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Topic: AES 2009 Audio Myths Workshop (Read 171388 times) previous topic - next topic
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AES 2009 Audio Myths Workshop

Reply #225 –
Quote from: Arnold B. Krueger on
The above are known as  circular defintions.

A circular definition is defined as a definition that uses the word being defined as part of the defiinition.

It is only circular if tracking it down leads you in a circle. In this case, it does not. If you look up "linear equation" you get a mathematical definition. If it were circular, you'd get referred back to "linear system".

AES 2009 Audio Myths Workshop

Reply #226 –
Quote from: 2Bdecided on
Quote from: Arnold B. Krueger on
This disagrees with the formal definition of linear distortion.
We've done this one before, haven't we?

Creating new frequencies is an effect of non-linear processing - it's not the definition.

The definition is really simple: a linear system is one that can be described by a linear equation.

A non-linear system is one that isn't linear.

http://en.wikipedia.org/wiki/Nonlinear_system


The actual source says far more than has been quoted above:

"In mathematics, a nonlinear system is a system which is not linear, that is, a system which does not satisfy the superposition principle, or whose output is not proportional to its input."

Quoting the above  sentence in just 7 words, some paraprhased, does not seem to correspond to the highest standards of intellectual practice. :-(

The definition offered as an alternative, being that a nonlinear system is one that creates new frequencies, is at least consistent with the complete sentence from the allegedly cited source.
 

AES 2009 Audio Myths Workshop

Reply #227 –
I hope this does not get deleted for being off-topic or ad hominem. That is not my intention. I think it is is justified, when a thread gets flooded with massive amounts of partly very well founded (why they probably aren't be deleted) but more and more rhetorical posts, to comment on that.

Arnold, I have unidirectionally known you for a couple of years. And I always enjoyed how you were able to fight for objectivity even when surrounded by the worst nuts one can think of. And often you have won and it was great. But I'm really somewhat saddened to see what you are doing here. You don't bring the issue forward anymore, but posts large amounts of word play, nit picking, and rhetorical generalizations. That's totally unnecessary and doesn't present you in the light you should be showing in.

Your experience and merit for the cause are unquestioned. I would love to see, that you list the parameters, you think are relevant regarding transparency with a short description, in a compact post and then we discuss that and leave the rest away.

AES 2009 Audio Myths Workshop

Reply #228 –
Quote from: Arnold B. Krueger on
That's all fine and good. However, the SOTA of audio measurements is that we have a pretty good understanding about how to characterize the sound quality of a wide range of more traditional audio components, while another range of newer kinds of audio components are far more difficult to deal with. IOW, anybody who wants to conflate lossy encoders and power amplfiiers is ignoring this well-known fact.
Either these measurements can guarantee an audio component is transparent, or they can't. You don't get to choose which components they apply to, and which they don't - otherwise you're saying "I know component X doesn't have any of distortion type Y, so I'm not even going to measure it" - I can think of examples where you'd be on fairly safe ground, but as a general principle, can't you see how ridiculous this is?

Quote
Anybody who wants to break into every discussion of traditional audio components and burden it with the new (actually now about 20 years old) problems related to lossy perceptual coding components does so at their own risk. If they make their problems into problems for everybody, then guess what the people who at least have part of their lives in some kind of order are going to do?
I don't know Arny - what are you doing to do? Keep pretending you have a set of measurements up your sleeve which will guarantee transparency exactly and only when you say they do?

Quote
Quote
When psychoacoustics are involved, an audio component may fail this test, and yet still be transparent.
The most common situation is the reverse. A component that does perceptually-justified lossy coding will often measure well in accordance with traditional measurements. It may still sound pretty bad.
The frequency response should be fine, but the Belcher intermodulation test will usually reveal how much junk it's adding about 30dB down - even though it's inaudible junk.

Quote
One rule of thumb is that perceptual components have to first pass the usual bank of traditional measurements.
You can't say that - you haven't defined this "usual bank" of measurements yet.

I can't believe you have the fundamental misunderstanding that psychoacoustic based codecs pass all traditional objective measurements. They add bucket loads of noise/distortion, and fairly basic tests (e.g. subtracting the input from the output and looking at the residual) can reveal this.

Cheers,
David.

AES 2009 Audio Myths Workshop

Reply #229 –
Quote from: googlebot on
I would love to see, that you list the parameters, you think are relevant regarding transparency with a short description, in a compact post and then we discuss that and leave the rest away.
+1

AES 2009 Audio Myths Workshop

Reply #230 –
Quote from: pdq on
It seems to me that the classification of FM distortion as nonlinear is rather arbitrary.


