MQA is Vaporware

[adamdea]

50 minutes ago, Shadders said:

Hi Fokus,

You have claimed i do not know what i am talking about, and this was not correct.

You have claimed that temporal blur is caused by ringing, and this is not correct.

You have claimed that temporal blur is not dispersion, and this is not correct.

You are trying to find fault where none exists.

Regards,

Shadders.

OK. Deep breath called for. Let's step back a moment.

"Temporal blur" may well be used in different (or even vague and undefinable) senses in some parts of the MQA literature, particularly relating to a general vague claim to undo something or other done wrong in the ADC process BUT

There can be no doubt that the main thrust of the MQA papers and the famous MQA Q and A was to do with targeting an impulse response equal to 10m of air. The critcism of conventional non MQA filters was also aimed at their impulse response and time blur seems to have been equated mainly with the width of the impulse response.

 

Now there may be all kinds of reasons why the MQA position is horseshit but it really does seem as though  it was the pre-and post ringing which amounted to the alleged "time domain" (actually meaning impulse response) characteristics of conventional filters which MQA  was attacking.

 

Of course it is difficult to speak definitively about what temporal blur is or isn''t for the same reason that it is is difficult to speak definitely about the breeding characteristics of unicorns.

 

[adamdea]

empty

[Shadders]

2 minutes ago, adamdea said:

OK. Deep breath called for. Let's step back a moment.

"Temporal blur" may well be used in different (or even vague and undefinable) senses in some parts of the MQA literature, particularly relating to a general vague claim to undo something or other done wrong in the ADC process BUT

There can be no doubt that the main thrust of the MQA papers and the famous MQA Q and A was to do with targeting an impulse response equal to 10m of air. The critcism of conventional non MQA filters was also aimed at their impulse response and time blur seems to have been equated with the width of the impulse response.

 

Now there may be all kinds of reasons why the MQA position is horseshit but it really does seem as though  it was the pre-and post ringing which amounted to the alleged "time domain" (actually meaning impulse response) characteristics of conventional filters which MQA  was attacking.

 

Of course it is difficult to speak definitely about what temporal blur is or isn''t for the same reason that it is is difficult to speak definitely about the breeding characteristics of unicorns.

 

Hi,

The AES paper from 2014 on page 2 defines blur as dispersion.

I will defend inaccurate claims made against myself.

Regards,

Shadders.

[Fokus]

1 hour ago, Shadders said:

I read the AES paper from 2014 which states on page 2  :

 

Same paper ("A Hierarchical Approach to Archiving and Distribution")

Figure 14.

 

[adamdea]

8 minutes ago, Shadders said:

Hi,

The AES paper from 2014 on page 2 defines blur as dispersion.

I will defend inaccurate claims made against myself.

Regards,

Shadders.

I dare say. But "The AES paper" is not the one Werner was referring to- which is by Craven (note not Stuart), and kicked off the minimum phase apodising filter thing (and I think it's referred to in the MQA documentation)

 http://www.aes.org/tmpFiles/JAES/20180125/JAES_V52_3_PG216.pdf
it's all about the impulse responses. But does not use the expression blur.

 

Anyway, whichever way you look at it  impulse response is supposed to be the MQA target (10m of air). It can be very confusing, because we are to a large extent, tilting at windmills. 

[Shadders]

13 minutes ago, Fokus said:

 

Same paper ("A Hierarchical Approach to Archiving and Distribution")

Figure 14.

 

Hi Fokus,

Please explain your reason that the stated Figure 14 is important.

Thanks and regards,

Shadders.

[Shadders]

14 minutes ago, adamdea said:

I dare say. But "The AES paper" is not the one Werner was referring to- which is by Craven (note not Stuart), and kicked off the minimum phase apodising filter thing (and I think it's referred to in the MQA documentation)

 http://www.aes.org/tmpFiles/JAES/20180125/JAES_V52_3_PG216.pdf
it's all about the impulse responses. But does not use the expression blur.

 

Anyway, whichever way you look at it  impulse response is supposed to be the MQA target (10m of air). It can be very confusing, because we are to a large extent, tilting at windmills. 

