MQA software decoding in Roon

I think the reason the bandwidth is the same in that plot is because it refers to a communication bandwidth, meaning the number of bits transmitted when delivering the digital (encoded/folded) MQA file in its FLAC container. A certain conclusion from these plots is that MQA compresses the original file such that the information in the music sampled at rates higher than 96kHz isn’t taking a lot of bits. You are inferring that because there aren’t many bits allocated to the high sampling rates that MQA actually stores no information captured by these sampling frequencies and it is simply “upsampling.” Based on the referenced provided on this thread and by the Roon team on MQA, I don’t think you are right. MQA is reconstructing the content originally sampled with high frequencies using an algorithm that decodes the original information content as close to the source analog signal as they can determine from the studio master (and its studio digitization.)

Your description of upsampling is certainly valid but it isn’t what MQA is doing in the decoding as far as I can tell from what I’ve read.

I think one reason there is much confusion on the thread (and elsewhere) about this is because people equate higher sampling frequency with higher information content. That is simply not the case. High frequency information content does require high frequency sampling rates to properly capture the signal but just because a signal was sampled at 352kHz it doesn’t mean it has 352kHz worth of information. That is solely a function of the original analog signal (and actually, the true information content was the live music in the studio, it is all a representation after recording, mastering, etc.). The MQA approach is to put less focus on the sampling rates and more on the actual analog signal information content.

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The reason is because MQA argues that the “language of digital” does not properly represent the true analog information content. For example, when you see a file is 24 bits / 192 kHz you infer this “high resolution” representation of the music is higher fidelity and better sound quality than a 16 bit /44.1 kHz file. As we have seen a number of times, the sampling is actually much less important than the mastering or the quality of the audio reproduction system and that’s because the sampling and bits (the digital domain parameters) don’t really represent completely the true fidelity of the digital file.

MQA argues digital is good for storage and distribution. Analog is where listening actually takes place. The MQA encoding/decoding process is intended to best present to your ears the actual information in the original master. Their scheme works because they have found that assigning 24 bits to a high resolution file has a lot of “wasted space” meaning many of the bits don’t carry “true information” (just the variations caused by analog-digital conversion). They are willing to throw away some of this digital data in order to use part of that space to encode the information that later gets unfolded during the decoding process.

I’m not a studio engineer or sound professional but I did take graduate-level linear mathematics and image processing courses and I remember distinctly that digital sampling is always an approximation of the original analog signal. You can get better approximation when you know something about the impulse response of the system (the system that converted the analog signal to a digital signal)…the MQA emphasis on knowing/controlling ADC’s used in mastering and DAC’s used in playback are an attempt to use the impulse response of the end-to-end system to improve audio reproduction.

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Thanks @Ronnie, I’ve some skepticism on the articles but I tend to agree the last paragraph what he said:

'In the end I’m confident that the free, readily available, high quality, open-source alternatives will win out. Lock down, centralisation and profiteering has a tendency towards failure.

In my opinion I saw this in the past and many didn’t make it. I guess only time can tell…

No matter how narrow the triangular information space becomes above 22.05/24 kHz, no matter how few bits are needed to encode that high frequency information, the bugaboo is that MQA after the first unfold somehow is able to pass subsequent unfold information potentially but successfully through intermediate DSP – such as surround processing, room correction, etc. If applied prior to the first unfold, that same DSP would destroy MQA encoding for the first unfold, which requires bit for bit accuracy. Furthermore, any subsequent unfolds can be accomplished by very low processing power renderers. So, something is materially different about those subsequent unfolds. And that arouses questions, rightly so.

AJ

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@erich6, thanks for the explanation. The argument of compromise digital data in order to get a better analog reproduction is based on their ‘claims’ not from engineering point of view.

In my line of engineering work, digital technology is used to capture data in great precision so we can analyse, process without any doubt. If compromise is being made then it will severely impact out our accuracy.

