Hello Folks,

Is there a low/no cost simulator tool for non-ideal digital filters, 
maybe from a university?

What I want to do is briefly simulate the effects of reduced coefficient 
granularity in filters such as WDF. IOW, play around a bit. I know I 
could do this with Matlab but that is an expensive piece of software 
that I wouldn't really need for anything else. Writing code for the PC 
or writing a huge spreadsheet routine is another option but takes too 
long. I am looking for something equivalent to what SPICE is for the 
analog world. Ideally where you could use test tapes piped in through 
the sound card.

I have some filter design software that came with DSP books but they 
don't go that far. They assume 'ideal' coefficient granularity base on 
the available word width. Didn't find anything with Google but maybe I 
hadn't used optimal search phrases.

Regards, Joerg

http://www.analogconsultants.com

Joerg wrote:

> Hello Folks,
> 
> Is there a low/no cost simulator tool for non-ideal digital filters, 
> maybe from a university?
> 
> What I want to do is briefly simulate the effects of reduced coefficient 
> granularity in filters such as WDF. IOW, play around a bit. I know I 
> could do this with Matlab but that is an expensive piece of software 
> that I wouldn't really need for anything else. Writing code for the PC 
> or writing a huge spreadsheet routine is another option but takes too 
> long. I am looking for something equivalent to what SPICE is for the 
> analog world. Ideally where you could use test tapes piped in through 
> the sound card.
> 
> I have some filter design software that came with DSP books but they 
> don't go that far. They assume 'ideal' coefficient granularity base on 
> the available word width. Didn't find anything with Google but maybe I 
> hadn't used optimal search phrases.
> 
> Regards, Joerg
> 
> http://www.analogconsultants.com

SciLab (http://www.scilab.com).  The last time I recommended it the 
fellow responded with "boy, it's about as user friendly as a chainsaw". 
  I had to disagree because chainsaws come with instruction manuals and 
finger guards.

But it's as powerful as MatLab, it's very MatLab-like in the way it 
works (although the details are quite different), it's free, it's being 
maintained, and it has good newsgroup support (on 
comp.soft-sys.math.scilab).  I find that for control systems work its 
better than Matlab because it comes with a native type for polynomial 
ratios that gives you transfer functions in s and z, and another one for 
representing state-space systems.

For your stuff you can use the z-domain transfer functions and force 
granularity on the coefficients.  If you need to investigate fixed-point 
arithmetic it has a discrete-time ODE solver that works well.

You may also want to look into Octave, which is also free but apparently 
no longer well maintained.  I keep it around because its nearly 100% 
MatLab compatible, but the version that comes with Cygwin doesn't really 
work right and the Cygwin-independent version doesn't play well with Cygwin.

-- 

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

Joerg wrote:

> Hello Folks,
> 
> Is there a low/no cost simulator tool for non-ideal digital filters, 
> maybe from a university?
> 
> What I want to do is briefly simulate the effects of reduced coefficient 
> granularity in filters such as WDF. IOW, play around a bit. I know I 
> could do this with Matlab but that is an expensive piece of software 
> that I wouldn't really need for anything else. Writing code for the PC 
> or writing a huge spreadsheet routine is another option but takes too 
> long. I am looking for something equivalent to what SPICE is for the 
> analog world. Ideally where you could use test tapes piped in through 
> the sound card.
> 
> I have some filter design software that came with DSP books but they 
> don't go that far. They assume 'ideal' coefficient granularity base on 
> the available word width. Didn't find anything with Google but maybe I 
> hadn't used optimal search phrases.
> 

Joerg,

The good book where you can find the treatment of the digital filter 
limited precision artifacts is:

Dietrich Schlichtharle. Digital Filters: Basics and Design.
Springer ISBN 3-540-66841-1

In most cases the analysis is not very complicated; there is really no 
point to do the simulation.


Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

http://www.abvolt.com

There is also Ptolomey.  It's free but it may be more than you want.  I 
haven't used it.



In article <stydnUmu99f5dDjeRVn-gw@web-ster.com>, Tim Wescott 
<tim@seemywebsite.com> wrote:
>Joerg wrote:
>
>> Hello Folks,
>> 
>> Is there a low/no cost simulator tool for non-ideal digital filters, 
>> maybe from a university?
>> 
>> What I want to do is briefly simulate the effects of reduced coefficient 
>> granularity in filters such as WDF. IOW, play around a bit. I know I 
>> could do this with Matlab but that is an expensive piece of software 
>> that I wouldn't really need for anything else. Writing code for the PC 
>> or writing a huge spreadsheet routine is another option but takes too 
>> long. I am looking for something equivalent to what SPICE is for the 
>> analog world. Ideally where you could use test tapes piped in through 
>> the sound card.
>> 
>> I have some filter design software that came with DSP books but they 
>> don't go that far. They assume 'ideal' coefficient granularity base on 
>> the available word width. Didn't find anything with Google but maybe I 
>> hadn't used optimal search phrases.
>> 
>> Regards, Joerg
>> 
>> http://www.analogconsultants.com
>
>SciLab (http://www.scilab.com).  The last time I recommended it the 
>fellow responded with "boy, it's about as user friendly as a chainsaw". 
>  I had to disagree because chainsaws come with instruction manuals and 
>finger guards.
>
>But it's as powerful as MatLab, it's very MatLab-like in the way it 
>works (although the details are quite different), it's free, it's being 
>maintained, and it has good newsgroup support (on 
>comp.soft-sys.math.scilab).  I find that for control systems work its 
>better than Matlab because it comes with a native type for polynomial 
>ratios that gives you transfer functions in s and z, and another one for 
>representing state-space systems.
>
>For your stuff you can use the z-domain transfer functions and force 
>granularity on the coefficients.  If you need to investigate fixed-point 
>arithmetic it has a discrete-time ODE solver that works well.
>
>You may also want to look into Octave, which is also free but apparently 
>no longer well maintained.  I keep it around because its nearly 100% 
>MatLab compatible, but the version that comes with Cygwin doesn't really 
>work right and the Cygwin-independent version doesn't play well with Cygwin.
>

