Disguising a Reference So Others Can Test Your Filter

Say someone boasts about having a new filter that, in certain
situations, can reduce noise more and faster than any other filter?

Is there any way to encode a reference that isn't directly
identifiable but still useful as a reference?  That way the reference
could be posted along with the noise for the test.

One way might be to make the noise in the reference the negative of
the noise in the signal times some factor.  Without the correct
factor, without the SNR, it could be difficult or impossible to
recover the original reference or signal.


Bret Cahill

On Mar 14, 4:09&#4294967295;pm, Bret Cahill <Bret_E_Cah...@yahoo.com> wrote:
> Say someone boasts about having a new filter that, in certain
> situations, can reduce noise more and faster than any other filter?
>
> Is there any way to encode a reference that isn't directly
> identifiable but still useful as a reference? &#4294967295;That way the reference
> could be posted along with the noise for the test.
>
> One way might be to make the noise in the reference the negative of
> the noise in the signal times some factor. &#4294967295;Without the correct
> factor, without the SNR, it could be difficult or impossible to
> recover the original reference or signal.
>
> Bret Cahill

The formulation of your question is a little less than complete and
coherent. But you might get an answer by clarifying your terms and
purpose.

What do you mean by "reference"?

How does the "reference" relate to testing a filter?

What parameters do you wish to demonstrate?

What information are you trying to obscure?

Dale B. Dalrymple

Can you imagine providing a CD of a tune that can be listened to but not recorded or displayed on an oscilloscope? Your association of "reference" with filters in this and other threads shows that if you know what you mean, you nevertheless don't express it with words that carry the meaning you want to convey.

Jerry
-- 
Engineering is the art of making what you want from things you can get.

Jerry Avins <jya@ieee.org> wrote:
> Can you imagine providing a CD of a tune that can be listened 
> to but not recorded or displayed on an oscilloscope? 

The record companies can imagine that.  I believe some have
even made "copy protected" CDs, that, as I understand, some
CD player can't play.

CDs also have SCMS, Serial Copy Management System, to restrict
copying through CD recorders.  I used to record on a minidisk
recorder, then copy to CD on a TEAC CD recorder.  According
to SCMS, I can't copy my own CDs!

SCMS allows for copying allowed (00), copy once (11) and
copy prohibited (10).  Ordinary CDs have the copy once bits,
such that you can make a legal back-up copy, but can't copy
that one (on a CD recorder).

However, computer CD recorders don't implement SCMS, so you
can make as many copies as you want on a computer.

HDMI includes special signals that restrict copy protected
sources from going to anywhere other than an appropriately
protected display device (TV set), but not to a recorder.

DVD has CSS, Content Scrambling System, that restricts
the ability to make bit copies of commercial DVDs.

See the wikipedia page Trusted_client

-- glen

In comp.dsp Bret Cahill <Bret_E_Cahill@yahoo.com> wrote:

> Say someone boasts about having a new filter that, in certain
> situations, can reduce noise more and faster than any other filter?
 
> Is there any way to encode a reference that isn't directly
> identifiable but still useful as a reference?  That way the reference
> could be posted along with the noise for the test.

(snip)

As I replied to Jerry's post, see the wikipedia page Trusted_client.

The problem of distributing software source, such that the
recipient can use it but not modify or reverse engineer it
comes up often, but there is no easy answer.  (More often
for HDL (hardware description language) code, but it is
the same problem.  

-- glen

On Mar 15, 12:09&#4294967295;am, Bret Cahill <Bret_E_Cah...@yahoo.com> wrote:
> Say someone boasts about having a new filter that, in certain
> situations, can reduce noise more and faster than any other filter?

Any one in particular you have in mind?

> Is there any way to encode a reference that isn't directly
> identifiable but still useful as a reference? &#4294967295;That way the reference
> could be posted along with the noise for the test.

The usual way to do these things is to publish a method
of design in one of the journals. That way the algorithm
to design the filter is reviewed by people who ought to
know the subject at hand.

> One way might be to make the noise in the reference the negative of
> the noise in the signal times some factor. &#4294967295;Without the correct
> factor, without the SNR, it could be difficult or impossible to
> recover the original reference or signal.

What use would the filter be, then? It doesn't work unless
you know the exact noise that corrupts the signal? It's a
ridiculous idea.

Rune

Copy protection comes down, in the end, to a hardware function. If I can play a CD, I can copy the signal(s) it produces, even if hardware prevents me from performing a bit-for-bit copy. At worst, a microphone can produce a decent facsimile.

Jerry
-- 
Engineering is the art of making what you want from things you can get.

On Mar 14, 5:09&#4294967295;pm, Bret Cahill <Bret_E_Cah...@yahoo.com> wrote:
> Say someone boasts about having a new filter that, in certain
> situations, can reduce noise more and faster than any other filter?
>

That's not a question.  Is English your native language?

> Is there any way to encode a reference that isn't directly
> identifiable but still useful as a reference? &#4294967295;That way the reference
> could be posted along with the noise for the test.
>

But, why would you want it to not be directly identifiable?

> One way might be to make the noise in the reference the negative of
> the noise in the signal times some factor.

Is this a one dimensional signal or an image?  I bet that I can detect
such an image "reference" noise by visual inspection with the "signal"
noise.

> Without the correct
> factor, without the SNR, it could be difficult or impossible to
> recover the original reference or signal.
>

Wrong.

Y1 = X + E

Y2 = C*E

where C is unknown scalar, X = uncorrupted signal matrix, E = noise
matrix

Solve:

min || Y1 + A*Y2 ||
 A

A = -1/C

E = -A*Y2

X = Y1 + A*Y2

Jerry Avins <jya@ieee.org> wrote:

> Copy protection comes down, in the end, to a hardware function. 
> If I can play a CD, I can copy the signal(s) it produces, 
> even if hardware prevents me from performing a bit-for-bit copy. 
> At worst, a microphone can produce a decent facsimile.

I believe that the hardware is allowed to internally go
through a DAC then ADC, then record the output onto CD.

-- glen

Bret Cahill wrote:

> Say someone boasts about having a new filter that, in certain
> situations, can reduce noise more and faster than any other filter?
> 
> Is there any way to encode a reference that isn't directly
> identifiable but still useful as a reference?  That way the reference
> could be posted along with the noise for the test.
> 
> One way might be to make the noise in the reference the negative of
> the noise in the signal times some factor.  Without the correct
> factor, without the SNR, it could be difficult or impossible to
> recover the original reference or signal.
> 
Just get any ol' sound source, like a recording of "The 1812 Overture,"
and sum it with some pseudorandom noise, such that either could be
recovered with a correlator of some kind?

Good Luck!
Rich