MQA, where is decoding done, what is required?

[Roland68]

I am not quite clear at which point MQA is decoded and what is required for this.

Does the decoding take place in the DAC chip or is an additional circuit or chip required?

I don't want to spark a discussion about MQA here, enough has already been said in the forum.
I'm only interested in the technical process of decoding in MQA.

 

[Jimbob54]

I am not quite clear at which point MQA is decoded and what is required for this.

Does the decoding take place in the DAC chip or is an additional circuit or chip required?

I don't want to spark a discussion about MQA here, enough has already been said in the forum.
I'm only interested in the technical process of decoding in MQA.

Well, as ever , it depends.... but from the horses mouth

http://bobtalks.co.uk/blog/science-mqa/mqa-playback/#

 

[solderdude]

1st unfold (to 88.2 or 96kHz) can be done in software (free essentially).
2nd unfold is only built into the DAC device (for which you pay) which can extend the frequency range to an equally inaudible 176.4 or 192kHz.
That is... assuming there is relevant audio info there anyway and your transducers can actually reach above 50kHz.

You end up with extended frequency extension but lower bit depth.
In the end audible resolution increase comes from bit depth, not frequency extension.
The lost bits do not return magically with unfolds.

 

[Roland68]

Thanks ever for the answers.

To me it really about the physical implementation.
The complete unfolding has to come from somewhere.
Is this done in a circuit in front of the DAC chip or in the Dac chip itself?

 

[solderdude]

In any case the 2nd unfold is done in the physical DAC device.
I assume DAC chips could have it on chip or it is done in some processing chip before the actual conversion.
This really does not matter.

 

[Jimbob54]

Thanks ever for the answers.

To me it really about the physical implementation.
The complete unfolding has to come from somewhere.
Is this done in a circuit in front of the DAC chip or in the Dac chip itself?

We are starting to see the MQA decoder on some new DAC chips- but take, for eg, the Topping D90- the MQA model has a different chip before the DAC chip that does the MQA decode/ unfold then passes to the DAC proper.

 

[SJ777]

1st unfold (to 88.2 or 96kHz) can be done in software (free essentially).
2nd unfold is only built into the DAC device (for which you pay) which can extend the frequency range to an equally inaudible 176.4 or 192kHz.
That is... assuming there is relevant audio info there anyway and your transducers can actually reach above 50kHz.

You end up with extended frequency extension but lower bit depth.
In the end audible resolution increase comes from bit depth, not frequency extension.
The lost bits do not return magically with unfolds.

Is it not the case that, for a full MQA decoder, both unfolds are done by the DAC? All that a full decoder MQA DAC needs is a bitperfect stream.

An MQA-renderer DAC can only do the 2nd unfold and so needs a software 1st unfold.

 

[solderdude]

Of course a hardware DAC can do 1st and 2nd unfold.
In software one can do the first unfold only, not the second unfold. For that you need a MQA DAC.
It makes sense when you want full MQA unfold to let the DAC device do it and is what everyone who owns an MQA DAC does.

It indeed wasn't quite clear from my reply.

 

[Glasvegas]

So, what exactly do you get if you stream a Tidal MQA track though a completely NON-MQA device e.g. Chromecast Audio. Do you end up with standard 16 bit/44.1kHz, something worse, something better?

 

[Jimbob54]

So, what exactly do you get if you stream a Tidal MQA track though a completely NON-MQA device e.g. Chromecast Audio. Do you end up with standard 16 bit/44.1kHz, something worse, something better?

Therein lies the rub. Read the article I linked to from Bob MQA Stuart. He says you get better than CD 16/44. Others I think would disagree. But thats taking this into territory the op wanted to avoid.

 

[Glasvegas]

Therein lies the rub. Read the article I linked to from Bob MQA Stuart. He says you get better than CD 16/44. Others I think would disagree. But thats taking this into territory the op wanted to avoid.

Well, I'm taking Bob's "better than CD" comment with a pinch of salt. That's why I asked here. Any link to a more reliable explanation would be appreciated.

 

[SJ777]

So, what exactly do you get if you stream a Tidal MQA track though s completely NON-MQA device e.g. Chromecast Audio. Do you end up with standard 16 bit/44.1kHz, something worse, something better?

It depends on the DAC. If your DAC is a full MQA decoder then, as long as CCA provides a bitperfect stream, the DAC will do all the work. As far as I know, other CCA streaming options will simply give 16/44.1 results.

It seems to be that, for software based 1st unfolding, every part of the stream needs to be able to handle MQA. With CCA you may start with a software unfold (e.g. the Tidal app), but CCA doesn't transport that unfold - so you're left with 16/44.1 at the end point. This is the same with Raspberry Pi solutions (until Tidal Connect comes to Volumio). An app like Mconnect can do the 1st unfold, but the UPnP renderer can't transport it (just like the CCA can't).

If you look at something like USB Audio Player Pro, this can transport a 1st unfolded stream to any DAC as there's no additional hardware in the chain. The only draw back is that you have to tether your phone to the DAC in order to use it.

I have no idea why I'm accumulating this information - I don't even use MQA!!!

