24bit vs 16bit, the myth exploded!
Jul 10, 2018 at 1:51 AM Post #4,906 of 7,175
Quantization noise fluctuates with signal level. Signal masks noise.
It's incidental, not intentional. If you define perceptual coding by only including the fact that masking occurs, then every recording system uses an early form of perceptual coding. That means RIAA is perceptual coding, Tape EQ is perceptual coding, heck the Edison wax cylinder employed an early form of perceptual coding. All of that is complete nonsense.

The part of coding that is specifically designed to exploit masking, the, "perceptual" part, is what's missing.

You need to work on your definitions, that's all I'm saying.
 
Jul 10, 2018 at 2:04 AM Post #4,907 of 7,175
Do you know who writes the Wiki articles? Anyone! Do you know who can edit them? Anyone!
Do you know who writes forum posts?

How would you define "perceptual coding"? I found a nice definition that seems good to me: "Perceptual Coding": Lossy compression that takes advantage of limitations in human perception. In perceptual coding, audio data is selectively removed based on how unlikely it is that a listener will notice the removal.

Do you know where the log relationship for A-law and µ-law come from? Look up Weber-Fechner for a clue.
 
Jul 10, 2018 at 3:21 AM Post #4,908 of 7,175
Do you know who writes forum posts?
It's how Wikipedia works: Anyone...even you!....could write an article. And anyone...even me!....could edit it and correct it. It's the entire principle behind the site.
How would you define "perceptual coding"? I found a nice definition that seems good to me: "Perceptual Coding": Lossy compression that takes advantage of limitations in human perception. In perceptual coding, audio data is selectively removed based on how unlikely it is that a listener will notice the removal.
Not bad. And by that definition, µ-law is not perceptual coding because it does not specificaly base it's action on the likelihood of a listener hearing what's been removed.
 
Jul 10, 2018 at 3:28 AM Post #4,909 of 7,175
Do you know who writes the Wiki articles? Anyone! Do you know who can edit them? Anyone!

Well, go and correct the mistakes then! You use a lot of energy correcting me, one person while anyone can read Wikipedia.
 
Jul 10, 2018 at 3:39 AM Post #4,910 of 7,175
It's incidental, not intentional. If you define perceptual coding by only including the fact that masking occurs, then every recording system uses an early form of perceptual coding. That means RIAA is perceptual coding, Tape EQ is perceptual coding, heck the Edison wax cylinder employed an early form of perceptual coding. All of that is complete nonsense.

The part of coding that is specifically designed to exploit masking, the, "perceptual" part, is what's missing.

You need to work on your definitions, that's all I'm saying.
Why would any sound quality reduction be intentional ? All of it is incidental, but in a controlled way. We know how harmful it is from perceptual point of view. Perceptual coding uses data reduction and you don't have that with analog formats. Even if wax cylinders were perceptual coding so what? Changes nothing.
 
Jul 10, 2018 at 5:06 AM Post #4,911 of 7,175
[1] Quantization noise fluctuates with signal level. Signal masks noise.
[2] Perceptual coding uses data reduction and you don't have that with analog formats. [2a] Even if wax cylinders were perceptual coding so what? Changes nothing.

1. That's great, it means there's no need whatsoever for dither because quantisation noise is apparently masked. All these decades of dither and dither development wasted ... do you think we should tell someone? :)

2. So now, in effect, you're contradicting yourself because µ-law/A-law are analogue processes!
2a. By your definition, wax cylinders are perceptual coding, vinyl with RIAA are perceptual coding, cassettes with bias are perceptual coding, CDs with emphasis are perceptual encoding, despite your claim in point #1, dither is perceptual coding and therefore pretty much all digital audio uses perceptual coding and every mix of every piece of commercial audio has EQ, mic placement, compression or a number of other factors/processes applied to improve perception. In other words, by your definition, everything uses perceptual coding. So, please answer these two questions: A. What is the point of the term "perceptual coding" if it means the same as "everything" and B. What new/different term should we use for actual perceptual coding?