Prove that it is linear.

Using the Wikipedia definition:

"In mathematics, a nonlinear system is a system which is not linear, that is, a system which does not satisfy the superposition principle, or whose output is not proportional to its input."

FM distortion does not satisfy the superpostion prinicple, and the output of a FM modulation process is not proportional to its input. For example, if you double the amplitude of the modulating waveform, the output waveform does not double in amplitude. Also true for amplitude modulation distortion.

Quote
Your other exception, half-wave rectification, is a special case where the non-linearity occurs only at zero signal level, making it a linear distortion.


Same 2 problems. Half wave rectification does not satisfy the superposition principle, and its output is not proportional to its input for negative inputs, that is inputs that drop below the zero line.

AES 2009 Audio Myths Workshop

Reply #231 –
Bob Pease sometimes writes about vacuum tube operational amplifiers (op-amp came later) at Philbrick. And how in 1958 they designed a transistor operational amplifier.
Kevin Graf :: aka Speedskater

AES 2009 Audio Myths Workshop

Reply #232 –
Quote from: 2Bdecided on
Quote from: Arnold B. Krueger on
That's all fine and good. However, the SOTA of audio measurements is that we have a pretty good understanding about how to characterize the sound quality of a wide range of more traditional audio components, while another range of newer kinds of audio components are far more difficult to deal with. IOW, anybody who wants to conflate lossy encoders and power amplfiiers is ignoring this well-known fact.


Either these measurements can guarantee an audio component is transparent, or they can't.


The range of audio components has gotten to be too large for it too be practical to demand that degree of universality at this time. Perceptual coders are orders of magnitude more complex than power amplifiers. There didn't used to be any perceptual coders at all.

Quote
You don't get to choose which components they apply to, and which they don't


I foresee a day when we have one-size-fits all audio measurements that are so easy to use that we just use something incredibly complex (by 2010 standards) for even simple tasks. That day is still coming. We've got work to do today!

Quote
otherwise you're saying "I know component X doesn't have any of distortion type Y, so I'm not even going to measure it"


Yes I am, but only justified by practical limitations that are likely to change, just not real soon.

Quote
Quote

Anybody who wants to break into every discussion of traditional audio components and burden it with the new (actually now about 20 years old) problems related to lossy perceptual coding components does so at their own risk. If they make their problems into problems for everybody, then guess what the people who at least have part of their lives in some kind of order are going to do?


I don't know Arny - what are you doing to do? Keep pretending you have a set of measurements up your sleeve which will guarantee transparency exactly and only when you say they do?


They are not just up my sleeve. I used to have them posted on my web site, but someone rolled them up into a little program that just about anybody can freely download and use.  I'm trying to tell you what they are and what their domain is.

Quote
Quote

Quote

Quote

When psychoacoustics are involved, an audio component may fail this test, and yet still be transparent.

The most common situation is the reverse. A component that does perceptually-justified lossy coding will often measure well in accordance with traditional measurements. It may still sound pretty bad.


One rule of thumb is that perceptual components have to first pass the usual bank of traditional measurements.


You can't say that - you haven't defined this "usual bank" of measurements yet.


I have. Two words: Audio Rightmark.


<remainder of post unanswered due to arbitrary conference limits on quoting>

AES 2009 Audio Myths Workshop

Reply #233 –
Quote from: Speedskater on
Bob Pease sometimes writes about vacuum tube operational amplifiers (op-amp came later) at Philbrick. And how in 1958 they designed a transistor operational amplifier.


I've seen that Philbrick tubed equipment in actual use. I maintained military radars that were based on electromechanical and tubed analog computers, but the parts were custom made for the purpose.

The first book I ever read about analog computers was full of all sorts of information about philbick tubed op amps and how to use them inanalog comptuers. There are/have been schematics of them on the web.

Like many things, the SS upgrades were far more useful. Incredibly higher performance and far more reliable. I cut my teeth on programming analog computers that were the first and second generation discrete SS versions.

A typical discrete SS op amp was a circuit board about 5 inches wide and maybe 10 inches long.

AES 2009 Audio Myths Workshop

Reply #234 –
Quote from: 2Bdecided on
Quote from: googlebot on
I would love to see, that you list the parameters, you think are relevant regarding transparency with a short description, in a compact post and then we discuss that and leave the rest away.
+1



I did it in the past few days and even added detailed descriptions for them:

Starting over again...

