Jump to content
IGNORED

MQA technical analysis


mansr

Recommended Posts

They say that during MQA encoding they employee DSP to delay the preresponses cause by the linear filters previously used in the recording process. Do you know this not to be the case? Have you tested (and could you test) any of the MQA 2L files against originals to try to determine whether they employed this "debluring?"

 

That sounds like a standard apodising filter. Nothing novel about that. Anyone can do it.

Link to comment
But if you get someone to encode test signals for you and then you publish the results... ;)

I doubt any of the select few with access to encoders would be willing to do this. If they did and MQA found out, they might find said access suddenly revoked. Is it even allowed to use an encoder unsupervised by MQA?

Link to comment
That sounds like a standard apodising filter. Nothing novel about that. Anyone can do it.

 

It has been a while since I read the patent and white paper. Was there something about a windowing function (doesn't mean they're currently employing it)?

 

 

Sent from my iPhone using Computer Audiophile

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.

Link to comment
I doubt any of the select few with access to encoders would be willing to do this. If they did and MQA found out, they might find said access suddenly revoked. Is it even allowed to use an encoder unsupervised by MQA?

 

They won't gain large scale user base if they would really want to know about ADC and mastering, unless they provide widely available plugins for DAW's like ProTools and Pyramix.

 

If person X publishes measurement results and doesn't tell who encoded the data, they won't have any means figuring out who did the encoding unless they store and inspect everything that was ever encoded to MQA. And if they do that, if I were recordig house, I would stay far away from MQA. But based on their FAQ one can make internal encoded variant for listening that doesn't go through their immense signing/DRM hoopla. And that's enough.

 

I really don't understand who could have slightest interest on some MQA big brother watching over and dictating all their stuff. Although all the Orwellian stuff seems to be in fashion these days I just feel sick of such.

Signalyst - Developer of HQPlayer

Pulse & Fidelity - Software Defined Amplifiers

Link to comment
It has been a while since I read the patent and white paper. Was there something about a windowing function (doesn't mean they're currently employing it)?

 

The patent is, as patents are, written as opaquely as possible. It is also impossible to tell how, if at all, it relates to the actual process. I was responding to the statement I quoted about removing pre-ringing introduced by linear phase filters.

Link to comment
That sounds like a standard apodising filter. Nothing novel about that. Anyone can do it.

 

But with existing recordings they claim upon encoding to be removing or lessening preresponse "blur" caused by processes such as sample rate conversion by delaying it relative to the response. Is this the same as using an apodizing filter on a DAC upon playback?

Link to comment
But with existing recordings they claim upon encoding to be removing or lessening preresponse "blur" caused by processes such as sample rate conversion by delaying it relative to the response. Is this the same as using an apodizing filter on a DAC upon playback?

 

There are well known techniques for removing ringing, at least one of which MQA appears to be employing currently, apodizing filters. By all indications, those they're using appear to prioritize subjective "excitement" over what is generally considered accuracy.

 

 

Sent from my iPhone using Computer Audiophile

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.

Link to comment
The patent is, as patents are, written as opaquely as possible. It is also impossible to tell how, if at all, it relates to the actual process. I was responding to the statement I quoted about removing pre-ringing introduced by linear phase filters.

I'm reading it this weekend. Along with whatever else is referenced in the file wrapper. my best friend from college who is a DSP engineer is also reviewing it and we are going to discuss our conclusions. We may not be able to discern anything more, but I do have 20 years experience with reading into patent specs.

 

image.thumb.jpeg.a4a84e289e35c7e49a6d3042fc9b2a99.jpeg

 

Link to comment
There are well known techniques for removing ringing, at least one of which MQA appears to be employing currently, apodizing filters.

Please could someone post (perhaps a link to) a sample of professionally published music that demonstrates audible ADC ringing?

If there are spectrums, spectrograms, etc. that show/measure the ringing, that would be great too.

Link to comment
That sounds like a standard apodising filter. Nothing novel about that. Anyone can do it.

 

Nope. There is a paper or a patent that describes an all pass filter with group delay severely peaking around the recording Fs/2, effectively lifting up the ringing and dropping it down after the main impulse. Their description, not mine.

 

A bit ridiculous, this obsession with a phenomenon that is only really triggered by a tiny portion of the music, and that has to be inaudible to all but the newly born.

 

You would think that if this really mattered at all they would stage a convincing demonstration of it at conferences and fairs, not? Just a single note or hit, with and without the magic applied. But no, what you get are videos of semi-celebs, running down the streets, tossing off their clothes and screaming how they have seen the light.

Link to comment
Bob Stuart stated more than once in the Q & A on here that MQA does not use apodizing filters, yet many people on this thread are stating that it does. It would be good to get some clarification on this.

 

That is correct. If we define 'apodising' the way Craven/Stuart/Meridian define it (i.e. minimum phase with the cut-off well below Fs/2, so that any pre-existing ringing at Fs/2 is sliced away), then MQA indeed does NOT use apodising filters.

