Looking for opinions on a DSP paper

Greetings Earthlings,
  Every now and then I run across a paper in 
the DSP literature that is SO different, 
so "odd", that I don't know how to evaluate 
the technical material in the paper.  "Is the 
author exceedingly clever, or an unfortunate 
victim of wild misconceptions?"

When you have nothing better to do, I'd sure 
like to hear anyone's opinion on the validity 
of the DSP paper found at:

http://jocoleman.info/pubs/papers/Spew2K/Spew.pdf

Thanks,
[-Rick-] 

On Wed, 03 Dec 2014 04:55:39 -0800, Rick Lyons wrote:

> Greetings Earthlings,
>   Every now and then I run across a paper in
> the DSP literature that is SO different,
> so "odd", that I don't know how to evaluate the technical material in
> the paper.  "Is the author exceedingly clever, or an unfortunate victim
> of wild misconceptions?"
> 
> When you have nothing better to do, I'd sure like to hear anyone's
> opinion on the validity of the DSP paper found at:
> 
> http://jocoleman.info/pubs/papers/Spew2K/Spew.pdf
> 
> Thanks,
> [-Rick-]

If he lectures as he writes, I'm very glad that I never had to take a 
class from him, or be his teaching assistant.

The points that I see here are:

1: What's so new about this approach?  With the exception of how he's 
weighting his impulses, this looks like how I was taught DSP.

2: The writing is exceedingly terse.  Way terse.  He's got at least 20 
pages of concepts that he's trying to present in 5 pages, and he's dealt 
with the issue by removing four paragraphs out of five.

3: The writing is disorganized.  This is perhaps a natural result of it 
being terse, but -- damn I'm glad I never took a class from this guy.

So to sum up:

The only divergence that I see here from normal practice is how he weights 
his impulses.  He does not even attempt to show how his "wonderful new" 
method relates to the existing chain-o-impulses method of teaching DSP, 
nor does he, in my mind, do a good job of showing how this makes multi-
rate DSP so loverly.  I think I just wasted 20 minutes of my life for you, 
Rick, and now that I'm over 50 I'm keeping track of that sort of thing!

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On Wednesday, December 3, 2014 6:55:53 AM UTC-6, Rick Lyons wrote:
> Greetings Earthlings,
>   Every now and then I run across a paper in 
> the DSP literature that is SO different, 
> so "odd", that I don't know how to evaluate 
> the technical material in the paper.  "Is the 
> author exceedingly clever, or an unfortunate 
> victim of wild misconceptions?"
> 
> When you have nothing better to do, I'd sure 
> like to hear anyone's opinion on the validity 
> of the DSP paper found at:
> 
> http://jocoleman.info/pubs/papers/Spew2K/Spew.pdf
> 
> Thanks,
> [-Rick-]

The URL of the paper includes the file name as Spew.pdf
which is enough to remove any inclination to actually 
look at the file (especially in view of Tim Wescott's
comments).

On Wed, 03 Dec 2014 13:39:12 -0800, dvsarwate wrote:

> On Wednesday, December 3, 2014 6:55:53 AM UTC-6, Rick Lyons wrote:
>> Greetings Earthlings,
>>   Every now and then I run across a paper in
>> the DSP literature that is SO different,
>> so "odd", that I don't know how to evaluate the technical material in
>> the paper.  "Is the author exceedingly clever, or an unfortunate victim
>> of wild misconceptions?"
>> 
>> When you have nothing better to do, I'd sure like to hear anyone's
>> opinion on the validity of the DSP paper found at:
>> 
>> http://jocoleman.info/pubs/papers/Spew2K/Spew.pdf
>> 
>> Thanks,
>> [-Rick-]
> 
> The URL of the paper includes the file name as Spew.pdf which is enough
> to remove any inclination to actually look at the file (especially in
> view of Tim Wescott's comments).

You should never let the opinions of some self-appointed "expert" 
influence your decisions.

