Stereophile Series on MQA Technology

[mansr]

51 minutes ago, beetlemania said:

OK, that's a start, Mr. Atkinson. Any chance you or Mr. Austin might highlight that in a full article rather than in the online comments at stereophile.com? It would be VERY useful to see this scaled for audiophile products rather than DVD players. How much more will a high-end DAC cost?

If the licence fee is a percentage of the product price, that could be quite a bit. If it's a fixed per-unit fee, it probably won't impact very expensive products much, seeing as relatively cheap ones can afford it. If the per-unit fee depends on the number sold, it could be anything.

[beetlemania]

2 minutes ago, mansr said:

If the licence fee is a percentage of the product price, that could be quite a bit. If it's a fixed per-unit fee, it probably won't impact very expensive products much, seeing as relatively cheap ones can afford it. If the per-unit fee depends on the number sold, it could be anything.

 

Yes, it's a big question mark and the leading print magazine will only talk about it where very few people are reading. My DAC already uses filtering very similar to what MQA does - but I'm supposed to believe that truncating the original file will make it sound even better? As a bonus, I get to pay even more if I want a new DAC!

[Galileo365]

On 12/7/2017 at 9:15 AM, Rt66indierock said:

Problem is MQA Ltd. hasn't developed the perfect filter. Charles Hansen was a friend and we recently had phone conversations about digital filtering. The last one seemed to be a brain dump on his filtering ideas shortly before he passed away. 

 

Isn't it the case that all "filters" cause temporal smearing and that, whether MQA actually does or not do this, interpolation of one kind or another (sinusoidal, B-spline, etc.) would work just like a filter does without the time smearing? I believe that Shannon indicated that interpolation is necessary to reconstruct an analog waveform and then someone else used a mathematical model to show that filtering was equal to interpolation in the frequency domain at a lower relative cost but did not address the issues of temporal smearing that such low-pass or brick wall filters cause?

[mansr]

1 minute ago, Galileo365 said:

Isn't it the case that all "filters" cause temporal smearing

No.

[Galileo365]

Just now, mansr said:

No.

 

Why not? Please explain in more detail if you don't mind.

[Audiophile Neuroscience]

10 minutes ago, Galileo365 said:

address the issues of temporal smearing

 

Does anyone actually understand what "temporal smearing" means, in contrast for example to "jitter", and what MQA purports to do to fix it ?

[Galileo365]

Just now, Audiophile Neuroscience said:

 

Does anyone actually understand what "temporal smearing" means, in contrast for example to "jitter", and what MQA purports to do to fix it ?

 

In so far as I understand it, jitter has to do with the rate at which a stream of bits travel from point A to point B or match an ideally perfect master clock governing a system from end-to-end (i.e, from the original ADC to the final DAC). It's metaphorically like making an analog recording at a given speed then playing it back at a slightly different speed or varying speeds creating a type of distortion in the sound.

 

Temporal smearing is when different analog frequency bands in a signal get pushed out of phase or synchronization with each other for whatever reason. In the same sense that white light is made up of red, orange, yellow, green, blue, indigo and violet light, an analog waveform can be composed of many different frequencies that stay aligned with respect to each other in nature, but fall out of sync somewhere along the line in digital sound reproduction (supposedly as a side of any brick wall filter that cuts the upper frequencies off abruptly assuming that the highest frequency in the signal or waveform is above the cut-off frequency of the brick wall filter) creating a type of distortion as well that is similar to, but not the same thing as,  jitter.

 

Observational evidence suggests that human hearing is far more sensitive to all types of temporal distortion than previously thought.

 

What MQA claims to do, independent of the compression or folding and and unfolding that occurs in the frequency domain, is to preserve the integrity of the time domain by avoiding excessive filtering, using interpolation instead to reconstruct the analog waveform, which has no practical effect in the time domain.

 

I have no way to prove or disprove what MQA claims to do or not do. It seems fairly clear, though, that we, as human beings, are far more sensitive to both jitter and frequency-dependent time or temporal "smearing" as described than was first thought.

[mansr]

37 minutes ago, Audiophile Neuroscience said:

Does anyone actually understand what "temporal smearing" means,

No, because it is meaningless.

[mansr]

14 minutes ago, Galileo365 said:

avoiding excessive filtering, using interpolation instead to reconstruct the analog waveform

Interpolation is a form of filtering.

[Galileo365]

33 minutes ago, mansr said:

Interpolation is a form of filtering.