Hi,

The challenge was that dispersion is not temporal blur, where i responded that temporal blur is dispersion, and provided proof.

Regards,

Shadders.

[adamdea]

Even if it is dispersion, I fear that it isn't going to help with the the point that the PCM output of a delta sigma adc with a conventional filter will end up  with whatever the (real or imagined) time domain thing is that MQA is supposed to cure.

[Shadders]

1 minute ago, adamdea said:

Even if it is dispersion, I fear that it isn't going to help with the the point that the PCM output of a delta sigma adc with a conventional filter will end up  with whatever the (real or imagined) time domain thing is that MQA is supposed to cure.

Hi,

As i stated earlier, i was responding to the claim that dispersion was not temporal blur.

Dispersion is an engineering term.

Regards,

Shadders.

[mansr]

19 minutes ago, adamdea said:

There can be no doubt that the main thrust of the MQA papers and the famous MQA Q and A was to do with targeting an impulse response equal to 10m of air.

This "10 m of air" talk makes no sense. The speed of sound in air is independent of frequency, so there is no dispersion. High frequencies are attenuated more than low ones. For 10 m of air at 50% relative humidity, the attenuation is 0.047 dB at 1 kHz, 1.6 dB at 10 kHz, 5.2 dB at 20 kHz, and 33 dB at 100 kHz (http://www.kayelaby.npl.co.uk/general_physics/2_4/2_4_1.html). I'd like to see explained how the MQA filters are derived from this.

[Fokus]

48 minutes ago, Shadders said:

Please explain your reason that the stated Figure 14 is important.

 

It shows the 'blur' of industry-standard linear phase 192k and 96k channels versus the MQA solution. The plots are (log-scale, rectified) impulse response versus time.

 

[Fokus]

30 minutes ago, mansr said:

This "10 m of air" talk makes no sense.

 

It is an appeal to emotions.

 

"Guys presented here, and Poppy, too, wouldn't it be nice if our audio systems where

as transparent as 10 meters of air? Fresh air ... Do you smell the grass? Do you feel the sun? With MQA all this can be yours."

 

[mansr]

8 minutes ago, Fokus said:

The plots are (log-scale, rectified) impulse response versus time.

As if that were in any way a meaningful thing to plot.

[manisandher]

36 minutes ago, mansr said:

This "10 m of air" talk makes no sense.

 

I am in no way saying that I agree with the content of the following, but here are some pics I took of Stuart's talk at Munich High End last year:

 

 

(This was a public talk, so I'm assuming it's OK posting these here. But Chris, if there's any issue with this then please remove.)

 

Mani.

[Shadders]

15 minutes ago, Fokus said:

 

It shows the 'blur' of industry-standard linear phase 192k and 96k channels versus the MQA solution. The plots are (log-scale, rectified) impulse response versus time.

 

Hi Fokus,

The diagram you referenced states it is the impulse response, and no mention of blur.

Again, please provide the reason for referencing this figure - what are you trying to explain ?

Thanks and regards,

Shadders.

[mansr]

5 minutes ago, manisandher said:

 

I am in no way saying that I agree with the content of the following, but here are some pics I took of Stuart's talk at Munich High End last year:

 

 

(This was a public talk, so I'm assuming it's OK posting these here. But Chris, if there's any issue with this then please remove.)

 

Mani.

He's committing the usual fallacy of equating temporal resolution to sample interval. Since he no doubt knows this is false, he is blatantly lying. No surprise there.

[Fokus]

2 minutes ago, Shadders said:

Again, please provide the reason for referencing this figure - what are you trying to explain ?

 

It shows the badness of the standard filters: wide = blur, against the goodness of MQA: narrow = unblurred.

[Fokus]

1 minute ago, mansr said:

Since he no doubt knows this is false, he is blatantly lying. No surprise there.

 

The aforementioned 2014 paper explicitly states that temporal resolution is at a fraction of the sample period, so, yes ...

 

 

[Shadders]

Just now, Fokus said:

 

It shows the badness of the standard filters: wide = blur, against the goodness of MQA: narrow = unblurred.