What digital technology does it captures analog in great precision (lossless) and if they claims otherwise then they need to support their ideas with engineering and scientific proofs. Making such ‘claims’ will simply raise many doubts and backlash.

Yeah, I agree something different is happening with the first unfold than subsequent ones. I haven’t dug deep enough in the technical references to figure it out yet.

@MusicEar, Fair comment. I suspect that for well-engineered masters and distributions MQA won’t make much of a difference in apparent sound quality. That’s certainly been the case for the limited samples I’ve tested. It is an interesting scheme for low-bandwidth digital distribution and it emphasizes good end-to-end engineering considerations…both are positive aspects of the approach.

What evidence exists that these 2nd and 3rd stage unfolds can happen with “low processing power” renderers??

If you’re simply referring to the Price of equipment like the Dragonfly and Explorer, then it must be remembered that the processing power within these devices are vastly greater than what was in “premium” DACS of 10 years ago…as processing power has vastly increased in power and reduced in price during that time

That does NOT make the Dragonfly / Explorer better DAC’s than those same 10-year premium DAC’s…but if you’re solely basing your claim of “low processing power” based on their price, then that would be a mistake IMHO

Price is not relevant, nor is comparison to 10 year old premium DACs. Processing power in renderers has been shown to be relatively limited.

AJ

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I don’t regard simply looking at a spec sheet to be “substantiation” of your claim of low processing power…as he admits himself, he doesn’t know what is else is within that design

Read the comments to the article. There is plenty more evidence. You are swimming against the current.

AJ

@Ronnie, What @WiWavelength said is correct, Dragonflys draw its power from the USB port, with such limited power it needs a very efficient microchip to the do processing but the downside to this is processing power has to be capped otherwise you going to run into power consumption issues. He is looking at the engineering point of view.

The input receiver of dragonfly is limited to 96k input sampling frequency and coupled to the limited processing power of the microchip, dragonfly will only act as a ‘renderer’ not capable of doing a full hardware decoding found in Mytek Brooklyn DAC.

The ‘renderer’ looks interesting to me. if Roon, for some reasons not able to do a full software decode, then a partial decode followed by ‘renderer’ resulted in a full decode. If they sell the ‘renderer’ as a plug-in dongles to their existing USB-DACs, it can achieve a full decoding together with Roon.

This solution is good in one sense that people don’t need to upgrade their existing USB-DACs, I think in some way, this will please a lot of people out there.

But. Whilst you pay your subscription you have acces to more music you could possibly afford in a ‘Hard’ Format that you own the right to enjoy outright.
For young people the task of collecting an instant library of all the music we oldies have collected over time is nigh impossible. Streaming is one answer.
Thoughts.

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Where you get this information from?

Ronnie, you can’t teach an old dog new tricks!
To be clear we are living in interesting times. I know teenagers who could interact using a game controller before they could talk. People who have always had access to digital content regardless of where they happen to be. For them the concept of “owning” a digital file is an alien concept. You own the players, the transports. That is where the value is to them. The means of access is where it is at, the gateway to all of those goodies. For them it has always been there. They can’t perceive any reason why that might change short of the end of the world! That leaves ownership very much in the domain of those of us with the collector gene. Owning physical music is no longer the way it has to be. It is just a personal preference.

Hi @Henry_McLeod
As the owner of a 20,000 album library, I’m aware of the “personal preference” involved in buying that library and the time and effort involved

But I am equally aware that since Streaming became a legal business about 5-7 years ago…and streaming of high res content [in most countries and at reasonable data rates] became possible 6 weeks ago…that “owning” a library remains as just a personal preference…whereas it used to be a legal requirement

Those of us in our 40’s to our 80’s have the same choices open to us in 2017…ones that weren’t available at all only a short time ago…and IMHO any analysis has to reflect that those choices as “preferences” and not a requirement

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I agree with pretty much every word.

Well there are 1,458 MQA albums listed on the Google spreadsheet on this site…and at the rate at which people are finding them, I’m sure there is more to come

I’m referring to Tidal streaming…