Go ahead.  Read it.  Make your own decision.  At just five pages, it'll be 
like wading through a very _small_ vat of molasses.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Rick Lyons <R.Lyons@_bogus_ieee.org> wrote:
 
> Greetings Earthlings,
>  Every now and then I run across a paper in 
> the DSP literature that is SO different, 
> so "odd", that I don't know how to evaluate 
> the technical material in the paper.  "Is the 
> author exceedingly clever, or an unfortunate 
> victim of wild misconceptions?"

(snip)

> http://jocoleman.info/pubs/papers/Spew2K/Spew.pdf

Not that I claim to understand all of it, but he starts out
showing that a discrete time signal can be considered a train
of appropriate amplitude delta functions in continuous time.

I think most of us know that in the back of our head, but don't
think about it often. 

Mostly we like to keep our continuous time signals and discrete
time signals separate, and not think of them at the same time.

In the recent discussion about the maximum reconstructed 
amplitude from a sampled signal, I thought again about how the
result at any time depends on samples from -infinity to +infinity.

That is obvious from the Fourier transform with the same limits
on the integral, but again, we don't think about it so often.

Consider a sampled signal that is zero for all times before t=0,
then +1 for zero and all even samples after t=0, and -1 for all
odd samples after t=0.

If I have it right, there is a huge peak a little before zero.

But OK, back to the paper. 

He starts out explaining that you can think of sampled signals
in continuous time, and then goes on to show some examples of
problems that might be hard in sampled time, but easier in 
continuous time. 

If you think of DSP as sample band-limited analog signal at a uniform
sample spacing, process it, convert back to analog signal, then 
it probably doesn't help.

I think he shows that some resampling problems are easier to think
of as trains of delta functions in continuous time, instead of just
as samples it time.

I don't think he shows non-uniform sampling at all, but that is
another case that is hard to do only in uniform sampled space.


-- glen

On Wed, 03 Dec 2014 16:17:22 -0600, Tim Wescott
<seemywebsite@myfooter.really> wrote:

>On Wed, 03 Dec 2014 13:39:12 -0800, dvsarwate wrote:
>
>> On Wednesday, December 3, 2014 6:55:53 AM UTC-6, Rick Lyons wrote:
>>> Greetings Earthlings,
>>>   Every now and then I run across a paper in
>>> the DSP literature that is SO different,
>>> so "odd", that I don't know how to evaluate the technical material in
>>> the paper.  "Is the author exceedingly clever, or an unfortunate victim
>>> of wild misconceptions?"
>>> 
>>> When you have nothing better to do, I'd sure like to hear anyone's
>>> opinion on the validity of the DSP paper found at:
>>> 
>>> http://jocoleman.info/pubs/papers/Spew2K/Spew.pdf
>>> 
>>> Thanks,
>>> [-Rick-]
>> 
>> The URL of the paper includes the file name as Spew.pdf which is enough
>> to remove any inclination to actually look at the file (especially in
>> view of Tim Wescott's comments).
>
>You should never let the opinions of some self-appointed "expert" 
>influence your decisions.
>
>Go ahead.  Read it.  Make your own decision.  At just five pages, it'll be 
>like wading through a very _small_ vat of molasses.

So far I've read the abstract, intro, and conclusion, and just from
those I can tell you that it is very, very poorly written.   There's
almost no info in any of those about what he wants to say about the
topic.




Eric Jacobsen
Anchor Hill Communications
http://www.anchorhill.com

On 04.12.2014 2:32, glen herrmannsfeldt wrote:
> In the recent discussion about the maximum reconstructed
> amplitude from a sampled signal, I thought again about how the
> result at any time depends on samples from -infinity to +infinity.
>
> That is obvious from the Fourier transform with the same limits
> on the integral, but again, we don't think about it so often.
>
> Consider a sampled signal that is zero for all times before t=0,
> then +1 for zero and all even samples after t=0, and -1 for all
> odd samples after t=0.
>
> If I have it right, there is a huge peak a little before zero.

The peak is not just "huge". It's _infinite_. Now you'll have to live 
with it. :-)

Evgeny.

