MQA Deep Dive - I published music on tidal to test MQA

[amirm]

Back to the beginning then... (1) What is the MQA advantage (compared to Redbook)? (2) What are the test signals to emphasize this advantage? (3) Where are the “acceptance test” results, expected in any decent industry to validate that a product meets its [claimed] performance?

1) It can in theory represent some of the spectrum above 22.05 kHz that is completely thrown away in Redbook. We know redbook represents zero data above its band limit. So anything that can be preserved can be technically called superior.

2) A signal that has the statistical content and amplitude of a suite of music. I know Meridian/MQA team had performed such an analysis and based on that, determined how much of that spectrum they needed to represent. In the extreme case, if content just disappears in noise, they could simply generate noise in the decode and not have to encode anything.

A proper encoder would analyze the ultrasonic content and determine what part of is correlated with music and what is not. The latter can be thrown out or just represented as noise. The former then can be heavily quantized down to only represent that correlation. Say the spectrum moves from -90 dB to -85 dB at 40 kHz. Then all you need is a single bit to represent that dynamic range. PCM audio has flat encoding where it wastes the full 24 bits whether there is any useful content.

There are HUGE assumptions in MQA encoding in this manner since that is how almost all music is. Violating that completely breaks the encoder as it can't remotely squeeze any paradoxical content into the container it has.

3) I expected MQA to publish such data in AES. And more controlled testing based on my conversations with Bob Stuart in early days. And of course encoders be available for sale (not free, but available to buy). None of this happened. Whether this indicates the above goals were not met, I don't know.

What I do know is that whatever it does, MQA lights up the "high-res master" light on the DAC. To the extent people can't hear ultrasonics anyway, that maybe the end goal that is needed to make people think MQA is better. And job is done. For good measure, they could and most definitely have, thrown in some content that they know is better master so any in-the-field comparison would be null and void in their favor.

 

[SKBubba]

So if I, as an artist, decide to include a test tone in my song, or something similar to a test tone for a specific effect, MQA will decide it isn't music and barf all over the track. How is that h-fi? How is that the "original true to source as intended by the artist" ?

Like Kraftwerk? Emerson Lake and Palmer? Heck, Edgar Winter's Frankenstein coda?

 

[jensgk]

Like Kraftwerk? Emerson Lake and Palmer? Heck, Edgar Winter's Frankenstein coda?

Aphex Twin "Acrid Avid Jam Shred" and "Ventolin [Video Version]" from the album "I care because you do"

 

[amirm]

So if I, as an artist, decide to include a test tone in my song, or something similar to a test tone for a specific effect, MQA will decide it isn't music and barf all over the track. How is that h-fi? How is that the "original true to source as intended by the artist" ?

If you put square wave in MP3, it sounds bad too. You can choose to not do that, or do as what artist do: they don't care as they don't think the audience is remotely that critical. I can't listen to DBS Satellite radio services due to massive amount of compression artifacts (they have bandwidth as low as 32 kbps!). Yet they have millions of customers so clearly fidelity is not critical as we all know. And content owners don't seem to care.

 

[Ralph_Cramden]

What I do know is that whatever it does, MQA lights up the "high-res master" light on the DAC. To the extent people can't hear ultrasonics anyway, that maybe the end goal that is needed to make people think MQA is better. And job is done.

Pavlov's bell

 

[dmac6419]

If you put square wave in MP3, it sounds bad too. You can choose to not do that, or do as what artist do: they don't care as they don't think the audience is remotely that critical. I can't listen to DBS Satellite radio services due to massive amount of compression artifacts (they have bandwidth as low as 32 kbps!). Yet they have millions of customers so clearly fidelity is not critical as we all know. And content owners don't seem to care.

I liked satellite radio when I'm on the road,didn't have to look for stations every 30 miles,just set it and forget it.

 

[LightninBoy]

If you put square wave in MP3, it sounds bad too. You can choose to not do that, or do as what artist do: they don't care as they don't think the audience is remotely that critical. I can't listen to DBS Satellite radio services due to massive amount of compression artifacts (they have bandwidth as low as 32 kbps!). Yet they have millions of customers so clearly fidelity is not critical as we all know. And content owners don't seem to care.

Yes, I am aware of all of that. But lossy MP3 and satellite radio isn't the standard we should set. More to the point, it isn't the standard MQA itself has set. Their stated standard is right in the name: Master Quality Authenticated. But as the OP proved, it is neither master quality nor authenticated.

 

[amirm]

I liked satellite radio when I'm on the road,didn't have to look for stations every 30 miles,just set it and forget it.

And hence its success. Fortunately with 4G cellular coverage, unless we are deep in the woods, I can stream content now using my phone so don't need that convenience. When we drop out, I have pre-downloaded content I play. Of course, fidelity is far better than Satellite.

 

[Tks]

Yes, I am aware of all of that. But lossy MP3 and satellite radio isn't the standard we should set. More to the point, it isn't the standard MQA itself has set. Their stated standard is right in the name: Master Quality Authenticated. But as the OP proved, it is neither master quality nor authenticated.

Be reasonable..

Master Quality, lossless, original artist intent..

It's all the same? Who can really say, right?

 

[amirm]

Yes, I am aware of all of that. But lossy MP3 and satellite radio isn't the standard we should set.

Why not? They all follow perceptual models of hearing to get their massive compression ratio. At 128 kbps, only 8% of the bandwidth is used. No way you can code pathological signals and expect to get anything near the quality that it normally produces for music. Same is true of MQA.