Hello Tim,

> SciLab (http://www.scilab.com).  The last time I recommended it the 
> fellow responded with "boy, it's about as user friendly as a chainsaw". 
>  I had to disagree because chainsaws come with instruction manuals and 
> finger guards.
> 

Thank you, I will try that out. If it's like a chainsaw I'll be comfy. 
The only somewhat tricky task with chainsaws is the correct sharpening 
of the chain when the fingers are almost frozen. Also, I don't trust 
those 'automatic' oilers anymore and always carry a pot of chain oil 
with me.

Just in case others are also interested, it's: http://www.scilab.org

Regards, Joerg

http://www.analogconsultants.com

Hello Vladimir,

> The good book where you can find the treatment of the digital filter 
> limited precision artifacts is:
> 
> Dietrich Schlichtharle. Digital Filters: Basics and Design.
> Springer ISBN 3-540-66841-1
> 

Thanks. I'll play around with Scilab and when that doesn't get me going 
I'll order the book. Luckily it is still available on Amazon, about $90. 
I was kind of surprised that IEEE doesn't carry it.


> In most cases the analysis is not very complicated; there is really no 
> point to do the simulation.
> 

I'll have to try it out somehow by piping in real test data and see what 
the noise levels will be. IOW how much of unwanted response each filter 
produces. It is hard to forecast that when things in the signal path can 
go non-linear as in my case.

Regards, Joerg

http://www.analogconsultants.com

Joerg wrote:
> Hello Folks,
> 
> Is there a low/no cost simulator tool for non-ideal digital filters, 
> maybe from a university?
> 
> What I want to do is briefly simulate the effects of reduced coefficient 
> granularity in filters such as WDF. IOW, play around a bit. I know I 
> could do this with Matlab but that is an expensive piece of software 
> that I wouldn't really need for anything else. Writing code for the PC 
> or writing a huge spreadsheet routine is another option but takes too 
> long. I am looking for something equivalent to what SPICE is for the 
> analog world. Ideally where you could use test tapes piped in through 
> the sound card.
> 
> I have some filter design software that came with DSP books but they 
> don't go that far. They assume 'ideal' coefficient granularity base on 
> the available word width. Didn't find anything with Google but maybe I 
> hadn't used optimal search phrases.

Octave. Scilab. Any program that plots filters with coefficients you 
give it -- modify ideal filters to suit your test.

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

Hello Jerry,
> 
> Octave. Scilab. Any program that plots filters with coefficients you 
> give it -- modify ideal filters to suit your test.
> 

After Tim mentioned Scilab I played with it a bit. Looks like quite a 
learning curve so maybe I just fire up the solder iron, get a 16bit ADC 
plus a good uC and try all this out in the lab.

Problem is, the lab is also where the Christmas cookie jar is and I 
can't stay away from it.

Tim: Scilab is more complicated than a chainsaw, at least for a hardware 
guy...

Regards, Joerg

http://www.analogconsultants.com

Joerg wrote:
-snip-

> 
> Just in case others are also interested, it's: http://www.scilab.org
> 
> Regards, Joerg
> 
> http://www.analogconsultants.com

Oops.

-- 

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

Joerg wrote:

> Hello Vladimir,
> 
>> The good book where you can find the treatment of the digital filter 
>> limited precision artifacts is:
>>
>> Dietrich Schlichtharle. Digital Filters: Basics and Design.
>> Springer ISBN 3-540-66841-1
>>
> 
> Thanks. I'll play around with Scilab and when that doesn't get me going 
> I'll order the book. Luckily it is still available on Amazon, about $90. 
> I was kind of surprised that IEEE doesn't carry it.
> 
> 
>> In most cases the analysis is not very complicated; there is really no 
>> point to do the simulation.
>>
> 
> I'll have to try it out somehow by piping in real test data and see what 
> the noise levels will be. IOW how much of unwanted response each filter 
> produces. It is hard to forecast that when things in the signal path can 
> go non-linear as in my case.
> 
> Regards, Joerg
> 
> http://www.analogconsultants.com

If you think that Scilab has a future with you get a copy of 
"Engineering and Scientific Computing with Scilab with CDROM"
by Claude Gomez.  Neither it nor the Scilab on-line documentation give 
you the complete picture, and even with both there are still holes, but 
it'll give you a good step up.  I found it particularly helpful with 
making decent graphs.

