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MQA is Vaporware


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1 hour ago, mcgillroy said:

 

Thx and yes that is an interesting development happening in the audio press. Noticed Dagadan's writing too and she is the only one on Stereophile who managed to sneak in a critical take on MQA into the publication:

 

Jana Dagadan: Any opinions on MQA? It doesn't make you want to revisit digital?

 

Jim Hagemann: No opinion other than it looks like a really clever technology. I don't know how it sounds but it's a clever way to combine everything and be compatible. I've heard some horrible stories about MQA and licensing. They're brutal with their licensing for manufacturers who want to use it and employ it. They sting you. For the small guy like me, I don't think I could afford to get into that business.

 

https://www.stereophile.com/content/industry-profile-jim-hagerman-hagerman-audio-labs

 

That's pretty damming and nowhere on Stereophile any follow up on it.

 

Secondly I think you are spot on with your typology of audio buyers. To expand on your description of #2 (young audio buyer) and my earlier notion that digital audio draws a different crowd with a different skillset I like to add the following observation:

 

There are plenty of well educated MINT-graduates rendered open-floorplan-dwellers by the tech-industry.

 

Their only chance of privacy are their headphones. These are well-paid kids and the explosion of headphone offerings in the past decade not least caters to this demographic with their ample purchasing power and appetite for distinction through gadgets.

 

Once people regularly started to pay $300.- and more for a headphone a subset of these became Head-Fi enthusiasts and/or audiophiles.

 

Now try to think of an audio-"innovation" that would challenge the curiosity, political sensibilities and technical competence of this demographic?! Basically software engineers familiar with tool-chains which are a mix of proprietary, FS and OS-software.

 

Let's see - it should include:

 

1. hyperbolic claims about shortcomings in information theory

2. ditto for the related sampling-theorem

3. obfuscation of the "science" behind these claims with meaningless graphs and numbers published only in high-quality journals like Stereophile and TAS.

4. disavowment of peer-reviewed research

5. ditto for independent listening tests

6. reliance on proprietary and closed source software

7. a licensing regime openly aiming to lock-in vendors

8. DRM hidden in plain-sight

9. NDAs galore to cover 1-8.

 

That's a brilliant marketing strategy to reach digital natives! Especially the well-educated ones with interest in audio-hard & software and enough discretionary income.

 

Bob S. and J. Atkinson really got themselves into some fun here. Let's make sure we all are stocked up well on Popcorn ;)

 

 

 

 

 

 

Wow. That's deep cynicism. Well written, though.

mQa is dead!

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18 minutes ago, JoeWhip said:

http://www.digitalaudioreview.net/2017/07/kih-46-mqas-missing-link/

 

another negative look inside MQA. The audiophile press will really have egg on their faces after all is said and done I believe.

This may be linked on John Darko's site, but it is not written by him... he is all on board with MQA.. jumped right in the pool when he saw the big mags fellate Bob Stuart..a real sycophant iIMO.

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14 hours ago, Fokus said:

 

No.

 

MQA's nemesis is the ringing visible before and after the main lobe in the impulse response of a linear phase filter.

 

They solve this by starting from a linear phase high sample rate recording, preferably 4x or higher, and then reduce this to 2x with an extremely leaky downsampling (anti-aliasing) filter, a filter with a very narrow impulse, but, obviously, with a lot of aliasing. They claim they analyse the source signal and then pick a downsampling filter so that the amount of aliasing that effectively hits the audible band does not exceed the natural noise already present in the audible band (i.o.w. the noise is to mask the aliasing). The 2x signal is then folded into 1x with the origami trick, for distribution (streaming, download, MQA-CD).

Upon replay the 1x signal is first unfolded to 2x (inverse origami), and then upsampled to the original rate with the leaky filters documented by Mansr here on CA. These filters obviously cause a lot of imaging, as can be seen here for a '192kHz' example:

 

ZkMCGbE.jpg

 

 

====

 

As for the audibility of pre-ringing. You can follow Jud's advice. But even more telling would be this:

 

-reverse the file (i.e. front becomes back)

-convert with a minimum phase filter (see Jud's post)

-reverse the file again

 

Now you have a maximum phase file: all pre-ringing, no post-ringing. Have a listen.

 

 

Hi,

Thanks. Been out today, hence the late reply.

What i am not sure about is the pre-ringing - for a causal filter, surely there cannot be pre-ringing ? (or is it a non-causal filter) ??

Regards,

Shadders.

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10 hours ago, Jud said:

 

You can also use a free test version of iZotope Rx itself and do the upsampling offline, then use mansr’s SoX fork if you wish to sigma-delta modulate to DSD format; or just use the SoX fork for the whole shebang.

