This article starts off well , with a relatively sane (for audiophile-speak) statement of what good upsampling can and cannot do:
http://www.pstracks.com/av/ham-fisted-upsampling/ (http://www.pstracks.com/av/ham-fisted-upsampling/)
but then we get to David Chesky on the defense against accusations that his HDtracks download service is doing 'ham fisted' or pointless upsampling:
David responds. “Why do we sell hi res files at 192/24 when there is no musical energy up at 96khz? Lets look at it like this. In the current state of digital technology we do not have A/D chipsets that work at 44.1/16 that do not have pre and post ringing. This ringing destroys the music in the audio band. Audiophile labels do not record at 192/24 to try to capture what many think is air up over 50K. They do this as to keep the nasty anti-aliasing digital A/D filters as far away from the audio band as they can. This insures less corruption down where the music is. The sound becomes much more analog and relaxed. Think of pre and post ringing like this. You are riding down a street in a Ferrari at 180 MPH over a cobblestone road and someone gives you a camera and ask you to take some photos out of the windows. All these little cobblestones will cause bumps and the camera will not be steady and you will loose the focus. This is what happens in current A/D conversion as well at 44.1/16. Doubling or quadrupling that rate helps smooth the analogous ride."
Emphasis mine.
See any listening test data in there anywhere?
Nah, me neither. Nor any reason why 192kHz versus , say, 96 or 88.2*. Just another inane analogy to sports cars and cameras.
It never ends, does it?
* (if I recall my Dan Lavry whitepapers correctly, the possible negative effects from pre- and post-ringing are taken care of at a SR of ~60kHz)
* (if I recall my Dan Lavry whitepapers correctly, the possible negative effects from pre- and post-ringing are taken care of at a SR of ~60kHz)
Not to mention that even going to 60kHz is irrelevant for distribution and playback. An oversampling DAC avoids the issue directly, even for 44.1kHz.
David's response = audiophile FUD and a weak attempt to distract from their mistakes
This article starts off well , with a relatively sane (for audiophile-speak) statement of what good upsampling can and cannot do:
http://www.pstracks.com/av/ham-fisted-upsampling/ (http://www.pstracks.com/av/ham-fisted-upsampling/)
but then we get to David Chesky on the defense against accusations that his HDtracks download service is doing 'ham fisted' or pointless upsampling:
David responds. “Why do we sell hi res files at 192/24 when there is no musical energy up at 96khz? Lets look at it like this. In the current state of digital technology we do not have A/D chipsets that work at 44.1/16 that do not have pre and post ringing. This ringing destroys the music in the audio band. Audiophile labels do not record at 192/24 to try to capture what many think is air up over 50K. They do this as to keep the nasty anti-aliasing digital A/D filters as far away from the audio band as they can. This insures less corruption down where the music is. The sound becomes much more analog and relaxed. Think of pre and post ringing like this. You are riding down a street in a Ferrari at 180 MPH over a cobblestone road and someone gives you a camera and ask you to take some photos out of the windows. All these little cobblestones will cause bumps and the camera will not be steady and you will loose the focus. This is what happens in current A/D conversion as well at 44.1/16. Doubling or quadrupling that rate helps smooth the analogous ride."
Emphasis mine.
See any listening test data in there anywhere?
Nah, me neither. Nor any reason why 192kHz versus , say, 96 or 88.2*. Just another inane analogy to sports cars and cameras.
It never ends, does it?
* (if I recall my Dan Lavry whitepapers correctly, the possible negative effects from pre- and post-ringing are taken care of at a SR of ~60kHz)
Consider the source. For another audiophile recording source that has gone off completely into the weeds, please see Mapleshade records:
Audiophile recordings and Tweeks, all in one online store! (http://www.mapleshaderecords.com/index.php)
Consider the source. For another audiophile recording source that has gone off completely into the weeds, please see Mapleshade records:
Audiophile recordings and Tweeks, all in one online store! (http://www.mapleshaderecords.com/index.php)
Wow...
The Mapleshade Records website features free MP3 samples and downloads. You'll be very pleasantly surprised by the sound quality of these MP3s, probably the best sounding 128k MP3s you've heard any where on the net. They are encoded with a Mapleshade proprietary signal path and process that we call Maplestreaming, a process that yields startling dynamics, stereo detail and a wonderfully resolved sound stage with ambience and depth you'd never expect from an MP3.
Wow...
The Mapleshade Records website features free MP3 samples and downloads. You'll be very pleasantly surprised by the sound quality of these MP3s, probably the best sounding 128k MP3s you've heard any where on the net. They are encoded with a Mapleshade proprietary signal path and process that we call Maplestreaming, a process that yields startling dynamics, stereo detail and a wonderfully resolved sound stage with ambience and depth you'd never expect from an MP3.
Just another commercial trick. They have encoded mono-like easy-compressible source into 128 kbps. Scam.
Upsampling does not remove the need for a sharp filter. The upsampling itself must use that sharp filter. So what are they talking about here? Allowing aliasing, and by doing that making the interchannel time resolution worse?
