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On NTSC Video, Blue Blurring, Chroma Subsampling
NEOGEOman writes "Something I've been fascinated with for a long time is video signals. On my website I've spent over six years collecting video and other hacks for game consoles. I've recently put together the fourth revision of my video signal primer and it's expanded to six pages now, including strange subjects like chroma subsampling, horizontal colour resolution and rather interesting revelation: your eyes suck at blue."
Can anyone possibly tell me why the hell this site is listed in my company's web filter as pornography?
Sony's PS2 unit goes so far as to disable the RGB output when playing DVDs, requiring a cable swap when changing from movie-watching to game-playing
Right off the first page. The PS2 uses a composite video cable and requires no switching of cabling to watch DVDs or to play games.
I have been pwned because my
My eyes suck especially badly at blue. a pure-blue image is something my eyes completely refuse to focus on. I can see the image is there, see that it's blurry, but whatever makes my eyes focus just doesn't work on blue. Light a room with pure blue light and I'm almost blind. gah!.
:)
Add some other colours and I'm fine. Curiously, given a red line of text, a green line of text and an off blue line of text, I have to focus differently for all three. (Fully blue is, of course, a complete waste of time
As linked on the blue-deficiency page, the blue-channel analysis had been done before (at least, I remember seeing it a couple years back... or was it months?).
Personally, I like this newer analysis better: the differences are more obvious with the RGB channels put side-by-side.
RGB is standard on most equipment as it is included in the SCART connector usually found on any TV/VCR/DVD sold in the last decade.
The real "Libtards" are the Libertarians!
Never Twice the Same Spelling
Another revelation is that your web server sucks.
Only 14 posts and the site appears to be Slashdotted...
Help Fight SPAM today!
Digital > RGB > Component > Svideo > Composite > RF modulator
The difference between Composite and SVideo is HUGE, please change if you are still using Composite!
You may want to read a report on misbehaving censorware. Blocking the the article as "pornography" is misbehavior. If your company's business has anything remotely to do with video production or video games, ask your IT department to review gamesx.com (the site on which the article is hosted) and consider whitelisting it.
who's the girl? She's hot ;)
It's well known; as our eyes drift to the blue and red end of the spectrum, we lose our sensitivity, off by many orders of magnitude from say, yellow. This is why you see blue, and more commonly, red, lights as "night" light sources.
The general reasoning: our eyes evolved with a single primary light source: the Sun. Which has quite the yellow tinge to it. Our eyes adapted to this, and as such, gave yellow the highest sensitivity and drifted off in a rough bell curve from there.
It was an interesting article, and certainly put the RGB sensitivity into perspective, but ... it's not entirely new or surprising, either. Nor does the human eye really respond at RGB -- its response curves (beta, gamma, and rho) more closely correspond to blue, green/yellow, and yellow/orange.
That all being said, thanks for letting us meet Traci. ;)
"All your base are belong to this file I send in order to have your advice."
I wonder what effect eye color has on color sensitivity. If one has a blue iris, it must affect the "input", right? As well, there should be some sort of effect for green, gray and brown irii, right?
And, yeah, I know that the pupil is where the light goes thru, but the iris is bigger (at times) area-wise and must be letting some light thru, right? And the iris is doing some sort of "color correction" on what light makes it thru, neh?
Any ideas?
Merry Christmas, Peace & Blessings,
bmac
For lasting peace & happiness, www.mihr.com
Manual Sig Generator 4.1ish
Look at a relatively recent book on human vision. If you look at a graphical map of the retina, you will notice that the there is a huge sea of green and red sensitive cone receptors, whereas the blue is dispersed in little, seemingly random, island like bunches.
Your eyes are not less sensitive to blue, in fact they are very sensitive to blue, it is just that they have virtually no blue resolving capability. Some people confuse resolution and sensitivity in this case, and say you are less sensitive to blue. This is not true.
Futhermore, this thing about blue has been known for years. That's why Bayer pattern filters have twice as many greens as red and blue.
At least that's what one of my grad school profs called it. And my eyes tend to agree: PAL is better.
Anyone know why?
Tonight, I'm gonna party like its December 31, 2006.
No wait.. NTSC isn't going away.. Or is it.. Yeah it is..
Just a friendly message from: ATSC -- Trying to eliminate NTSC broadcasting since 1996
I realise this competely off topic, but is it ever a small world... I went to high school with the lady in the picture laying on the car (Traci). A year after high school I moved 400km's away to a large city and about 2.5 years after that I ran to her working at the Red Robin a block from my house. Now I see her picture on Slashdot of all places, whats the chance of that happening? :)
To top it off, the guy who apparently owns the website (gamesx.com) runs (or ran?) a console game rental store in my home town, and used to date my sister!
Open Source Time and Attendance, Job Costing a
I'm red-green colorblind, and the pictures on the LEFT, with the low-resolution red images, look as good to me as the original or the one with the low-res blue. Does anyone else notice this?