If someone would fund me, and if I thought the Scilab team would pay 
attention, I'd love to dig in and write _good_ documentation for that 
package.

-- 

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

Try Octave! The syntax is very much similar to MATLAB

Hello Sivakanth,

> Try Octave! The syntax is very much similar to MATLAB
> 


Would love to. But I am not a great MATLAB user either. I need something 
that is simple, like some of the configurable FFT programs out there. A 
few of these almost do what I need but stop just short of coefficient 
granularization.

Regards, Joerg

http://www.analogconsultants.com

Joerg wrote:
> I have some filter design software that came with DSP books but they
> don't go that far. They assume 'ideal' coefficient granularity base on
> the available word width. Didn't find anything with Google but maybe I
> hadn't used optimal search phrases.

Out of curiosity: What is "coefficient granularity"?
Never heard the term before.

Rune

Hello Tim,

> 
> If someone would fund me, and if I thought the Scilab team would pay 
> attention, I'd love to dig in and write _good_ documentation for that 
> package.
> 

That's exactly the point. Many excellent SW packages and even some uC 
are so poorly documented that they don't make it into mainstream for 
that reason. Academians often won't go below the highest level of 
abstraction and there are no "Heathkit style" grunt work examples. But 
all this will be needed to get engineers on board. Especially the busy 
ones who can't spend weeks reading up on stuff.

Even in many books it's like that. My favorite here is Haddad Parsons 
but when it comes to practical implementation they immediately assume 
you can always have the horsepower of a TMS320. Well, it just ain't so 
with most projects. Sometimes you'll simply have to concede and accept 
that there absolutely will not be a HW multiplier because it's 50 cents 
too much. It is like the farmer who has to make do with his old F250 
because he can't have that new truck with the Cummins in there.

Regards, Joerg

http://www.analogconsultants.com

Joerg wrote:
> Hello Tim,
>
> >
> > If someone would fund me, and if I thought the Scilab team would pay
> > attention, I'd love to dig in and write _good_ documentation for that
> > package.
> >
>
> That's exactly the point. Many excellent SW packages and even some uC
> are so poorly documented that they don't make it into mainstream for
> that reason. Academians often won't go below the highest level of
> abstraction and there are no "Heathkit style" grunt work examples. But
> all this will be needed to get engineers on board. Especially the busy
> ones who can't spend weeks reading up on stuff.

Academics don't know what the term "documentation" means. A couple of
weeks ago, the professor who took up the methods and techniques I used
to work with, called me and wanted to discuss some questions. The
questions concerned a computer I last worked with 5 years ago, that I
got
10 years ago from somebody who had modified 15 years old public domain
code. The "documentation" of the original PD code consisted of a 6-page
short summary of a general technique, where some variables were
stated "without proof". In the program (Fortran 77) the variables
were named as "acc", "bb", "cmn"... with no comments and apparently
with no connection to the article. The program was written in the
"implicit declaration" style that fortran allows, where a variable
needs
not be declared but where its data type (real, complex, integer) is
implicitly given by its name. An utter nightmare. The professor had
spent two months getting the thing to compile and run, due to the less
than standardized way fortran works. It would have been way faster to
write the program from scratch.

I'm happy that other people take over those tasks; I'm pretty fed up
with the stuff. But if I ever get a call like that again, I'll charge
$250 per
hour.

So what I have done in my programming projects, is to write the
basics in LaTeX and document the code so that HTML documents
can be generated with Doxygen. These tools are free, and are
available to students, but can not necessarily be used by companies.
Are there alternatives available that can be used in commercial
projects,
that can be used for other programming languages than C/C++?

Rune

Hello Rune,

> So what I have done in my programming projects, is to write the
> basics in LaTeX and document the code so that HTML documents
> can be generated with Doxygen. These tools are free, and are
> available to students, but can not necessarily be used by companies.
> Are there alternatives available that can be used in commercial
> projects,
> that can be used for other programming languages than C/C++?
> 

No idea, I don't code much. But if I do I document everything in HTML. 
Code, module specs, schematics, revision history and so on. I am a 
strong believer that source code comments are not a sufficient form of 
documentation.

Regards, Joerg

http://www.analogconsultants.com

Rune Allnor wrote:

> Joerg wrote:
> 
>>I have some filter design software that came with DSP books but they
>>don't go that far. They assume 'ideal' coefficient granularity base on
>>the available word width. Didn't find anything with Google but maybe I
>>hadn't used optimal search phrases.
> 
> 
> Out of curiosity: What is "coefficient granularity"?
> Never heard the term before.
> 
> Rune
> 
Jeorg:  You mean quantization, right?

You shouldn't overlook data quantization, either.  Both coefficient and 
data quantization can be easily modeled and analyzed without having to 
simulate, although its usually a good idea to simulate so you'll find 
out what you forgot to account for.

-- 

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

Hello Rune,
> 
> Out of curiosity: What is "coefficient granularity"?
> Never heard the term before.
> 

The reduction of the total available number of coefficients to less than 
the word width would theoretically allow. IOW causing the selection to 
be more granular than usual.