David responds. “... Think of pre and post ringing like this. You are riding down a street in a Ferrari at 180 MPH over a cobblestone road and someone gives you a camera and ask you to take some photos out of the windows. All these little cobblestones will cause bumps and the camera will not be steady and you will loose the focus. This is what happens in current A/D conversion as well at 44.1/16. Doubling or quadrupling that rate helps smooth the analogous ride."
So what would the doubling or quadrupling be in the Ferrari analogy? Driving 720 mph instead of 180? What a stupid comparison. What he actually describes is a visualization of dither*... which can be a good thing...
Just another commercial trick. They have encoded mono-like easy-compressible source into 128 kbps. Scam.
The tao1.mp3 demo on that page is quite stereo, but more than 95% of the time the bandwidth is limited to 13 kHz. Probably audibly low-pass to quite a few people when compared to the lossless source.
Chris
* or recording noise in general
Upsampling does not remove the need for a sharp filter. The upsampling itself must use that sharp filter. So what are they talking about here? Allowing aliasing, and by doing that making the interchannel time resolution worse?
Wow, I never thought about that little twist! ;-)
I guess the answer to your question is that upsampling is a way of making the playback of a file less dependent on the quality of the brick wall filter in the playback device. The brick wall filter in the upsampler tends to supercede the brick wall filter in the playback device since the latter generally is at a far higher frequency.
Wow, I never thought about that little twist! ;-)
I guess the answer to your question is that upsampling is a way of making the playback of a file less dependent on the quality of the brick wall filter in the playback device. The brick wall filter in the upsampler tends to supercede the brick wall filter in the playback device since the latter generally is at a far higher frequency.
I doubt the upsampling algorythm is using a lowpass with far higher frequency as the build in the DAC one. I even wonder if many of these upsamplers use lower corner frequencies as a default DAC when decoding 44.kHz to prevent any pre-ringing.
You shouldn´t also forget when you upsampled lets say from 44.1 to 96kHz that besides the ~20kHz in the upsampling routine another lowpass is applied in the DAC at ~40kHz at playback.
So with upsampling you trade the single 20kHz LP in the DAC for 44.1kHz material against a 20kHz LP in the upsampler + a second LP in the DAC at higher frequency.
Wow, I never thought about that little twist! ;-)
I guess the answer to your question is that upsampling is a way of making the playback of a file less dependent on the quality of the brick wall filter in the playback device. The brick wall filter in the upsampler tends to supercede the brick wall filter in the playback device since the latter generally is at a far higher frequency.
I doubt the upsampling algorythm is using a lowpass with far higher frequency as the build in the DAC one.
I wouldn't expect a higher corner frequency, but I might expect a better filter as regards to in-band ripple, sharpness of cutoff, phase and therefore impulse response, etc.
I even wonder if many of these upsamplers use lower corner frequencies as a default DAC when decoding 44.kHz to prevent any pre-ringing.
You can read all about that, as illustrated by real world examples, here:
Sample rate conversion technical tests (http://src.infinitewave.ca/)
You shouldn´t also forget when you upsampled lets say from 44.1 to 96kHz that besides the ~20kHz in the upsampling routine another lowpass is applied in the DAC at ~40kHz at playback.
So with upsampling you trade the single 20kHz LP in the DAC for 44.1kHz material against a 20kHz LP in the upsampler + a second LP in the DAC at higher frequency.
[/quote
The effects of the 48 KHz brick wall on operations at 22 KHz should be pretty small.
I think there's two different issues.
The first is taking a 44.1kHz or 48kHz digital recording, and upsampling it, and then charging people for the privilege. Well, if you tell them what you've done, why not? Let them decide whether they want to pay you for that service, or buy the CD and upsample it themselves, or just play it as normal (which will oversample it anyway!). Whereas if you claim your result is somehow natively 96kHz or 192kHz or whatever, it's a scam. Plain and simple.
The second is taking an analogue recording, and digitising it at whatever sample rate. The analogue recording itself may have little content above 20kHz. Again, if the provenance of the recording is made clear, that's fine. Whereas if you pop a brick wall LPF at 20kHz, this again is a scam IMO.
I've put aside whether or not it sounds better - the point is, if higher sample rates could sound better, to you or a bat or whatever, then when people sell "hi res audio", it should have the potential to offer this advantage.
Unless of course the whole thing is a placebo induced con - in which case you can take the analogue output of a $99 CD player, re-digitise it at 192kHz/24-bits, sell it as HD, and it'll sound better to the purchaser.
Cheers,
David.
You can read all about that, as illustrated by real world examples, here:
Sample rate conversion technical tests (http://src.infinitewave.ca/)
Not conclusive and lets open what filter you prefer, Aliasing over Pre-ringing or other evils that are non-issues, like always. And imagine the 44.1KHz version was downsampled already. What kind of filter did they use? If i apply the same filter again, may it hurt or clip?
I better trust the DAC designer that he chooses a LP in the DAC itself that doesn´t cause to much side-effects.
The first is taking a 44.1kHz or 48kHz digital recording, and upsampling it, and then charging people for the privilege. Well, if you tell them what you've done, why not? Let them decide whether they want to pay you for that service, or buy the CD and upsample it themselves, or just play it as normal (which will oversample it anyway!). Whereas if you claim your result is somehow natively 96kHz or 192kHz or whatever, it's a scam. Plain and simple.