 

You sure you don’t have a DAC, like reasonable sound card and headphones?  The point is to have not only something you can see, but something you can hear (or can’t).

HI,

Thanks - no DAC or sound card - only a PC motherboard sound - which may do it - will examine one of my PC's to see if it meets the requirements.

New to the audio processing too - will try the iZotope RX 6 in  a VM.

Regards,

Shadders.

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6 minutes ago, Shadders said:

Hi,

Thanks. Been out today, hence the late reply.

What i am not sure about is the pre-ringing - for a causal filter, surely there cannot be pre-ringing ? (or is it a non-causal filter) ??

Regards,

Shadders.

 

Doesn’t violate causality.  (It’s not reverb, so don’t think of it as that.)

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature.

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4 hours ago, Digital Assassin said:

This may be linked on John Darko's site, but it is not written by him... he is all on board with MQA.. jumped right in the pool when he saw the big mags fellate Bob Stuart..a real sycophant iIMO.

 

 

"Science draws the wave, poetry fills it with water" Teixeira de Pascoaes

 

HQPlayer Desktop / Mac mini → Intona 7054 → RME ADI-2 DAC FS (DSD256)

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7 hours ago, Digital Assassin said:

This may be linked on John Darko's site, but it is not written by him... he is all on board with MQA.. jumped right in the pool when he saw the big mags fellate Bob Stuart..a real sycophant iIMO.

 

I think that's to simple. Darko has published essential critical material on MQA on his site before. On the other hand he recently touted the MQA horn.

 

But the fact that Ebaen comes with an MQA skeptical article is highly significant. He is a major taste-maker in the business and many small and medium audio-firms rely on his 6 Moons website for exposure.

 

I bet the mail he cites was not the only one which has landed on his desk recently. If Ebaen feels confident enough to publicly confront MQA + the established audio press he has heard more than a single vendor raising serious concerns.

 

Not a good day at MQA-headquarters.

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1 hour ago, mcgillroy said:

 

I think that's to simple. Darko has published essential critical material on MQA on his site before. On the other hand he recently touted the MQA horn.

 

But the fact that Ebaen comes with an MQA skeptical article is highly significant. He is a major taste-maker in the business and many small and medium audio-firms rely on his 6 Moons website for exposure.

 

I bet the mail he cites was not the only one which has landed on his desk recently. If Ebaen feels confident enough to publicly confront MQA + the established audio press he has heard more than a single vendor raising serious concerns.

 

Not a good day at MQA-headquarters.

Let's hope their many more bad days....

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14 hours ago, Jud said:

 

Doesn’t violate causality.  (It’s not reverb, so don’t think of it as that.)

HI Jud,

I checked the books - and for the ringing to start before the main impulse, this is a non-causal system. As such, are you referring to digital filters (example) where non-causal filters can be implemented. (in general, not possible in the analogue domain).

Regards,

Shadders.

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46 minutes ago, Shadders said:

HI Jud,

I checked the books - and for the ringing to start before the main impulse, this is a non-causal system. As such, are you referring to digital filters (example) where non-causal filters can be implemented. (in general, not possible in the analogue domain).

Regards,

Shadders.

 

Hi Shadders.  Yes, the terminology may quite properly refer to "non-causal," but of course in a larger sense the laws of physics don't permit violations of causality.

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature.

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By the way, Shadders, while looking for a good explanation for you of why "non-causal" filters don't violate the laws of physics (haven't found one yet as clear as I recall seeing a couple of years ago, so still looking), I ran across this interesting bit at the website of the Stanford University Center for Computer Research in Music and Acoustics (CCRMA), from the text "Introduction to Digital Filters with Audio Applications," by Julius O. Smith III, (September 2007 Edition):

 

Quote

Since we are listening to a lowpass-filtered impulse, it is reasonable to define the ideal expected sound as a "lowpass-filtered click," or some kind of "compact thump." We may therefore ask which signal sounds more like a lowpassed click? In the minimum-phase case, all filter ringing occurs after the main pulse, while in the zero-phase case, it is equally divided before and after the main pulse. Listening tests confirm that the "pre-ring" of the zero-phase case is audible before the main click, giving it a kind of "chirp" quality. Most listeners would say the minimum-phase case is a better "click." Since forward masking is stronger than backward masking in hearing perception, the optimal distribution of ringing is arguably a small amount before the main pulse (however much is inaudible due to backward masking, for example), with the rest occurring after the main pulse.

 

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature.

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28 minutes ago, Jud said:

By the way, Shadders, while looking for a good explanation for you of why "non-causal" filters don't violate the laws of physics (haven't found one yet as clear as I recall seeing a couple of years ago, so still looking), I ran across this interesting bit at the website of the Stanford University Center for Computer Research in Music and Acoustics (CCRMA), from the text "Introduction to Digital Filters with Audio Applications," by Julius O. Smith III, (September 2007 Edition):

 

 

Hi Jud,

Thanks - do not have that book - but can you confirm (i think you did in the other post) that the pre-ringing is solely in the digital domain and is a non-causal filter ?

