MQA is Vaporware

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8 hours ago, Lee Scoggins said:

 The MQA encoded files sounded better to my ears in each instance.

 

Better enough to warrant the creation of landfill?

 

Better enough to obsolete present-day DSP-enabled systems?

 

Better enough in a way that a mastering professional cannot achieve with regular tools?

 

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2 hours ago, firedog said:

with such a tone?  I'm sorry, there's and edge to this post that isn't warranted.

 

No tone, and no negativity intended.

 

The questions are genuine: if someone thinks this really sounds better, then one wants to know if the quality difference really is worth the consequences of adopting this format: the wholesale dumping of incompatible DACs and DSP gear.

 

Apart from this ... censeo MQAm delendam esse, yes.

 

 

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31 minutes ago, Lee Scoggins said:

The real problem here are armchair idiots like yourself who can't respect a differing opinion.  Go back to school and take a Debating 101 course and learn how to present some points backed up by some evidence before slamming the journalists who are working hard to explore audio.

 

The real problem here are industry idiots like yourself who can't respect a differing opinion.  Go back to school and take a Debating 101 course and learn how to present some points backed up by some evidence before slamming the hands-on amateurs (I hope you understand Latin?) who have worked hard to explore what MQA really is.

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28 minutes ago, Norton said:

I'm sure MQA would argue they actually support streaming up to 384kHz, but I am aware that subsequent unfolds are consider by many to be simply proprietary upsampling

 

Not 'considered'. 'Considered' still has the possibility that it is not more than an opinion, whereas it is a hard, objective fact that after the (misnamed) 'first unfold' only upsampling happens. And this upsampling remains under the MQA aegis until the original master's sampling rate is reached.

 

This is the process for a 384k master:

 

-downsample to 192k with leaky MQA filter

-downsample to 96k with leaky MQA filter

-fold into 48k space using Quadrature Mirror Filter pair 1 (*)

=============================================

-unfold 48k to 96k using Quadrature Mirror Filter pair 2

-upsample to 192k using leaky filter

-upsample to 384k using leaky filter

-light the blue LED

 

 

(* As an aside: the output of QMF1 is what people without MQA decoding have to listen to.

QMF1 has to be optimised to allow a lossless split-join in the origami folding step. This is an

extremely limiting constraint. This means that QMF1 cannot likely be optimised, at the same time,

for optimal sound quality for non-MQA listening. This is mathematics.)

 

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11 minutes ago, Norton said:

 I come  back with the fact that my DAC tells me it's receiving a MQA stream at 96kHz which in turn sounds to me every bit as good, if not better,  than my 24/96 non-MQA download copy.

 

Even if MQA's sound was utterly and consistently sublime, MQA itself, and especially its current implementation, would still be a very bad idea for the consumer.

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21 minutes ago, Norton said:

 Tidal/MQA is offering me what I consider to be, in certain cases at least, true  96kHz streaming today.  I'm not aware that anyone else offers that, other than maybe Qobuz.

 

There is nothing wrong with a streaming provider using proprietary technology to transport data between their servers and their proprietary app as installed on your PC, phone, whatever.

 

It gets totally wrong when, without any valid justification, you are required to purchase a new DAC (presumably ditching the old one), and in the case of a fully digital system (i.e. a system where the DAC cannot be replaced), to purchase a large part of that system anew (presumably ditching the old bits).

 

Now from a manufacturer's point of view ...

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4 minutes ago, Norton said:

Maybe ... And new DAC not required.

 

Enjoy.

 

But know that in the original plans MQA had for us this scenario was explicitly not allowed. You had to buy a new DAC.

 

I'd like to think that after the initial wave of critique on various forums in 2015-2016 (but not in the audio press!)  MQA compromised and opened the door for partial decoding in software. But so far this decoding is only available from Tidal and from the Node2 streamer.

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2 minutes ago, mansr said:

The decoder may or may not upsample to the original rate of the master. It depends on the capabilities of the DAC chip and other parts. The blue light comes on regardless, of course.

 

Assuming sufficient capabilities, of course.

 

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46 minutes ago, Shadders said:

What is the type and order of the Quadrature Mirror Filter ?