Like they tried to sell High bitrate/kHz stuff here until a customer noticed the content ended sharp at ~22kHz. After complaining the studio admitted to use that for sonically reasons for preventing to "distort" the electronics behind with to high content. LOL!
http://www.computeraudiophile.com/Kent-Poo...ogue-III-Review (http://www.computeraudiophile.com/Kent-Poon-Audiophile-Jazz-Prologue-III-Review)
It's hardly any surprise that there's almost no-one left who gives a damn about this (high resolution audio, I mean).
People say "oh, the kids have got used to mp3 - they don't know what high quality sound is, or care".
B*ll*cks!!!!
People have been watching SD video for years, and when they see HD, they mostly go "wow" and save up to buy a nice big TV. They never go "oh, I've got so used to low quality low bitrate SDTV that I really don't need HD".
The reason they don't go "wow" with HD audio has nothing to do with mp3 or not caring - it's because there's nothing to say "wow" to. High resolution audio fixes a problem that either doesn't exist, or (at best) is very small.
When you think of all the wonderful things the audio industry could be doing (better transducers, "you are there" binaural, holographic multi-channel etc), and then see people selling upsampled 2-channel audio as "the next big thing", well... it makes me so angry! (you'd never guess, would you? )
Cheers,
David.
B*ll*cks!!!!
I second that
Really depressing when for example 2 titan´s of self-proclaimed diamond ears start to argue what sounds better. More kHz or more bits?
It may be fun to read all the superlative word-creations when reading such threads but when reading this at many places more and more often makes me really fear of what comes next!!
The reason they don't go "wow" with HD audio has nothing to do with mp3 or not caring - it's because there's nothing to say "wow" to. High resolution audio fixes a problem that either doesn't exist, or (at best) is very small.
Hmm, makes me think. CD audio is 30 years old. Which other media technology for consumers from the early 1980s is still being used today? VHS? Compare how far we've come in 2D video (VHS -> Full-HD BluRay) and stereo audio (CD -> lossly compressed CD )
Isn't CD stereo audio actually the equivalent/counterpart of 2D Full-HD video? The CD specification was ahead of its time (or video far behind). I think the recording industry tried for years to come up with much-better-than-CD stereo sound in order to keep the market alive. Even though they failed again and again, some still try, like Chesky records.
I fully agree with David, what's still missing is "you are there" binaural sound over head- or earphones. Convincing surround sound
for-here or
to-go, so to speak The keys to that are not 24 bit or 96 kHz. It's listener motion tracking and coding
more than two channels, or even a channel-number agnostic approach to surround sound coding.
I hope the music industry will have realized this before I'm old and deaf...
$0.02 from Chris
...
I fully agree with David, what's still missing is "you are there" binaural sound over head- or earphones. Convincing surround sound for-here or to-go, so to speak The keys to that are not 24 bit or 96 kHz. It's listener motion tracking and coding more than two channels, or even a channel-number agnostic approach to surround sound coding.
I hope the music industry will have realized this before I'm old and deaf...
$0.02 from Chris
Why do you think that some people are willing to pay for "3D" tvs and Bluray players, and wear silly glasses? Why wont they do the same for audio?
-k
I'm not against surround sound or any other approach to realism, but I have no enthusiastic longing either. I have no place for a proper multi-speaker setup and I suggest that only a very small, mostly wealthier part of the population does either. I don't see any way for that to change for the better.
I do have a two channel setup that produces a half way decent stereo field. There is frequently a spread of performers across the room, and occasionally some obvious depth. The image of a few (very few), recordings seem to be wider, and occasionally deeper, than the room. Results are very dependent on the material being played.
I have some evidence that more is possible with the hardware I have, but there is no practical way to realize it. I cannot dedicate a suitable room, or any room, to the configuration and specialization necessary to achieve it.
My limited stereo setup is definitely more enjoyable (to me, anyway) than the haphazard arraignment used by about 98% of the population. I've occasionally pointed out the deficiency but gave up doing so years ago. Response were either disinterested or "I know, but ...", indicating that the equipment being convenient out of the way (with the speakers close together, or even pointing away from the listener) had an overwhelming priority. This also applies to people who have spent significant money on "theater" or "surround sound" systems.
I think the vast majority of people don't even know what stereo really is. I've had a couple or so, well educated to the convention standards and far from indigent, freeze in open mouthed surprise upon hearing the instruments of a recording coming from different, distinct positions in my modest front room. It was their first such experience.
But I've also heard some amazing recordings on headphones. Perhaps this is my general ignorance coming through, but a few made-for-headphone-listening binaural recordings I've purchased have not been particularly impressive. On the other hand, I've heard a few others that have.
One in particular I found on line some years ago was made on a minidisk player/recorder by someone walking down an alley. I don't recall if there was more information on technique provided, but there was nothing used that was not readily available years ago in the hardware. This was true surround, with sounds coming from ahead, behind, to the sides, and from above, all very clearly placed.
Like they tried to sell High bitrate/kHz stuff here until a customer noticed the content ended sharp at ~22kHz. After complaining the studio admitted to use that for sonically reasons for preventing to "distort" the electronics behind with to high content. LOL!
http://www.computeraudiophile.com/Kent-Poo...ogue-III-Review (http://www.computeraudiophile.com/Kent-Poon-Audiophile-Jazz-Prologue-III-Review)
Ugh. I made it as far as the references to James Boyk's and Milind Kuncher's work as evidence for the necessity of >22kHz content in recordings, then gave up.