For example let's say a certain project cannot afford a device with a HW 
multiplier and must also run on batteries, limiting the processor clock 
frequency. To save on processor cycles the amount of ones in an eight 
bit data word that is to be used as a multiplier may have to be limited 
to, say, four or five.

Granularity is probably not a common word in the DSP world. It is often 
used in radar and ultrasound beamforming which is my home turf.

Regards, Joerg

http://www.analogconsultants.com

Hello Tim,

> Jeorg:  You mean quantization, right?
> 

Kind of. It's like picking the low hanging fruit, coefficients that have 
the least number of ones in there. I have pretty much given up on the 
luxury of a HW multiplier for the project at hand (or the proposal 
thereof). Too expensive.


> You shouldn't overlook data quantization, either.  Both coefficient and 
> data quantization can be easily modeled and analyzed without having to 
> simulate, although its usually a good idea to simulate so you'll find 
> out what you forgot to account for.
> 

True. In my case it might not easily work though because I have to 
filter first and then 'level select'. I need a huge dynamic range. 
Ranging before the filters would cost too much precious horsepower and 
RAM. So data will be 16 bits while the coefficients are probably going 
to have to be 6-8 bits.

Regards, Joerg

http://www.analogconsultants.com

Joerg wrote:

> Hello Rune,
> 
>>
>> Out of curiosity: What is "coefficient granularity"?
>> Never heard the term before.
>>
> 
> The reduction of the total available number of coefficients to less than 
> the word width would theoretically allow. IOW causing the selection to 
> be more granular than usual.
> 
> For example let's say a certain project cannot afford a device with a HW 
> multiplier and must also run on batteries, limiting the processor clock 
> frequency. To save on processor cycles the amount of ones in an eight 
> bit data word that is to be used as a multiplier may have to be limited 
> to, say, four or five.
> 
> Granularity is probably not a common word in the DSP world. It is often 
> used in radar and ultrasound beamforming which is my home turf.
> 
> Regards, Joerg
> 
> http://www.analogconsultants.com

You should stick to "quantization" if you want us poor DSP types to 
understand.

Restricting the precision of the multiplication to save time works for me.

-- 

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

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:0PGpf.43240$6e1.27620@newssvr14.news.prodigy.com...
> Hello Rune,
> >
> > Out of curiosity: What is "coefficient granularity"?
> > Never heard the term before.
> >
>
> The reduction of the total available number of coefficients to less than
> the word width would theoretically allow. IOW causing the selection to
> be more granular than usual.

I'm fairly sure that we've had discussions on comp.dsp where the filter
coeffs were restricted to powers of two - this would help eliminate the need
for hw multipliers. I remember there was atleast one paper cited in the
discussion. You might want to google with 'fir' and 'power of 2 coeffs' or
something similar to see if you can find this thread.
Here is one paper that seems to talk about this
http://www.ittc.ku.edu/Projects/FPGA/Filters_and_CAD.pdf
I think Y.C.Lim is another author that has done some work in this area - you
can try using his name in your search criteria as well.

Ah...here is the thread I was talking about
http://tinyurl.com/dt9td


Cheers
Bhaskar


>
> For example let's say a certain project cannot afford a device with a HW
> multiplier and must also run on batteries, limiting the processor clock
> frequency. To save on processor cycles the amount of ones in an eight
> bit data word that is to be used as a multiplier may have to be limited
> to, say, four or five.
>
> Granularity is probably not a common word in the DSP world. It is often
> used in radar and ultrasound beamforming which is my home turf.
>
> Regards, Joerg
>
> http://www.analogconsultants.com

Hello Bhaskar,
> 
> Ah...here is the thread I was talking about
> http://tinyurl.com/dt9td
> 
> 
Thank you. That thread also mentioned the other important term you DSP 
guys use, Canonic Signed Digit. So now I can search some more.

I can afford some shift-adds, just not a whole lot. HW multipliers must 
be like those premium channels on cable TV that you only get when you 
pay a whole lot more (we don't have cable TV at all...).

Regards, Joerg

http://www.analogconsultants.com

Hello Tim,
> 
> You should stick to "quantization" if you want us poor DSP types to 
> understand.
> 

Ok, I'll try to be better in the future. Quantization it is. I guess 
I'll also have to lose some other slang, apodization, CFAR and all that.

Regards, Joerg

http://www.analogconsultants.com

Joerg wrote:

> Hello Tim,
> 
>> Jeorg:  You mean quantization, right?
>>
> 
> Kind of. It's like picking the low hanging fruit, coefficients that have 
> the least number of ones in there. I have pretty much given up on the 
> luxury of a HW multiplier for the project at hand (or the proposal 
> thereof). Too expensive.
> 
> 
>> You shouldn't overlook data quantization, either.  Both coefficient 
>> and data quantization can be easily modeled and analyzed without 
>> having to simulate, although its usually a good idea to simulate so 
>> you'll find out what you forgot to account for.
>>
> 
> True. In my case it might not easily work though because I have to 
> filter first and then 'level select'. I need a huge dynamic range. 
> Ranging before the filters would cost too much precious horsepower and 
> RAM. So data will be 16 bits while the coefficients are probably going 
> to have to be 6-8 bits.
> 
> Regards, Joerg
> 
> http://www.analogconsultants.com

I'm not sure what you mean by 'level select'.

