Bob Stuart launches blog to explain MQA

[jparvio]

1 hour ago, Em2016 said:

 

Ah, gotta love the internet. 

 

Not sure what I said that makes you think this... Context is very important. Have a look at what I have quoted above - I was only replying to very specific comments (which I quoted above), like "And I'm still skeptical about the Pro-Ject." and "I find it hard to believe the same type of resources were invested that little inexpensive DAC from Pro-Ject."

 

Price is not always the best indicator of measured performance. And note I only commented on measured performance... I never commented about sound quality... (subjective performance). JA's measured performance is what is is and he said (his words, not mine...) it measures almost state of the art... that's all I have quoted.

 

I'm a little more careful than to go down the path you thought I went 😉

 

 

You are right, my bad, I am sorry 😌...

 

 

 

 

[Kal Rubinson]

2 hours ago, mansr said:

What DAC supports such files?

A stack of three Mytek Brooklyn DACs.

[mansr]

4 minutes ago, Kal Rubinson said:

A stack of three Mytek Brooklyn DACs.

So the MQA is simply three separately coded stereo streams?

[STC]

31 minutes ago, mansr said:

So the MQA is simply three separately coded stereo streams?

 

I am guessing they are just like any other 5.1 multi channel tracks. 

[mansr]

3 minutes ago, STC said:

I am guessing they are just like any other 5.1 multi channel tracks. 

"Any other" 5.1 audio isn't MQA.

[STC]

5 minutes ago, mansr said:

"Any other" 5.1 audio isn't MQA.

 

I should have kept my mouth shut since I don’t and never will use MQA but as a Mytek user that’s how you play multichannel tracks with Mytek DAC which is MQA enabled or whatever fancy name they are using. 

[mansr]

2 minutes ago, STC said:

I should have kept my mouth shut since I don’t and never will use MQA but as a Mytek user that’s how you play multichannel tracks with Mytek DAC which is MQA enabled or whatever fancy name they are using. 

The question was specifically how multi-channel MQA is coded. If the file is split into 2-channel pairs, do you get three valid MQA files?

[Kal Rubinson]

3 hours ago, mansr said:

The question was specifically how multi-channel MQA is coded. If the file is split into 2-channel pairs, do you get three valid MQA files?

The original file is a single PCM file just like any other multichannel file.

The file, of course, must be separated into channels for playback, just like any other multichannel file.  Typically, that is done in a multichannel DAC but it can be done separately as, for example, with a miniDSP U-DIO8 which splits it into 3-4 S/PDIF or AES3 outputs.

It can be done in a processor such as with JRiver running on a Mac which recognizes the 3-4 Myteks as individual stereo devices but can combine them into a "virtual" multichannel device.

In other words, MQA is handled just like any PCM file because MQA is embedded into the PCM data and none of these processes see it (until it gets to a suitable DAC).

[mansr]

1 hour ago, Kal Rubinson said:

The original file is a single PCM file just like any other multichannel file.

The file, of course, must be separated into channels for playback, just like any other multichannel file.  Typically, that is done in a multichannel DAC but it can be done separately as, for example, with a miniDSP U-DIO8 which splits it into 3-4 S/PDIF or AES3 outputs.

It can be done in a processor such as with JRiver running on a Mac which recognizes the 3-4 Myteks as individual stereo devices but can combine them into a "virtual" multichannel device.

In other words, MQA is handled just like any PCM file because MQA is embedded into the PCM data and none of these processes see it (until it gets to a suitable DAC).

How to route multi-channel audio to several stereo DACs wasn't the question. I was asking only about how the MQA data is encoded. I'm guessing it's simply done in channel pairs using the same format as stereo MQA, given that it can be decoded on separate DACs. That does mean you need to pair the channels correctly, of course.

[Ralf11]

10 hours ago, jparvio said:

 

Are You suggesting that this little overachiever is putting a show against the known heavyweights like dcs, totaldac, MSB and alike..? Soundwise that is. If so, I beg to disagree. Near SOTA digital performance is not the same as saying it sounds as good. In audio "nearly as good" can mean all the difference in the World.

 

All in all it is lovely design and well worth the money.

 

Just saying. 

 

 

did you/your colleagues do a comparison listening session?

 

if so, is it posted somewhere?

[Kal Rubinson]

3 hours ago, mansr said:

How to route multi-channel audio to several stereo DACs wasn't the question. I was asking only about how the MQA data is encoded. I'm guessing it's simply done in channel pairs using the same format as stereo MQA, given that it can be decoded on separate DACs. That does mean you need to pair the channels correctly, of course.

MQA data is always buried in each channel of the PCM and, regardless of whether it is stereo or multichannel. 

[mansr]

1 minute ago, Kal Rubinson said:

MQA data is always buried in each channel of the PCM and, regardless of whether it is stereo or multichannel. 

No, that's not how it works. In stereo files, the MQA data is split between the channels. One channel on its own is useless; it can't even be recognised as MQA.

[crenca]

1 hour ago, mansr said:

No, that's not how it works. In stereo files, the MQA data is split between the channels. One channel on its own is useless; it can't even be recognised as MQA.