You're following the exact same path you always follow. You make some incorrect claim/assertion of fact which is refuted and then instead of holding your hand up and admitting it or just dropping it, you defend it to the death for post after post, make more and more ridiculous assertions to support your position, even to the point of contradicting yourself, and dig a deeper and deeper hole for yourself until eventually you back yourself into a logical cul de sac. At which point you usually post something along the lines that you feel like a useless human being. My last question of this post is therefore: Why follow that same path, why put yourself through all this time after time?

G
 
Jul 10, 2018 at 7:29 AM Post #4,912 of 7,175
Wow. You missed both my points. I must have been unclear.

It's how Wikipedia works: Anyone...even you!....could write an article. And anyone...even me!....could edit it and correct it. It's the entire principle behind the site.
I know how Wikipedia works. I was not trying to elevate Wikipedia articles. I was pointing out that forum posts (like yours.... and mine!!!) are also written by anyone. The big difference is that I can't edit yours and vice-versa. So you or I or anyone can say whatever we want (subject to TOS) and it can't be edited/corrected (other than mods)

Not bad. And by that definition, µ-law is not perceptual coding because it does not specificaly base it's action on the likelihood of a listener hearing what's been removed.
Hmmm, µ-Law is perceptual coding because it does take advantage of limitations of human perception (logarithmic scaling (Weber-Fechner)) and it does selectively remove data based on how unlikely it is that a listener will notice the removal (in the form of speech intelligibility). "Notice" not "hear", and notice is usage dependent.
 
Jul 10, 2018 at 8:19 AM Post #4,913 of 7,175
Hmmm, µ-Law is perceptual coding because it does take advantage of limitations of human perception (logarithmic scaling (Weber-Fechner)) and it does selectively remove data based on how unlikely it is that a listener will notice the removal (in the form of speech intelligibility). "Notice" not "hear", and notice is usage dependent.

You're missing the point. Using the definition of "taking advantage of limitations of human perception" covers everything! Music takes advantage of the limitations of human perception; the perception of relationships between note pitches (Harmony and melody) and/or the perception of relationships between the timing of events (rhythm and beats), so just about all music, recorded or not is, by this definition, "perceptual coding" and in fact, so is all commercial audio (TV, film, radio) because in addition; EQ, compression and various other effects are always employed to take advantage of the limitation of human perception. In practice, the term "perceptual coding" specifically means the use of a perceptual model of frequency and timing masking (auditory masking) used as a reference for removing data. It's therefore a term which only applies to certain lossy audio codecs rather than being a meaningless term because it applies to everything.

G
 
Jul 10, 2018 at 9:39 AM Post #4,914 of 7,175
You're missing the point. Using the definition of "taking advantage of limitations of human perception" covers everything! Music takes advantage of the limitations of human perception;
No. I shouldn’t have abbreviated the quote. Perceptual Coding is lossy compression that takes advantage of limitations in human perception. In perceptual coding, audio data is selectively removed (compressed) based on how unlikely it is that a listener will notice the removal.
Music is not lossy compression.

In practice, the term "perceptual coding" specifically means the use of a perceptual model of frequency and timing masking (auditory masking) used as a reference for removing data. It's therefore a term which only applies to certain lossy audio codecs rather than being a meaningless term because it applies to everything.
That is true for modern codecs, but it is not a general rule/definition.

1. Maybe the difficulty you were/are having is that you were trying to separate the issue into two different "domains" (amplitude and frequency)? While it's sometimes useful to do this for the sake of "vizualization" in reality they are not separate/different domains, they're exactly the same thing. A sine wave (for example) is effectively defined as: An increasing amplitude until a "peak" is reached, then a decreasing amplitude until the "trough" is reached and then an increasing amplitude again until the starting point is reached. We call this a "cycle" and frequency is simply the number of cycles per second. In other words, Frequency = Amplitude (over time).
In your exchange with ILoveMusic, there are several ideas that are unclear, misleading, garbled or incorrect. Not all of that from you(!) in the above quote(!!), but rather in the entire exchange.
If you’re so inclined, perhaps you can comment on the following facts:

