Article: MQA: A Review of controversies, concerns, and cautions

[Archimago]

1 hour ago, miguelito said:

I read this review on the magazine. All I can say is "Bravo!" for the restoration of this recording. I will also say that's there's nothing that standard PCM could not do here - I much rather get the full-res restored version than the MQA version.

 

Sadly, all I can find is an AAC version of the MQA release on iTunes! So not only is it 16/48, it is 16/48 already compressed! 

 

Take away that Bravo!!!

 

Correct, it's an old 16/50 digital recording which sounds like has been remastered/restored to 16/48 (presumably 24-bit or 32-bit processing applied). I guess there must be some kind of MQA-CD 16/44.1.

 

I'm still curious about what they did to the DR with the new Toneff/Dogrobosz Fairytales! If that has been altered significantly, we wouldn't be able to compare the original CD with this MQA version "apples to apples" and would reflect more than just pitch correction and "deblurring".

[Archimago]

7 minutes ago, adamdea said:

What sort of AA filter did the pcm 1630 have?

 

Check this page out:

http://www.gammaelectronics.xyz/s_1987-8_sony_r-dat.html

 

I see a bunch of minimum phase steep filters. Not sure if this applies through the whole Sony production chain back in the day...

 

[adamdea]

6 minutes ago, Archimago said:

 

Check this page out:

http://www.gammaelectronics.xyz/s_1987-8_sony_r-dat.html

 

I see a bunch of minimum phase steep filters. Not sure if this applies through the whole Sony production chain back in the day...

 

Thanks Arch

Confusingly the 1630 manual refers to sone sort of linear phase compensation in the a/d.

https://www.manualslib.com/manual/452275/Sony-Pcm-1630.html?page=5#manual

Don't quite grasp how that works, or what it would not show up in figure 11 of the gamma electronics

[Archimago]

47 minutes ago, adamdea said:

Thanks Arch

Confusingly the 1630 manual refers to sone sort of linear phase compensation in the a/d.

https://www.manualslib.com/manual/452275/Sony-Pcm-1630.html?page=5#manual

Don't quite grasp how that works, or what it would not show up in figure 11 of the gamma electronics

 

Yeah, I wondering if others have experience with these old Sony devices...

 

Just to put this into context also, we're talk mid-80's technology and that PCM R-DAT link was from 1987 :-). I don't know about you guys, but that was more than half a lifetime ago for me. Whether MQA improves time domain performance on these old digital recordings or not could be somewhat interesting for those of us interested in remastered "dad rock" and the first generation of classical albums, I guess...

 

But man, if we're honestly talking "high resolution", none of these recordings - digital or analogue - from that era were high-res anyway by today's standards!

[sullis02]

Speaking of  'time domain performance' correction--  remember Plangent processing?  It "basically uses recovery of the bias tone off analog recordings to "realign" the audio to the state it was in while being tracked or mixed."   So I'd guess the time domain aberrations being corrected with PP (tape wow/flutter) are likely orders of magnitude worse than the ADC-based (non?)issues MQA is aiming at...but then again I don't really know what MQA is aiming at!  

 

http://audiophilereview.com/analog/plangent---a-better-way-to-transfer-analog-tape.html

 

 

[miguelito]

51 minutes ago, sullis02 said:

Speaking of  'time domain performance' correction--  remember Plangent processing?  It "basically uses recovery of the bias tone off analog recordings to "realign" the audio to the state it was in while being tracked or mixed."   So I'd guess the time domain aberrations being corrected with PP (tape wow/flutter) are likely orders of magnitude worse than the ADC-based (non?)issues MQA is aiming at...but then again I don't really know what MQA is aiming at!  

 

http://audiophilereview.com/analog/plangent---a-better-way-to-transfer-analog-tape.html

Very cool!

[miguelito]

1 hour ago, Archimago said:

But man, if we're honestly talking "high resolution", none of these recordings - digital or analogue - from that era were high-res anyway by today's standards!

I don't think you can say this for analog! There are some truly amazing sounding analog tapes from the 50's, 60's...

[Archimago]

8 minutes ago, miguelito said:

I don't think you can say this for analog! There are some truly amazing sounding analog tapes from the 50's, 60's...