I'm not against surround sound or any other approach to realism, but I have no enthusiastic longing either. I have no place for a proper multi-speaker setup and I suggest that only a very small, mostly wealthier part of the population does either. I don't see any way for that to change for the better.
Technology progression? Flexible capture/distribution formats that can be presented at any playback venue using speakers etc as best possible. Cheap distributed loudspeaker panels that can be hidden in the decor of the room, or directive "soundbars" that use room-reflections to create virtual sources.
One in particular I found on line some years ago was made on a minidisk player/recorder by someone walking down an alley. I don't recall if there was more information on technique provided, but there was nothing used that was not readily available years ago in the hardware. This was true surround, with sounds coming from ahead, behind, to the sides, and from above, all very clearly placed.
It is sad that we see so little commercial binaural recordings of good content. I know that I am willing to pay, and there have to be some iPod/Phone/Pad users out there who are willing?
-k
I'm not against surround sound or any other approach to realism, but I have no enthusiastic longing either. I have no place for a proper multi-speaker setup and I suggest that only a very small, mostly wealthier part of the population does either. I don't see any way for that to change for the better.
...but that's the problem we should be looking to solve. There are some very convincing ways of making sounds come from locations where there are no speakers. The commercialised versions of this technology are generally poor, but there's great stuff in various universities and research labs (well, there was a decade or more back).
I do have a two channel setup that produces a half way decent stereo field. There is frequently a spread of performers across the room, and occasionally some obvious depth. The image of a few (very few), recordings seem to be wider, and occasionally deeper, than the room. Results are very dependent on the material being played.
But this audiophile beloved trick with stereo is just that: a trick. That's why it falls apart so easily, and is so recording, equipment, and room specific. It is possible to create a wonderful, almost 3D effect with simple mic'd 2 channel stereo - it's very impressive - except when compared with doing it "properly" (i.e. more channels, proper breadth/depth clues, etc) which just blow it out of the water.
My limited stereo setup is definitely more enjoyable (to me, anyway) than the haphazard arraignment used by about 98% of the population. I've occasionally pointed out the deficiency but gave up doing so years ago. Response were either disinterested or "I know, but ...", indicating that the equipment being convenient out of the way (with the speakers close together, or even pointing away from the listener) had an overwhelming priority. This also applies to people who have spent significant money on "theater" or "surround sound" systems.
I think the vast majority of people don't even know what stereo really is. I've had a couple or so, well educated to the convention standards and far from indigent, freeze in open mouthed surprise upon hearing the instruments of a recording coming from different, distinct positions in my modest front room. It was their first such experience.
Yes, most people put their speakers where they will look nice. That said, in 2011, we really ought to be able to make sonically near-transparent speakers that blend into the decor, for a reasonable price.
You've made a point though: good audio is still a jaw-dropping experience. How has the industry failed to commercialise it as effectively as good video?
Cheers,
David.
P.S.
One in particular I found on line some years ago was made on a minidisk player/recorder by someone walking down an alley. I don't recall if there was more information on technique provided, but there was nothing used that was not readily available years ago in the hardware. This was true surround, with sounds coming from ahead, behind, to the sides, and from above, all very clearly placed.
It's quite easy to do with half-decent microphone mounted at the sides of your head. There are two problems:
1) try it with music, and often it's not quite as satisfying or convincing.
2) such recordings sound pretty awful over speakers.
...given how popular headphone listening is, it still surprises me that there's not a "binaural" (or whatever you choose to name it) version in iTunes for various releases.
Why do you think that some people are willing to pay for "3D" tvs and Bluray players, and wear silly glasses? Why wont they do the same for audio?
Good question. I think because
1) you don't have to wear silly additional gadgets to experience 3D audio, just your headphones, maybe with motion sensors built into them. You can do the rest in software.* But it hasn't been done, at least not in an affordable way.
2) the binaural sound is most of the time not convincing for everybody. See also David's post above. Each person has a different head and ear shape, so there's no "standard" binauralization. In principle you'd need a custom binaural profile for each listener (or at least a preset which comes close). See the fine differences between individuals' HRTFs.
Chris
* The same also goes for 3D TV, by the way. Wearing silly glasses is indeed silly. You could do without, as some prototypes have demonstrated.
2) the binaural sound is most of the time not convincing for everybody. See also David's post above. Each person has a different head and ear shape, so there's no "standard" binauralization. In principle you'd need a custom binaural profile for each listener (or at least a preset which comes close). See the fine differences between individuals' HRTFs.
Chris
But my stereo is not customized for my ears, either.
The question is if generic binaural can bring us a significant step towards the ideal compared to regular stereo. Having adaptation to individual head shape and dynamic head tracking would be a welcome refinement.
I guess that our eyes have slightly different inter distance as well, and current "3D" displays show a static viewpoint (no headtracking), still people find it useful. The analogy is not a very good one, but anyways...
-k
But my stereo is not customized for my ears, either.
Doesn't need to be though - it doesn't bypass your head and outer ear.