1. Time domain (amplitude vs. time) and frequency domain (amplitude or power vs. frequency) are indeed different domains. The same information is represented in different forms. An example of the difference is it allows one to use a point-by-point product in one domain instead of convolution in the other. The analog signal from a microphone, the signal on an analog interconnect, the output of a DAC or the signal on the speaker wire from an analog amplifier are all voltage amplitude vs. time (time domain). Frequency information is not available unless one transforms the signal, using a spectrum analyzer for analog data or a Fourier transform for digital data. The fact that the unit of frequency is Hertz, equivalent to cycles/second, and the word second implies you have time is meaningless.
2. 16 bit in not perfect. If I have an original signal, convert it to 16 bit resolution, and use that to create a reproduced signal, the original and reproduced will not be identical. That is, subtracting the two does not give all zeroes. If the intention is to say that the imperfection is not audible, that is different from saying it is perfect. Yes, I know BigShot is itching to say “in the context of this forum, inaudible is perfect”, but “16bit is already perfect there is no "better" than perfect” is misleading.
3. 1 bit delta-sigma coding (used in DSD and SACD) is not the same as 1 bit LPCM coding. Usually, talking about 16 bits implies linear pulse code modulation.
4. Shannon-Nyquist tells us we need to sample at greater than twice the highest frequency of interest, not greater than or equal to twice. Twice the highest frequency is inadequate.
 
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Jul 10, 2018 at 10:26 AM Post #4,915 of 7,175
For the purposes of listening to recorded music in the home with human ears....
 
Jul 10, 2018 at 11:21 AM Post #4,917 of 7,175
Right on cue...
Thanks! :smile_phones:
That is the context you mean. I think in the context of Shannon-Nyquist, "perfect" has a different meaning :wink:
Saying "the imperfections of 16-bit are inaudible" is different from saying "16-bits is perfect".

That is why, since the early 1990s I guess, production has moved from 16/44.1/-96 to 24, 32-float/44.1, 88.2, 96, 192/-144 to -infinity dynamic range, instead of remaining at the same specs as Redbook, as it did through most of the eighties.

Every time processing is done, in the digital domain, quantization occurs, and thus dither must be applied. Producing(recording, mixing, mastering), and delivering all at 16/44.1/-96 could result in an effective 6bit/44.1/-36 PUDDING as delivered on CD!
 
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Jul 10, 2018 at 11:34 AM Post #4,918 of 7,175
Help me out again here. Is this just another argument about whether Redbook specs are adequate to serve the limits of human hearing, or are there ways in which a digitally reproduced signal is non-perfect with respect to the input, even in an absolute sense? (assuming you remain within bandwidth and dynamic range limitations.)
 
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Jul 10, 2018 at 11:48 AM Post #4,919 of 7,175
In what ways is a digitally reproduced signal non-perfect with respect to the input, even in an absolute sense? (assuming you remain within bandwidth and dynamic range limitations.)
If you remain within the bandwidth limits, the resolution of a 16-bit digital signal has a limit on its dynamic range, that the original signal might not have. Keep in mind that many here can and should point out that if each stage of your analog electronic chain before you digitize doesn't have better than 16-bit resolution, the noise from your analog chain will be in the dynamic range of the digital signal. Many will also like to challenge the audibility of whatever 16-bits can't capture.
Or is this just another argument about whether Redbook specs are adequate to serve the limits of human hearing?
No, it is an argument about whether 16-bits can be used to "perfectly" reconstruct the signal. That is, whether there is no difference between original and reproduced. Audibility is not part of that statement.
 
Jul 10, 2018 at 11:59 AM Post #4,920 of 7,175
Well, ignoring for the moment that any errors beyond audibility are irrelevant in the real world, are you saying that in musical performances it's possible (meaning in any reasonable and non-pedantic sense) to exceed a 96 dB dynamic range?
 
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