Their stated standard is right in the name: Master Quality Authenticated.

"Quality" is a subjective thing. And application is clearly music, not test signals.

 

[dmac6419]

And hence its success. Fortunately with 4G cellular coverage, unless we are deep in the woods, I can stream content now using my phone so don't need that convenience. When we drop out, I have pre-downloaded content I play. Of course, fidelity is far better than Satellite.

I used to do long haul, before they had cellular service (towers) on all the major interstates .

 

[jensgk]

It is just that you can't test lossy codecs, specially layered ones like MQA in this manner.

Why not? If you want to know it's limits?

MQA is a pretty secret codec, so testing the limits, seems a like good way to find the pros and cons.

 

[jensgk]

And application is clearly music, not test signals.

The same thing can be said about all the other things, you test with test tones on this site.

 

[PierreV]

I'm with you there, but where is that definition of lossy derived from? Like is there an AES official definition of "lossy" ?

You could go back to 1937-1938 with the invention of PCM by Alec Harvey Reeves.

At that point, while the compression/sound reproduction method is lossy - I guess everyone is aware of that then - there is no formal definition of what the loss is because, a bit like some audiophiles today, you could think the analog wave contains an infinite amount of data/information. Information still being a vague term as well then.

Wait 10 years, and you have Shannon et al clarify all this by defining what information is and how it can be minimally encoded, leading to the Shannon sampling theorem in 1949, which leads to the notion that, within some constraints, a signal (in the very large sense of the term) can be losslessly represented.

lossy/lossless is not an "audio" concept, it is a fundamental Information Theory concept. Should the AES have a different opinion, no one would care

A history of lossy compression by one of the luminaries of the field.

https://ee.stanford.edu/~gray/dcc15.pdf

 

[LightninBoy]

"Quality" is a subjective thing. And application is clearly music, not test signals.

You got that exactly backwards, Quality here is objective - whatever data is on the master should be delivered to me bit for bit. Music is subjective and may include test tones.

 

[Raindog123]

Thanks! To make sure I understood correctly:

1) It can in theory represent some of the spectrum above 22.05 kHz that is completely thrown away in Redbook. We know redbook represents zero data above its band limit. So anything that can be preserved can be technically called superior.

So, the 24/96 will be equally superior, if one subscribes to the "there is still something musical and worth preserving above 22kHz", correct? And for those subscribing to the "human listening is limited by 20kHz", this preserving is just useless waste (just like reproducing anything at 100kHz...)?

2) A signal that has the statistical content and amplitude of a suite of music... A proper encoder would analyze the ultrasonic content and determine what part of is correlated with music and what is not. The latter can be thrown out or just represented as noise... There are HUGE assumptions in MQA encoding in this manner since that is how almost all music is.

Amir, so with your substantial experience... Is there anything musical above 20kHz? Yes or no? [Again, if not, then all this dancing about "with HUGE assumptions" is just wasteful (and deceiving)... But if it is, an accurate 96kHz (and/or 192kHz) sampling would be (a) more accurate (eg, for the aforementioned Kraftwerk's square-waves), while (b) supporting all "traditional" test vectors/cases in this ultrasonic region, correct?]

3) I expected MQA to publish such data in AES. And more controlled testing based on my conversations with Bob Stuart in early days... None of this happened. Whether this indicates the above goals were not met, I don't know... MQA lights up the "high-res master" light on the DAC. To the extent people can't hear ultrasonics anyway, that maybe the end goal that is needed to make people think MQA is better. And job is done

Thank you [for reinforcing our point].

 

[PierreV]

"Quality" is a subjective thing. And application is clearly music, not test signals.

You mean like that Devialet amplifier you tested?
Just like MQA it reorganizes noise, doesn't waste watts in the high frequencies and, is not designed to handle test signals.
It could fairly be described as a "lossy perceptual amplifier".
Could it also be closer to the intent of the artist?

 

[mSpot]

Spotify has a storied past in failed attempts to launch a HD tier. They made several announcements and attempted launches

Spotify made their official announcement in February. Previously, they had only sent market research questionnaires to random subscribers, which resulted in people on the internet shouting that Spotify was about to launch CD quality streaming. Show us where Spotify had made "several announcements and attempted launches".

 

[oldandintheway]

I think we should stop and acknowledge the original poster here. I am not competent to judge the technical technical merits of the codec, but I can read. And thanks to the original poster the "lossless" marketing lies have been exposed and even the defenders of MQA have retreated to a you can't evaluate a lossy codec that way argument. Which may in fact be true, but what is the benefit to the consumer? The only thing I see is the increasingly irrelevant smaller file size. Prove that your lossy codec sounds better or go away. Widely used and open lossless codecs are common, in fact much more so than this stuff. I have made my decision, and I won't pay a penny more for MQA anything, what about the rest of you?

 

[dmac6419]

I think we should stop and acknowledge the original poster here. I am not competent to judge the technical technical merits of the codec, but I can read. And thanks to the original poster the "lossless" marketing lies have been exposed and even the defenders of MQA have retreated to a you can't evaluate a lossy codec that way argument. Which may in fact be true, but what is the benefit to the consumer? The only thing I see is the increasingly irrelevant smaller file size. Prove that your lossy codec sounds better or go away. Widely used and open lossless codecs are common, in fact much more so than this stuff. I have made my decision, and I won't pay a penny more for MQA anything, what about the rest of you?

I'm enjoying MQA right now been listening all day,my cat is so relaxed,we just chilling.