 

No, actually, it's not at all. In mathematics, interpolation is defined as, "the process of determining the value of a function [or signal] between two points at which [the signal] has [specific] values", and filtration is defined as, "[the act of] pass[ing] (a liquid, gas, light, or sound) through a device to remove unwanted material." In short, interpolation restores missing information whereas filtration removes, as an example, hypothetically unwanted information. Shannon's proof rested specifically on the notion of interpolation, "Shannon's proof of the theorem is complete [when] he goes on to discuss reconstruction via sinc functions, what we now call the Whittaker–Shannon interpolation formula [...]"; it was only later that someone (I honestly don't have a name) found that, "The interpolation formula [as] derived in the Nyquist–Shannon sampling theorem [...] can also be expressed as the convolution of an infinite impulse train with a sinc function [...]. This is equivalent to filtering the [signal] with an ideal (brick-wall) low-pass filter."  However, a brick-wall filter is defined as, "A certain type of low-pass filter exhibiting a steep cutoff slope which resembles a 'brick wall.' These filters are often found in A/D [and D/A] converters to prevent aliasing; while they are acceptable for this purpose their steep slope introduces unwanted side-effects on the audio signal, such as [frequency-selective] phase shift."--https://musicterms.artopium.com/b/Brickwallfilter.htm. I'm not sure if you're being a troll or just haven't done any real research/experimentation of your own, but all of what I quoted is a matter of fact, not opinion.

[Audiophile Neuroscience]

1 hour ago, mansr said:

No, because it is meaningless.

Care to explain why?

[Audiophile Neuroscience]

27 minutes ago, Galileo365 said:

 

No, actually, it's not at all. In mathematics, interpolation is defined as, "the process of determining the value of a function [or signal] between two points at which [the signal] has [specific] values", and filtration is defined as, "[the act of] pass[ing] (a liquid, gas, light, or sound) through a device to remove unwanted material." In short, interpolation restores missing information whereas filtration removes, as an example, hypothetically unwanted information. Shannon's proof rested specifically on the notion of interpolation, "Shannon's proof of the theorem is complete [when] he goes on to discuss reconstruction via sinc functions, what we now call the Whittaker–Shannon interpolation formula [...]"; it was only later that someone (I honestly don't have a name) found that, "The interpolation formula [as] derived in the Nyquist–Shannon sampling theorem [...] can also be expressed as the convolution of an infinite impulse train with a sinc function [...]. This is equivalent to filtering the [signal] with an ideal (brick-wall) low-pass filter."  However, a brick-wall filter is defined as, "A certain type of low-pass filter exhibiting a steep cutoff slope which resembles a 'brick wall.' These filters are often found in A/D [and D/A] converters to prevent aliasing; while they are acceptable for this purpose their steep slope introduces unwanted side-effects on the audio signal, such as [frequency-selective] phase shift."--https://musicterms.artopium.com/b/Brickwallfilter.htm. I'm not sure if you're being a troll or just haven't done any real research/experimentation of your own, but all of what I quoted is a matter of fact, not opinion.

Mansr is def not a troll and is highly knowledgeable. He can be a little dismissive at times but due to his young age...19??....we make allowances in deference to prodigious talent ?

[Ralf11]

temporal smear is usually made on a bagel - I suggest toasting them and choosing something taxonomically distant

[Galileo365]

7 minutes ago, Audiophile Neuroscience said:

Mansr is def not a troll and is highly knowledgeable. He can be a little dismissive at times but due to his young age...19??....we make allowances in deference to prodigious talent ?

 

OK, I see, Audiophile Neuroscience. Thank you. I was once 19, too, and naturally gifted (or so I have been told) in the areas of predicate logic, binary math, and software design and development, relying primarily on my intuition until I more formally educated myself both at college and afterwards. I just learned early on not to dismiss any idea out of hand simply because it contradicted my own thoughts or ideas; but that's more an issue of personal style and humility than anything else. I will say, just because I'm in the mood to do so, that whatever prodigious talent Mansr has, if he or she wants to grow and learn and hone his or her own skills, that listening before you talk or a least explaining why you believe something to be true will likely get you farther than being dismissive. Although, that is his or her burden to bear alone.

[Dr Tone]

Grabs some ?

[Galileo365]

9 minutes ago, Dr Tone said:

Grabs some ?

 

Hey, in my first full-time job as a software developer and designer, I heard the expression, "Find someone who gives a damn and tell them", just enough times to phrase things more as questions than blanket statements ... (true story).