How I just hate Web sits with a full page with welcome logo, you have to click on, not good for Blind users, and it looks like one of the pay for porn sites, Hey her is a tip, try to see if you are able to get the site cetf by http://bobby.watchfire.com/bobby/bobbyServlet?URL= http%3A%2F%2Fwww.gamesx.com%2F&output=Submit&gl=wc ag1-aaa&test=
I just hate bit SPAM, (www.netnoise.com.kh)
IIRC, the irises are actually opaque; the only light that gets through to the retina passes only through the cornea and pupil. Colored contacts, likewise, don't color light because they have a transparent "dot" in the middle of the lens.
Beyond that, I also remember reading that it's actually the brain that does all of the color (and gamma) correction; nothing in the eye's machinery--it's all done in the (pre?) processing.
And you're color blind because the game section is purple :p
I thought Blue was just as bad as red (which is...not all that bad) However, that old link (here, worked a little better. First two images were damn near identical
Look it's a joke about my sig IN MY SIG! LOL!
Our eyes suck at seeing blue for an even better reason - there are very few blue things that:
From an evolutionary perspective, that's the most important thing. We're get good at seeing green, because many green things are edible, and some things that want to kill us are good at hiding in green areas. So people who were especially good at seeing movement in green areas, and finding edible green things tended to survive, while those who didn't died out.
"How perfectly Goddamn delightful it all is, to be sure" Charles Crumb
MOD PARENT UP!!!
I recommend you remove the Allan W. Jayne, Jr. link from your references and add the following:
* http://www.lurkertech.com
* http://www.poynton.com/GammaFAQ.html
Poynton's got some other good stuff on his site, plus some very good books (latest is Digital Video and HDTV Algorithms and Interfaces). No, I have no affiliation with him - I'm just a fellow video geek and am impressed by his lucid and well-researched works.
That Jayne guy has some shady and blatantly incorrect information on his site that he represents as facts (rather than conjecture). For one thing, he could sure use a course in DSP.
Especially when I make them all red. My lungs are another story.
Not necessarily.
SCART connectors are huge chunky things that can handle a number of video formats, including RGB, S-Video and Composite (maybe others too). But that's not the same as saying that a given SCART cable or socket will support all those formats. Many cheaper cables only support Composite (fewer wires means cheaper cost). And on some high-end TVs with multiple SCART inputs, only some of those will support RGB.
So if you're playing your PS2 or whatever through a SCART cable, the TV might be using the SVideo or Composite signal rather than RGB.
The lesson is, be sure to check your TV inputs, and always buy good quality cables!
"Can anyone possibly tell me why the hell this site is listed in my company's web filter as pornography?"
The web page uses the word suck.
Sorry. I wasn't looking at her blue elements. And what's this about making something 9 times larger?
Wait, weren't you saying something about TVs?
Please help metamoderate.
ok, i'm in love with traci - with or without the green! ;)
It's only RGB after decoding.
e rt/
NTSC video uses the YIQ color space, very similar to YUV (used in PAL, JPEG, DVD, & stuff). Y is the brightness, which gets the highest resolution, and I & Q (or U & V) are the chroma values, which can be greatly subsampled because they have no effect on brightness (when everything's working correctly).
Most lossy image compression formats involve first transforming the image to the yuv color space. The RGB->YUV transform is also used by many paint programs for things like estimating differences between colors for color reduction & such.
First match on google for "YIQ YUV":
http://astronomy.swin.edu.au/~pbourke/colour/conv
"Your eyes suck at blue"
Which is why red light districts do so much better than the ones in blue.
JPEG also relies on this. But JPEG could provide considerably more compression if it didn't introduce those highly visible high-frequency artifacts.
North American TV is NTSC which stands for Never Twice Same Color. MiniDV uses a 4x subsampling of the colour channels, with the luminance at full resolution. So even though its touted as lossless digital, it's really cutting your color information to a quarter and uses compression at 5:1. Thats probably the worse of the digital formats. A better format is 4:2:2 which is a 3.3:1 compression format where the color information is halved instead. DVCPRO runs at 50Mbps 4:2:2, while good consumer DV is 25Mbps.
If you save JPEG files at maximum quality or 100%, JPEG will use a 4:4:4 color sampling scheme, meaning all colour information remains intact. Saving at 75% or high quality, JPEG will use a 4:2:2 color scheme, similiar to DVCPRO50. Thats how JPEG is able to compress like it does. A newer compression format is JPEG2000 which is based on wavelet technology, which is about 300% more efficient that DCT JPEG. Apple's Pixlet technology is based on wavelet, but higher performance on desktop computers. You'll be hearing more of JPEG2000 in the coming years.