The question is if generic binaural can bring us a significant step towards the ideal compared to regular stereo.
It needs decent headphones to work well and sound natural, with a known frequency response.
Mismatched HRTFs make it sound very unnatural.
Without head tracking, and without reverb, the image collapses into the head.
Most significantly, lots of music just doesn't sound as fun presented in half-decent binaural compared with a normal mix. The normal mix sounds more immediate and exciting, even over headphones.
I guess that our eyes have slightly different inter distance as well, and current "3D" displays show a static viewpoint (no headtracking), still people find it useful. The analogy is not a very good one, but anyways...
I can't disagree - it's an interesting and reasonable analogy. Then again, we've had binaural and 3D for years (both with varying degrees of technical success!). Now it seems 3D's time has come.
Cheers,
David.
You've made a point though: good audio is still a jaw-dropping experience. How has the industry failed to commercialise it as effectively as good video?
My guess: golden cables make more money so the incentive isn't focused on real quality audio, and given that we're eye-creatures, pretty pictures are a much easier sale than pretty audio.
The same bollocks trend is now emerging for HD televisions. Going from DVD to full-HD is a big step, but beyond that there's little to be gained. I know of a TV that has special yellow subpixels because they supposedly make the image seem more alive over "common" HD. The benefits of a dedicated yellow subpixel are dubious. I expect it's not the last trick to be invented, and before long, we'll have true pure-blood videophiles. When that happens, it's time for hydrogenvideo.org to be registered.
The benefits of a dedicated yellow subpixel are dubious.
Whoa, hold the phone there. If you look at the color rendering space of standard RGB, it can not reach into some of the "yellow" colors. It's due simply to the spectra of the various emitters and the sensitivity of your eye.
Now, in order for it to work, you do need the information sent from one end to the other, and therein is a problem, but the benefits of having a dedicated yellow phosphor that can fill in the rest of the color space (well, except for some very far indigo and red, which are also missing in standard RGB, but they aren't common in scenes either, unlike yellow) do exist IF you have the information to know when to use them.
Whoa, hold the phone there. If you look at the color rendering space of standard RGB, it can not reach into some of the "yellow" colors. It's due simply to the spectra of the various emitters and the sensitivity of your eye.
Now, in order for it to work, you do need the information sent from one end to the other, and therein is a problem, but the benefits of having a dedicated yellow phosphor that can fill in the rest of the color space (well, except for some very far indigo and red, which are also missing in standard RGB, but they aren't common in scenes either, unlike yellow) do exist IF you have the information to know when to use them.
A consumer television is not marketed for the science lab, but for showing pictures off of optical media, tv broadcasts, etc. I am very sceptical about the current value of a "yellow" pixel in that context.
-k
You do understand that the human eye has no yellow receptors? The spectral response of the red and green receptors overlaps, so "yellow" light stimulates both, which your brain interprets as yellow. Your brain gets exactly the same response if the eye is stimulated by red and green together.
The benefits of a dedicated yellow subpixel are dubious.
Whoa, hold the phone there. If you look at the color rendering space of standard RGB, it can not reach into some of the "yellow" colors. It's due simply to the spectra of the various emitters and the sensitivity of your eye.
Now, in order for it to work, you do need the information sent from one end to the other, and therein is a problem, but the benefits of having a dedicated yellow phosphor that can fill in the rest of the color space (well, except for some very far indigo and red, which are also missing in standard RGB, but they aren't common in scenes either, unlike yellow) do exist IF you have the information to know when to use them.
Yes, but then we're heading into the same territory as 16 vs 24 bit, and 44.1 vs 96KHz, aren't we?
But truth be told, I currently don't have an LCD or similar modern TV (this ye olde CRT does just fine; I watch little TV), and the only problems I'm aware of when I see someone else's huge flat TV are hyper-saturation and completely overdriven sharpness. I don't think the subtleties of alleged better yellow detail will be apparent under such circumstances.
You do understand that the human eye has no yellow receptors? The spectral response of the red and green receptors overlaps, so "yellow" light stimulates both, which your brain interprets as yellow. Your brain gets exactly the same response if the eye is stimulated by red and green together.
The tri-stimulus that have been defined as the "official" human response cannot be recreated by most display/printer technology, and certainly not by the common transmission standards. I dont know the exact reason, but it could be that it is hard to design spectral filters with the exact required response - or that the filters that are sharp enough will filter out too much light, resulting in reduced max brightness and power efficiency. I think
Any mechanism that allows a better coverage of the CIE space could/should lead to some improvement in perception - if it is implemented end-to-end.
(http://upload.wikimedia.org/wikipedia/commons/6/60/Cie_Chart_with_sRGB_gamut_by_spigget.png)
-k
Sharp Quattron review (http://www.hdtvtest.co.uk/news/sharp-lc46le821e-lc40le821e-20100628755.htm). Ouch.
The unfortunate truth is that widened colour gamuts have almost no real-world use in consumer TVs.
Yes, but then we're heading into the same territory as 16 vs 24 bit, and 44.1 vs 96KHz, aren't we?
No.
You do understand that the human eye has no yellow receptors? The spectral response of the red and green receptors overlaps, so "yellow" light stimulates both, which your brain interprets as yellow. Your brain gets exactly the same response if the eye is stimulated by red and green together.
