is popular at this point - you can now cut your lots by 768 stage into a mix of 1024x768 4:3 and 1366x768 16:9 screens, and can therefore get more usable screens from the same vertical cut.
Welp, that's it then
-- _foolmo_ 'It's easy to get yourself in trouble if you start quoting people who don't like you in your signature' - Mods
From: SMOKEDOG42O | #013 I was mostly referring to, for example, television manufacturers.
Television manufacturers are not the most scrupulous corporations in the world. A group of some of the most profitable manufacturers recently settled a price fixing antitrust claim a couple weeks ago. Their illegal activities went on for 7 years before anything was done, and they (Sharp, Samsung, Sony) were forced to pay over $500 million in fees. That sounds like a lot, but considering that the fine is split between all of the corporations, and the amount in fines is likely an incredibly small amount compared to the profits they earned during that time, it really isn't.