Thanks for being so polite about it :-D, is this motivated by envy because PAL is so far superior to NTSC (Never The Same Colour twice), you do realise that with digital we'll all be even again at last.
in my life God comes first.... but Linux is pretty high after that
Francis Smit
This site linked by the video primer, says that "Until the advent of version 8 of JASC Paint Shop Pro, Adobe Photoshop was capable of producing better quality JPG's for web and on-screen use, because Photoshop disabled chroma subsampling at highest quality settings. As of version 8, Paint Shop Pro moved ahead, offering the user full control of chroma subsampling. Especially for web use where file size is crucial and images are generally low resolution, Paint Shop Pro's greater flexibility is a considerable asset." But... PSP is no Photoshop, and this is a considerable asset indeed, so what to do? Buy both, and use PSP only to compress images? What a waste. Does the newest version of Photoshop give more control? The latest I've used is 7.0 and it does not AFAIK.
"where words meet intent, lies rhetoric's lament"
NEOGEOman, I just wanted to say gret job on the signal primer. I had always been a bit curious about video signals, though I had never looked into the subject. So I just wanted to to thank you for making an easy to understand document that covered everything I wanted to know (and more).
There is no dark side of the moon really, matter of fact it's all dark
There is a lot of evidence in literature that our eyes have evolved to see the color blue over time. A lot of biblical and Grecian writings describe the sea to be the color of wine (purplish)... and... their are a lot of other examples, but that is the one I can think of off the top of my head.
This page was generated by a Barrel of Circus Midgets, and that is the way I like it!!!
After fooling around with video for quite some time now, I have came to the same conclusion that NEOGEOman gets: Macrovision and the entire industry blows. Sure, we all know that the MPAA sucks, but the drop so low that to mess with the video to the point of almost unwatchable is absurd. Here's a small list of things they do to mess up composite video (NTSC):
- variation of the black level (confuses AGCs)
- phase modulation of the color burst (later macrovision versions, like DVD players)
- removal of lines from one field and putting them on the other field.
- bursts in the VBI
And then the industry refuses to move on until they can get some other "protection" on the video feed. Who do they worry about? The "Casual copier," "hobbyist," "hacker," "small scale pirate," and the "professional pirate" (DDWG powerpoint presentation [http://www.ddwg.org]). The cost? Remotely decent video and your right to fair use.
Arg!
</rant>
As a side note, if you're interested in chroma sampling and how it can go wrong, check out this page: http://www.hometheaterhifi.com/volume_8_2/dvd-ben
It's an interesting read.
I've never used Photoshop, I believe in purchasing the software I use and Photoshop is priced beyond the grasp of mortals. PSP uses the same filters and costs $100 ($50 upgrade) and gets vastly better with each revision. I recommend it - the chroma subsampling control is just one feature I use a lot.
http://www.jasc.com - get PSP here. =)
--
I am not a corporate shill!
Good info. I agree with everything except for the general reasoning, simplely because "evolutionary" explaintions tend to be made up without any scientific evidence and can as easily be created to counter: eg. our eyes would adapt so we see more of the other wavelengths of light.
s ponse.ht m
Evolution itself is a pretty good scientific theory.. however specific reasons for traits backed up by the "evolutionary" explaintion tend to rank right up there with "God did it" as far as science goes.
Anyways here's a decent link on the actual numbers and response ratio for our cones.
http://www.unm.edu/~toolson/human_cone_re
I thought *I* had red-green color blindness, but I can only see jaggies in the center picture. Perhaps my color blindness is more severe than I'd thought.
Well, I'm a student so I have access to Photoshop at the University (just not now, as I'm not enrolled this quarter, too poor hehe). I'm quite accustomed to Photoshop, and prefer it over PSP a great deal. I'm fairly sure I can use PSP at the university as well, but ideally I'd like to buy a copy of Photoshop to use at home, and I'd rather not have to pay for PSP too (because I'll be poor enough after buying Photoshop). Regardless, this functionality is really needed in Photoshop. I wonder if it's included in CE (is that the new version?) or if there is some 3rd party plugin to add it.
"where words meet intent, lies rhetoric's lament"
you would realize that most of the image data is infact in the blue range on NTSC M RGB sysytems Blue holds nearly 85% of the image data.
This is all the more obvious these days with all the blue LED Christmas lights around. I find these really hard to see when it is very dark. They are almost invisible until I am within 100 m or so. At any greater distance they only show up as sort of a dark subliminal smudge.
Oddly enough, they seem brighter when used in dimly lit building interiors.
Merry Christmas to all, and to all a good night.
Please tell me that the author did NOT just split an image interpolated from a digital camera, which probably used sensor with pixels layed out in a bayer pattern*, using a CCD type of sensor which tranditionally shows the most noise in the blue channel...
Well DUH the green channel is going to have more detail -- there are twice as many green pixels on the sensor. And DUH the blue channel is going to be the fuzziest, given that is the shade digital cameras have the hardest time capturing (take a picture of a blue sky if you don't believe me)...