Yes, now you do see the color space plotted below,yes?
All I'm saying is that since the human eye has only three kinds of color sensors, it should be possible to combine three monochromatic light sources to produce any color that the human eye can perceive. If your light sources are not monochromatic then there may be some advantage in using more light sources in order to overcome their limitations.
I know this isn't audio-related, and as such not directly subject to TOS#8, but I no longer find graphs all that compelling, especially when my RGB monitor can't even display them.
It seems that there seems to be some confusion that because the Eye "only sees 3 colors" you can represent any color w/ any 3 other colors. This would be true in the conditions that you had very well chosen "other 3 colors" and that they eye only sees 3 colors. However, that interpretation of the eye is rather fundamental and naive. The eye does have 3 different types of chromatic sensors, but these are not just some sort of trivial "it tells you how much red a given color has" sensors. Each sensor will output a value for any given input, and these values vary based on the input light frequency. Shown in this graph are these response curves, color coded to what you typically see people calling the Red, Green, and Blue sensors as defined in the CIE standard (what is most commonly believed to be the most accurate description of color).
(http://upload.wikimedia.org/wikipedia/commons/thumb/8/8f/CIE_1931_XYZ_Color_Matching_Functions.svg/1000px-CIE_1931_XYZ_Color_Matching_Functions.svg.png)
If you have these response curves, you can treat any color as a point in 3-space in terms of these stimulus values (aka, "Tristimulus values"), When plotted in 3-Space, the resulting volume is all visible color. Because this is hard to represent graphically and not frequently needed, color gamuts were introduced to give a 2 Dimensional representation of a color space's expressible range (a color space being the full range of all colors displayable by a device). These basically take a slice through that 3D volume of color in such a way that makes all colors in that plane have the same brightness, so only chromaticity is displayed. The pictures posted above are graphical representations of 2 color gamuts. The outer, horseshoe shaped one (which really can't be colored correctly on a monitor, or even in RGB space itself) is the CIE color space, or, all colors that the normal human eye can see.
edit: since your monitor can't actually display many of the colors, a more accurate representation of this gamut may be this:
(http://upload.wikimedia.org/wikipedia/commons/d/d3/CIExy1931_srgb_gamut.png)
where the gray is colors at this brightness that your eyes can see, and what your monitor can display is what's in the triangle.
If your color space is defined by a linear combination of 3 colors (i.e. R + B + G), then the entire color gamut can be drawn as a triangle with vertices at the chosen 3 colors. The internal triangle in the above posted color gamut is that of the RGB color space used to express colors on digital displays (note here that individual displays will actually color things differently and that most displays can only draw 252k of the 16.7M colors described by the integer 0-256 RBG scale). Note here how the RGB color gamut is a triangle because it's a linear combination of 3 colors, where the CIE gamut is much different shaped because it has much more specific combinations of colors (via its color matching functions that aren't linear).
Hopefully by now it's clear why digital displays (or any display or printer for that matter to date) doesn't display the full range of chromaticity that our eye can pick up. So where does this yellow come in? What if your color space is a linear combination of 4 colors instead of 3? Your color gamut would be the smallest convex shape that encloses all of those colors. It's obvious here that adding another color outside of your RGB color gamut can expand the amount of colors displayable. So, why yellow? If you'll look at the response curves of the color matching functions, you'll see that our eyes are particularly sensitive to yellow, making yellow an easy color to use here.
All this being said, there still is very little use for a yellow primary color in your display. Why? Because your source material is still that of either PC RGB or NTSC RGB, etc. Despite the display's ability to display a wider range of colors, no newer colors are actually being told to be drawn. I guess there may be some tiny advantage when using a color space not displayed by a normal TV, like, you might get a few more colors out of PC RGB compared to a TV that only draws NTSC RGB (but I don't actually know if these two are different, so it may very well be a completely moot point). All in all, yes, the display can display more colors that ARE seeable by the human eye, however, in the end, it doesn't actually matter if you have no source material using those colors.
I may not be very good at explaining this, or if you want to read more, Wikipedia has good articles about this in the CIE color space page and the Color Gamut page.
If you have these response curves, you can treat any color as a point in 3-space in terms of these stimulus values (aka, "Tristimulus values"), When plotted in 3-Space, the resulting volume is all visible color. Because this is hard to represent graphically and not frequently needed, color gamuts were introduced to give a 2 Dimensional representation of a color space's expressible range (a color space being the full range of all colors displayable by a device). These basically take a slice through that 3D volume of color in such a way that makes all colors in that plane have the same brightness, so only chromaticity is displayed. The pictures posted above are graphical representations of 2 color gamuts. The outer, horseshoe shaped one (which really can't be colored correctly on a monitor, or even in RGB space itself) is the CIE color space, or, all colors that the normal human eye can see.
Is it not true that the CIE definition necessitates "negative" power in order to be physically realizable using 3 primaries in both camera and display?
My interpretation of this curve (although I think it is a bit hard to analyze without having bothered to understand the mathematics) is that one would need an infinite amount of "primaries" to be lineary added to each other in order to strictly capture and reproduce every single color nuance that the HVS can distinguish, but that triangles are good enough (partially because very saturated colors are uncommon in nature, and because not having them does not cause to much annoyance).