You can still analyze for the effect of coefficient quantization.  It 
doesn't get as much attention as data quantization in the DSP world, 
perhaps because its a better defined problem -- data quantization must 
be treated as noise or simulated, with coefficient quantization you can 
just calculate the transfer functions post-quantization and go from there.

If you are analyzing things in the frequency domain you can generate 
trial filters and generate bode plots for them with a number of packages 
(including Scilab).  If you're doing stuff in the time domain then yes, 
you'll have to simulate (but Scilab will do that pretty quick, too).  If 
you have something advanced like Scilab, Matlab or Octave you can give 
it some rules for finding coefficients that don't have too many ones and 
do a massive search for the 'best' one.

-- 

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

Joerg wrote:

> Hello Bhaskar,
> 
>>
>> Ah...here is the thread I was talking about
>> http://tinyurl.com/dt9td
>>
>>
> Thank you. That thread also mentioned the other important term you DSP 
> guys use, Canonic Signed Digit. So now I can search some more.
> 
> I can afford some shift-adds, just not a whole lot. 

I recall seeing a paper from IEEE CCS about efficient ways of 
implementing multiplies for coefficients with lots of ones.  It boiled 
down to recognizing that (for example) 15 = 16 - 1, so computing (x << 
4) - x was quicker that computing (x << 3) + (x << 2) + (x << 1) + x and 
came up with the same result.  You ended up with at worst 1/2 as many 
shift-and-adds (with a coefficient that goes 10101010...) as the maximum 
for a coefficient of 11111111.

You could even write an assembler macro for this if you had a good 
enough macro assembler.

> HW multipliers must 
> be like those premium channels on cable TV that you only get when you 
> pay a whole lot more (we don't have cable TV at all...).

We have a cable modem.  It really ticks my kid off that we don't also 
have cable TV.

-- 

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

Hello Tim,
> 
> I'm not sure what you mean by 'level select'.
> 

It is the determination of how much energy there is in one frequency 
range versus the others. There can also be nothing there, just unwanted 
spectra or noise. The level of the input signal is not known except that 
it will (have to) fit into 16 bits.


> You can still analyze for the effect of coefficient quantization.  It 
> doesn't get as much attention as data quantization in the DSP world, 
> perhaps because its a better defined problem -- data quantization must 
> be treated as noise or simulated, with coefficient quantization you can 
> just calculate the transfer functions post-quantization and go from there.
> 

Alfred Fettweis did that for WDF and maybe I can find a copy of his 1986 
IEEE paper. The other paper was from Ulrich Kaiser but almost as long 
ago in a German magazine so maybe that one is gone by now.


> If you are analyzing things in the frequency domain you can generate 
> trial filters and generate bode plots for them with a number of packages 
> (including Scilab).  If you're doing stuff in the time domain then yes, 
> you'll have to simulate (but Scilab will do that pretty quick, too).  If 
> you have something advanced like Scilab, Matlab or Octave you can give 
> it some rules for finding coefficients that don't have too many ones and 
> do a massive search for the 'best' one.
> 

I'd love to but I am not that good with programs like Scilab. It's a 
steep learning curve. I'll probably wing it to get something prototyped 
and then analyze and verify that it is stable. Or punch a behaviorial 
model into SPICE and simulate that.

Meantime I also found good design hints in a book from Otto Mildenberger 
(only got the German version). It came with a DOS design tool that I 
bought in the late 80's and where it might thus be possible to hack the 
coefficients. The only question now is where'd I put it? Luckily I kept 
an old 5 1/4" floppy drive.

Regards, Joerg

http://www.analogconsultants.com

Hello Tim,

> I recall seeing a paper from IEEE CCS about efficient ways of 
> implementing multiplies for coefficients with lots of ones.  It boiled 
> down to recognizing that (for example) 15 = 16 - 1, so computing (x << 
> 4) - x was quicker that computing (x << 3) + (x << 2) + (x << 1) + x and 
> came up with the same result.  You ended up with at worst 1/2 as many 
> shift-and-adds (with a coefficient that goes 10101010...) as the maximum 
> for a coefficient of 11111111.
> 
> You could even write an assembler macro for this if you had a good 
> enough macro assembler.
> 

That would be neat. Looks like one more reason why this stuff usually 
isn't done in C.


>> HW multipliers must be like those premium channels on cable TV that 
>> you only get when you pay a whole lot more (we don't have cable TV at 
>> all...).
> 
> We have a cable modem.  It really ticks my kid off that we don't also 
> have cable TV.
> 

It's a good thing that you don't have cable TV. I see it destroy healthy 
family living all around us in the neighborhood. But how did you manage 
to get cable modem w/o TV? They send all these fliers around but when I 
called they told me that the bargain rates are only applicable when also 
subscribing to their TV. No way. Without TV the cable modem monthly rate 
shoots up to well above DSL. So I kept DSL.