On top of that, the author is assuming that the colors are represented in his picture in equal quantity. The blue/red channels might not be as bright because there isn't as much red/blue in the picture as green (the photo does appear to have a yellow tint to it).
His assertion may be true, but his demonstration doesn't prove a dang thing.
* Bayer pattern:
RGRGRG
GBGBGB
RGRGRG
GBGBGB
where R = red pixel, G = green pixel, and B = blue pixel
"From an evolutionary perspective, that's the most important thing. We're get good at seeing green, because many green things are edible, and some things that want to kill us are good at hiding in green areas. So people who were especially good at seeing movement in green areas, and finding edible green things tended to survive, while those who didn't died out."
e ecolor/ata ble.html
You just made that completely up.
First off green isn't the best color that we can see. (Yellow and Oranges tend to be best)
Second very few edible green things (aka vegitation) get up and move around. We have much better ways of distinguishing whether they're editable (smell, taste).
Third being able to see green well has absoultely nothing to do with being able to pick out predators unless those predators are also green. (in fact color is virtualy useless in trying to pick out predators who blend in with shadow and texture, what you want is more Rods to be able to distinguish movement.... hell cows don't even have any cones too see color with)
While the argument we see x coulor because of prey could be a fair argument for some species that have specific prey, it doesn't work that well for omnivores.
Point of fact is the "evolutionary perspective" ain't worth shit when it comes to science. It tends to be done without any real observations, but rather hypotetical and selective senarios that would suggest an advantage or disadvantage which then uses "evolution" as the justification for it.
Anyone can create an evolutionary senario to give an explaination for an observed phenomninom, but it's no more than fiction until they have evidence and observations for the full spectrum of circumstances sorrunding proposed evolutionary change.
Your argument would be better made if you took a selective animal that hunts a certian color prey. But we're omnivores/scavangers and that pretty much screws everything over.
Anyrate here's some info on other animals and the colors they see (makes you wonder why squirles can see blue and yellow.)
http://askabiologist.asu.edu/research/s
Your eyes (and mine) "suck" at blue for two very clear physiological reasons:
1. Very few blue-sensing cones. Your retinas have two kinds of light receptors. There are "black and white" light intensity sensors called rods, and color-sensitive sensors called cones. Of the cones, only a few (something like 1% or 2%, I don't recall exactly) are sensitive to blue light, while the rest are sensitive to either red or yellow-green.
2. Blue-sensing cones are outside the fovea. The part of the retina that we depend on for sharp detail is called the fovea, and it's densely packed with red and green cones. The blue cones are outside the fovea, and therefore not so good for viewing sharp detail.
Interestingly, your eyes also suck at red under some circumstances. The aforementioned rods don't provide color information, but they are nevertheless more sensitive to some wavelengths than they are to others. Rods happen to be incredibly sensitive to short (blue) wavelengths, but they're not at all sensitive to longer (red) wavelenths. (Now that I think of it, many black and white photograhic fims also have this characteristic.) That's why astronomers and other people who need to maintain their night vision light their work area with red light. That's also why you can see faint blue and white stars on a dark night, but you have a hard time seeing relatively brighter red stars. And finally, that's why stagehands use red lasers to target spotlights -- the audience just doesn't notice the red dot that appears a second or two before the spotlight flicks on.
My school's web filter has everything from images.google.com listed as pornography.
Browse at -1, because trolls are often the most creative part of
Yes there is evidence that we developed blue sensitivity last, say 10,000 years ago or so. But that's not necessarily why greeks and bible writers would describe things differently. Color blindness, for example, is fairly common among men and, guess what, the most common form is the inability to see blue.
Clear, Dark Skies
that's the most fucking stupid pro evolution comment i've ever heard.
We suck at seeing blue because, of the three kinds of cones in the retina (most sensitive to red, green, and blue) light, we have far fewer of the blue kind than the other two. The two kinds of red/green color blindness do not impair visual acuity because the pigment from red cones is used in the green cones, or vice versa; so all the cones are still useful, but all respond to the same thing. There is a very rare form of color blindness in which (it is suspected) the blue cones have no pigment at all. Because there are so few blue cones, even though they are completely useless, vision is not harmed much.
You can read more here.
Buy both, and use PSP only to compress images?
GIMP also allows control of subsampling ratios independent of the DCT scalefactors. Use Photoshop Elements ($100) to do those few things to your images that GIMP can't do, and then save them as 24-bit PNG. Then use GIMP to fine-tune JPEG compression.
Photoshop is priced beyond the grasp of mortals. PSP uses the same filters and costs $100
I thought Adobe Photoshop Elements (that is, Photoshop without prepress features) cost 100 USD as well.
the chroma subsampling control is just one feature I use a lot.
GIMP's JPEG writer has a GUI for controlling chroma subsampling as well.
Hah!
Try looking at it through glasses.
Unless I am looking at it exactly head-on, the lines of text are not aligned on the left-hand side.