EDIT: My wording above is, I think, inaccurate. The streaming on the CCA and RPi is done by the CCA and the RPi respectively. The control point (app) doesn't do the work so it's wrong of me to say that Mconnect (or the Tidal app) does the 1st unfold. It doesn't. No matter what the control point is saying it's doing, it can only so what the renderer allows it to do. It's yet to be seen how Volumio will handle Tidal Connect!

 

[Jimbob54]

Well, I'm taking Bob's "better than CD" comment with a pinch of salt. That's why I asked here. Any link to a more reliable explanation would be appreciated.

I would suggest you browse through @mansr posts on the subject as a starting point. And /or read the mqa controversies thread if you can handle it

 

[Glasvegas]

It depends on the DAC. If your DAC is a full MQA decoder then, as long as CCA provides a bitperfect stream, the DAC will do all the work. As far as I know, other CCA streaming options will simply give 16/44.1 results.

It seems to be that, for software based 1st unfolding, every part of the stream needs to be able to handle MQA. With CCA you may start with a software unfold (e.g. the Tidal app), but CCA doesn't transport that unfold - so you're left with 16/44.1 at the end point. This is the same with Raspberry Pi solutions (until Tidal Connect comes to Volumio). An app like Mconnect can do the 1st unfold, but the UPnP renderer can't transport it (just like the CCA can't).

If you look at something like USB Audio Player Pro, this can transport a 1st unfolded stream to any DAC as there's no additional hardware in the chain. The only draw back is that you have to tether your phone to the DAC in order to use it.

I have no idea why I'm accumulating this information - I don't even use MQA!!!

Me neither.

However, many tracks on Tidal are now MQA only. So long as I’m still getting CD quality I’m happy.

I‘ve read somewhere that some of the “bits” in MQA are used for decoding. So long as it isn’t any of the 16 bits I need.

For what it‘s worth, I can’t hear any difference between MQA and standard CD Tidal tracks on my system. I suppose that‘s all that matters.

Still curious though.

 

[Vincent Kars]

So long as it isn’t any of the 16 bits I need.

There is a watermark hidden in the bits 1 to 16.
If the DAC detects this pattern, it will apply minimum phase filters and up-sampling.

 

[abdo123]

Therein lies the rub. Read the article I linked to from Bob MQA Stuart. He says you get better than CD 16/44. Others I think would disagree. But thats taking this into territory the op wanted to avoid.

That’s not true, Tidal application is a software decoder (first step) so you immediately get higher than CD.

 

[abdo123]

It depends on the DAC. If your DAC is a full MQA decoder then, as long as CCA provides a bitperfect stream, the DAC will do all the work. As far as I know, other CCA streaming options will simply give 16/44.1 results.

It seems to be that, for software based 1st unfolding, every part of the stream needs to be able to handle MQA. With CCA you may start with a software unfold (e.g. the Tidal app), but CCA doesn't transport that unfold - so you're left with 16/44.1 at the end point. This is the same with Raspberry Pi solutions (until Tidal Connect comes to Volumio). An app like Mconnect can do the 1st unfold, but the UPnP renderer can't transport it (just like the CCA can't).

If you look at something like USB Audio Player Pro, this can transport a 1st unfolded stream to any DAC as there's no additional hardware in the chain. The only draw back is that you have to tether your phone to the DAC in order to use it.

I have no idea why I'm accumulating this information - I don't even use MQA!!!

EDIT: My wording above is, I think, inaccurate. The streaming on the CCA and RPi is done by the CCA and the RPi respectively. The control point (app) doesn't do the work so it's wrong of me to say that Mconnect (or the Tidal app) does the 1st unfold. It doesn't. No matter what the control point is saying it's doing, it can only so what the renderer allows it to do. It's yet to be seen how Volumio will handle Tidal Connect!

Tidal doesn’t support Master quality streaming at all with CCA, it instantly changes the quality to ‘Hi-Fi’ (CD).

 

[Jimbob54]

That’s not true, Tidal application is a software decoder (first step) so you immediately get higher than CD.

2 things. Who says you have to use the tidal app? Who says you have to enable software mqa decoding if you do? I could use UAPP on my phone and not pay for the mqa add in. Or other solutions.

Also, what isn't true? What the creator of mqa says or what I said in posting a link to him?

 

[abdo123]

@Glasvegas
We can’t really answer your questions since this whole thing is patented and little is out in the open.

We can make educated guesses based on what has been reverse engineered by members @mansr

a 24/44.1 MQA file will basically provide CD quality with a bit lower bit depth if it is not unfolded at all (1-1.5 bits so not really audible).

This however is never the case since Tidal does the first unfold all the time (unless you change the settings so it wouldn’t). So you shouldn’t worry about that.


I’m not sure whether the bit depth increases or not after the first unfold, or whether the extra bits just contain ultrasonic frequencies

 

[abdo123]

2 things. Who says you have to use the tidal app? Who says you have to enable software mqa decoding if you do? I could use UAPP on my phone and not pay for the mqa add in. Or other solutions.

Also, what isn't true? What the creator of mqa says or what I said in posting a link to him?

the OP is using Tidal, and he’s asking in that particular context. He’s not purchasing MQA tracks and playing them independently.

Edit: Sorry there are two people asking questions here, and only one of them said that they’re using Tidal.