 

Yes, they sound great... And I suppose some of the material can benefit from high samplerate like 96kHz to capture all the content. Not sure they would need >16-bit resolution.

 

In any event... Another big debate apart from MQA .

[FredericV]

9 hours ago, miguelito said:

Why can't I put step 'b' in step '3'? Are you saying that the lossy MQA compression is inextricable from 'b'? Why would that be? And if there's some processing done in 'c' that is part of 'b', why couldn't I still put it in '3'?

 

Looking at Archimago's & Mansr's research, I believe this is exactly what they do in the renderer in combination with dithering and upsampling.

Why would they need 32 filters, where every file has one pre-defined applied filter out of those 32 available filters?
The coordinates of those filters were also dumped and reverse engineered.

[Archimago]

1 hour ago, sullis02 said:

... So I'd guess the time domain aberrations being corrected with PP (tape wow/flutter) are likely orders of magnitude worse than the ADC-based (non?)issues MQA is aiming at...but then again I don't really know what MQA is aiming at!  

...

 

 

And this is why we're back to square one. You're right, with analogue tape/vinyl wow and flutter we are talking about audible temporal anomalies easily measured (fixable with PP), and in many cases easily audible. In the world of decent digital, we are talking about picoseconds and some of the worst devices measuring in the nanosecond range for jitter.

 

After more than 3 years, we don't even know IF MQA does anything special in the time domain, much less be able to judge that this "thing" is beneficial!

 

In the legal world and at times related to my day job, if an "expert" (say BS) were to be allowed admissible evidence before the courts, there is in the United States something called the "Daubert standard". This is a test of whether something passes an adequate level of "scientific knowledge" (as opposed to unreliable pseudoscience) as to be seriously considered. Let's quote from Wikipedia the criteria:

 

 

Quote

 

1. Whether the theory or technique employed by the expert is generally accepted in the scientific community;
2. Whether it has been subjected to peer review and publication;
3. Whether it can be and has been tested;
4. Whether the known or potential rate of error is acceptable; and
5. Whether the research was conducted independent of the particular litigation or dependent on an intention to provide the proposed testimony.

 

 

So for the concept of "deblurring", based on what has been produced by the MQA claims/Bob Stuart:

 

1. There is no evidence that the scientific community has been able to scrutinize the time-domain claims.

2. As far as I am aware, the "deblur" technique has not been published about in a peer-reviewed way in the audio engineering world.

3. We have no way to test the "deblurring" independent from the compression/"origami"/bit-depth reduction, due to the "packaging" MQA uses.

4. Not exactly applicable since we're not specifically concerned about "false positive" or negatives. The main thing is we don't have much evidence that the technique seems all that impressive (eg. my Internet Blind Test does not show impressive benefits, and many people have voiced both good and bad to the resulting sound quality).

5. We have seen no independent research on MQA's "deblurring" apart from claims from the company. (Maybe the McGill study can shed some light if they have access to just the "deblurring" effect.)

 

Now, obviously we're not entering evidence in the court of law... But I think it's fair to say that so far, the "scientific evidence" is absent and there is no way we can even test the claims ourselves without MQA's cooperation. I honestly think that until there is something of substance to be said, it's actually fair to dismiss claims that MQA does anything of value as a "deblur" technique.

 

Until even the definition of what "deblurring" is can be made clear, there is nothing here to talk about. This is like the audiophile version of Fleischmann & Pons' "cold fusion" - but even they had a paper published .

[tmtomh]

3 hours ago, sullis02 said:

Speaking of  'time domain performance' correction--  remember Plangent processing?  It "basically uses recovery of the bias tone off analog recordings to "realign" the audio to the state it was in while being tracked or mixed."   So I'd guess the time domain aberrations being corrected with PP (tape wow/flutter) are likely orders of magnitude worse than the ADC-based (non?)issues MQA is aiming at...but then again I don't really know what MQA is aiming at!  

 

http://audiophilereview.com/analog/plangent---a-better-way-to-transfer-analog-tape.html

 

 

 

For years I've been wishing there'd be a computer audio editor plugin for the Plangent Process.

[Ralf11]

AFAIK, it is very involved, and requires a team of humans. 