This is due to chromatic abberation of the lenses, and is much more pronounced in the newer, thinner lens materials.
In fact, I noticed a severe change when I switched from thicker glass lenses to the thinner plastic (polycarbonate) ones.
It took a while for the color fringing, which occurs everywhere except in the exact center of the lens, to be less distracting, and I'm still not used to it.
The other thing that I've noticed is that when red text is on a blue background, or vice versa, they seem to be different distances away (a kind of 3-D effect).
This seems to happen whether or not I am wearing my glasses, and even if I am looking at the text with one eye closed.
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
This article started me on one of those "Slashdot sucks" rants. So human eyes are weak at the blue part of the spectrum. Big news I guess. They've only been selling blue-blocking glasses since forever ago. Then, on the site, we have this one example picture which contains hardly any colors at all - it's all white, gray, and a little bit of skin tone, which contains very little blue, which is why the movie industry uses blue screens, and this somehow constitutes "incontrovertible proof" that the human eye doesn't use its rare blue receptors to resolve edges. Color me (get it? ha ha) unimpressed. IANAO*, but your eyes suck at ultraviolet, too. Anyway, so the site says we (as consumers of DVDs) are being "bilked" because the compression scheme takes away the resolution of the blue channel, which we don't really notice anyway. What's next, being "bilked" out of high frequencies with mp3s? I'll be sure to mention this so whomever I'm talking with next, just to lord some technical knowledge over them. That will prove I am superior! In any case, good thing Slashdot is green, or I wouldn't be able to read that logo in the corner.
*I Am Not An Opthalmologist
The page that demonstrates the effects of a noisy blue channel contains an error: DVD doesn't encode video in RGB. MPEG uses a YUV color space, in which there's a luma component, encoding the light intensity, and two chroma components, encoding the color. Typically, the chroma channels are encoded at half the resolution of the luminance. While working with MPEG encoders and decoders I got to "experiment" with the luma channel (read: I had horrible bugs that kept it either at its minimum or maximum intensity), and the chroma channels look very blurry, and hardly recognizable when displayed on their own. They obviously carry a lot less information than you'd guess.
So, how much better is PAL than NTSC?
:)
And another interesting question - why is it that a lot of (even really cheap stuff) PAL-gear can also play NTSC, but not the other way around?
I live in Australia, got 2 DVD players that can output into either NTSC 3.58 (proper NTSC) NTSC 4.43 (bastardized NTSC for Semi-NTSC compatble TV's - uses the PAL subcarrier I believe) and PAL. The TVs are also capable of the same, and quite a few dvd's sold here are REGION4 - NTSC.
Oh, and yes - there is a noticable difference. To me NTSC simply looks like a PAL TV with the sharpness control turned right down or the focus out a bit. The colours also look a little more drab and not as vibrant. Is that a pretty good laymans comparison?
You have to focus on different colors differently because red, green, and blue light are all different wavelengths and therefore are refracted slightly differently by your eye (shorter wavelengths, i.e. blue, refract more, longer wavelengths - red - refract less). You have to focus closer in on a red light than a blue light for it to be sharp, if you can even do so.
Something I don't understand is that blue light seems to exaggerate my mild astigmatism; I have a Logitech mouse that drives me crazy if I try to focus on the blue taillight. Red lights I can focus on quite clearly and from further away (I am also nearsighted) than any other color lights.
Fun related trivia bit (and forgive me if this is common knowledge):
If you have a decent old 35mm SLR camera with a normal lens (other lenses may have this too) look at the focus ring. There is a marker for where to line up the focus ring in normal conditions, and then there should also be a little red dot a fraction of an inch to the side of it to show where to line up the ring when shooting on infrared film. You have to focus the lens closer for infrared than for visible light, because longer wavelengths refract less.
This is all related the prism rainbow effect, too.
The slow merging of HDTV and film technology is pushing to eliminate subsampling and Y'CbCr (YUV) color space entirely. George Lucas, after shooting Episode II in 4:2:2 Y'CbCr, insisted that Sony develop 4:4:4 RGB equipment for Episode III.
I *hope* this will continue to the point where Y'CbCr can be dropped entirely (there isn't much use for it aside from chroma subsampling), as well as interlacing. These things cause serious problems in computing... Every time you see stair-step artifacts, improper telecine, mis-matched black levels, banding in gradients, or black rectangles in screenshots of media players, you can thank interlacing and Y'CbCr color space.
(but they *are* quite effective as compression algorithms, and also clever hacks, in their time - how *else* are you going to send full-color motion video in 6MHz of radio bandwidth using 1950's technology?)
... look too hard for evidence of evolution in the Bible; you'll strain your eyes.
I have one odd little hobby... I collect foreign language dictionaries. One of the funny things you notice when you browse through languages is that the less "sopisticated" ones have fewer color words. Some of the lesser-known tribal languages have one word that stands for both blue and green, because the difference is really not very important to the average guy living way out in the middle of nowhere.
