The Second Law of Thermodynamics

[Ralf11]

"...in absolute terms, doing anything to the signal can only degrade it. The Second Law of Thermodynamics implies that while you may achieve a certain desired improvement in one particular area, the overall effect will still be negative."

—John Atkinson, 1991

[fas42]

Which suggests the best thing to do is to pass the signal through the reproduction chain with absolutely minimal alteration of that signal - something I agree with 100%.

[John Dyson]

8 minutes ago, Ralf11 said:

"...in absolute terms, doing anything to the signal can only degrade it. The Second Law of Thermodynamics implies that while you may achieve a certain desired improvement in one particular area, the overall effect will still be negative."

—John Atkinson, 1991

There is a lot of truth to that statement.  However, there have been cases of a willfull tradeoff of some temporary 'distortion' in the signal up-front to avoid another impairment.  Correction by undoing/correcting the 'willfull' distortion helps to mitigate the effects of both impairments (both the willfull and the undesired problem being worked around.)  Most importantly any willfull distortion is a bad thing unless really needed.   Willfull distortion usually follows that rule of thermodynamics -- therefore not a good thing.

 

Stuff like MQA or mindlessly using DolbyA on a digital recorder -- those are folly because the 'willfull' distortion and recovery don't cover up any other impariments.  The signal quality is not somehow 'protected' like in the intended original use of DolbyA/SR/B/C/S, where tape recorders created audible hiss and other kinds of noise.

 

IMO it is insane to create new DolbyA material nowadays unless it is for some obscure compatibility requirement -- just as it is kind of silly to use other distortion methods (and subsequent recovery) for no substantial/practical   benefit.

 

John

[esldude]

One has to accept the logical leap between signal and thermodynamics. Should I mention dither?

[Ralf11]

it shows what happens when you dither with things you don't understand...

 

 

[pkane2001]

22 minutes ago, esldude said:

One has to accept the logical leap between signal and thermodynamics. Should I mention dither?

 

Leap accepted. Shannon made the connection between entropy and information entropy 70 years ago. As long as signal is information that's represented by a physical system, the second law applies to it also.

 

The best way to eliminate the unnecessary entropy in the sound path is to have a direct, short wire directly into the brain. Of course, it should be soldered for best results, as Frank often recommends  

 

[Ralf11]

interesting irony loop, as I was doing a search on audiophile solder when I ran across the quote

[fas42]

The cliche I prefer is, a chain is only as strong as the weakest link - audiophiles are notoriously incapable of understanding this; hence the need to chase things like "audiophile solder" ... if the problem is contact noise, causing significant subjective degradation - even though it may be hard to measure - then it's rather foolish to ignore those sorts of "weak links".

[esldude]

1 hour ago, pkane2001 said:

 

Leap accepted. Shannon made the connection between entropy and information entropy 70 years ago. As long as signal is information that's represented by a physical system, the second law applies to it also.

 

The best way to eliminate the unnecessary entropy in the sound path is to have a direct, short wire directly into the brain. Of course, it should be soldered for best results, as Frank often recommends  

 

I was aware that Shannon used entropy in his 1948 paper.  I didn't understand that it was directly the same as thermodynamic entropy. 

 

I mentioned dither because I thought I remembered an analysis showing subtractive dither can be used with all the good effects of additive dither without changing information entropy.  As well as showing that good implementations of additive dither come very, very close to not changing entropy.  

 

Would FLAC not be a case of doing something to a signal without degrading it, and without changing information entropy? There is a thermodynamic change in entropy to perform those operations, but it would not seem to be informational entropy change.  Is that incorrect?

[pkane2001]

47 minutes ago, esldude said:

I was aware that Shannon used entropy in his 1948 paper.  I didn't understand that it was directly the same as thermodynamic entropy. 

 

I mentioned dither because I thought I remembered an analysis showing subtractive dither can be used with all the good effects of additive dither without changing information entropy.  As well as showing that good implementations of additive dither come very, very close to not changing entropy.  

 

Would FLAC not be a case of doing something to a signal without degrading it, and without changing information entropy? There is a thermodynamic change in entropy to perform those operations, but it would not seem to be informational entropy change.  Is that incorrect?

 

I don’t think random dither ever results in information preservation. Additive or subtractive is the same, some amount of information is destroyed in the process. It is designed to not affect the important parts of the signal, and may help reduce some unwanted artifacts, but it still destroys some information, usually about 1/2 a bit.

 

There are many things in this world that temporarily decrease entropy, in an apparent contradiction to the second law. The explanation is usually that this is a temporary and/or local condition that’s balanced by an increase in entropy elsewhere or elsewhen. This might be, for example, the generator that causes an increase in entropy by burning fuel that is converted to electricity that is then used to  power the computer to encode the FLAC file.