All this being said, there still is very little use for a yellow primary color in your display. Why? Because your source material is still that of either PC RGB or NTSC RGB, etc. Despite the display's ability to display a wider range of colors, no newer colors are actually being told to be drawn. I guess there may be some tiny advantage when using a color space not displayed by a normal TV, like, you might get a few more colors out of PC RGB compared to a TV that only draws NTSC RGB (but I don't actually know if these two are different, so it may very well be a completely moot point). All in all, yes, the display can display more colors that ARE seeable by the human eye, however, in the end, it doesn't actually matter if you have no source material using those colors.
If you are showing still-images from your PC that has been captured in the native camera space and have profiled your screen, then the image rendering software has all the information it needs to do a good color reproduction - potentially better than sRGB (limited by camera and screen, but not arbitrary distribution standards).
I believe that certain home-video cameras support avchd and "deep color" through HDMI.
Someone wants Bluray + HDMI to be the killer color app. But I think that the combination of available content and available standards means that we are not there yet.
-k
Is it not true that the CIE definition necessitates "negative" power in order to be physically realizable using 3 primaries in both camera and display?
My interpretation of this curve (although I think it is a bit hard to analyze without having bothered to understand the mathematics) is that one would need an infinite amount of "primaries" to be lineary added to each other in order to strictly capture and reproduce every single color nuance that the HVS can distinguish, but that triangles are good enough (partially because very saturated colors are uncommon in nature, and because not having them does not cause to much annoyance).
If you pick any 3 points and just make an affine (0-1 as coefficients) combination, you can only get a triangle, if you include negative amounts of some of the colors, then you can reference any point in that plane. So to use an affine combination of colors to describe all of CIE, you would either need to reference colors that we cannot see, or to use every border color (an infinite amount). But yes, the sRGB color space does tend to give enough colors to be reasonable (I don't know the exact reasoning why).
If you are showing still-images from your PC that has been captured in the native camera space and have profiled your screen, then the image rendering software has all the information it needs to do a good color reproduction - potentially better than sRGB (limited by camera and screen, but not arbitrary distribution standards).
I believe that certain home-video cameras support avchd and "deep color" through HDMI.
Someone wants Bluray + HDMI to be the killer color app. But I think that the combination of available content and available standards means that we are not there yet.
-k
I didn't realize HDMI could transport a larger than "expected" color space. If that's the case, then I guess it is possible to make use of the larger color gamut, but it still won't be present in TV, DVDs/BluRay, or games
I didn't realize HDMI could transport a larger than "expected" color space. If that's the case, then I guess it is possible to make use of the larger color gamut, but it still won't be present in TV, DVDs/BluRay, or games
HDMI 1.3 and later supports "Deep color" (http://en.wikipedia.org/wiki/Deep_Color#Beyond_truecolor) and XvYCC (http://en.wikipedia.org/wiki/XvYCC)
http://en.wikipedia.org/wiki/HDMI#Version_1.4 (http://en.wikipedia.org/wiki/HDMI#Version_1.4)
Deep color is a term used to describe a gamut comprising a billion or more colors
In a paper published by Society for Information Display in 2006, the authors mapped the 769 colors in the Munsell Color Cascade to the BT.709 space and to the xvYCC space. 55% of the Munsell colors could be mapped to the sRGB gamut, but 100% of those colors could map to the xvYCC gamut.[4] Deeper hues can be created - for example a deeper red by giving the opposing color (cyan) a negative coefficient.
...
xvYCC is not supported by DVD-Video or Blu-ray, but is supported by the high-definition recording format AVCHD and PlayStation 3.
xvYCC is not supported by DVD-Video or Blu-ray, but is supported by the high-definition recording format AVCHD and PlayStation 3.
That's not really true, as is hinted further up the wikipedia article - xvYCC is supported by any and all YUV conventionally 16-240 digital video formats (DVD, DVB, SDI, you name it) - just use the values outside this range with the matrices defined for xvYCC.
The problem is that signalling to say "this is xvYCC" is not defined for most of those formats. The thing is though: the 16-240 range is the same as it's always been, so treating everything as xvYCC shouldn't be a problem in theory. In practice, I bet some displays do chose to treat it differently, with one or other representation tweaked in a not strictly accurate way.
Cheers,
David.
Cool, an off-topic discussion about color vision!
The chart SCOTU doesn't show the sensitivity of the cones, it's the color matching functions that are used in the CIE XYZ color spaces "standard observer."
Here's the normalized response spectra for the three different visual receptors (cone cells) :
(http://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Cone-fundamentals-with-srgb-spectrum.svg/500px-Cone-fundamentals-with-srgb-spectrum.svg.png)
The short wavelength cones sensitivity peaks nearer to violet, the middle ones are more or less at green, and the long ones yellow with a large overlap with the middle ones.
The problem with making a trichromatic display that covers the whole gamut of visible color is that the red and blue primaries have to be so far near the edges of the visible spectrum (so that they stimulate only the short and long receptors) that they have to be extra bright to make up for the reduced sensitivity. Lasers are one option, but then you get problems with speckle patterns (http://en.wikipedia.org/wiki/Speckle_pattern).
xvYCC is not supported by DVD-Video or Blu-ray, but is supported by the high-definition recording format AVCHD and PlayStation 3.