 

It is not a filter type, but rather a relationship between two filters, so that when combined they satisfy (free of error) a specific criterion. In this case two QMF pairs have to be used to split a 96k signal into two bands that each can be sampled at 48k, so that after recombination the original 96k signal is obtained again.

 

https://en.wikipedia.org/wiki/Quadrature_mirror_filter

 

It is my suspicion that the two origami folding QMFs do not reach their stop band exactly at 24kHz(*). In other words, both would alias badly when resampled to 48k. A direct consequence of this is that the baseband signal of a hi-res MQA file must be infected with aliasing. If and when the true nature of the encoding QMFs is revealed then this would constitute mathematical proof that the undecoded MQA signal is objectively inferior to CD-rate, contrary to MQA's claims.

 

 

(* Why? Well ... this universe was not created for the sake of audiophiles, otherwise playing LPs properly would not be an insolvable problem. It would be one hell of a coincidence if a set of filters would at the same time satisfy an audiophile's needs and the double QMF criterion.)

 

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12 minutes ago, Shadders said:

I do believe that there must be an order to the filter -

 

Of course. But with the present public knowledge we cannot know that order. It would be immensely interesting to have access to an MQA encoder. My first test would consist of pink noise steeply filtered below, and then above, exactly 24kHz, in each case studying the undecoded output signal.

 

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11 minutes ago, Shadders said:

 yet they use extremely high order filters (QMF) which will cause significant dispersion, and this is not corrected.

 

1) there is nothing that forces the QMFs to be extremely steep, so your assertion is based on no evidence.

 

2) due to the QMF property the recombination of the two bands is totally lossless. This is proven: passing a 96k original through MQA gives a pretty decent copy of that original.

 

 

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6 minutes ago, FredericV said:

Why does MQA encoding downsample twice, instead of downsampling directly from 384K to 96K in one step?

 

That was just for the explanation. Maybe MQA uses sequential steps, maybe all in one go. It probably depends on whether they have developed their filter herd for /2 steps only, of for all possible source and target rate combinations. But this does not matter. We are discussing concepts, not implementations.

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Just now, Shadders said:

, if the recombination is totally lossless, then dispersion is not an issue, hence MQA is not required.

 

No. MQA's fight with blur is at the top of the signal band, in our 96k example at 48kHz.

If the QMFs injected their own blur, for whatever reason, then this would affect the area

of 24kHz. But we know from spectral analysis that after unfolding the 24kHz area does not

seem to be damaged: 'pretty good'.

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20 minutes ago, mansr said:

"Temporal blur" doesn't need to be anything at all beyond a made-up marketing term.

 

Come on.

 

Ever since Craven's first papers on the subject, back in 2006 or so, we surely all know they are on a crusade against the ringing seen in the impulse response of steep low-pass digital filters, especially linear phase filters.

 

The audiophile face of MQA is all about avoiding visible ringing by not using any steep filters in the signal path. Leaky filters are selected, allegedly on a per-case base, so that any aliasing falling below 20kHz is of the same order as the programme's innate noise.

 

 

This of course ignores the inconvenient fact that the aliasing can only be low when the signal content at the filter's transition is low too, in which case its ringing would be low as well.

 

When it comes to blur, MQA is a solution without a problem. When it comes to streaming hi-res, MQA is a solution without a problem.

 

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18 minutes ago, Shadders said:

Dispersion appears across the entire audio band -

 

Think linear phase. Still the standard in production ADCs and SRCs.

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11 minutes ago, Shadders said:

MQA are not specifically stating that the ADC and SRC's are the only issue. The filters used may be other types in the recording chain.

 

Reading between the lines, ADC and DAC are what they are after. Compensating for anything else is simply not feasible, nor actually desireable. Although I have a feeling that MQA would not object to people thinking they are trying to compensate for everything, which indeed has happened on overheated forums  ;-)

 

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6 hours ago, Shadders said:

Advertising standards hopefully would examine these aspects. I do not think that only having half the information is subjective - it is factual.

 

Don't be naive. For an AS body to take this on it needs access to impartial expertise. Impartial almost implies people from outside the music or sound industry, and as for expertise ... my guess is that not even 10% of trained engineers totally and deeply understand sampling as it pertains to audio.