 

One of the people involved mentioned they are trying to apply it ot cassette tapes, but have been unsuccessful so far.

[miguelito]

3 hours ago, Archimago said:

it's actually fair to dismiss claims that MQA does anything of value as a "deblur" technique.

I am fairly convinced at this point that “deblurring” refers to the use of very slow rolloff filters on rendering. Until proven otherwise...

[miguelito]

2 hours ago, tmtomh said:

 

For years I've been wishing there'd be a computer audio editor plugin for the Plangent Process.

Surely this is done in software, no? The wideband reading head retrieving the music and discerning the modulation out of that, and then applying these corrections in software?

 

I imagine you’d need to have a special filter to get the actual music from the readout given the signal is probably tilted towards the high frequencies more than normal.

[Rt66indierock]

On 3/14/2018 at 8:41 AM, Doug Schneider said:

 

IMO, MQA wouldn't have had any traction anywhere had a couple (or few) print and online magazines so enthusiastically promoted it at the beginning. IT types dismissed it, recording engineers had no clue what it was, but a few hi-fi reviewers went so over the top with their praise without even knowing what it really was, it managed to gets some wind in its sails. If the latter hadn't happened, we wouldn't be talking about it today. I firmly belive that. With that in mind, the magazine that did go so over the top wasn't yours -- in fact, it's not even discussed her. Charley Hansen -- the most vocal anti-MQAer there was -- wouldn't even discuss them because, in his words, "they are a lost cause." To many, ComputerAudiophile.com was lumped in that camp. What helped shake that was Chris's insistence not to pull down the "MQA is Vaporware" thread, which, for the longest time, gave the hi-fi world the most in-depth look at another side to a story that most of the print and online press was pretending wasn't there. I know that some wanted to see it gone, but it's there. I just looked -- that thread was started January 2, 2017. Not as long a go as I think it should've started -- January 2, 2016 would have been more like it -- but it's been well over a year now, so credit for that. In the last week, we now have Archimago's article, which is having an enormous impact. 

 

That initial time for MQA promotion began about 3 years ago. You cite recent and current examples of taking a more critical approach. But do you think the first 2.5 years of coverage helped contribute to what Jon Iverson just wrote in your magazine: "I just hope it's not too late"?

 

I know you'll make up some excuse why you won't answer, but I'm sure others will.

 

Doug 
SoundStage!

 

Doug,

The thought process for “MQA is Vaporware” started in June of 2016 after T.H.E. Show Irvine California. The vibe around MQA just felt wrong and the promotion was a bad combination of Golf Channel ads, OS/2’s rollout and the pitches I get from wealth managers.  It took a while to analyze the issues and what was real and what was just marketing without any substance behind it.  Sorry I couldn’t do it quicker.

[Doug Schneider]

1 minute ago, Rt66indierock said:

 Sorry I couldn’t do it quicker.

 

Forgiven -- hindsight is 20/20. ;-)

 

Doug

[Archimago]

2 minutes ago, miguelito said:

I am fairly convinced at this point that “deblurring” refers to the use of very slow rolloff filters on rendering. Until proven otherwise...

 

You could be right...

 

If that truly is all it is, makes this the most underwhelmingly overhyped "revolutionary" "paradigm" of a "format" to date!!!

[tmtomh]

Our old friend Lee Scoggins is at it again over at the Hoffman forums, including some passive-aggressive character assassination of both @Archimago and @The Computer Audiophile:

 

http://forums.stevehoffman.tv/threads/mqa-a-clever-stealth-drm-trojan-ccc-talk.735825/page-6#post-18296864

[asdf1000]

2 hours ago, miguelito said:

I am fairly convinced at this point that “deblurring” refers to the use of very slow rolloff filters on rendering. Until proven otherwise...

 

Like this?

 

"This “slow roll-off” filter reduces the time smear by a factor of ~20x compared to conventional digital filters. The net result is a much more musically natural sound, as the ear-brain is very sensitive to time-related distortions. This filter provides an outstanding compromise between frequency response and transient response, and for ten years was the mainstay of Ayre’s digital audio filters."

