MQA pt II
- Thread starter Jim Audiomisc
- Start date
mansr
Objectionist
I'm from Sweden and lived in Norway for a while. Spoken Danish can be a challenge, though.
Maybe MQA can deblur it.
Rosewind
Lost in Translation
"
Bruno Putzeys
about 4 years ago
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.
________
* 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."
https://www.hifisentralen.no/forumet/threads/mqa-the-awakening.101158/post-3291298
Bruno Putzeys
about 4 years ago
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.
________
* 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."
https://www.hifisentralen.no/forumet/threads/mqa-the-awakening.101158/post-3291298
Rosewind
Lost in Translation
Wavelets, spline wavelets, b splines, pyramid algorithm = Origami.
Does this ring a bell? See the links in the post.
https://www.hifisentralen.no/forumet/threads/mqa-the-awakening.101158/post-3291130
Does this ring a bell? See the links in the post.
https://www.hifisentralen.no/forumet/threads/mqa-the-awakening.101158/post-3291130
adamdea
You are not a sound quality evaluation device
Is “Kamelasa” Danish for “Fork handles”?
mansr
Objectionist
It's kamelåså, and I don't think it means anything at all.
adamdea
You are not a sound quality evaluation device
Sorry my weak joke. It reminded me of
Jim Audiomisc
pfm Member
I'm wondering if there is an element that is beyond being iron-y...
The ground seems to have moved from systems tested to see if their losses are audible to a dictate handed down on tablets of stone as to what is or is not 'music'.
Oddly, the BBC's aac seems to do a decent job on the prom I referenced. Although I regret the loss of 320k from their TV files/streams.
Jim Audiomisc
pfm Member
Perhaps the root of this problem was that too many copies of the reduced-size Abramowitz and Stegun have been sold. All too easy to open it at random and find pretty gems to technobabble. Or should I blame "Numerical recipies..." ? 8-]
A few weeks ago I saw an interview via a 'zoom' with an arty type on TV. They had a copy of 'Gravitation' (MTW) on their bookshelf. Obvious from its spine. I wondered if their location had a particularly warped space to get it there. But decided that it was a fake backdrop to show how clever they were.
davidsrsb
pfm Member
Designing and supplying backdrop shelves to impress is a genuine job this year.
mansr
Objectionist
It's the other way around. Tidal "hifi" supplies MQA-CD data without activating its built-in decoder. If you have a DAC with full MQA support (and bit-perfect exclusive mode audio output), you get almost CD quality, otherwise you're stuck with substantially less.
kaolin
Active Member
I've listened to a Hifi album (no equivalent Master version) and my streaming option is set to Master.
The sound quality is MQA like with a sense of focus a little cleaner, but when I set my streaming option to HiFi the sound quality is the same as my CD-rip.
mansr
Objectionist
Exactly what gets delivered with each setting depends on the album. If there is no MQA version available, you probably get the same content at either setting. An MQA decoder can't do anything with non-MQA data, so are you sure you're not imagining the difference? Can you do a digital capture (loopback or virtual sound card) of whatever the Tidal app outputs? That would give a definitive answer.
kaolin
Active Member
trial was over 3 days ago.