[71 dB]

I have been writing too much here. My own life suffers. I need to eat, spend free time out etc. Many discussion boards online are sadly dead. Not this one. The activity level is crazy.

 

[sunjam]

Youtube videos can of course be just as reliable as textbooks depending on who makes them and for what purpose. Students may find Youtube videos more pleasant and engaging way of learning. I have learned a lot of things watching Youtube videos (for example music theory which I didn't learn at all in school).


I watched the Monty video some years ago. I don't remember it 100 %, but I don't recall anything wrong with it. I wonder what about it shocks you so much...


The signal level of that is something like -72 dBFS. That is incredibly quiet. If you listen to levels where the peaks (assume 0 dBFS) go to 100 dB, this signal is 28 dB which means a quiet living room. The noise from AC is likely to mask this signal even when listening to such a loud levels. Also when listening to loud music, your hearing threshold gets temporarily raised. I ask you to think critically how accurately you need signals this quiet to be reconstructed? Now compare that to how accurately they are constructed.

Thanks a lot for your reply.

Yes, "Youtube videos can of course be just as reliable as textbooks depending on who makes them and for what purpose" <== I totally agreed with you especially the "for what purpose" (i.e. intention) part.

To me, the intention of the Monty's video is to prove that he is right about his claim in his earlier writing 24/192 Music Downloads are Very Silly Indeed (xiph.org):

He claimed that in his article:
(I recomended you read his article first and then watch the video)

He created the video to support his claim (the vidoe is his "Digital Show & Tell)

Please look at the highlighted statement above in his article. Is it 100% correct? Or just "correct but not absolutely"?

A lot of qualifiers of the statement are missing (intentionally, IMO) from the above statement? Why, with qualifiers added, it would indicate he was wrong (or at least mis-leading) when he wrote the statement.

Is he one of the brilliant MIT graduates who misunderstood the Sampling Theory (as he mentioned above in my first screen capture) so he didn't know about those qualifiers? <=== I doubt it as I think he should be smart enough to know about those qualifiers.

Or

He left out those qualifiers intentionally in order to achieve something (e.g. to show he is right)?

I have to agree that other parts of his video are interesting. I considered those are "by-product" for his intention to show he is right regarding the stair step waveform.

Why I am shocked?

One of my latest writing shown below may give you some idea:

A "valid but not absolutely" claim? Hey, what are you talking about?​

If an expert (e.g. a MIT graduate in Electrical Engineering) claim the following:

"The analog signal can be reconstructed losslessly, smoothly, and with the exact timing of the original analog signal [by using CD format]" (the claim)

What would you think about such claim?

I bet most people would understand the claim as the following:
"Using 44.1kHz / 16 bit digital source (i.e. CD format) would allow us to reconstruct the original analogy signal perfectly. "

Is it your understanding too?

You may said, "Yes, of couse. That's what the claim means. They are talking the same thing. Are you that stupid to ask such simple question?"

I thought the same too. But I think going forward when I discuss something in any audio science forum, I may need to ask them, is it "absolutely valid" or just "valid but not absolutely"

The answer I got from many members in audio science forum is "no, they are not the same" (they may not use the exact wordings but that's what they meant).

Why they said so?

Reconstructed losslessly, smoothly, and with the exact timing of the original analog signal?

Let's have a look of the following simulation of the analog signal reconstruction. (note: the following are simulation)

The following graph shows an original analog signal (i.e. a perfect analog sine wave input)


Figuare 1: A perfect sharp sine wave analog input signal

By digitizing the analog signal to 44.1k Hz / 16 bit and then reconstructing an analog signal from the digitized source via a DAC with perfect reconstruction filter, the output would be something like the following:




Figure 2: the simulated output from a DAC with perfect reconstruction filter
The reconstructed output would look like a "smooth" sine wave but with a smeared line (sorry for my hand-drawing, the above graph should look like a "smooth" sine wave with a smeared line. The level of the smearing may not be in scale with the actual ouput from a DAC as the above graph is for indicating the effect of various artifacts in the reconstruction process.)

The smearing of the output analog signal is due to vaious artifacts introduced in the ADC and DAC processes. For example, dithering is one of the source of such artifacts. (Note: dithering is a technique used to make the quantization errors of the final reconstructed analog signal looks "smooth" rather than "rough")

Ok, back to the claim, i.e. "The analog signal can be reconstructed losslessly, smoothly, and with the exact timing of the original analog signal [by using CD format]"

Would you describe a perfectly reconstructed analog output with smeared signal as "losslessly, smoothly, and with the exact timing of the original analog signal?