[kumakuma]

26 minutes ago, Galileo365 said:

 

OK, I see, Audiophile Neuroscience. Thank you. I was once 19, too, and naturally gifted (or so I have been told) in the areas of predicate logic, binary math, and software design and development, relying primarily on my intuition until I more formally educated myself both at college and afterwards. I just learned early on not to dismiss any idea out of hand simply because it contradicted my own thoughts or ideas; but that's more an issue of personal style and humility than anything else. I will say, just because I'm in the mood to do so, that whatever prodigious talent Mansr has, if he or she wants to grow and learn and hone his or her own skills, that listening before you talk or a least explaining why you believe something to be true will likely get you farther than being dismissive. Although, that is his or her burden to bear alone.

 

Before you embarrass yourself any further by drawing conclusions based on erroneous information, you should know that Audiophile Neuroscience's comment about Mansr being 19 was a reference to his youthful appearance, not his actual age. 

[Galileo365]

5 minutes ago, kumakuma said:

 

Before you embarrass yourself any further by drawing conclusions based on erroneous information, you should know that Audiophile Neuroscience's comment about Mansr being 19 was a reference to his youthful appearance, not his actual age. 

 

Oh, well, what can I say? I'm new here. <grin>

[Galileo365]

23 minutes ago, kumakuma said:

 

Before you embarrass yourself any further by drawing conclusions based on erroneous information, you should know that Audiophile Neuroscience's comment about Mansr being 19 was a reference to his youthful appearance, not his actual age. 

 

Plus, I have to say that, regardless of Mansr's age or level of experience, I still feel ethically-bound to offer him the same unsolicited advice.

[Audiophile Neuroscience]

24 minutes ago, Galileo365 said:

 

Plus, I have to say that, regardless of Mansr's age or level of experience, I still feel ethically-bound to offer him the same unsolicited advice.

Haha yes my apologies .it was a good natured dig at his youthful appearance ....and sometimes his replies.i think he is in his 30s or maybe 40s but only guessing. Still a young age.

he is the maintainer of sox.

Welcome to the forum!!Cheers 

[kumakuma]

1 hour ago, Galileo365 said:

 

Plus, I have to say that, regardless of Mansr's age or level of experience, I still feel ethically-bound to offer him the same unsolicited advice.

 

Welcome to CA!

 

 

[Don Hills]

2 hours ago, Galileo365 said:

..  if he or she wants to grow and learn and hone his or her own skills, that listening before you talk or a least explaining why you believe something to be true will likely get you farther than being dismissive. ...

 

You would do well to take your own advice.

He was right, by the way. In the current context, interpolation is performed with a filter. He knows this because he's disassembled and analysed the software in several MQA decoders.

 

[Galileo365]

7 minutes ago, Don Hills said:

He was right, by the way. In the current context, interpolation is performed with a filter. He knows this because he's disassembled and analysed the software in several MQA decoders.

 

I specifically said that I wasn't referring to MQA but to interpolation versus filtering in the broader context. If he had said, "... in the context of MQA", that would have made more sense. Plus, if you mean that he's actually extracted the firmware from a non-FPGA-based DAC chip, disassembled it, found the part of the code related specifically to MQA, and has proved with certainty that filtering is used in place of interpolation, that would--indeed--be very impressive and convincing. With regard to, "You would do well to take your own advice," I did ask politely several times for him to elaborate, but he choose not to do so; so I did perform due diligence. Regardless of all that, Bob Stuart has openly said that MQA uses B-spline interpolation, a form of interpolation often applied to reconstructing complex curves--not just pure sine waves--from sparse data points. Maybe Bob lied, I don't know; but I honestly don't care how much authority or street-credibility someone has. I want to see the evidence myself or at least have it explained. I will not put any faith into a comment or conclusion made by someone who's only defense appears to be, "Because I said so".

[MikeyFresh]

9 minutes ago, Galileo365 said:

I want to see the evidence myself or at least have it explained. I will not put any faith into a comment or conclusion made by someone who's only defense appears to be, "Because I said so".

 

Right, for instance someone like Bob Stuart?

[Galileo365]

1 minute ago, MikeyFresh said:

 

Right, for instance someone like Bob Stuart?

 

Please read exactly what I just said, "Maybe Bob lied, I don't know [...]". I wasn't being sarcastic, I meant I really just don't know.