 

Very very interesting.  Just what sort of MQA did Kal receive then.  Any guesses Kal?   How many channels did you receive, and is it divisible by 2?

[Kal Rubinson]

2 hours ago, mansr said:

No, that's not how it works. In stereo files, the MQA data is split between the channels. One channel on its own is useless; it can't even be recognised as MQA.

OK.  I was presuming how MQA data is embedded in stereo files.   Still, if that's how its done for stereo, it is likely the same is done for multichannel and, to be honest, it is likely that only Bob Stuart knows for sure.  But, since multichannel PCM is sorted out in pairs without MQA, having MQA data should not make any difference.  I handled those files as I have all multichannel files with many DACs.

 

Added in edit:  I found a metadata tag on one of the 4.0 tracks: "6ch MQA as pairs L R 0 0 Ls Rs."  I also found there were channel test tracks provided.

[Kal Rubinson]

2 minutes ago, crenca said:

 

Very very interesting.  Just what sort of MQA did Kal receive then.  Any guesses Kal?   How many channels did you receive, and is it divisible by 2?

Sure.  They were either 4.0 (from some old sources) or 5.1 (6).

[STC]

15 minutes ago, Kal Rubinson said:

Added in edit:  I found a metadata tag on one of the 4.0 tracks: "6ch MQA as pairs L R 0 0 Ls Rs."  I also found there were channel test tracks provided.

 

 But that doesn’t explain how center and bass can be processed as a pair?

 

Interesting to know that MQA requires stereo or a pair. Isn’t it the same as what MP3 does by converting  to joint stereo to reduce the file size further?  That alone would sound slightly different from the original. 

[Kal Rubinson]

1 hour ago, STC said:

 But that doesn’t explain how center and bass can be processed as a pair?

Why need they be processed any differently from the L/R pair of channels?

[esldude]

Does this mean if Disney releases A Star Wars movie in  MQA surround that Darth Vader and Luke Skywalker have to sign off on it first or it's not Authenticated?

[STC]

3 minutes ago, esldude said:

Does this mean if Disney releases A Star Wars movie in  MQA surround that Darth Vader and Luke Skywalker have to sign off on it first or it's not Authenticated?

 

3 hours ago, mansr said:

No, that's not how it works. In stereo files, the MQA data is split between the channels. One channel on its own is useless; it can't even be recognised as MQA.

 

Just wondering since center and LF are mono. 

[jparvio]

9 hours ago, Ralf11 said:

 

 

did you/your colleagues do a comparison listening session?

 

if so, is it posted somewhere?

 

Yes, it was tested, listened and measured on our Magazine 05/2017. It measured well as Mr Atkinson stated. It is a price point product and a very good one I might add.   

 

The article can be purchased online:

https://www.lehtiluukku.fi/esikatselu/hifimaailma-05-2017/157172.html

[firedog]

6 hours ago, esldude said:

Does this mean if Disney releases A Star Wars movie in  MQA surround that Darth Vader and Luke Skywalker have to sign off on it first or it's not Authenticated?

From what we know about the "authentication" process, it could be Mickey or Donald signing off on it. 

[mansr]

9 hours ago, STC said:

 But that doesn’t explain how center and bass can be processed as a pair?

 

Interesting to know that MQA requires stereo or a pair. Isn’t it the same as what MP3 does by converting  to joint stereo to reduce the file size further?  That alone would sound slightly different from the original. 

Almost all codecs, lossless ones included, use channel decorrelation one way or another to improve the compression ratio.

[John Dyson]

On 5/7/2019 at 5:02 AM, John Dyson said:

Half-way commenting on the notion of 'Blur' that Hifi Bob brought up (not that he is advocating for it), but as an EE/DSP person, not really an audio person, the 'blur' thing is confounding -- because I know the math and know what filters do.

 

I have a SUPER important clarification here -- I want to apologize if this quote has been rude, but I didn'[t mean to be rude... My language skills sometimes suck badly...

When I used the phrase 'not that he is advocating for it',  I wasn't intending to claim that he was advocating for it EITHER WAY, but rather that I MEANT:

 

Bob brought it up (an interesting thing), and not considering anyone's (Bobs) advocacy *either way* for the Blur concept.

 

I feel bad about what I (in a confusing way) wrote that HiFi Bob might be advocating for something that he isn't (or is.)  I really try to avoid making assertions about how other people feel -- doing so is a very slippery slope.  (I try to be a good boy. :-)).  Eventually, such comments can degrade into 'he/she is a bad boy/girl' type comments :-).

 

(thanks for letting me waste bandwidth to help me avoid a problem with my conscience.)

John

[Fokus]

22 hours ago, mansr said:

So the MQA is simply three separately coded stereo streams?

 

Kal's article on improvised multichannel MQA is here:

 

https://www.stereophile.com/content/music-round-84-multichannel-mqa

[Kal Rubinson]

4 hours ago, Fokus said:

Kal's article on improvised multichannel MQA is here:

https://www.stereophile.com/content/music-round-84-multichannel-mqa

Please note the linked follow-up:  https://www.stereophile.com/content/music-round-84-multichannel-mqa-multichannel-mqa-again