The more urban/technical a culture is, the more words for color the average person knows.
Does your blue vision suck? Pop some Viagra!
Oh, I think we've got decades of Y'CbCr to look forward to. it's really an advantageous format in a lot of ways.
First, a 4:2:0 Y'CbCr is half the bandwidth of 4:4:4 RGB. We're a long way away from having half the processing power required, bandwidth, storage, etcetera simply not mattering. My RAID is 2 TB formatted, but I regularly have projects that take up over 50% of the space.
Second, Y'CbCr is a better native space for video processing, since the channels align better with what we want to filter. Luma filters like gamma or contrast are more than 3x faster in Y'CbCr than in RGB, since only one channel needs to be processed. Saturation is more than 6x faster in 4:2:0, since only two channels, each at 25% bandwidth, need to be processed. Plus a lot of filters have to convert from RGB to another color space to run. Y'CbCr is closer to those other spaces, and often doesn't require any conversion. You can say whatever you will about Moore's law, the difference between 4 and 8 real-time layers will matter for a while. Even the audio guys, who have it a lot easier, still run into performance limits with enough simultaneous tracks and such.
Lastly, our entire video infrastructure is build around subsampled Y'CbCr. Never underestimate the lock-in of standards like this. If computer people couldn't kill interlaced video in HDTV, they're never going to kill subsampling for lots of applications. Color video has always been Y'CbCr, and that's how everyone works and thinks for decades now.
That said, Hollywood is likely to pick a >8-bit RGB solution for digital projection. For digital projection, bandwidth is a non-issue, and quality, and quality like that of film. Film guys live in RGB. Plus, it's a win for that industry to have digital cinema be as INCOMPATIBLE with consumer digital video tech as possible, in order to reduce the ease of piracy, and to maintain an advantage of the theatrical experience over home theater.
FWIW, I'm a member of the SMPTE groups working on both video compression and digital cinema.
My video compression blog
Now I know the truth.
Albuquerque PC
I agree. This guy isn't a professional in this space. He makes a lot of the assumptions and errors I made five years ago. But they're smart errors and assumptions, and I'm sure he'll find the Slashdot experience a great way to get all your errors pointed out quickly :).
He really hasn't done the math to realize the advantages of Y'CbCr are more about bandwidth reduction, interoperability with existing color video technology, and easier signal processing. While we certainly could build an RGB DVD player for roughly the cost of a Y'CbCr one, it'd only get half the run time, and would look worse on standard television (only VGA is natively RGB for signal).
Full agreement on Macrovision. Like most CD audio protection, it's the kind of copy protection that irritates users without providing any effective deterrent against skilled pirates.
My video compression blog
Sometimes when watching stuff frame by frame like certain kinds of animation, I can see the color appear in a place on the screen before the rest of the stuff gets there. This is especially noticeable on something like South Park when a bright character moves a good bit from one frame to the next.
The hardware here is a Sony satellite receiver and a 4 year old standalone Tivo. That's how I can do the frame advance stuff. I'm pretty sure it's not the Tivo, since it can be detected even when looking at "raw" video off the back of the satellite box.
So, is this another MPEG decoder problem like the 'chroma upsampling error' linked from the bottom of this page, or just something stupid with Sony and/or Directv?
I'm sure this causes the video to look blurred when it's moving at the normal speed, since half of the picture data is getting there 1/30th of a second before the rest fills in behind it. Ugh.
heh learn something every day, didn't even think of that.
Load up that guy's link again and take off my glasses (granted I have to damn near paste my nose to the screen to read it but that's not the point here) much of my difficulty focusing goes away.
It's still there a bit, but it's much less pronounced.
One of my coworkers used to tell me that NTSC stood for "Never Twice the Same Color". Didn't find that very funny until today.
"Derp de derp."
... so my vision just sucks, you insensitive clod!
- I post anonymously so you don't have to.
Cool article on Blue. I will have to read the rest of your Website as it seems rather interesting. It's cool to see sites and research by regular folk like this.
"If you are a dreamer, a wisher, a liar, A hope-er, a pray-er, a magic bean buyer
Remember, when you videotape Santa coming down your chimney, remember his red suit is comprised 4 parts Luminance, and 1 equal parts U and V.
...and they still won't stop talking about TV systems on slashdot *disapears down the student union*
The reason there's so little blue visible is that there's so little blue in that picture.
Of course it doesn't make a difference if you blur the blue, because it's already 20 dB down from the other colors.
I'd like to see this with calibrated images.
(note I have 15 years doing TV hardware and software - I have a little experience in this field) ...
My main complaint with his pages are that he busts on component video (vs. RGB) because of macrovision - they're really two different things (you can but MV on RGB BTW). The main reason component exists (YPrPb) is because color TV has always worked that way (YIQ/YUV) these are all color spaces that have a luminance component (Y) basicly the brightness and a color vector component (PrPb/UV/IQ) and they use a lot more bandwidth for the Y - because that's where all the usefull information is. Component is basicly just the native color space (tweaked a little) coming out of MPEG/DVD/analog TV - by convention this is done in the TV.
