Dustin Forman (who designed the IC) told me in an email it was 22.5. My guess as to the discrepancy is that they're referring to the overall measurement of the eval board, so the limiting factor there is probably the Analog Devices opamp.
> the AES is in the business of publishing 'interesting ideas', and the papers run the gamut of careful science to raving lunacy
Whoa, how did I not notice all those years! Thanks for the warning--I rush now to cancel my subscription!
PS this has absolutely nothing to do with digital compression. The problem is the fourier transform the ear does is with a very narrow window, and a combination of nonlinear and hysteresis effects make preresponse perceptible even when its fundamental frequency is outside the usual audio band. Preringing can be fully avoided if instead of symmetric FIR filters (linear phase) one uses IIR filters (minimum phase). However, this has other problems associated with it, such as audible perception is the phase variation of the latter is not smooth enough. The solutions usually implemented are a FIR filter with some compensation (thus the word "apodizing") which allows one to specify where in between the two extremes it is.
Preringing is what the linear-phase oversampling filter in the DAC chip in the player creates. Which is also the place to fix it, by putting an apodizing filter there, and some semiconductor manufacturers do exactly that (Wolfson Micro, etc.). Dolby's approach makes no sense--they oversample 2x during mastering (needed or the apodizing filter doesn't work) and then you have to store twice the data. Why? If the DAC is doing it, then you can just feed it the usual 44.1 or 48 k. Moreover, since the DAC's filter usually oversamples by 8x to allow simpler analog filters post-DAC, it can do the apodizing much better anyway. Once again Dolby takes legit technology and implements it poorly into a lousy gimmick to sell. Instead of reading dumb marketing material and even dumber article summary on slashdot, read some peer reviewed papers discussing preringing and apodizing filters, say http://www.aes.org/e-lib/browse.cfm?elib=12992
In the last few years there have been quite a few ADCs that exceed 20 bit, but achieve that through aggressive noise-shaping and not throughout the full audio band.
This is stupid since it's much more efficient to do it on the DAC side, instead of having to store twice as much data. Indeed, some DAC chips do exactly this by allowing you to vary whether you want linear phase, no preringing, or somewhere in between (plus, since DACs usually oversample by 8x, the filter there is much more precise).
Apodizing filters in audio were introduced a few years ago in DAC chip oversampling filters by Wolfson Micro. They are still FIR filters, with a compensation that allows one to smoothly set the amount of preringing reduction (really, shift to postringing so the filter can be continuously varied between linear phase and something similar to minimum phase). What's more interesting is that preringing outside the usual audio band still seems to be perceptible; follow the references in the paper http://www.aes.org/e-lib/browse.cfm?elib=12992
You don't need a DSP. DAC chips whose integrated oversampling filters had the option to be set to do apodizing to tweak the preresponse have been out for years. A couple of semiconductor manufacturers have been producing such. I think one of those was Wolfson or Burr Brown. This also shows how little sense Dolby's approach makes. They have to oversample during mastering in order to apply the filter, and then you have to store twice the data on the Blu-Ray or whatever. Whereas if it's on the DAC side, you don't have this inefficiency and can feed it the usual 44.1 or 48 k, plus the filter is much better because it's 8x rather than 2x oversampling. On top of this, if your equipment already uses a DAC chip with such apodizing filter, then you feed it this Dolby format, you'll end up with even stronger filtering. This is an epic fail by Dolby, though I suppose not as bad as squandering the only true HDR display technology when they swallowed up Brightside.
You mean like any other professional journal? By the way, your comment is flippant, and also sad: whether it's worth paying should be judged not on the merits of arguing with me, but on the merits of further educating yourself.
The artifacts are not during recording, but during reconstruction on the DAC side. Of course, Dolby is way late to the game as usual. A major semiconductor manufacturer added apodizing to their DAC chips' oversampling digital filter years ago to remove preringing. It makes a lot more sense than Dolby's approach as well, because 1) you don't need to _store_ the audio at 96 kHz the way Dolby is doing it during mastering, and 2) the DAC digital filter usually oversamples to 8x (to make the subsequent analog filter simpler with a slower roloff) so that the apodizing can be done with more precision. The article and article summary are both really bad in this case.