Else, are you indicating that non-causal filters exist in the analogue domain ?

Thanks and regards,

Shadders.

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2 hours ago, Shadders said:

Hi Jud,

Thanks - do not have that book - but can you confirm (i think you did in the other post) that the pre-ringing is solely in the digital domain and is a non-causal filter ?

Else, are you indicating that non-causal filters exist in the analogue domain ?

Thanks and regards,

Shadders.

 

Sorry for the confusion Shadders, I'm not discussing filters at all, just fundamental physics that says the cause must precede the effect in time.  If you Google, you will see people who first run into the phenomenon of pre-ringing saying "How can this be - it violates the laws of physics to have an effect preceding a cause!"  And then people give more or less good explanations about how no, this isn't a violation of the very laws of physics on which the universe is based, this is how it works....

 

This is entirely aside from the fact that the specialized terminology that is used to talk about these filters indeed refers to them as "non-causal" due to pre-ringing.

 

The Smith book goes into this and more, and is available online.  Because it is from 2007 I don't know whether various bits are outdated, but you seem to be asking some fundamental questions that I believe may be answered there.  Here's a link:

 

https://ccrma.stanford.edu/~jos/filters/

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature.

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2 hours ago, Shadders said:

Else, are you indicating that non-causal filters exist in the analogue domain ?

 

Below is a nice general explanation from a producer on the gearslutz forum.  The question he is answering is (summarized), "Why would anyone want to use linear phase filtering?  The pre-ringing messed up my kick drum sound."  Note he says nearly all analog filters are IIR.  But the crossovers in my speakers are linear phase filters, so they in fact are analog "non-causal" filters.

 

Quote

It's a good question, unfortunately the answer isn't very intuitive. But let's take a stab at it!

There are two general filter "architectures": 1. those with infinite impulse responses (IIR), and 2. those with finite impulse responses (FIR). IIR filters have infinite response because they use feedback -- the output depends on the input as well as previous outputs. Almost all analog filters are IIR. FIR filters, on the other hand, don't use feedback; the output depends only on the (scaled) input. FIR filters are trivial to implement digitally.

Now let's consider the phase response of a filter, which represents how the filter affects the phase of each frequency as the signal passes through it. One way to think about phase is as a frequency-dependent delay. Thus when we say that a filter is zero phase, we are saying that the filter passes each frequency without any delay (its phase response is a horizontal line at 0). When we say that a filter is linear phase, we're acknowledging that the filter will delay each frequency, but by a constant amount (phase response is a straight diagonal line over the passband). And if we say that a filter has nonlinear phase, we're saying that the delay is frequency-dependent (curved phase response).

It is a physical and mathematical property of filters that their phase response is determined by their impulse response symmetry. Picture the impulse response as an x-y graph, with time on the horizontal axis (x-axis) and amplitude on the vertical y-axis. If the impulse response (IR) is symmetrical about the point x=0, then the filter will be zero phase. If it is symmetrical about some other point other than x=0, then it will be linear phase. And if it does not have left-right symmetry, then the filter will be nonlinear phase.

Consider the zero-phase filter: it is symmetrical about x=0, which represents time at the "zero point". The zero point of time is of course the beginning of when we start our test (or measure our IR). But for the IR to be symmetrical, that must mean it looks the same at x=-1 as it does at x=1, and the same at x=-2 as it does at x=2, and so on. But negative numbers on the x-axis represent negative time, which (unfortunately!) we cannot access. So while it is possible to create zero-phase filters using clever tricks, it is much more straight forward to simply move the symmetry from x=0 to some positive number.

For example, let's say we have a 9-sample IR. If we center it at x=4, then the left-most sample in the IR will fall on x=0 and the right-most sample will fall on x=8. By shifting the IR to the right in time, we have maintained symmetry but lost the zero-phase property. Thus we have a linear phase filter. But remember that x=0 is time "zero", the beginning, so the shifting has introduced a delay of of 4 samples. In the real world, IRs are often several hundred (or even thousands) samples long, so the delays are correspondingly longer -- this is why you get latency when you switch to linear phase mode in your EQ.

Finally we can explain the "ringing". It's convenient (and accurate) to think of the IR as representing inertia in the filter. Like stretching a spring and letting go, the IR represents how the filter reacts to energy; it gives us a visualization in the time domain of how long it takes that energy to dissipate. This dissipating energy, in the form of oscillations, is what we call ringing, and all filters ring. IIR filters have nonlinear phase, which means they don't have left-right symmetry: the impulse response starts at its highest value with progressively damped oscillations trailing off to the right (in time), theoretically forever. Their ringing happens after the IR's "spike".

