MQA bails on Rocky Mountain Audio Fest*

one never knows if

Has any mastering engineers ever chimed in? Barry would probably have some welcome opinions.

 

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Bruno Putzeys
on Saturday
This isn't a prelude to suddenly becoming active on FB but I felt I had to share this.

Yesterday there was an AES session on mastering for high resolution (whatever that is) whose highlight was a talk about the state of the loudness war, why we're still fighting it and what the final arrival of on-by-default loudness normalisation on streaming services means for mastering. It also contained a two-pronged campaign piece for MQA. During it, every classical misconception and canard about digital audio was trotted out in an amazingly short time. Interaural timing resolution, check. Pictures showing staircase waveforms, check. That old chestnut about the ear beating the Fourier uncertainty (the acoustical equivalent of saying that human observers are able to beat Heisenberg's uncertainty principle), right there.

At the end of the talk I got up to ask a scathing question and spectacularly fumbled my attack*. So for those who were wondering what I was on about, here goes. A filtering operation is a convolution of two waveforms. One is the impulse response of the filter (aka the "kernel"), the other is the signal.
A word that high res proponents of any stripe love is "blurring". The convolution point of view shows that as the "kernel" blurs the signal, so the signal blurs the kernel. As Stuart's spectral plots showed, an audio signal is a much smoother waveform than the kernel so in reality guess who's really blurring whom. And if there's no spectral energy left above the noise floor at the frequency where the filter has ring tails, the ring tails are below the noise floor too.

A second question, which I didn't even get to ask, was about the impulse response of MQA's decimation and upsampling chain as it is shown in the slide presentation. MQA's take on those filters famously allows for aliasing, so how does one even define "the" impulse response of that signal chain when its actual shape depends on when exactly it happens relative to the sampling clock (it's not time invariant). I mentioned this to my friend Bob Katz who countered "but what if there isn't any aliasing" (meaning what if no signal is present in the region that folds down). Well yes, that's the saving grace. The signal filters the kernel rather than vice versa and the shape of the transition band doesn't matter if it is in a region where there is no signal.
These folk are trying to have their cake and eat it. Either aliasing doesn't matter because there is no signal in the transition band and then the precise shape of the transition band doesn't matter either (ie the ring tails have no conceivable manifestation) or the absence of ring tails is critical because there is signal in that region and then the aliasing will result in audible components that fly in the face of MQA's transparency claims.

Doesn't that just sound like the arguments DSD folks used to make? The requirement for 100kHz bandwidth was made based on the assumption that content above 20k had an audible impact whereas the supersonic noise was excused on the grounds that it wasn't audible. What gives?

Meanwhile I'm happy to do speakers. You wouldn't believe how much impact speakers have on replay fidelity.

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* Oh hang on, actually I started by asking if besides speculations about neuroscience and physics they had actual controlled listening trials to back their story up. Bob Stuart replied that all listening tests so far were working experiences with engineers in their studios but that no scientific listening tests have been done so far. That doesn't surprise any of us cynics but it is an astonishing admission from the man himself. Mhm, I can just see the headlines. "No Scientific Tests Were Done, Says MQA Founder".

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The whole streaming and digital music world appears to be dominated by Apple, Spotify, Pandora, and Amazon. I just don't see how alternative digital music files and streaming are ever going to take hold unless those providers adopt them...regardless of fidelity improvements. I imagine someday Apple will have a new format for folks to stream or rebuy. I just don't the demand is there for the big boys to change which means formats like MQA may see the same fate as DVD-A.

 

In order:

• Spotify - 60 million paid subscribers
• Apple Music - 28 million paid subscribers
• Amazon Music Unlimited - 16 million paid subscribers
• Deezer - 12 million paid subscribers
• Google Play - no official numbers. Estimates vary - some say near Spotify numbers in the US
• SoundCloud - 175 million unpaid users
• Tidal - 3 million paid subscribers
• Pandora - US only. Don't have subscriber numbers

 

That is streaming. What about digital downloads for purchase?

 

Do you know how many of the supposed 3 million Tidal subs are on the "hifi" tier?

I was told by a good source 100,000.

Also include YouTube, and you can add hundreds of millions.

 

For lossless....Infinitesimal. A pin prick.

 

Indeed. Hard to quantify. A Google acquisition.

 

On the way out.

 

Maybe, but they aren’t gone yet.

 

No, but for this little black duck, they are a non-starter.

