Technicals of MQA


Why MQA  What is MQA  33bowls Remastered  The Art of Listening  The Technical details  Clearing up misinfo


Technicals of MQA:

A gentle reminder that presuming a partial map matches the territory is a recipe for insidious disaster, and designing any system, audio or otherwise, to that partial map is likewise a recipe for insidious disaster.

We may be made of stardust, but we exist in time and space. Frequency is a convenient tool at times, but is an abstract space, a partial map that only translates to the physical world in linear systems. Any element of a system that is non linear, and the time/frequency presumption falls part. Our ears, being highly non-linear, can discriminate timing of events a full order of magnitude better in the real, physical world of time and space, than frequency analysis would predict.


https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.044301


That is the dirty little secret: nyquist PCM digital audio was designed primarily in the frequency domain, with time domain errors being swept under the rug. We are into second and third generations of listeners raised on such artifacts, and we either voice our music systems to partially compensate for the inherent time smear, or adapt to such smeared sonics as the new normal. MQA elegantly and completely solves that.

One "thing" that low bit up and oversampling schemes, based on frequency analysis miss is: single event fidelity. They are all averaging phenomena, with the inevitable tradeoff between steady state and transient behaviour. MQA, designed with the time domain in mind, has a unique way of coding and decoding single event transients, with low time smear (or blur) and sufficient time resolution to be truly transparent. Aperture uncertainty low enough to be similar to a couple meters of air. No other system can do that.

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Let's clear one mis-conception up.

Confusing data with information, and referring to MQA a "lossy" or "compressed" format is naive at best, and often deliberately disingenuous. The question is more appropriately: is any format audibly transparent?

As much as lossy/lossless appears to be a concrete left brain term with accompanying clear definition; ironically in the real world, it is a nebulous, abstract term that evokes strong, irrational emotional reactions with accompanying endless circular arguments, frequently over misunderstood or deliberately twisted semantics.

With  MQA, the PCM baseband is backwards compatible (which is categorically bit for bit lossless, as backwards compatible within existing PCM standards); in addition the ultrasonic information is coded and buried in the dither when folded to baseband. Unlike MP3, AAC, DTS, the actual lossy formats which greatly increase noise modulation while discarding audio information to save bandwidth and file size, MQA keeps noise modulation to a minimum and does not throw away audio information. Repeat: MQA does NOT throw away any audio information.

Information versus data: What is perceptually significant in the ultrasonic spectrum is not a crude stair-step approximation with time smear, which traditional nyquist PCM including so called hi-res gives when close to the nyquist frequency; rather what is important, the perceptually significant information, is the slope and timing of the small "squiggles" in that ultrasonic spectrum, that correlate with larger signals in the (consciously) audible baseband spectrum.

With MQA, this encoded ultrasonic information is buried in the backwards compatible baseband PCM as sonically benign dither using spread spectrum techniques to keep noise modulation to an absolute minimum.


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There is no "mystery" about the process, nor about the neuroscience behind perceptually significant phenomena that MQA is based upon. There are a number of AES papers describing the research.

MQA could produce de-blurred DXD files, at 352.8 or 384 Khz sampling rate, and stop prior to the  pre folding stage, that would be both backwards compatible with "hi-res" playback, and recognized as MQA when played back. Those would keep the bit prefect crowd happy, at a cost of roughly an order of magnitude larger file size. However, they are audibly indistinguishable from, and measurably equivalent to folded and decoded MQA files at 44.1/48 Khz. Less than 4 microseconds aperture uncertainty, and no ringing or time smear, same as 2 meters of air. So, stop complaining, guys.

Again, MQA leaves the baseband redbook/CD PCM data intact, backwards compatible and sonically improved when played back on legacy equipment; and efficiently encodes perceptually significant information from the ultrasonic octaves: the timing and slope of low level signals that while not consciously audible, are in practice viscerally sensed as a more real, more transparent emotionally connected experience.

There is more to it than just throwing more bits at it; there is more than just frequency response.

Link to a series of AES papers from 2019


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How in the world does one bury information in the dither, which looks like noise? Cool trick.