 

https://www.ayre.com/pdf/Ayre_MP_White_Paper.pdf

 

 

[Archimago]

1 hour ago, tmtomh said:

Our old friend Lee Scoggins is at it again over at the Hoffman forums, including some passive-aggressive character assassination of both @Archimago and @The Computer Audiophile:

 

http://forums.stevehoffman.tv/threads/mqa-a-clever-stealth-drm-trojan-ccc-talk.735825/page-6#post-18296864

 

Looks like the same arguments he had a month ago before the previous thread on MQA got taken down after 50 pages or so at Steve Hoffman's. Of course, back then @The Computer Audiophile wasn't on his "hit list" as I recall .

 

@Lee Scoggins, I see you're not banned from here, so feel free to let us know the experiment results with those A/B files... Hmmm, did you ever publish a "part 2" to your MQA report? I thought you were going to do some research beyond being impressed by the "thousands of albums are coming and it sounds good to me"...

[jimtranr]

53 minutes ago, tmtomh said:

Our old friend Lee Scoggins is at it again over at the Hoffman forums, including some passive-aggressive character assassination of both @Archimago and @The Computer Audiophile:

 

http://forums.stevehoffman.tv/threads/mqa-a-clever-stealth-drm-trojan-ccc-talk.735825/page-6#post-18296864

I didn't think his commentary was that "passive". But he blew the effort the instant he uttered "almost all of the musical information". I'm no techie by any stretch, just an interested lurker, but 15-to-17-bit horseshoes and hand grenades are not what hi-rez is supposed to be about, is it. 

[Fokus]

15 hours ago, miguelito said:

Where did you get that from?? So you're saying that deblurring cannot be done on any recording done to redbook format such as Dire Straights's "Brothers in Arms"??? It is precisely in these early digital cases where it would make the most sense.

 

Where? By deeply understanding, since 2014, what MQA is about.

 

There are two approaches to deblurring in this story.

 

1) Start at 192k or higher, and downsample to 96k with a narrow-impulse, leaky filter that injects aliasing (but hopefully not too much) and that (also hopefully) puts a null at the original ADC's filter transition frequency. It is totally clear that this is exactly what MQA are doing today for such originals.

 

2) Start at 96k or lower. In this case there is no downsampling possible, so they will have to revert to eq-style solutions. This can be additional narrow-impulse low-pass filtering for a 96k original (i.e. apodising in Meridian-speak). For 44.1k and 48k not even this is possible, so all that could be done is some phase/group-delay equalisation, perhaps also level equalisation, at the treble end.

[Fokus]

11 hours ago, adamdea said:

What sort of AA filter did the pcm 1630 have?

 

All Sonys at that time used encapsulated multi-pole (presumably elliptic) analogue minimum phase filters. I have the phase or group delay plot of one of these at home. Attenuation at Fs/2 is also not to be sniffed at. Years ago I ran a bunch of my oldest CDs (most of them would have been passed through a PCM16*0) through an analyser and found that the energy above 20kHz tended to be significantly less that in the case of more modern CDs (mastered with linear-phase half-band filters).

 

The site Archimago linked to shows the impulse response of a 1630:

 

 

There are also partial frequency responses there. If a restoration process had access to the exact ADC that was used in a mastering, they potentially could characterise its individual frequency magnitude and phase responses, as well as linearity errors, and compensate for this. Assuming, of course, that the thing hadn't drifted through ageing. And that's a big stretch ...

 

 

 

[Fokus]

11 hours ago, adamdea said:

Thanks Arch

Confusingly the 1630 manual refers to sone sort of linear phase compensation in the a/d.

 

 

Not linear phase. Presumably an additional all-pass network that reduces the non-linear phase component in its response somewhat. I'll see if I can find that old group delay plot.

 

 

Edit: got it.

 

Look in this document at Figure 3 and the text below it.

 

http://www.audio-focus.com/Townsend/pdf/Why_supertweeters.pdf

 

 

(Apparently with thanks to Peter Baxandall...)

[Don Hills]

29 minutes ago, Fokus said:

 

All Sonys at that time used encapsulated multi-pole (presumably elliptic) analogue minimum phase filters. ...

 

Just to complicate things, there was also an aftermarket filter set for the Sonys that was quite popular. The brand name escapes me at the moment...