Hi,

This is not correct. The impulse response does NOT prove the relevant dispersion of a filter.

The phase across the frequency band provides the dispersion effect to a signal.

If the phase is non-linear then a signal will experience dispersion.

The entire reason for linear phase filters is to ensure constant group delay - that is, all the required frequencies are delayed by the same amount, and hence NO dispersion.

Regards,

Shadders.

[Fokus]

13 minutes ago, mansr said:

As if that were in any way a meaningful thing to plot.

 

Pioneered by Craven and for a while picked up in a few audio magazines.

 

These plots make it easy to depict anything that is not the main central lobe as distortion, at levels of -20dB, no less.

 

You have to scare the audience before presenting a solution.

[Fokus]

1 minute ago, Shadders said:

The entire reason for linear phase filters is to ensure constant group delay - that is, all the required frequencies are delayed by the same amount, and hence NO dispersion.

 

Yes. And what does this have to do with MQA?

 

MQA is a fight against the widening of the impulse response due to any system action that limits bandwidth, both linear phase and minimum phase (i.e. dispersive). MQA achieves its goal simply by almost entirely omitting the necessary AA and AI filters. The width of the resulting log-plotted impulse response is their figure of merit.

 

 

[Shadders]

1 minute ago, Fokus said:

 

Yes. And what does this have to do with MQA?

 

MQA is a fight against the widening of the impulse response due to any system action that limits bandwidth, both linear phase and minimum phase (i.e. dispersive). MQA achieves its goal simply by almost entirely omitting the necessary AA and AI filters. The width of the resulting log-plotted impulse response is their figure of merit.

 

 

Hi Fokus,

You referenced the figure 14. I do not see why your statement :

34 minutes ago, Fokus said:

It shows the 'blur' of industry-standard linear phase 192k and 96k channels versus the MQA solution. The plots are (log-scale, rectified) impulse response versus time.

is proved.

The figure 14 from the AES paper is the ""Impulse responses: upper and middle as dB magnitude and lower as amplitude"

Again, the impulse response does not prove the dispersion effect.

That is, a wide or slim impulse response does not mean a dispersive, or non-dispersive effect of a filter.

The phase of the filter determines whether the signal undergoes a dispersive effect.

As long as the filter phase is linear across the required signal bandwidth then there is no dispersion to those frequencies of interest.

Regards,

Shadders.

[adamdea]

1 hour ago, mansr said:

This "10 m of air" talk makes no sense. The speed of sound in air is independent of frequency, so there is no dispersion. High frequencies are attenuated more than low ones. For 10 m of air at 50% relative humidity, the attenuation is 0.047 dB at 1 kHz, 1.6 dB at 10 kHz, 5.2 dB at 20 kHz, and 33 dB at 100 kHz (http://www.kayelaby.npl.co.uk/general_physics/2_4/2_4_1.html). I'd like to see explained how the MQA filters are derived from this.

Obviously it's pretty much horseshit, but the claim never was about group delay or dispersion in any specific technical sense, (even if, like many sciencey-sounding things, the term dispersion is borrowed here or there) it was about the impulse response of 10m of air. It's enough of a straw man as it is not to need to be dressed up further as a straw man. 

[botrytis]

We are having this same discussion on Audiokarma. It seems people really don't want to understand or have been sold a bill of goods as to how good MQA is and believe it. Kind of sad really.

[adamdea]

7 minutes ago, Shadders said:

H

Again, the impulse response does not prove the dispersion effect.

That is, a wide or slim impulse response does not mean a dispersive, or non-dispersive effect of a filter.

The phase of the filter determines whether the signal undergoes a dispersive effect.

As long as the filter phase is linear across the required signal bandwidth then there is no dispersion to those frequencies of interest.

Regards,

Shadders.

Shadders please,

you are arguing yourself round in a circle.The property which MQA is targeting is not dispersion in the sense you are using it. QED.

The MQA argument is about some alleged time property of filters shown here in the slide attached by manisandher. Whatever it is, a linear phase filter has it. It is not dispersion in the sense you use it. That may mean that somewhere along the line the MQA literature has used the word in one sense and then again in another. No surprises there