 

Life itself is an apparent contradiction of the second law, as it results in a decrease in entropy by causing information to be ‘created’ out of organic material and water and oxygen. This is also balanced by all the ‘exhaust’ that life generates in the process that ultimately increases overall entropy. So, it goes, the second law is upheld after all

[esldude]

http://www.aes.org/e-lib/browse.cfm?elib=13033

 

I believe this is the paper on subtractive dither I remembered.  Don't see anywhere to get it other than the AES currently. 

 

You would have to transmit the applied subtractive dither to the other end in order to subtract it.  

 

Same author with a section here on subtractive dither.  

https://uwspace.uwaterloo.ca/bitstream/handle/10012/202/nq22246.pdf?sequence=1&isAllowed=y

 

Craven and Gerzon are mentioned as having worked on ways to embed subtractive dither in the signal and use common look up tables to prevent having to transmit the dither signal separately.  It was implied in MQA related patents this technique was being used in MQA.  

 

[pkane2001]

4 minutes ago, esldude said:

http://www.aes.org/e-lib/browse.cfm?elib=13033

 

I believe this is the paper on subtractive dither I remembered.  Don't see anywhere to get it other than the AES currently. 

 

You would have to transmit the applied subtractive dither to the other end in order to subtract it.  

 

Ah, so add it then subtract it. That will not destroy information in the signal itself, but it’ll certainly use extra computing resources resulting in more entropy in the end.

[esldude]

1 minute ago, pkane2001 said:

Ah, so add it then subtract it. That will not destroy information in the signal itself, but it’ll certainly use extra computing resources resulting in more entropy in the end.

So thermodynamic entropy yes, but this wouldn't appear to alter informational entropy.  BTW, I added a link to a paper you can see on the web.  Has an MQA connection. 

[fas42]

34 minutes ago, pkane2001 said:

Life itself is an apparent contradiction of the second law, as it results in a decrease in entropy by causing information to be ‘created’ out of organic material and water and oxygen. This is also balanced by all the ‘exhaust’ that life generates in the process that ultimately increases overall entropy. So, it goes, the second law is upheld after all

 

Personally, I see the universe as it is currently known as being a big smack in the face of the Second Law - most times after a Big Bang, one just just sees a huge pile of chaotic rubble, which will just hang around forever, unless someone does something about it ...

[pkane2001]

7 minutes ago, esldude said:

So thermodynamic entropy yes, but this wouldn't appear to alter informational entropy.  BTW, I added a link to a paper you can see on the web.  Has an MQA connection. 

 

They are the same, that’s the beauty of Shannon and the following interpretations. Everything in the universe can be treated as information and entropy itself is defined in terms of information.

 

What I think you’re saying is that the digital audio signal information is not subject to increased entropy. That’s true (assuming no losses or errors) but the second law of thermodynamics can be violated locally and/or temporarily, as long as the overall larger system entropy continues to increase.

[esldude]

11 minutes ago, pkane2001 said:

 

They are the same, that’s the beauty of Shannon and the following interpretations. Everything in the universe can be treated as information and entropy itself is defined in terms of information.

 

What I think you’re saying is that the digital audio signal information is not subject to increased entropy. That’s true (assuming no losses or errors) but the second law of thermodynamics can be violated locally and/or temporarily, as long as the overall larger system entropy continues to increase.

Yes, my view on it was digital audio signal information is not subject to increased entropy the way JA's statement,  "....in absolute terms, doing anything to the signal can only degrade it" would imply.  I understand the thermodynamic laws (not as well versed in informational terms though I get the connection).  I was not implying the laws are broken, as obviously total system entropy increases, but in isolated ways that doesn't appear to alter digital signals.  

[pkane2001]

4 minutes ago, esldude said:

Yes, my view on it was digital audio signal information is not subject to increased entropy the way JA's statement,  "....in absolute terms, doing anything to the signal can only degrade it" would imply.  I understand the thermodynamic laws (not as well versed in informational terms though I get the connection).  I was not implying the laws are broken, as obviously total system entropy increases, but in isolated ways that doesn't appear to alter digital signals.  

 

I don’t have the full context, but have to assume JA’s statement was about analog signal rather than digital.

[fas42]

2 minutes ago, pkane2001 said:

 

I don’t have the full context, but have to assume JA’s statement was about analog signal rather than digital.

 

Which is exactly how I would interpret it, too.

[fas42]

For those who are curious, the original in full, https://www.stereophile.com/content/cables-case-solder.

[Blackmorec]

6 hours ago, Ralf11 said:

interesting irony loop, as I was doing a search on audiophile solder when I ran across the quote

Soldering irony?