Actually there are few interesting video artifacts he gave very short shrift to - dot crawl which is caused by the NTSC color subcarrier being dropped over a hi freq portion of the luminance signal so that it overlaps - if the rate of change along a scan line is too fast then it stomps on the color SC and changes the color of the spot on the screen - it means you can't do alternating black/white pixels on the screen and as a result you can't do test well. It also means you can wear clothing on US TV with fine detail - fine stripes, checks, tartans etc Before color TV people wore checked ties, houndstooth jackets etc etc - all that stuff went away because people don't see it being worn on TV and so don't consider it stylish - everything's all solid colors
A similar artifact is cause by the low refresh rate - the eye can't really see 60Hz but a single pixel high horizontal line only appears on every other field in an interlaced screen and flickers like mad at 30Hz (another reason why fine text doesn't work).
Secondly NTSC's color gamut sucks - you can't both represent skin tones and saturated colors - so you don't really see bright colors in american TV. PAL is different - try watching the green grass on a golf game some time - it's a mixed blessing though, PAL systems tend to have much more garish advertising - lots of bright oranges that you just can't see in the US:-(.
Finally a word about MPEG (ie DVD and digital cable or TV). Sadly they kept the luminence gamma correction that was originally put into the original B/W TV systems to reduce the cost of the TV sets - vacuum tubes are not really linear beasties rather than adding a circuit to fix this in each set they just put the circuit in back in back at the studio. That was a good idea in it's time but it results in compression of luma in a such a way that when the signal is digitized to 8 bits there are far fewer codes available to represent dark colors than bright colors - this results in banding artifacts (often the color is off for this reason) in dark scenes (check out Blade Runner on DVD some time - the dark scenes with smoke in them are a great example). I predict that in the future directors will avoid these sorts of dark scenes because they will know that they don't do well on the later DVD release (in much the same way no one wears checked ties any more)
Hehe, I was watching a SECAM signal two days ago from the Atlantic Bird satellite at 5W. It's HORRIBLE. Even a slight bit of ghosting will mess up the colour. Not to mention the colour resolution is very low. NTSC is better. I've read that even in countries that use SECAM (France mainly) they use PAL for all there production. It's only ever converted to SECAM at transmission.
.. has anyone noticed that different colours can appear to be at different distances? On a few TV's with teletext the colour blue always appears to be deeper into the screen than red.
On another note
Could just be my eyes, or the TV. Maybe blue really *is* deeper in the screen?
*shrugs*
My goodness, it's Christmas day and I'm talking about television standards!
And what are your impressions of "little Asian she-boy" based on?
I guess you're either the absolute rawshawk for human behavior or incredibly dumb (and angry).
One guess at which one's more likely.
The difference you're seeing with glasses is due to the ABBE number of the materials.
Glass has the best ABBE numbers , but most people these days go for plastic lenses. The cheap CR-39 lenses actually have the best rating of the plastics, but they're also big, thick, and heavy. My guess is that a lot of people are wearing polycarbonate lenses, because they're light, have a relatively high index, and are VERY impact resistant. Downside? Really crappy ABBE number. I just switched to trivex lenses which have a slightly better ABBE number and there is a noticeable difference. (similar to polycarb in safety and thickness, can be drilled for rimless frames, but much better lens characteristics)
I hope people can see this.
Since we suck at seeing blue, couldn't the blue bit depth be reduced in the video codec? Or even a indexed blue pallete with less colors?
That would make for better video compression right?
You've got to be joking. She looks like some ugly little Asian she-boy.
I guess, you have never seen a real little Asian she-boy, have you? (NSFW)
Future Wiki -- If you don't think about the future, you cannot have one.
Hey I thought the people on slashdot were at least somewhat immune to beeing led to think with their other brain, and all it takes is some moderately hot chick on a car to make everyone look at the pictures instead of the text?
DVDs use YUV (or YPrPb, I forgot which one, but for they are close enough) colors, just as JPEG does, to have a look at the results of this, open traci.png in gimp and do Image/Mode/Decompose/HSV, which is almost the same as well.
I've been in the TV postproduction business for the last umpteen years, and here it's a given that Charles Poynton knows more than you & I when it comes to video & color.
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
this is why i read at -1.
No, it's due to the phosphor or LCD strips on your monitor actually not putting red, green and blue right on top of each other. (Which is what subpixel rendering tries to take advantage of.)
Im sorry, but "4:1:1" and "4:2:0" are the same thing
As I understand it, 4:a:b means that even lines have a chroma samples for every luma sample, and odd lines have b chroma samples for every luma sample. Thus, 4:2:0 is JPEG/MPEG resampling (halved horizontally, giving the 4:2, and halved vertically, tossing out half the lines' chroma entirely and giving the :0 at the end), and 4:1:1 is another kind of resampling (chroma decimated to one-quarter horizontally in both even and odd lines).