Regards, Joerg

http://www.analogconsultants.com

Joerg wrote:
> Hello Tim,
> 
>> I recall seeing a paper from IEEE CCS about efficient ways of 
>> implementing multiplies for coefficients with lots of ones.  It boiled 
>> down to recognizing that (for example) 15 = 16 - 1, so computing (x << 
>> 4) - x was quicker that computing (x << 3) + (x << 2) + (x << 1) + x 
>> and came up with the same result.  You ended up with at worst 1/2 as 
>> many shift-and-adds (with a coefficient that goes 10101010...) as the 
>> maximum for a coefficient of 11111111.
>>
>> You could even write an assembler macro for this if you had a good 
>> enough macro assembler.
>>
> 
> That would be neat. Looks like one more reason why this stuff usually 
> isn't done in C.
> 
> 
>>> HW multipliers must be like those premium channels on cable TV that 
>>> you only get when you pay a whole lot more (we don't have cable TV at 
>>> all...).
>>
>>
>> We have a cable modem.  It really ticks my kid off that we don't also 
>> have cable TV.
>>
> 
> It's a good thing that you don't have cable TV. I see it destroy healthy 
> family living all around us in the neighborhood. But how did you manage 
> to get cable modem w/o TV? They send all these fliers around but when I 
> called they told me that the bargain rates are only applicable when also 
> subscribing to their TV. No way. Without TV the cable modem monthly rate 
> shoots up to well above DSL. So I kept DSL.
> 
> Regards, Joerg
> 
> http://www.analogconsultants.com

(a) it's an itty bitty telephone cooperative & cable TV company
(b) when I called about DSL they told me "we don't do that; for 
broadband we do cable modems"
(c) I didn't ask about rates for the modem if I succumbed to the TV 
thing.  We have enough trouble pulling the kids off of the half-dozen 
channels that we get, why should I want to get 50 or 100?

-- 

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

Hello Tim,

> (c) I didn't ask about rates for the modem if I succumbed to the TV 
> thing.  We have enough trouble pulling the kids off of the half-dozen 
> channels that we get, why should I want to get 50 or 100?
> 

What entices them to watch? We get the same aerial coverage, actually a 
dozen channels but half of them in Spanish. Thought there'd be some good 
old Christmas movies this week but when the TV guide came with the 
morning paper we found a grand total of three. Pretty sad.

I found the Mildenberger filter program in the CAD binder to try if I 
can do coefficient wiggling with it. Cool. Whenever I fire up one of 
those old DOS dinosaurs I am amazed how fast they are. It states that an 
IBM XT with at least 300K of RAM is required and now it probably thinks 
it's sitting on a rocket.

Regards, Joerg

http://www.analogconsultants.com

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message 
news:FXIpf.35147$dO2.14183@newssvr29.news.prodigy.net...
>>
>> We have a cable modem.  It really ticks my kid off that we don't also have 
>> cable TV.
>>
>
> It's a good thing that you don't have cable TV. I see it destroy healthy 
> family living all around us in the neighborhood. But how did you manage to get 
> cable modem w/o TV? They send all these fliers around but when I called they 
> told me that the bargain rates are only applicable when also subscribing to 
> their TV. No way. Without TV the cable modem monthly rate shoots up to well 
> above DSL. So I kept DSL.

Around here, the cable company charges about $10 extra per month if you get 
cable modem without some type of cable TV service.  The cheapest cable TV you 
can get (basic service, which includes the local over-air channels and a few 
extras) costs slightly more than $10.  So usually people opt to get the basic 
service since it is essentially almost free.  But you can choose to pay the 
extra $10 instead if you want.  In the hilly area I live in, over-air reception 
can be bad to non-existent for many people even with a good antenna, so the 
basic cable service is popular. 

Joerg wrote:
> Hello Tim,
> 
>>
>> You should stick to "quantization" if you want us poor DSP types to 
>> understand.
>>
> 
> Ok, I'll try to be better in the future. Quantization it is. I guess 
> I'll also have to lose some other slang, apodization, CFAR and all that.

What is CFAR? Apodization is from the realm of optics, dealing with 
control of diffraction. The corresponding DSP term is windowing. The 
equivalence of diffraction patterns and side lobes doesn't immediately 
strike one, but of course they are in essence the same phenomenon.

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

Tim Wescott wrote:

   ...

> We have a cable modem.  It really ticks my kid off that we don't also 
> have cable TV.

A buddy of mine has your setup, and the cable crews kept disconnecting 
him. He wasn't signed up for cable TV, so they figured it was an illegal 
tap. We finally climbed the pole and nailed a note to it near the drop.

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

Jerry Avins <jya@ieee.org> writes:

> What is CFAR? 

CFAR = Constant False Alarm Rate

It's a way of choosing thresholds based on how many false alarms your
system can deal with. Zero is not an option; something less than 99.9%
is easier to deal with.

Ciao,

Peter K.

Jerry Avins wrote:
> Joerg wrote:
> 
>> Hello Tim,
>>
>>>
>>> You should stick to "quantization" if you want us poor DSP types to 
>>> understand.
>>>
>>
>> Ok, I'll try to be better in the future. Quantization it is. I guess 
>> I'll also have to lose some other slang, apodization, CFAR and all that.
> 
> 
> What is CFAR? Apodization is from the realm of optics, dealing with 
> control of diffraction. The corresponding DSP term is windowing. The 
> equivalence of diffraction patterns and side lobes doesn't immediately 
> strike one, but of course they are in essence the same phenomenon.
> 
> Jerry

CFAR is term generally associated with radar and sonar. You want your 
radar to CFAR, don't you? So, you need a Constant False Alarm Rate 
device to control the rate of detections, and maximise sensitivity 
without flooding the system's back end with false alarms. Its a form of 
adaptive filter, though there are many variations on the basic theme.