(1) linear distortion

(2) nonlinear distoriton

(3) Random noise

(4) Deterministic interferring signals

AES 2009 Audio Myths Workshop

Reply #235 –
I'm pretty much with 2BDecided here.

In an absolute sense a component or protocol has a particular transfer function (or set of transfer functions) between input and output.  There exists an objective measure of what that is.  There's no reason to qualify that, beyond perhaps applying a proper scale to the measurement suite, to appropriately show relevant detail.

Naturally, things like lossy perceptual encoding will drop into their own class, compared to things like mic preamps or line amps or turntables or ADCs. 

The measurement doesn't DEFINE the audibility, it provides a means to QUANTIFY audibility.  Just because we need to apply a different interpretation for things like perceptual encoding, doesn't mean we don't use the same measurements?

For example, the lossy encoder will "measure" poorly, but audition very well.  that tells me something very interesting, which is that the lossy encoded program is appropriate for end-listener distribution, but perhaps less appropriate as the intermediate artifact in a music master production(on a case-by-case basis).  At the very least, using an mp3 in a mix will require some compensations compared to it's lossless counterpart.

Of course, this COMPLETELY ignores the "needs" of the marketing and sales department.

AES 2009 Audio Myths Workshop

Reply #236 –
I've snipped the deeply embedded quotes - you'll have to read back to get context. Basically Arny claiming that lossy codecs pass all traditional measurements, me saying they don't, but it's a silly argument because Arny hasn't defined what "traditional measurements" he's talking about, then...

Quote from: Arnold B. Krueger on
I have. Two words: Audio Rightmark.

Audio Rightmark certainly does include measurements that reveal the noise/distortion introduced by mp3 encoders.

See here for mp3 vs wav:

http://www.jensign.com/RMAA/ZenXtra/Comparison.htm

Scroll down to THD and IMD graphs - quite revealing.

Cheers,
David.

AES 2009 Audio Myths Workshop

Reply #237 –
Quote from: Arnold B. Krueger on
Quote from: 2Bdecided on
Either these measurements can guarantee an audio component is transparent, or they can't.
The range of audio components has gotten to be too large for it too be practical to demand that degree of universality at this time. Perceptual coders are orders of magnitude more complex than power amplifiers. There didn't used to be any perceptual coders at all.

Quote
You don't get to choose which components they apply to, and which they don't
I foresee a day when we have one-size-fits all audio measurements that are so easy to use that we just use something incredibly complex (by 2010 standards) for even simple tasks. That day is still coming. We've got work to do today!

Quote
otherwise you're saying "I know component X doesn't have any of distortion type Y, so I'm not even going to measure it"
Yes I am, but only justified by practical limitations that are likely to change, just not real soon.

OK, but lossy codecs don't fall into this category - it far too easy to measure their faults, not too difficult. See my previous post - in answer to the "is it transparent?" question, false negatives are OK - it's false positives that, I would hope, you can avoid.

Are you telling me that you can't propose a set of measurements, together with a set of "pass/fail" criteria, than guarantee transparency for any arbitrary audio component that can be measured?

You see, I'd have thought that was possible.

In fact, I'd have thought that it was trivial. Let me help:

Take the time domain signal. Subtract the input from the output. The result must be less than -120dB wrt full signal level.

There you go. No false positives. A few false negatives .

Once we start down this route, we can figure out how far we can relax the requirements, which other measurements are needed if we do, which ones interact (i.e. each individual measurement might not have a binary pass/fail, but some may work in combination), etc etc etc.

This, to my mind, is a useful approach. You might actually get somewhere.

Cheers,
David.

AES 2009 Audio Myths Workshop

Reply #238 –
Quote from: 2Bdecided on
the metal in the valves sings along with the music ... tap the valves, you can hear the tapping through the speaker.

I suppose you could call that reverb, but I call it ringing because it has a single dominant frequency. Either way, it's one very good reason to avoid tubes in all audio gear.

Quote
I hope you don't think I'm being too harsh, but this renders the whole exercise a bit meaningless for me. It's turning from "this characterises any audio component" to "this characterises any audio component, except the ones it doesn't". There's a problem: who is to decide which ones it doesn't characterise?

It's not meaningless IMO. The whole point of the "four parameters" is to define what affects audio reproduction. This word is in the title of my AES Workshop, and it's also clear in the script which I uploaded the other day and linked to in an earlier post in this thread. The script is HERE, and the exact wording is:

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The following four parameters define everything needed to assess high quality audio reproduction:

Defining what affects audio reproduction has always been the entire point of my four parameters. I go out of my way to explain in forums (again and again and again) that I don't include intentional "euphonic" distortion in the list because that's a creative tool. As is reverb. This is why some people get so upset when I claim that a $25 SoundBlaster card has higher fidelity than the finest analog tape recorder. They immediately see red, and go on about how people prefer the sound of analog tape. And tubes. And hardware having transformers. And all the rest. But subjective preference was never my point or my intent.