Highly compressed JPEG images become blocky, rather than blurry. Humans are far more tolerant of blur than of edge-like artifacts.
JPEG2000 fixes this. Its wavelet basis doesn't have sharp edges, allowing the data reduction to be pushed quite a bit harder with less annoying signal degradation.
I just realized that my Panasonic TU-DST52 HDTV tuner has the interlace vs progressive chroma streaking problem. One of the channels (the local Austin WB station) is apparently being broadcast in progressive, because both the main channel and the second channel (a weather radar) show evidence of the chroma being decoded to the wrong scanlines. I don't know for sure, because the tuner doesn't tell anything about the resolution of the MPEG2 stream, but I'm clearly seeing the effect shown on the page that was linked from the article.
#naabhaprzrag, #sverubfr-000, #agi-fcbafberq, negvpyr[pynff*=' negvpyr-ary-'] { qvfcynl: abar !vzcbegnag; }
I just wanna see more of Traci!
I once read somewhere that the perception of blue (a fairly high frequency of light, correct?) may be a recent development in human evolution.
I think that one piece of evidence was that in ancient Greek writings, the sky and the Mediterranean are both referred to as gray, or wheat-colored, or something like that.
I'm not sure whether I buy it, but if it were true it would be pretty interesting.
Try clarifying that DVD Video and game FMV are stored as [Y, R-Y, B-Y], where R-Y and B-Y are downsampled by a factor of two in each direction, and B-Y might actually be blurred a bit more before decimation so that more of the higher-order DCT coefficients collapse to zero. Blurring B-Y would have nearly the same perceptual effect as blurring B.
I just noticed something. I printed out the pages in greyscale and in fast mode. I then read the article and checked out the pictures. The "blue" picture doesn't look messed up there either. It almost seems like the software and/or hardware used to make the images is actually at fault, not your eyes. Print it out in grey scale and take a look!
I remembered that the most common form is called "red/green" but for some reason I misremembered "red/green" as meaning "can only see red and green".
Thanks.
Clear, Dark Skies
post more traci pics! I don't know why she had to take her shirt off for the picture, but i'm certainly not complaining!
There is _very little_ difference between them.
Taking the 525/625 line stuff aside...
PAL is better described as NSTC-PAL - it's a NTSC drivative.
What are the changes?
1: The chroma signal carrier is suppressed apart from synchronisation bursts.
This reduces transmit power - The information is in the sidebands and those are still transmitted.
2: The phase of the chroma signal is inverted every other line.
This takes care of the colour shifting problem on broadcast signals. If you look closely on a ghosted PAL signal you will see colourshifts on each line but from normal viewing distances they cancel each other out.
I have seen 625 line NSTC signals and 525 line PAL - these _are_ real broadcast standards, if somewhat wierd.
In addition, the effect is several phosphor groups wide, so it can't be due to simple phosphor displacement anyway.
(and it's not due to possible misalignment of the RGB electron guns, because a white line on a black background looks pretty solid on my monitor (except for a very slight fringe due to the phosphor displacement that you mentioned).)
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
Consumer NTSC sucks. Broadcast NTSC is fookin amazing. I worked at Sony Canada in the broadcast center for a while and seeing video come off a D2 deck into a DVM monitor you'd never recognize it as NTSC.
I also found a non NTSC HDTV VTR and monitor in the back room that was in for repair from the National Film Board and loaded a tape and pressed play. MY GOD! The color bars at the beginning were so crisp you could have cut them with a razor blade.
This was 1991. I note with disgust HDTV is still not out some 13 years later; widescreen NTSC doesn't cut it, sorry.
Disclaimer: if you see commercials on CBC that's my software that compiles and plays those dub reels to air. But don't look at me I don't watch TV.
Need Mercedes parts ?
And wern't really terribly significant to the overall evolution of man in the big scheme of thigns.
Smithsonian magaznine once ran an article on exotic fruits (cherimoya, starfruit etc) and the next months issue had a letter from an irate redenck asking them why they did this and didn't run an article about AMERICAN foods. The magazines response was that the only native America foods were blueberries, cranberries and jerusalem artichokes.
Actually I think there were 5, but don't rememeber the other two (and am not really sure cranberries was actually one of them).
Need Mercedes parts ?
I once went to a public toilet in city, and noticed it was lighted with blue light.
I heard the purpose of that is to make the veins in your arms invisible so drugs users couldn't inject drugs.
Breasts, dick... best of both worlds. :P
I think this is due to the fact the the blue content of the image is rather low in detail. Really depends on the choice of picture..Anyway, the fact the we are so bad at seeing blue is because nature does not have a lot of stuff that would require good blue vision. We are really good at green, which happens to be the color of plant..not surprising.