The article summary is misleading. You should have done more digging before posting here, such as reading the peer-reviewed research that deals with the topic in question: http://www.aes.org/e-lib/browse.cfm?elib=12992
The issue at hand is removing artifacts on the reconstruction side, specifically, preringing, which audible outside the audio band (the ear uses a very narrow fourier transform window and is highly sensitive to preresponses; follow the references in the paper). Of course, Dolby is way late to this as I remember a major semiconductor manufacturer adding apodizing filters exactly for this reason to their DAC chips years ago. Dolby's approach is also stupid as this technique should be performed purely by the digital OS filter on the DAC side. Instead, Dolby does it during mastering, so that now you need to store 96 kHz data... and this way the apodizing is not nearly as effective than on the DAC side where audio usually is oversampled 8x rather than 2x (normally done so slow-rolloff analog filter can be used to remove the HF images and prevent them from causing nonlinear effects and intermodulation in the subsequent analog electronics).
The primary mechanism of ultrasound perception seems to be bone conduction: http://en.wikipedia.org/wiki/Ultrasonic_hearing and also see http://ieeexplore.ieee.org/iel5/5286202/5291232/05291285.pdf?arnumber=5291285 and there were some other related studies showing ultrasound that is not necessarily consciously perceptible does affect perception of music. In any case, for this article the 96 kHz thing is a red herring. The audible difference is due to the use of filters other than the usual symmetric FIR filters which cause preringing in reconstruction. Of course, Dolby is way late to the game here, as a few major semiconductor manufacturers added apodizing filters to their DAC chips years ago after people realized preringing was audible even outside of the usual audio band. See the paper on apodizing filters and preringing: http://www.aes.org/e-lib/browse.cfm?elib=12992
Of course you're right about the square wave issue. My comment is regarding your last sentence. The DAC reconstruction filter is analog, not digital, and has a roloff with a limited slope. I think you're confusing it with the digital oversampling filter which brings Fs to around 8x in most configurations so that the images are at a high enough frequency that the analog filter response is sufficiently low dB at those frequencies to essentially remove them.
The article summary is misleading. This isn't about removing sampling artifacts, but about removing reconstruction artifacts (by the DAC's digital filter)--specifically, preringing. The 96 kHz thing here is a red herring. And as usual, Dolby is way late to the game. A few major semiconductor manufacturers added apodizing filters to their DAC chips years ago after studies showed preringing was audible.
"I'd rather entrust the government of the United States to the first 400 people listed in the Boston telephone directory than to the faculty of Harvard University." --William F. Buckley, Jr.
Just read the paper. Otherwise, this sort of discussion is worthless. This shit isn't even new. Apodizing filters were integrated into the DACs made by several major semiconductor manufacturers years ago after blind tests showed preringing was audible. People also conveniently forget that the fourier transform-analogue that the ear carries out uses a very narrow time window.
Eh? The grandparent posted a link to peer-reviewed research published by the AES, a serious engineering journal. To imply that the AES is going to be shilling for an audio company is like implying that the Lancet is going to be shilling for a medical device manufacturer.
It's really sad how people like you who jump to conclusions and have an ideological axe to grind have brought down the level of discussion on Slashdot over the last few years. This place actually used to be good.
The ear operates both in the time and frequency domains, in a manner analogous to using a very short fourier transform window when calculating a waterfall plot.
As for sound above 20 kHz not being audible, studies show 120 kHz is perceptible through bone conduction: http://en.wikipedia.org/wiki/Ultrasonic_hearing and also see
http://ieeexplore.ieee.org/iel5/5286202/5291232/05291285.pdf?arnumber=5291285 and other related studies showing ultrasound that is not necessarily consciously perceptible does affect perception of music.
The best part is you can build one yourself. The worst part is that nixie tubes haven't been manufactured in quite a few decades and spare ones for your watch will run out.
Slashdot Mirror
I mean subscription. http://www.aes.org/e-lib/subscribe/
Dustin Forman (who designed the IC) told me in an email it was 22.5. My guess as to the discrepancy is that they're referring to the overall measurement of the eval board, so the limiting factor there is probably the Analog Devices opamp.