--Ethan
I believe in Truth, Justice, and the Scientific Method

AES 2009 Audio Myths Workshop

Reply #239 –
Quote from: googlebot on
Arnold, I have unidirectionally known you for a couple of years. And I always enjoyed how you were able to fight for objectivity even when surrounded by the worst nuts one can think of. And often you have won and it was great. But I'm really somewhat saddened to see what you are doing here. You don't bring the issue forward anymore, but posts large amounts of word play, nit picking, and rhetorical generalizations. That's totally unnecessary and doesn't present you in the light you should be showing in.

This should not be about winning; it should be about learning. You don't learn much if you'd rather argue than listen. I don't learn much reading tit-for-tat posts.

AES 2009 Audio Myths Workshop

Reply #240 –
Quote from: Ethan Winer on
Defining what affects audio reproduction has always been the entire point of my four parameters. I go out of my way to explain in forums (again and again and again) that I don't include intentional "euphonic" distortion in the list because that's a creative tool. As is reverb. This is why some people get so upset when I claim that a $25 SoundBlaster card has higher fidelity than the finest analog tape recorder. They immediately see red, and go on about how people prefer the sound of analog tape. And tubes. And hardware having transformers. And all the rest. But subjective preference was never my point or my intent.

The merit to this approach is that it is objective and quantifiable. The weakness is that it does not take into account how people hear. By the measurements a soundblaster is better than tape. You seem to accept this result. But, by the same measurements, 256-kbit MP3 is about as bad as 12-bit audio. Do you accept this result?

AES 2009 Audio Myths Workshop

Reply #241 –
Quote from: 2Bdecided on
Take the time domain signal. Subtract the input from the output. The result must be less than -120dB wrt full signal level.

There you go. No false positives. A few false negatives .


That sounds like a good approach. For every parameter you can begin by asking, what would, for example, my frequency response have to look like to accomplish that goal. It gets a little tricky once you get to the details. A flat FR +/- n dB could do the job. But also a much higher n when the dip is limited to a very tiny band. So what kind of scale would be most applicable? Speaking of bands. The -120 dB would have to be limited to a to be agreed upon bandwidth.

AES 2009 Audio Myths Workshop

Reply #242 –
Quote from: Notat on
The weakness is that it does not take into account how people hear.

That's a separate issue, and is the reason I invited JJ and Poppy Crum onto my panel. It is knowable at what level artifacts such as noise and distortion can be heard, and how much frequency response error is needed to notice. So my four parameters concept attempts to 1) catalog everything that affects reproduction, and 2) identify the amounts needed for a device to be considered transparent.

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by the same measurements, 256-kbit MP3 is about as bad as 12-bit audio. Do you accept this result?

I honestly don't know enough about lossy compression to have an opinion. I do know that "static" tests for the four parameters are not applicable to lossy compression because the compression changes how it behaves constantly as the music changes.

--Ethan
I believe in Truth, Justice, and the Scientific Method

AES 2009 Audio Myths Workshop

Reply #243 –
Quote from: John Eppstein on
This is an ongoing problem when trying to discuss audio with mathemeticians.......
What a tired argument.  Care to substantiate with something other than an anecdote?

Quote from: John Eppstein on
As far as I know, DSD converters are not Sigma-Delta. Somebody correct me if I'm wrong........
Other than the fact  that DSD is a marketing term, yes, DSD is based on sigma-delta; you are wrong.

Quote from: John Eppstein on
Quote from: greynol on
...and yes, there are things in the Audio Myths Workshop video that do not fulfill TOS #8.

Which is why it is so utterly infuriatingly frustrating to attempt to carry on any rational discussion of this topic on this site, and why the discussion is per se biased in Ethan's favor - you allow him to present HIS "illegal" arguments, but the opposition is not allowed to reply in kind. Not fair. No disrespect intended, but I'm tearing my hair out here!
Please quote one single thing on this forum that Ethan has posted *here* that violates TOS #8.

Quote from: John Eppstein on
Because some listeners can in fact differentiate some equipment
Really?  Show me!