Mis-leading to High School Students

As @gregorio demonstrated earlier, most people would have the following belief about MIT graduate "No, I’ve never met or even heard of a primary school kid who knew more about digital audio than a MIT graduate with a masters degree degree in computer science and a bachelor’s degree in electrical engineering who invented certain widely used audio codecs (Monty). Please give us an example of one."
(FYI, I don't have the above belief as, personally, I had worked with quite a lot of MIT graduates up to the PhD level. I bet I know pretty well how they works. <=== for this, I could be biaed based on my own perosnal experience with them. LOL.)

Just imagine what would high school students think when their teachers show the "Montys video" to them in a classroom?

Would the students be that knowledgeable in audio science so that they can add back those missing qualifiers for the mis-leading statement themselves?

Or they would just simply interpret the statement as "Using 44.1kHz / 16 bit digital source (i.e. CD format) would allow us to reconstruct the original analogy signal perfectly." (i.e. the Interpretation)

I hope by now, you can understand why I am so concerned about these mis-leading / pseudo science claims passing around on the net and giving wrong understanding to, especially, high school students.

p.s. Based on my experience with various people in audio science, there are quite a lot of people got tricked and truely believe in the Interpretation shown above too.

 

[VNandor]

The reason you have to resort to poorly drawn ms paint pictures to show "smearing" instead of posting actual pictures of oscilloscopes showing the signal is because the smearing does not happen the way you imply it on your paint pictures. This thread could have been closed right after the second post by @Quazar as that post actually shows exactly how the reconstructed signal looks. You continuously ignore the fact that any DAC that focuses on high fidelity signal reproduction instead of marketing gimmicks will oversample the signal to well over the MHz range and properly filters it to help with high quality reconstruction. You keep pushing you agenda about "Hi-Res" while you conflate hi-res with upsampling. You recently showed that not only you don't know how sampling works, you also don't know how quantization works. Dithering does not smear the signal, it adds noise to the signal to remove any potential errors that could correlate with the analog signal, effectively removing all distortion products caused during the quantization. If by "smearing" you mean low level added noise then you are correct by saying dither smears the signal. Let me remind you that no recording is free of noise as they have to exist in a real space called a "studio" and this so called studio will have its own noise level. A recording usually employs multiple microphones so this noise level is recorded multiple times and it's summed together into 2 channels eventually. On top of that, the preamps and the recording audio interface will also all add their own noise into the recording as well although ideally this noise will be well below the studio's noise level. A sufficiently noisy analog signal may very well be self-dithering rendering the additional dither noise an unnecessary step for proper quantization. Despite this, dither noise is still added to the signal to make absolutely sure (instead of just simply unlikely) the quantization error won't correlate with the signal at all.

 

[castleofargh]

The reason you have to resort to poorly drawn ms paint pictures to show "smearing" instead of posting actual pictures of oscilloscopes showing the signal is because the smearing does not happen the way you imply it on your paint pictures. This thread could have been closed right after the second post by @Quazar as that post actually shows exactly how the reconstructed signal looks. You continuously ignore the fact that any DAC that focuses on high fidelity signal reproduction instead of marketing gimmicks will oversample the signal to well over the MHz range and properly filters it to help with high quality reconstruction. You keep pushing you agenda about "Hi-Res" while you conflate hi-res with upsampling. You recently showed that not only you don't know how sampling works, you also don't know how quantization works. Dithering does not smear the signal, it adds noise to the signal to remove any potential errors that could correlate with the analog signal, effectively removing all distortion products caused during the quantization. If by "smearing" you mean low level added noise then you are correct by saying dither smears the signal. Let me remind you that no recording is free of noise as they have to exist in a real space called a "studio" and this so called studio will have its own noise level. A recording usually employs multiple microphones so this noise level is recorded multiple times and it's summed together into 2 channels eventually. On top of that, the preamps and the recording audio interface will also all add their own noise into the recording as well although ideally this noise will be well below the studio's noise level. A sufficiently noisy analog signal may very well be self-dithering rendering the additional dither noise an unnecessary step for proper quantization. Despite this, dither noise is still added to the signal to make absolutely sure (instead of just simply unlikely) the quantization error won't correlate with the signal at all.

I'm sure he will take all that into consideration, look up some information, and come back with a different and objectively accurate take on digital audio.


I don't know what to do with people who don't know shame. I do have an urge to delete this thread and all his BS with it. It's been on my mind since page one, indeed.

 

[gregorio]

@gregorio What if Y db is not below 'min' dB

If -30 is not below -23 then all math is wrong and the modern world doesn’t exist.