 

It is remarkable that the Explorer2, when reproducing standard non-MQA CD-rate material, also does NOT use a Meridian-style apo filter, but rather an extremely leaky minimum phase ... monstrosity.

See figures 2 and 4. Meridian Explorer2 D/A headphone amplifier Measurements | Stereophile.com

 

--

 

Which brings me back to an earlier question of mine: given that the above 'bad' filter also features in the Mytek DAC we can assume it is part of the MQA standard. Does this filter play a role in the folding/unfolding part, and what does this imply for the replay of non-decoded MQA material?

Or, to put it bluntly, if this leaky filter is mandatory part of MQA replay, does this then also imply a leaky filter used during the pre-folding band splitting, thus infecting the baseband with severe aliasing that remains present during non-decoded replay?

Link to comment
That is correct. If we define 'apodising' the way Craven/Stuart/Meridian define it (i.e. minimum phase with the cut-off well below Fs/2, so that any pre-existing ringing at Fs/2 is sliced away), then MQA indeed does NOT use apodising filters.

 

When dealing with high-resolution material, that distinction is mostly academic since there isn't anything in the transition region of a "traditional" apodising filter anyway. Recall that ringing only occurs when the input has energy at the Nyquist frequency, which at high sample rates normal music doesn't.

 

It is remarkable that the Explorer2, when reproducing standard non-MQA CD-rate material, also does NOT use a Meridian-style apo filter, but rather an extremely leaky minimum phase ... monstrosity.

See figures 2 and 4. Meridian Explorer2 D/A headphone amplifier Measurements | Stereophile.com

 

--

 

Which brings me back to an earlier question of mine: given that the above 'bad' filter also features in the Mytek DAC we can assume it is part of the MQA standard. Does this filter play a role in the folding/unfolding part, and what does this imply for the replay of non-decoded MQA material?

 

Those terrible filters are mostly used in the "rendering" part. The "core" decoding works differently, although if the original was 44.1/48 kHz it is followed by an upsampling step using a somewhat less horrible filter.

 

Or, to put it bluntly, if this leaky filter is mandatory part of MQA replay, does this then also imply a leaky filter used during the pre-folding band splitting, thus infecting the baseband with severe aliasing that remains present during non-decoded replay?

 

I'd be somewhat surprised if this wasn't the case.

Link to comment

Mansr: pretty much all I wrote above was for baserate, not at all about the renderer filters. Mytek/Explorer2 measuments are very relevant because they make one ask why the hell they chose a reconstruction filter for baserate with zero attenuation at Fs/2 and a first null at Fs. It simply does not match Meridian's past philosophy. So what forces them to do this?

 

 

--

 

The renderer's filters may be horrible, at least they fit MQA's published philosophy, and they are supposed to be mostly harmless.

Link to comment

When a certain other Audiophile Social Media Personality swaggers in here to take others to task, the clear motivation is to "protect" his business.

 

 

And he told me to tell you to grow up. I see that you and "Mansr" continue with your silly views about other people's motives which only serves to put yours into question.

 

Just so I'm clear, what I'm saying is that you don't know what you're talking about but for some reason you enjoy making shit up at other people's expense. This isn't me protecting my business, it's me telling you to fuck off.

Link to comment
And he told me to tell you to grow up. I see that you and "Mansr" continue with your silly views about other people's motives which only serves to put yours into question.

 

Just so I'm clear, what I'm saying is that you don't know what you're talking about but for some reason you enjoy making shit up at other people's expense. This isn't me protecting my business, it's me telling you to fuck off.

 

If you've been following this thread, you should have seen (as I did) multiple requests to keep this out of the thread. It's off topic. You're more than welcome to start a new thread to air your grievances if it will help you to feel better.

Link to comment
If you've been following this thread, you should have seen (as I did) multiple requests to keep this out of the thread. It's off topic. You're more than welcome to start a new thread to air your grievances if it will help you to feel better.

I have not been following this or any other thread. I was alerted to your not subtle reference to me. So I figured I'd swagger in here and tell you to fuck off. That's it. No more conversation is necessary.

 

TIP: if you don't enjoy my input here, leave me out your comments.

Link to comment
And he told me to tell you to grow up. I see that you and "Mansr" continue with your silly views about other people's motives which only serves to put yours into question.

 

Just so I'm clear, what I'm saying is that you don't know what you're talking about but for some reason you enjoy making shit up at other people's expense. This isn't me protecting my business, it's me telling you to fuck off.

 

Thank you for your kind words.

Link to comment
Lavorgna, create your personal thread, for example 'Lavorgna personal analysis'.

You are here offtopic.

I'm responding to comments made about me/AudioStream. If this is off topic, then I'd suggest the original comments re. same do not belong here. If you want me to stop responding to comments about me/AudioStream, then the solution is very simple.

 

I have no interest, as in zero, of pursuing any topic here.

Link to comment

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



×
×
  • Create New...