Linear phase filters, on the other hand, have left-right symmetry. If we compare the exact middle of the IR -- the "spike" -- with that of the non-symmetrical IIR filter, the left half of the linear phase filter can be seen as pre-ringing. This is usually easiest to hear on low-frequency transients (such as kick drum), where it sounds like the transient is being "smeared".

So why use linear phase filters at all? If we think of filters as physical systems responding to energy, it is easier to understand the tradeoffs of each design. The IIR filter is unruly in phase (and feedback can cause them to become wildly unstable), but its energy dissipation -- its ringing -- is easily masked because it always occurs after the impulse. FIR filters are perfectly stable and have beautiful phase response at the expense of dissipating their energy both in the forward and backward directions. It's a tradeoff, and the engineer must decide the appropriate tool for the task at hand. A linear phase filter is a bad tool on the kick drum, but it may be just the ticket on a top- and bottom-miked snare. Experiment and go with what your ear tells you, but a good rule of thumb is to use IIR unless phase response is critical.

Hope that helps; have fun!

 

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature.

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2 hours ago, Jud said:

 

Sorry for the confusion Shadders, I'm not discussing filters at all, just fundamental physics that says the cause must precede the effect in time.  If you Google, you will see people who first run into the phenomenon of pre-ringing saying "How can this be - it violates the laws of physics to have an effect preceding a cause!"  And then people give more or less good explanations about how no, this isn't a violation of the very laws of physics on which the universe is based, this is how it works....

 

This is entirely aside from the fact that the specialized terminology that is used to talk about these filters indeed refers to them as "non-causal" due to pre-ringing.

 

The Smith book goes into this and more, and is available online.  Because it is from 2007 I don't know whether various bits are outdated, but you seem to be asking some fundamental questions that I believe may be answered there.  Here's a link:

 

https://ccrma.stanford.edu/~jos/filters/

Hi Jud,

Thanks for clarifying. The link is very good allows ease of skipping to the relevant parts.

Regards,

Shadders.

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2 hours ago, Jud said:

 

Below is a nice general explanation from a producer on the gearslutz forum.  The question he is answering is (summarized), "Why would anyone want to use linear phase filtering?  The pre-ringing messed up my kick drum sound."  Note he says nearly all analog filters are IIR.  But the crossovers in my speakers are linear phase filters, so they in fact are analog "non-causal" filters.

 

 

Hi Jud,

Thanks. I searched for the impulse response of analogue filters - they are all causal, and their impulse response is not symmetrical.

http://www.analog.com/media/en/training-seminars/design-handbooks/Basic-Linear-Design/Chapter8.pdf

The above text (gearslutz reference, not analog.com) i think is for digital filters - as the analysis mentions samples, and may be a non-causal implementation. Terminology and context seem to be quite important here :D

Regards,

Shadders.

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Just now, Shadders said:

Hi Jud,

Thanks. I searched for the impulse response of analogue filters - they are all causal, and their impulse response is not symmetrical.

http://www.analog.com/media/en/training-seminars/design-handbooks/Basic-Linear-Design/Chapter8.pdf

The above text (gearslutz reference, not analog.com) i think is for digital filters - as the analysis mentions samples, and may be a non-causal implementation. Terminology and context seemto be quite important here :D

Regards,

Shadders.

 

OK, I could easily be wrong.  I do know they are linear phase.

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature.

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3 minutes ago, Jud said:

 

OK, I could easily be wrong.  I do know they are linear phase.

Hi Jud,

It is possible that mathematical treatment is different to real world - similar to positive and negative frequencies of an FFT, where as in the real world you only see/measure positive frequencies.

Regards,

Shadders.

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On another forum I used a less technical but a more logical approach to be critical about the claims that MQA makes:

 

- if MQA is designed to battle ringing effects caused by ADCs, it will break digital recordings and recordings using samples.

- you need to have access to the original recordings to be able to distinguish analogue and digital parts, effectively meaning you need to manually remaster most if not all studio recordings after 1980 (or 1930 if you start at the rhythmicon) to be sure you don't fix things that aren't broken. The amount of effort that will take means MQA cannot get a huge library.

- if MQA does have a large library, it means they just used a somewhat generic filter over an already mastered album, which will have very unreliable effects.

Bonus question:

- lossy formats have ringing effects because math tells them they should. How weird is it to introduce ringing while trying to battle ringing?

 

A marketing director of Meridian (long story) wasn't able to find faults in my reasoning, and obviously neither can I. So, does my reasoning make any sense or am I wrong?

 

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