Steve

Hello John,

> Around here, the cable company charges about $10 extra per month if you get 
> cable modem without some type of cable TV service.  The cheapest cable TV you 
> can get (basic service, which includes the local over-air channels and a few 
> extras) costs slightly more than $10.  So usually people opt to get the basic 
> service since it is essentially almost free.  But you can choose to pay the 
> extra $10 instead if you want.  In the hilly area I live in, over-air reception 
> can be bad to non-existent for many people even with a good antenna, so the 
> basic cable service is popular. 
> 

Very different here. They offer Internet for between $20 and $30 but w/o 
subscribing to their TV it's $55 or more IIRC. DSL is $50 so it's a 
better deal. No idea why the cable guys do that, I guess most people 
must have cable TV.

AFAIK the basic cable TV is already over $40. Not worth it IMHO. 
Terrestrial reception is spotty as we live in the hills. You can see 
ghosting over several lines, meaning the ghost image is vertically and 
horizontally separated. Sometimes you have to train your antenna on that 
ghost because it's more intelligible than the direct path. I could 
imagine that DTV will be a failure around here. Instead of a somewhat 
intelligible screen we might just see a garbled mess of data. Oh well, 
it won't be a great loss anyway.

Regards, Joerg

http://www.analogconsultants.com

Hello Jerry,

>> We have a cable modem.  It really ticks my kid off that we don't also 
>> have cable TV.
> 
> A buddy of mine has your setup, and the cable crews kept disconnecting 
> him. He wasn't signed up for cable TV, so they figured it was an illegal 
> tap. We finally climbed the pole and nailed a note to it near the drop.
> 

In California this might have required a bilingual note ;-)

I wonder, if they send most basic channels unscrambled how do they avoid 
somebody from tapping the line at the modem input and connect the TV to 
that?

Regards, Joerg

http://www.analogconsultants.com

Jerry Avins wrote:

> Tim Wescott wrote:
> 
>   ...
> 
>> We have a cable modem.  It really ticks my kid off that we don't also 
>> have cable TV.
> 
> 
> A buddy of mine has your setup, and the cable crews kept disconnecting 
> him. He wasn't signed up for cable TV, so they figured it was an illegal 
> tap. We finally climbed the pole and nailed a note to it near the drop.
> 
> Jerry

What! Cable employees that can read.
I hand delivered a note to local cable company giving formal notice that 
their sales people were to stay away from me of suffer civil and/or 
criminal penalties.

Before handing it over, I asked if the was anyone in the office who 
could read [with provocation I can be sarcastic ;]

I 'gentleman', identifying himself as OFFICE MANAGER, "I graduated from 
.... {the local state university}."

I replied "But I asked if there was anyone who could read."
Haven't been bothered in last ten years ;}

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:UaYpf.35338$dO2.12978@newssvr29.news.prodigy.net...
> Hello Jerry,
>
> >> We have a cable modem.  It really ticks my kid off that we don't also
> >> have cable TV.
> >
> > A buddy of mine has your setup, and the cable crews kept disconnecting
> > him. He wasn't signed up for cable TV, so they figured it was an illegal
> > tap. We finally climbed the pole and nailed a note to it near the drop.
> >
>
> In California this might have required a bilingual note ;-)
>
> I wonder, if they send most basic channels unscrambled how do they avoid
> somebody from tapping the line at the modem input and connect the TV to
> that?

This is why most cable providers (atleast here in San Jose, CA) make you pay
the $10 extra if you want only their cable modem services. They can't block
the basic cable content since it isn't scrambled. So if you subscribe to
their broadband services, you can tap into their basic channels.

Cheers
Bhaskar

>
> Regards, Joerg
>
> http://www.analogconsultants.com

Hello Bhaskar,

>>I wonder, if they send most basic channels unscrambled how do they avoid
>>somebody from tapping the line at the modem input and connect the TV to
>>that?
> 
> This is why most cable providers (atleast here in San Jose, CA) make you pay
> the $10 extra if you want only their cable modem services. They can't block
> the basic cable content since it isn't scrambled. So if you subscribe to
> their broadband services, you can tap into their basic channels.
> 

Well, I don't want TV. It isn't just $10 here, it's more like $40 and 
IMHO absolutely not worth it. Why can't they just filter the TV band out 
good enough so that the resulting picture quality after an illegal tap 
would be miserable?