 

Not everything about audio engineering gets published. And even less info about audio engineering will show up in a general Google search. Proprietary R&D does not get published, or really even talked about publicly.

Ask some digital audio engineers how to design a ADC and DAC pair that sound especially good together. The ones who know what they're doing will probably talk about optimizing the filters for the AD and DA to optimize the timing of each and other factors so they pair especially well together. They may never use the word "temporal" and certainly won't use the phrase "temporal blur", but what they explain will demonstrate that they do understand the ideas and importance of optimizing the filters to work together. Meridian didn't invent a whole new theory of digital audio. This is stuff that has been known. What's interesting with Meridian's MQA approach is that it's a way to optimize that timing and minimize the temporal blur with many different AD/DA pairs rather than just one specific AD to one specific DA. Just because those specific phrases and words about digital audio don't show up in a Google search doesn't mean that knowledgeable engineers didn't already know of the ideas and weren't already applying some of them in their own work.

This minimizing of temporal blur with the filter modifications is the only part of MQA that I find interesting. I'm curious if that is offering audible benefits and what that sounds like compared to regular unadulterated high-res PCM. The rest of MQA with the folding and origami and lossy encoding is not interesting to me at all and undesirable.

 

We also shouldn't inadvertently imply that none of us hear the benefits of high-res vs 16-bit redbook audio. I just did the test with "Fortunate Son" that Steve mentioned. I finally have the ability to play SACD on my system. Just got that Creedence Clearwater Revival SACD today. Did the listening test. I hear it. But then again, I'm already a high-res convert and hear the benefits of high-res over 16-bit CD in many other recordings. I'm also 50 and recovering from a double ear infection. My hearing is not fully recovered from that ear infection. Yet I'm still able to hear the difference of high-res vs. CD. This doesn't require bat like hearing. I'm proof.

MQA seems to be mostly about optimizing the digital filters. Differences in digital filters can be subtle. I wouldn't expect those differences to be obvious. I would expect those sorts of differences to be the sorts of things you need to concentrate on to hear. Similar to the differences between high-res and CD.

 

When I used to make presentations one the most difficult issue I had with slides was to convert a technical feature into a real benefit for the end user. Out of 10 points, I usually managed to get about 3-4 right, which is better than what you might get from a typical corporate marketing drone. I admit that it's been years since I had a relapse of PowerPointism but for the life of me I can't find a single benefit to the end user in the whole MQA saga.

Perhaps this is what prompted the bailout from the MQA panel? I mean, 3 years down the road and you get on one side a block of audio gear manufacturers who blackballed the technology and on the other side a group of users who start wondering where exactly are the benefits of changing one set of DSP and filters for another set, but this time its a set that won't allow you to add or integrate other filters. That's not exactly the audience anyone want to face during an open session panel.

 

I'm 52 and I had the same, or a similar, ear condition, albeit some years ago. Neither of us are proof. Rather, we're anecdotal. Let's not confuse one person's anecdotal experience with proof across the board. Big difference.

 

It's proof to me that you don't need to be a teenager with perfect youthful hearing to hear the benefits of high-res over CD. You just need to know what to listen for and have gear that allows you to hear that. The ear infection experience also demonstrated to me that even when I reach 70 I'll still be able to hear the benefits of high-res and the benefits of whatever gear I have then. You don't need golden hearing to hear these things.

It's funny that it's usually old guys trying to convince the younger people that high-res has audible benefits. Youthful hearing is wasted on the youth.

 

Youth is wasted on the young.

 

I think it's funny that even after all this time some old guys are still convinced medium trumps mastering. Didn't the Genesis SACDs teach us anything...

 

Apple does not need a new format. Apple lossless is already a smaller file size and works on all the Dacs out their. From what i have been told, All of apple’s music content is stored on their servers at 16/44 or higher. The music is downsampled on output ( streaming purchases, etc). So apple can turn on lossless anytime.

 

Yes I agree, it´s surprisingly odd, to put it mildly.

 

I would like to believe that. But ...

 

Who asserted that all hi-res bests 16/44 irrespective of mastering? Member Ham certainly suggested nothing of the sort.

 

It's a common thing. Introduce the "next big thing" and it's all hands on deck. Format alone is no guarantee.

 

That is a straw man. I have never claimed, nor do I believe, that medium trumps mastering. A bad mastering in high-res is not going to sound better than a good mastering on CD.

With equal masters, high-res can sound better than CD. Not always. Depends on how well they did the recording and mastering.