 

And this is even without touching the entirely subjective nature of things, as well as the non-standard language used in the MQA claims.

 

MQA is too slippery, too sneaky for this.

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10 minutes ago, Lee Scoggins said:

MQA may be advantageous as it can enhance 24/48 and 16/44 files as well.

 

So you believe ...

 

But then anyone can enhance 1x files. No need for a closed system with Trojan DRM and misleading claims.

 

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6 minutes ago, Norton said:

The 2l site shows that a MQA a file is c. half the size of 24/96, presumably that has something to do with it's "stream-ability" ?

 

You should compare with 18/96. It has been shown that this compresses as good as or better than MQA.

It is trivial to generate an 18/96 copy of a 24/96 original. This does not tax the server side at all.

 

6 minutes ago, Norton said:

The 2l site shows that a MQA a file is c. half the size of 24/96, presumably that has something to do with it's "stream-ability" ?

 

I am coming at this from the assumption that, ... where ... the MQA stream decodes  at 96kHz to my non-MQA DAC,  then what I am getting is no less than what a ...24/96 download would offer at the same resolution.  

 

It is less. The unfolded MQA is equivalent to 17-18/96, not 24/96.

 

Again, MQA is a solution without a problem. Therefore it is not a solution.

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5 minutes ago, Shadders said:

The number of engineers that understand sampling etc., in other engineering domains such as RF, communications, and other areas of electronics, dwarfs the audio industry.

 

I was specifically targetting engineers outside of audio. I know many of these. I am two of them myself. Specific branches of RF and comms left aside, trust me that many do not properly understand sampling in all of the nuances that matter in audio. That is because of lacunes in education, and because of the little fact that sampling in many disciplines is resource-constrained and hence is implemented via shortcuts and approximations that have become totally embedded in thinking. Audio is about the only discipline where everything can be done by the book. But then you have to read the right book.

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1 minute ago, Shadders said:

In essence, the fact that the MQA DAC for 192kHz sampling has half the bandwidth empty, and MQA are claiming that you are receiving the entire 96kHz bandwidth, is fraud.

 

It is not fraud, because MQA do not explicitly claim that they convey the entire 96kHz payload band of a 192kHz original. What they do claim is that they convey the sub-48kHz part plus an overall impulse response commensurate with the original 192k (or 384k) sample rate. The Blue LED is there

1) to tell you the original rate

2) to assure you that no-one has tampered with the file between creation and delivery.

 

Look at it this way: the people behind MQA are rather smart (really). They are smart enough not to claim something that can be refuted easily for a jury of relative laypeople.

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12 minutes ago, Shadders said:

You cannot hear what was recorded in the studio for the 2nd and 3rd unfold if that bandwidth is empty.

 

But you also cannot hear that if that part of the spectrum is not empty. When will you see that all of their claims are in the subjective realm, and thus nearly impossible to attack?

 

Anyway, the 2014-2015 MQA papers explicitly state that humans do not hear ultrasonics, that the ultrasonic sound can safely be removed, and that this operation can be called 'subjectively lossless'.

 

 

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2 minutes ago, mansr said:

What's the difference?

 

The avoidance of anti-aliasing filters, knowing that the original signal has next-to-no content above fs/2.

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48 minutes ago, FredericV said:

This means the first unfold has no purpose. The first unfold just recovers one more octave in the ultrasonic range, which we can't hear.

 

Certainly not. MQA lives by tolerating aliasing from above 48kHz. Given the nature of music the impact on the audible band is negligible (at least in some cases).

 

But they cannot tolerate aliasing from the 24-48kHz band, it would simply overwhelm the music's highest audible octave. And MQA also cannot properly filter at 24kHz, because filters are evil. So they have to pass on 96k, in this case via the (Japan-invented) origami method.

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11 minutes ago, Em2016 said:

Are we now all in agreement it's not worse (technically) than CD quality?

 

I fully expect, sooner or later, objective proof that the filtering necessary for the origami band splitting is damaging to the quality of the CD-rate baseband signal in MQA.