That's not really true, as is hinted further up the wikipedia article - xvYCC is supported by any and all YUV conventionally 16-240 digital video formats (DVD, DVB, SDI, you name it) - just use the values outside this range with the matrices defined for xvYCC.
The problem is that signalling to say "this is xvYCC" is not defined for most of those formats. The thing is though: the 16-240 range is the same as it's always been, so treating everything as xvYCC shouldn't be a problem in theory. In practice, I bet some displays do chose to treat it differently, with one or other representation tweaked in a not strictly accurate way.
Cheers,
David.
If wikipedia is wrong on this, someone should fix it.
When you playback DVD/Bluray on your PC (and perhaps some embedded boxes?), the video may be converted umpteen times between 16-235/240, 0-255, YCbCr and sRGB - depending on the divers, OS, hardware, interface, etc. There are guides for how to "hack" you Nvidia/ATI driver into messing up as little as possible - and often they will only work for either SD or HD media using specific application software. Bah... What are the odds that ALL of those conversions will pass the codes outside the regular range unharmed? To be shown on a LCD display with highly non-gamma-ish native response and 6 native bits, dithering 8-bit input. And many intermediate calculations are bound to be requantized to 8 bits, probably without any dithering.
Even though a full 8 bits (or is it 255-2 codes?) are allowed, displays and lossy codecs are allowed to do whatever they want to them. I do believe that xvYCC needs signalling and certification to be of practical use.
-k
xvYCC is not supported by DVD-Video or Blu-ray, but is supported by the high-definition recording format AVCHD and PlayStation 3.
That's not really true, as is hinted further up the wikipedia article - xvYCC is supported by any and all YUV conventionally 16-240 digital video formats (DVD, DVB, SDI, you name it) - just use the values outside this range with the matrices defined for xvYCC.
The problem is that signalling to say "this is xvYCC" is not defined for most of those formats. The thing is though: the 16-240 range is the same as it's always been, so treating everything as xvYCC shouldn't be a problem in theory. In practice, I bet some displays do chose to treat it differently, with one or other representation tweaked in a not strictly accurate way.
Cheers,
David.
If wikipedia is wrong on this, someone should fix it.
When you playback DVD/Bluray on your PC (and perhaps some embedded boxes?), the video may be converted umpteen times between 16-235/240, 0-255, YCbCr and sRGB - depending on the divers, OS, hardware, interface, etc. There are guides for how to "hack" you Nvidia/ATI driver into messing up as little as possible - and often they will only work for either SD or HD media using specific application software. Bah... What are the odds that ALL of those conversions will pass the codes outside the regular range unharmed? To be shown on a LCD display with highly non-gamma-ish native response and 6 native bits, dithering 8-bit input. And many intermediate calculations are bound to be requantized to 8 bits, probably without any dithering.
Even though a full 8 bits (or is it 255-2 codes?) are allowed, displays and lossy codecs are allowed to do whatever they want to them. I do believe that xvYCC needs signalling and certification to be of practical use.
I wouldn't dream of claiming that most PCs handle standard Rec.601 and 709 colour space correctly, never mind xvYCC. They often clip the range, introduce banding, and output 0-255 sRGB.
But if you're talking about stand-alones, with either analogue or digital connections in YUV space, most just send what's on the disc. I've tested this.
lossy codecs don't treat values outside the "valid" range any differently from values within in. Some VFW codecs specifically require RGB or YUV, which doesn't help, but as long as it accept YUV, it doesn't care whether a pixel is 15 or 17 - I've never found an encoder clamps internally.
FWIW
most consumer camcorders generate luma (Y) over the range 16-255 - i.e. making full use of the "super white" range above 235. So handling out of range values isn't a new problem. It goes back to the analogue days.
Cheers,
David.
FWIW most consumer camcorders generate luma (Y) over the range 16-255 - i.e. making full use of the "super white" range above 235. So handling out of range values isn't a new problem. It goes back to the analogue days.
But handling as in "do not crash, burn or show purple dancing dots" is not the same as "taking advantage of to show superior images that would otherwise be impossible". For many (most?) end-users, you might substitute a clipper early in the distribution chain for a clipper late in the distribution chain, adding some redundant information that makes life a little harder for codecs.
I think that the headroom/footrom was added so as to allow for linear processing by scalers etc that might be daisychained, analog as well as digital.
I do agree that it has some nice properties for introducing superior quality in a "soft" way, where end-users can upgrade components one at a time, and at some point in the future be able to gain the full benefit. How large is that benefit anyways? 32/255 is not a whole lot more added information, but perhaps coarse, right-ish information is enough for the bright highlights and the very dark shadows and the very saturated colors?
-k
Consumer camcorders don't do it to look genuinely better, just brighter. It's a bit like the "louder = better" thing.
The headroom was to allow for inevitable overshoots due to sharpening, processing etc.
The xvYCC use of the chroma headroom is clever. The way they defined the curve below 16 (and the way this creates "negative" RGB values) makes for a surprisingly large area of extra colour - though very few images really need it.
Cheers,
David.