Regards, Joerg

http://www.analogconsultants.com

Bhaskar Thiagarajan wrote:

>"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
>news:UaYpf.35338$dO2.12978@newssvr29.news.prodigy.net...
>  
>
>>Hello Jerry,
>>
>>    
>>
>>>>We have a cable modem.  It really ticks my kid off that we don't also
>>>>have cable TV.
>>>>        
>>>>
>>>A buddy of mine has your setup, and the cable crews kept disconnecting
>>>him. He wasn't signed up for cable TV, so they figured it was an illegal
>>>tap. We finally climbed the pole and nailed a note to it near the drop.
>>>
>>>      
>>>
>>In California this might have required a bilingual note ;-)
>>
>>I wonder, if they send most basic channels unscrambled how do they avoid
>>somebody from tapping the line at the modem input and connect the TV to
>>that?
>>    
>>
>
>This is why most cable providers (atleast here in San Jose, CA) make you pay
>the $10 extra if you want only their cable modem services. They can't block
>the basic cable content since it isn't scrambled. So if you subscribe to
>their broadband services, you can tap into their basic channels.
>
>Cheers
>Bhaskar
>  
>
So, if they are charging you the full value of the basic unscrambled 
channels, what are they charging the other $9.98 for? :-)

Mary Christ'sMa
Steve

>  
>
>>Regards, Joerg
>>
>>http://www.analogconsultants.com
>>    
>>

Bhaskar Thiagarajan wrote:
> "Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
> news:UaYpf.35338$dO2.12978@newssvr29.news.prodigy.net...
> 
>>Hello Jerry,
>>
>>
>>>>We have a cable modem.  It really ticks my kid off that we don't also
>>>>have cable TV.
>>>
>>>A buddy of mine has your setup, and the cable crews kept disconnecting
>>>him. He wasn't signed up for cable TV, so they figured it was an illegal
>>>tap. We finally climbed the pole and nailed a note to it near the drop.
>>>
>>
>>In California this might have required a bilingual note ;-)
>>
>>I wonder, if they send most basic channels unscrambled how do they avoid
>>somebody from tapping the line at the modem input and connect the TV to
>>that?
> 
> 
> This is why most cable providers (atleast here in San Jose, CA) make you pay
> the $10 extra if you want only their cable modem services. They can't block
> the basic cable content since it isn't scrambled. So if you subscribe to
> their broadband services, you can tap into their basic channels.

A frequency selective filter could stop that. Basically, they want 
subscribers to boost their advertising revenue. It's no different with 
print magazines.

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

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message 
news:y7Ypf.35336$dO2.27017@newssvr29.news.prodigy.net...
> Hello John,
>
>> Around here, the cable company charges about $10 extra per month if you get 
>> cable modem without some type of cable TV service.  The cheapest cable TV you 
>> can get (basic service, which includes the local over-air channels and a few 
>> extras) costs slightly more than $10.  So usually people opt to get the basic 
>> service since it is essentially almost free.  But you can choose to pay the 
>> extra $10 instead if you want.  In the hilly area I live in, over-air 
>> reception can be bad to non-existent for many people even with a good 
>> antenna, so the basic cable service is popular.
>
> Very different here. They offer Internet for between $20 and $30 but w/o 
> subscribing to their TV it's $55 or more IIRC. DSL is $50 so it's a better 
> deal. No idea why the cable guys do that, I guess most people must have cable 
> TV.
>
> AFAIK the basic cable TV is already over $40. Not worth it IMHO. Terrestrial 
> reception is spotty as we live in the hills. You can see ghosting over several 
> lines, meaning the ghost image is vertically and horizontally separated. 
> Sometimes you have to train your antenna on that ghost because it's more 
> intelligible than the direct path. I could imagine that DTV will be a failure 
> around here. Instead of a somewhat intelligible screen we might just see a 
> garbled mess of data. Oh well, it won't be a great loss anyway.
>
> Regards, Joerg
>
> http://www.analogconsultants.com

Where is "here" for you, Joerge?  For me it is Seattle, Washington (USA).  FYI, 
my cable company (Comcast) doesn't advertise the cheap "broadcast channels" 
package at all on their web site.  You have to call them up and ask for it. 
There was legislation a while back that required them to offer the service, but 
they try their best to make it hard to find!

-- 
Jon Harris
SPAM blocker in place:
Remove 99 (but leave 7) to reply

Hello Jon,

> Where is "here" for you, Joerge?  For me it is Seattle, Washington (USA).  FYI, 
> my cable company (Comcast) doesn't advertise the cheap "broadcast channels" 
> package at all on their web site.  You have to call them up and ask for it. 
> There was legislation a while back that required them to offer the service, but 
> they try their best to make it hard to find!
> 

"Here" is Cameron Park, California, about 30 miles east of Sacramento. 
Highway 50 to Lake Tahoe. It's also Comcast out here. When I called them 
up they said that the competitive pricing offer on cable modem service 
is only valid if I also take their "basic" cable TV package. That was 
just under $40 back then but has gone above that now AFAIK. I just don't 
need home and garden TV and all that.

In fact, when we moved here from overseas we truly forgot about TV. 
Eight months later we wanted to check the local weather and only then it 
dawned on us that our TV wasn't US standard and would not work. Duh. So 
I went to town and bought a TV set. About five (!) years later we 
re-roofed and upon taking down the antenna I realized that it had a 
pre-amp that did not and could not work the whole time. After fixing 
that we can receive twice as many channels. Did that enhance our TV 
experience? Nope.

Regards, Joerg

http://www.analogconsultants.com