Pseudo random noise routines, straightforward on software, can be done in hardware with a bunch of xor gates, super easy with PECL/ECL xor gates. So a signal, that looks to the outside analog world like random noise, actually has a pattern if one knows what to look for, the secret handshake, to then be unlocked and decoded. It is a highly efficient mode of coding information. Spread spectrum modulation was at one time primarily a military phenomena, and is now widely used in telecom, CDMA cell networks. Also, HDCD used a similar trick to bury a control channel in the LSB dither. At the time of the HDCD patent application, the examiner considered such a claim as highly unlikely, some kind of a perpetual motion scheme, and requested an in person demo, which KOJ and Pflash provided. This IP is one of the reasons Microsoft bought the company. I will refrain from confirming or denying what and how MQA does a similar trick when doing the origami fold into the noise floor with dither. However, that magic, and the lack of understanding with an accompanying reaction of incredulity, is likely one of the factors fanning the denial of detractors, of which there seem to be some otherwise smart individuals, who when "arguing" are clearly lacking an understanding of what they are denying. Maybe Bob and crew could make a neat little demo box with blinking LEDs to show that the process does indeed do what is claimed.


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PCM up/over sampling (typically 44.1/48 kHz to 8x that) just means more stairsteps defining a filter function of the original base sampling frequency. This finer texture is supposedly better, and can lead to incremental improvements. Unfolding which MQA does is entirely different; MQA also includes intra sample timing information to give a time resolution in the single digit microsecond range, which traditional up/oversampling does not.

If one ignores time smear, and just looks at the frequency domain, basic digital theory stipulates that the encode and decode filters must match for full resolution to be reproduced within the nyquist band. In the real world, they rarely if ever do. That is a yuuuuuge issue with digital audio, there is no standard for conjugate matching filters, except for MQA.

Conjugate encode/decode filters are a basic presumption in a nyquist/shannon/fourier digital sampling system: the goes-intos need to match the goes-outas. The gibbs phenomena ringing on transients of brickwall filtering will rarely if ever match between encode and decode, as there is no standard! Early digital recorders had analog minimum phase encode filters, with post event ringing only. Later generations incorporated digital encode filters, known as linear phase, with both pre and post event ringing. There is, again, no format standard for those filters, other than a big fuzzy whatever. If the encode/decode filters actually match, again, which is the textbook ideal that rarely if ever happens in the real world, then for the full resolution to 16 bits or better there needs to be a couple seconds both before and after the event for the ringing pre and post event to line up for full resolution. However, that is the inevitable time smear or blur of the old PCM nyquist paradigm, with it's attendant tradeoff between time and frequency that has been swept under the rug until now with the advent of MQA.

It must be emphasized, again and again ad infinitum it seems, how important matching conjugate encode/decode filters are for any digital audio, or sampled system in reconstructing the nuances; DSD does not have that, Redbook CD 44.1 kHz nyquist PCM does not have that, "hi-res" PCM does not have that; however, MQA does have matching conjugate encode/decode filters. Ironically, truly lossy compression algorithms such as mp3, AAC, DTS do have standardized reconstruction filters, giving uniform mediocrity as their trade-off for reduced data bandwidth and file size.

Low pass filters do not “just” roll off high frequencies; they smear fast events out in time. Think of area under a curve. The high frequency energy does not magically go away, it is is in effect smeared, spread out, a pop gets transmogrified into a blub. One can argue about group delay, linear vs. minimum phase, apodizing, but that is what low pass filters do: shove it under the rug. Unlike a water filter for instance, which collects undesirable elements and needs maintenance as cleaning or replacing, electrical filters redistribute energy. Unless you are a fundamentalist or flat earther, look at (so to speak) the CMB, Cosmic Microwave Background Radiation: that is the remnants of a very fast event, the Big Bang, now spread out in time. The question is how one can optimize the function, preferably with a matching conjugate filter between encode and decode of a digital sampling system. Even the nomenclature of "filter" is a reference to frequency domain mindset; what MQA does is more akin to conjugate interpolation of the digitized waveform. Again, MQA is an efficiently done non-brickwall backwards compatible verifiable end to end conjugate filtering system with sufficiently low modulation noise, time smear and sufficiently high time resolution to be truly transparent.


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To summarize: MQA is the only digital audio system or format that can reproduce audio with 4 microseconds aperture uncertainty, which is what current neurobiology indicates is the time resolution of the ear/brain. That is as transparent as about 2 meters (6 feet for the USA) of air. No other system or format even comes close. If digital audio was tested with the same scrutiny that is placed on analog components, only MQA would pass the test.


Geek out.



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and coherence of the Universal Aum;
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