> the AES is in the business of publishing 'interesting ideas', and the papers run the gamut of careful science to raving lunacy
Whoa, how did I not notice all those years! Thanks for the warning--I rush now to cancel my subscription!
>Very few ADCs/DACs reach 20 bits SNR.
Huh? For a few years already DACs like those from ESS have exceeded that. ES9018 is beyond 22 bits.
PS this has absolutely nothing to do with digital compression. The problem is the fourier transform the ear does is with a very narrow window, and a combination of nonlinear and hysteresis effects make preresponse perceptible even when its fundamental frequency is outside the usual audio band. Preringing can be fully avoided if instead of symmetric FIR filters (linear phase) one uses IIR filters (minimum phase). However, this has other problems associated with it, such as audible perception is the phase variation of the latter is not smooth enough. The solutions usually implemented are a FIR filter with some compensation (thus the word "apodizing") which allows one to specify where in between the two extremes it is.
Preringing is what the linear-phase oversampling filter in the DAC chip in the player creates. Which is also the place to fix it, by putting an apodizing filter there, and some semiconductor manufacturers do exactly that (Wolfson Micro, etc.). Dolby's approach makes no sense--they oversample 2x during mastering (needed or the apodizing filter doesn't work) and then you have to store twice the data. Why? If the DAC is doing it, then you can just feed it the usual 44.1 or 48 k. Moreover, since the DAC's filter usually oversamples by 8x to allow simpler analog filters post-DAC, it can do the apodizing much better anyway. Once again Dolby takes legit technology and implements it poorly into a lousy gimmick to sell. Instead of reading dumb marketing material and even dumber article summary on slashdot, read some peer reviewed papers discussing preringing and apodizing filters, say http://www.aes.org/e-lib/browse.cfm?elib=12992
In the last few years there have been quite a few ADCs that exceed 20 bit, but achieve that through aggressive noise-shaping and not throughout the full audio band.
This is stupid since it's much more efficient to do it on the DAC side, instead of having to store twice as much data. Indeed, some DAC chips do exactly this by allowing you to vary whether you want linear phase, no preringing, or somewhere in between (plus, since DACs usually oversample by 8x, the filter there is much more precise).
Apodizing filters in audio were introduced a few years ago in DAC chip oversampling filters by Wolfson Micro. They are still FIR filters, with a compensation that allows one to smoothly set the amount of preringing reduction (really, shift to postringing so the filter can be continuously varied between linear phase and something similar to minimum phase). What's more interesting is that preringing outside the usual audio band still seems to be perceptible; follow the references in the paper http://www.aes.org/e-lib/browse.cfm?elib=12992
You don't need a DSP. DAC chips whose integrated oversampling filters had the option to be set to do apodizing to tweak the preresponse have been out for years. A couple of semiconductor manufacturers have been producing such. I think one of those was Wolfson or Burr Brown. This also shows how little sense Dolby's approach makes. They have to oversample during mastering in order to apply the filter, and then you have to store twice the data on the Blu-Ray or whatever. Whereas if it's on the DAC side, you don't have this inefficiency and can feed it the usual 44.1 or 48 k, plus the filter is much better because it's 8x rather than 2x oversampling. On top of this, if your equipment already uses a DAC chip with such apodizing filter, then you feed it this Dolby format, you'll end up with even stronger filtering. This is an epic fail by Dolby, though I suppose not as bad as squandering the only true HDR display technology when they swallowed up Brightside.
You mean like any other professional journal?
By the way, your comment is flippant, and also sad: whether it's worth paying should be judged not on the merits of arguing with me, but on the merits of further educating yourself.
The artifacts are not during recording, but during reconstruction on the DAC side. Of course, Dolby is way late to the game as usual. A major semiconductor manufacturer added apodizing to their DAC chips' oversampling digital filter years ago to remove preringing. It makes a lot more sense than Dolby's approach as well, because 1) you don't need to _store_ the audio at 96 kHz the way Dolby is doing it during mastering, and 2) the DAC digital filter usually oversamples to 8x (to make the subsequent analog filter simpler with a slower roloff) so that the apodizing can be done with more precision. The article and article summary are both really bad in this case.
