Energy

Steve Underwood skrev:
> Rune Allnor wrote:
> > Another filter will bring back entropy. The demonstration is the
> > whitening filter used in speech encoders. No (passive) filter
> > can bring back energy or power in analog domain. Hence, the
> > analogy between entropy in digital domain, and power and energy
> > in analog domain, does not hold to scrutiny.
>
> A passive physical filter can re-whiten the signal just as well as any
> other.

That's what I said in the paragraph above. But ony an amplifier
can bring back power.

> If it removes energy in those places where the first filter
> didn't, you are back to a white signal. Its smaller in amplitude now,
> but just as chaotic.

Which is why I never posted the argument about entropy
being a digital domain analog to energy in analog domain;
it just does not hold.

> Surely a mere scaling factor doesn't mean we have
> not brought back the entropy?

My point exactly. Entropy is back. Energy (in analog domain)
has gone. Energy/power is a different concept than entropy.
So basing the understanding of one on the analogy with the
other is very dangeorus, and is likely to cause more confusion
than it resolves.

Rune

Andrew Reilly skrev:
> On Thu, 12 Oct 2006 00:32:53 -0700, Rune Allnor wrote:

> > No (passive) filter
> > can bring back energy or power in analog domain. Hence, the
> > analogy between entropy in digital domain, and power and energy
> > in analiog domain, does not hold to scrutiny.
>
> No, it doesn't, but the relationship is closer than you're giving it
> credit.

What have I missed?

> >> and entropy
> >> can be connected to energy.
> >
> > Only because of practical matters due to us humans and our
> > computers existing in a physical world, and our interest in maths.
>
> Entropy exists in the physical world, independent of maths.  The laws of
> thermodynamics (which are, admitedly, usually written down in mathematical
> terms.)

Everybody know that physics can be described in terms of maths.That's
not the discussion here. The OP wanted to understand properties of
DSP systems -- mathematical operators that happen to be useful in
a physical setting, as far as I am concerned, -- in terms of physics.

I think that's a very bad idea.

> > I don't see why a physical world is required for the existence
> > of maths. But now we are enetering philosophical grounds
> > I believe best left untouched.
>
> Well, I've always thought (at least since I discovered it, in one of my
> undergrad classes) that the fact that the entropy that prevented perpetual
> motion machines and controls refrigerators was the same as the entropy
> measured by compression algorithms and encoding schemes, and that it could
> be measured in bits, was most profound.

It is one of the fundamental factors in physics. But we are talking
about maths. The key is to keep physics and maths apart. 

Rune

Rune Allnor wrote:
> Steve Underwood skrev:

   ...

>> A passive physical filter can re-whiten the signal just as well as any
>> other.
> 
> That's what I said in the paragraph above. But ony an amplifier
> can bring back power.

It is simply wrong to treat entropy as if it were energy. We all know 
better, but sometimes we do it anyway while waving our arms.

   ...

Jerry
-- 
        "The rights of the best of men are secured only as the
        rights of the vilest and most abhorrent are protected."
            - Chief Justice Charles Evans Hughes, 1927
���������������������������������������������������������������������

Jerry Avins wrote:

(snip)

> It is simply wrong to treat entropy as if it were energy. We all know 
> better, but sometimes we do it anyway while waving our arms.

dU=T dS  The connection between energy and entropy is temperature.
At constant temperature they are proportional.  (Simplifying
things a little bit more than I probably should.)

-- glen

glen herrmannsfeldt skrev:
> Jerry Avins wrote:
>
> (snip)
>
> > It is simply wrong to treat entropy as if it were energy. We all know
> > better, but sometimes we do it anyway while waving our arms.
>
> dU=T dS  The connection between energy and entropy is temperature.
> At constant temperature they are proportional.

And the temperature relation between, say, an ASCII text and its
corresponding Huffman code is...?

> (Simplifying
> things a little bit more than I probably should.)

I think you did.

Rune

glen herrmannsfeldt said the following on 12/10/2006 06:50:
> Rune Allnor wrote:
> 
> (snip)
> 
>> While the laws of physics have to comply the laws of maths,
>> the converse is not true. This is why digital filters can do stuff
>> that is not possible with analog filters.
> 
> I agree so far.
> 
>> More to the point what
>> this thread is concerned, the concepts of "energy" and "power"
>> make no sense in the mathematical world.
> 
> Entropy makes sense in the mathematical world, and entropy
> can be connected to energy.
> 
> The first time I saw this discussed had to do with the
> energy of computation.  Can you design a binary adder
> that, theoretically, uses no energy?  If you represent
> bits through moving balls on ramps, in theory it is
> possible to design an adder using frictionless balls.
> A binary non-saturating adder does not lose any information.
> 
> It is the process of forgetting that takes energy.  In
> thermodynamic terms, it requires a non-reversible system,
> and that goes along with an increase in entropy and
> decrease in free energy.

However, the amount of energy required is unrelated to the input signal. 
  The number of bits that alter (and hence energy that is consumed) from 
sample point to sample point is essentially uncorrelated with any 
characteristic such as the frequency response, or even amplitude, of the 
input signal.

And if we could somehow implement the filter in a different numerical 
base, such as ternary, the number of ternary digits (tits?) that would 
change would be unrelated to the number that changed in the binary system.



-- 
Oli

Oli Charlesworth wrote:

>   ... the number of ternary digits (tits?) ...

Trits.

Jerry
-- 
        "The rights of the best of men are secured only as the
        rights of the vilest and most abhorrent are protected."
            - Chief Justice Charles Evans Hughes, 1927
���������������������������������������������������������������������

Jerry Avins said the following on 15/10/2006 17:09:
> Oli Charlesworth wrote:
> 
>>   ... the number of ternary digits (tits?) ...
> 
> Trits.

How disappointing...


-- 
Oli

Oli Charlesworth <catch@olifilth.co.uk> writes:

> ternary digits (tits?) 

How many tits does your computer have? This is particularly
apropo for the .sig below (which is randomly generated)!
-- 
%  Randy Yates                  % "I met someone who looks alot like you,
%% Fuquay-Varina, NC            %             she does the things you do, 
%%% 919-577-9882                %                     but she is an IBM."
%%%% <yates@ieee.org>           %        'Yours Truly, 2095', *Time*, ELO   
http://home.earthlink.net/~yatescr

Oli Charlesworth wrote:

> Jerry Avins said the following on 15/10/2006 17:09:

>> Oli Charlesworth wrote:

>>>   ... the number of ternary digits (tits?) ...

>> Trits.

> How disappointing...

There is an old joke with the punchline

"Silly Wabbit, kicks are for trids."   Close enough for me.

-- glen