I would believe textbooks are much reliable than YouTube video (even from the so-called expert).

Then try reading some.

Nowadays, students are watching a lot YouTube video in high school during classroom time. I was shocked to know that they use the Monty's video for teaching. I am very worried about our next generation.

Yes, students commonly watch a great deal of YouTube videos, the vast majority of which are nonsense clickbait (just like your blog) so it is somewhat shocking when they watch one that’s actually factually true/correct! Although not so shocking if they’ve been directed to do so by a teacher who hopefully knows more than kindergarten child.

With dithering, where the "uncorrelated noise" goes? IMO, it is shown as the smearing of the final audio output.

Right but by your own admission, your opinion is that of a kindergarten child! In the given case, the “uncorrelated noise” in the critical band does NOT “go out” of the transducers because it is below -23dBSPL. If it doesn’t even get reproduced by the speakers how can it be audible?

The rest of your most recent posts appear to summarise as: “Hi-res is better because I’ve used the digital equivalent of different sized crayons to draw some pictures that have nothing to do with anything and furthermore, Archimago is better than Monty because he mentions broken DACs while Monty only demonstrates typical DACs that aren’t broken.” - Great, at least there is a common thread, which is your kindergarten level of understanding and debate! Well done.

G

 

[sunjam]

The reason you have to resort to poorly drawn ms paint pictures to show "smearing" instead of posting actual pictures of oscilloscopes showing the signal is because the smearing does not happen the way you imply it on your paint pictures. This thread could have been closed right after the second post by @Quazar as that post actually shows exactly how the reconstructed signal looks. You continuously ignore the fact that any DAC that focuses on high fidelity signal reproduction instead of marketing gimmicks will oversample the signal to well over the MHz range and properly filters it to help with high quality reconstruction. You keep pushing you agenda about "Hi-Res" while you conflate hi-res with upsampling. You recently showed that not only you don't know how sampling works, you also don't know how quantization works. Dithering does not smear the signal, it adds noise to the signal to remove any potential errors that could correlate with the analog signal, effectively removing all distortion products caused during the quantization. If by "smearing" you mean low level added noise then you are correct by saying dither smears the signal. Let me remind you that no recording is free of noise as they have to exist in a real space called a "studio" and this so called studio will have its own noise level. A recording usually employs multiple microphones so this noise level is recorded multiple times and it's summed together into 2 channels eventually. On top of that, the preamps and the recording audio interface will also all add their own noise into the recording as well although ideally this noise will be well below the studio's noise level. A sufficiently noisy analog signal may very well be self-dithering rendering the additional dither noise an unnecessary step for proper quantization. Despite this, dither noise is still added to the signal to make absolutely sure (instead of just simply unlikely) the quantization error won't correlate with the signal at all.

Smearing?

"If by 'smearing' you mean low level added noise then you are correct by saying dither smears the signal." <=== thanks for your confirmation.

NOS filter mode with internal upsampling DAC

"You continuously ignore the fact that any DAC that focuses on high fidelity signal reproduction instead of marketing gimmicks will oversample the signal to well over the MHz range and properly filters it to help with high quality reconstruction" <=== Sorry, I don't think I ignore that fact that "any DAC that focuses on high fidelity signal reproduction instead of marketing gimmicks will oversample the signal to well over the MHz range and properly filters it to help with high quality reconstruction". I am not sure why you have such feeling. In fact, I did write a few times explicitly that modern DAC do indeed perform internal upsampling.

To me, I think many people here continuously ignore the fact that any DAC that focuses on high fidelity signal reproduction instead of marketing gimmicks will oversample the signal to well over the MHz range and properly filters it to help with high quality reconstruction. NOS mode filter is one of properly built filters in a DAC that designed for Hi-Res music reconstruction.

Hi-Res or Upsampling?

"You keep pushing you agenda about 'Hi-Res' while you conflate hi-res with upsampling" <=== Not sure why you have such impression. I mean Hi-Res. The topic of this thread is Hi-Res. Please don't confliate Hi-Res with upsampling. (I only mentioned upsampled music when we were talking about hearing experience). If you have HQPlayer or any external upsampler in your mind, please remove them in our discussion as we are talking about Hi-Res.

Noise free?

"Let me remind you that no recording is free of noise" <=== Of course, I didn't say Hi-Res is perfect or noise free. Did I?

 

[castleofargh]

Last post for clarity.
To fully define sunjam's posts in this thread and his blog, all you need is this:

Read his posts again, almost all of them have one or more of those characteristics.
Me putting a stop to his grand standing operation, is merely my belief that there should be some degree of accountability for shamelessly dishonest people.