The article summary is misleading. You should have done more digging before posting here, such as reading the peer-reviewed research that deals with the topic in question: http://www.aes.org/e-lib/browse.cfm?elib=12992
The issue at hand is removing artifacts on the reconstruction side, specifically, preringing, which audible outside the audio band (the ear uses a very narrow fourier transform window and is highly sensitive to preresponses; follow the references in the paper). Of course, Dolby is way late to this as I remember a major semiconductor manufacturer adding apodizing filters exactly for this reason to their DAC chips years ago. Dolby's approach is also stupid as this technique should be performed purely by the digital OS filter on the DAC side. Instead, Dolby does it during mastering, so that now you need to store 96 kHz data... and this way the apodizing is not nearly as effective than on the DAC side where audio usually is oversampled 8x rather than 2x (normally done so slow-rolloff analog filter can be used to remove the HF images and prevent them from causing nonlinear effects and intermodulation in the subsequent analog electronics).
The primary mechanism of ultrasound perception seems to be bone conduction: http://en.wikipedia.org/wiki/Ultrasonic_hearing and also see http://ieeexplore.ieee.org/iel5/5286202/5291232/05291285.pdf?arnumber=5291285 and there were some other related studies showing ultrasound that is not necessarily consciously perceptible does affect perception of music. In any case, for this article the 96 kHz thing is a red herring. The audible difference is due to the use of filters other than the usual symmetric FIR filters which cause preringing in reconstruction. Of course, Dolby is way late to the game here, as a few major semiconductor manufacturers added apodizing filters to their DAC chips years ago after people realized preringing was audible even outside of the usual audio band. See the paper on apodizing filters and preringing: http://www.aes.org/e-lib/browse.cfm?elib=12992
Of course you're right about the square wave issue. My comment is regarding your last sentence. The DAC reconstruction filter is analog, not digital, and has a roloff with a limited slope. I think you're confusing it with the digital oversampling filter which brings Fs to around 8x in most configurations so that the images are at a high enough frequency that the analog filter response is sufficiently low dB at those frequencies to essentially remove them.
The article summary is misleading. This isn't about removing sampling artifacts, but about removing reconstruction artifacts (by the DAC's digital filter)--specifically, preringing. The 96 kHz thing here is a red herring. And as usual, Dolby is way late to the game. A few major semiconductor manufacturers added apodizing filters to their DAC chips years ago after studies showed preringing was audible.
This has little to do with the 96 kHz part and everything to do with the preringing-reducing filters. The article summary is misleading.
Read the paper. There are citations for the audibility of preringing outside the audio band. Moreover, see my other post here http://slashdot.org/comments.pl?sid=2857759&cid=40038179
Buttle is dead...
"I'd rather entrust the government of the United States to the first 400 people listed in the Boston telephone directory than to the faculty of Harvard University." --William F. Buckley, Jr.
Just read the paper. Otherwise, this sort of discussion is worthless. This shit isn't even new. Apodizing filters were integrated into the DACs made by several major semiconductor manufacturers years ago after blind tests showed preringing was audible. People also conveniently forget that the fourier transform-analogue that the ear carries out uses a very narrow time window.
Eh? The grandparent posted a link to peer-reviewed research published by the AES, a serious engineering journal. To imply that the AES is going to be shilling for an audio company is like implying that the Lancet is going to be shilling for a medical device manufacturer.
It's really sad how people like you who jump to conclusions and have an ideological axe to grind have brought down the level of discussion on Slashdot over the last few years. This place actually used to be good.
The ear operates both in the time and frequency domains, in a manner analogous to using a very short fourier transform window when calculating a waterfall plot. As for sound above 20 kHz not being audible, studies show 120 kHz is perceptible through bone conduction: http://en.wikipedia.org/wiki/Ultrasonic_hearing and also see http://ieeexplore.ieee.org/iel5/5286202/5291232/05291285.pdf?arnumber=5291285 and other related studies showing ultrasound that is not necessarily consciously perceptible does affect perception of music.
The best part is you can build one yourself. The worst part is that nixie tubes haven't been manufactured in quite a few decades and spare ones for your watch will run out.
Gates hasn't left anything: he's still chairman.