AES 2009 Audio Myths Workshop

Reply #244 –
Quote from: Ethan Winer on
I honestly don't know enough about lossy compression to have an opinion. I do know that "static" tests for the four parameters are not applicable to lossy compression because the compression changes how it behaves constantly as the music changes.

--Ethan


Static tests that don't take into account both the short-term signal and error spectra don't mean squat, of course.
-----
J. D. (jj) Johnston

AES 2009 Audio Myths Workshop

Reply #245 –
Quote from: John Eppstein on
Which is why it is so utterly infuriatingly frustrating ... I'm tearing my hair out here!

I think the level of frustration in JE's post is very telling. I honestly don't understand why people get so emotional about this stuff. It's just audio!

I hope the above doesn't violate a TOS. It certainly seems relevant to me.

--Ethan
I believe in Truth, Justice, and the Scientific Method

AES 2009 Audio Myths Workshop

Reply #246 –
Quote from: googlebot on
A definition doesn't become circular just because two sentences contain the same term.

The definition was indeed very precise. Deriving a to be defined term from an already well defined one, as linear equations are, is not circular.


"Linear phenomena are those described by linear equations" is indeed precise. However, as a definition it is useless by itself: whether a description of a phenomenon is linear or not is a property of the description, not the phenomenon.

There are lots of examples. A random one is the Burger's equation, a nonlinear partial differential equation for a simple model of shock waves in viscous flows. Since the equation is nonlinear, according to this definition, the phenomenon is nonlinear. But a simple transformation of the variables gives a linear equation (which can immediately be solved, thus giving the solution to the original equation); so is the phenomenon, occurring somewhere in the world, changing its properties because I decided to transform a variable?

And the opposite is of course trivial to do: if you have some linear equation for some variable p, say K*p=0 (with K some integral, differential or whatever operator not depending on p), I can obviously transform to eg t=exp(p) whence my equation for t is immediately nonlinear!

I realise that this is pedantic, but so is most of the rest of this thread (and dominated by egos, too). So hey!

But it's obvious that everybody is saying the same thing, ie, linear in terms of the input and output signals, and not some arbitrary functions of them. I was merely pointing out, in my humble way, that trying to sound sophisticated can backfire if one doesn't know what one is talking about (consider also the quasinormal distribution mentioned earlier!)

Actually the whole discussion is a series of pissing matches and word games. Fun to watch! Keep it up!

AES 2009 Audio Myths Workshop

Reply #247 –
Quote from: Ethan Winer on
I honestly don't understand why people get so emotional about this stuff. It's just audio!


Because, right or wrong, they do it for a living and they care?
-----
J. D. (jj) Johnston

AES 2009 Audio Myths Workshop

Reply #248 –
Quote from: googlebot on
Quote from: 2Bdecided on
Take the time domain signal. Subtract the input from the output. The result must be less than -120dB wrt full signal level.

There you go. No false positives. A few false negatives .


That sounds like a good approach. For every parameter you can begin by asking, what would, for example, my frequency response have to look like to accomplish that goal. It gets a little tricky once you get to the details. A flat FR +/- n dB could do the job. But also a much higher n when the dip is limited to a very tiny band. So what kind of scale would be most applicable? Speaking of bands. The -120 dB would have to be limited to a to be agreed upon bandwidth.


But (and I think that is his point) the interesting part of doing this (ie, starting with a measurement that guarantees transparency and removing things while keeping it transparent) is to determine which new measurements, apart from things like FR etc, will help. Because, as has been mentioned, things like perceptual encoders measure much worse than they sound (even though I understand this intellectually, the first time I subtracted a 256kbit mp3 from the original and listened to the difference my jaw dropped).

AES 2009 Audio Myths Workshop

Reply #249 –
Quote from: Ethan Winer on
Quote from: Notat on
The weakness is that it does not take into account how people hear.

That's a separate issue, and is the reason I invited JJ and Poppy Crum onto my panel. It is knowable at what level artifacts such as noise and distortion can be heard, and how much frequency response error is needed to notice. So my four parameters concept attempts to 1) catalog everything that affects reproduction, and 2) identify the amounts needed for a device to be considered transparent.

That's a reasonable approach to take but you need to realize the implications of the limitation. Using this approach, it is definitely not fair to say that a soundblaster "sounds better" than analog tape. You can say that it is "more accurate" or that it "measures better" or is more "transparent". You'll have to agree on a definition of "high-fidelity" before you can make any claims around that or chastise others for their claims. You have to be careful with your language, because, as I'm sure you're aware, and despite what they may tell you, accuracy is not what everyone considers to be the most important characteristic in a reproduction system.