Evgeny Filatov <e.v.filatov@ieee.org> wrote:

(snip, I wrote)

>> In the recent discussion about the maximum reconstructed
>> amplitude from a sampled signal, I thought again about how the
>> result at any time depends on samples from -infinity to +infinity.

>> That is obvious from the Fourier transform with the same limits
>> on the integral, but again, we don't think about it so often.

>> Consider a sampled signal that is zero for all times before t=0,
>> then +1 for zero and all even samples after t=0, and -1 for all
>> odd samples after t=0.

>> If I have it right, there is a huge peak a little before zero.
 
> The peak is not just "huge". It's _infinite_. Now you'll have to live 
> with it. :-)

So no comment on causality?  It is only infinite if the source
system stays together until t=infinity.  Since we don't know that
it will, how can we know that it is infinite already?

-- glen

On 12/3/14 6:32 PM, glen herrmannsfeldt wrote:
> Rick Lyons<R.Lyons@_bogus_ieee.org>  wrote:
>
>> Greetings Earthlings,
>>   Every now and then I run across a paper in
>> the DSP literature that is SO different,
>> so "odd", that I don't know how to evaluate
>> the technical material in the paper.  "Is the
>> author exceedingly clever, or an unfortunate
>> victim of wild misconceptions?"
>

neither.  (except the misconception that he is contributing something 
novel.  just because it's a little incoherent, doesn't mean that there 
is a jewel of novelty in the midst of it.)

> (snip)
>
>> http://jocoleman.info/pubs/papers/Spew2K/Spew.pdf
>
> Not that I claim to understand all of it, but he starts out
> showing that a discrete time signal can be considered a train
> of appropriate amplitude delta functions in continuous time.
>
> I think most of us know that in the back of our head, but don't
> think about it often.

i think about it all the time.  but instead of impulse functions, i run 
them deltas through an ideal brickwall LPF in my head.

>
> Mostly we like to keep our continuous time signals and discrete
> time signals separate, and not think of them at the same time.
>

well, if we do anything with fractional-sample or precision delay or 
with sample rate conversion, then we have to think about both at the 
same time.

> In the recent discussion about the maximum reconstructed
> amplitude from a sampled signal, I thought again about how the
> result at any time depends on samples from -infinity to +infinity.
>

ONLY on the whiteboard or chalkboard.  that example:

  ... +1, -1, +1, -1, +1, -1, +1, -1, -1, +1, -1, +1, -1, +1, -1, +1 ...

(note the +1 removed in the middle.)

is a *theoretical* exercise if your reconstruction is precisely that 
prescribed by the Shannon/Whittaker formula:

             +inf
    x(t)  =  SUM{ x[n] sin(pi(t-n)) / (pi(t-n)) }
            n=-inf

(assuming unity sampling period.  for integer k, x(k) = x[k].)

we get an infinite value for some x(t) because we're adding up an 
infinite number of samples in both directions (and the sinc() function 
decreases like 1/t so an infinite series of it *can* blow up.)

but we never actually add up an infinite number of samples in both 
directions.  so this is only a theoretical consideration.

> But OK, back to the paper.
>
> He starts out explaining that you can think of sampled signals
> in continuous time, and then goes on to show some examples of
> problems that might be hard in sampled time, but easier in
> continuous time.

<yawn>

> If you think of DSP as sample band-limited analog signal at a uniform
> sample spacing, process it, convert back to analog signal, then
> it probably doesn't help.
>
> I think he shows that some resampling problems are easier to think
> of as trains of delta functions in continuous time, instead of just
> as samples it time.

what other way is there to think of it?  this is standard electrical 
engineering linear systems or DSP textbook stuff.  big deel.





-- 

r b-j                  rbj@audioimagination.com

"Imagination is more important than knowledge."

On 04.12.2014 19:29, glen herrmannsfeldt wrote:
(snip)

> So no comment on causality?  It is only infinite if the source
> system stays together until t=infinity.  Since we don't know that
> it will, how can we know that it is infinite already?
>
> -- glen
>

I agree. The signal _might_ be infinite at t=-0.5, but we would never 
know that, because we would have to record infinite number of samples to 
figure that out.

Evgeny.