HDTenEightyP/NetNews huggingface dataset:
From: alien@essex.ac.uk ("Adrian F Clark")
Newsgroups: comp.dsp
Subject: Re: Array organization. Was: FFT in 2D
Date: 30 Sep 92 13:02:32 GMT
Organization: University of Essex, UK
In-reply-to: dak@kaa.informatik.rwth-aachen.de's message of 30 Sep 92 08:25:19 GMT

In article <dak.717841519@kaa> dak@kaa.informatik.rwth-aachen.de (David Kastrup) writes:

> What's wrong with the left upper corner? Index (0,0) is where it belongs.

How about the following:

1.  When a 2-D Fourier transform happens in the real world, one
    normally find the zero frequency in the middle of the pattern.
    For example, look at Airy's disc in any decent optics textbook.

2.  When progrmming up a Fourier filter (e.g., a low-pass filter) it
    is much easier (and shorter, faster) to calculate the distance
    from the middle of the image than it is from all the corners.
    With the zero frequency at the upper left of an image, the
    distance from it increases along the rows/columns and then
    decreases; and evaluating the radial distance is not a one-liner
    (in Fortran or Pascal, at least).

3.  I'm not aware of any image processing package that chooses to
    calculate Fourier spectra with the origin anywhere else than at
    the centre (someone will now post the name of one that does; sigh).

> If you want to somehow have a "logical" order with 0 in the middle, remember
> that a frequency component of -1/N Hz is ABSOLUTELY indestinguishable
> from (N-1)/N Hz due to sampling aliasing. The transform is based on
> that fact (at least the fast algorithms), and why mangle up the indexing?

Shifting the origin of the spectra cannot introduce aliasing!  It is
present irrespective of where one chooses to put the origin.

The way in which most people shift the origin to the middle of an
image is by pre- and post-gridding (i.e., multiplying alternate
elements by -1).  This applies to both 1D and 2D transforms,
incidentally.  Hence, there is no need to fiddle with the indexing:
one can simply put a wrapper around an upper-left-origin 2D FFT.

> DISPLAY it shifted by whatever you want, but do not mangle the data
> structure, because that tends to COMPLICATE things instead of making
> them easier, especially since all the theorems of DFT are usually
> formulated for indexes 0..N-1.

It's equally easy to define the DFT in terms of a centred origin all
the theorems then follow, since the two representations are of course
equivalent.  However, for physicists and most flavours of engineer at
least, having a software FT produce results similar to the real world
is more important than mathematical purity.

--
 Dr Adrian F. Clark                                   JANET: alien@uk.ac.essex
 INTERNET: alien%uk.ac.essex@nsfnet-relay.ac.uk          FAX: (+44) 206-872900
 BITNET: alien%uk.ac.essex@ac.uk              PHONE: (+44) 206-872432 (direct)
 Dept ESE, University of Essex, Wivenhoe Park, Colchester, Essex, C04 3SQ, UK.
Newsgroups: comp.dsp
From: davidm@sfsuvax1.sfsu.edu (David Morgenstern)
Subject: Request for Information
Organization: California State University, Sacramento
Date: Mon, 5 Oct 1992 23:37:43 GMT


Dear Digital Signal Processors:

I've been given the assignment to report on Higher Education kinda
news for MacWeek. This is a very wide-ranging area, but I'm
focusing on new projects from universities, technologies that are
starting to be used in the academic environment, and anything else
that looks interesting. It doesn't have to be all Macintosh,
although that helps! 

My first report covered the SUIT cross-platform C-language graphic
software, the Tripwire security software for UNIX, and the EndNote
TagLink (a commercial program) support for the TAGS bibliographic
file format developed by the UC Library. 

I'd like to hear about what you're working on, if there's something
you think that people should know about, a new technology, or a new
tool. If a colleague is doing something interesting, can you pass
this on to them?  Any other news that might be of interest to
MacWeek readers is always welcome!
 
Thanks,

David Morgenstern, davidm@sfsuvax1.sfsu.edu 
-- 
 David Morgenstern, BMUG CheerLeader davidm@sfsuvax1.sfsu.edu
    "Miracles do occur - but they rarely provide food." 
         --  Talmud: Shabbat, 53b
Xref: sparky comp.dsp:2275 comp.lsi.cad:984
From: wang@ics.uci.edu
Subject: 5th-order elliptic filter and its linear difference equation
Newsgroups: comp.dsp,comp.lsi.cad
Date: 1 Oct 92 18:34:38 GMT


I am looking for the linear difference equation that describes the response
of the 5th-order elliptic filter, appeared in the following reference,

P. Dewilde, E. Deprettere, and R. Nouta,
``Parallel and pipelined VLSI implementation of signal
processing algorithms'', pp. 257-276,  VLSI and modern signal processing,
S. Y. Kung, H. J. Whitehouse, T. Kailath, editors,  Prentice-hall, 1985.

Any help would be gratefully appreciated.

Haigeng Wang
wang@ics.uci.edu
Xref: sparky comp.dsp:2308 comp.sys.ibm.pc.soundcard:2416
From: shaehnic@sdcc13.ucsd.edu (Steve - Happy Hacker!)
Newsgroups: comp.dsp,comp.sys.ibm.pc.soundcard
Subject: Re: realtime dsp with soundcards
Date: 6 Oct 92 15:12:22 GMT
Article-I.D.: sdcc12.39074
Reply-To: shaehnic@ucsd.edu
Followup-To: comp.dsp
Organization: HyperHack - San Diego, CA.
In-reply-to: deanaj@elec.canterbury.ac.nz's message of 4 Oct 92 03:50:37 GMT

--=}>> On 4 Oct 92 03:50:37 GMT, deanaj@elec.canterbury.ac.nz (A. J. Dean) said:
> Nntp-Posting-Host: betelgeux.canterbury.ac.nz

> Nicolas Alejandro Arauz (na0s+@andrew.cmu.edu) wrote:
> : Maybe someone can answer this question for me:
> : > this, so I'll ask you.  My question that I wasn't sure about was whether
> : > or not ANY of these cards would all simultaneous input/output from the
> : > ADC/DAC do do digital effects?  Or perhaps even switch so fast that you

> I've had a go a doing a similar thing with my soundcard (for guitar
> effects, etc). BTW, it's a SB pro version 1. I think it may be able
> to do simultaneous ADC and DAC (not in DMA mode) but even if it does
> the audio routing/mixing circuitry won't. For a start, you can't
> turn off the input monitor without turning down everything else
> including the DAC, ie you always get some of your original signal
> straight through (though I did think about subtracting it).

Well, this is the case only for the Line and CD audio inputs.  It
seems that the microphone level can be reduced to silence, and it will
still record at normal volume.  It's as if the Mic level does not
adjust the input level, but just the "thru" level.

> Also, selecting the DAC disconnects any sound from the ADC (well, it
> gives random values - could be used as part of the ADC).

Yeah.. You have to turn "DAC Output" off before recording.  They don't
mention that in the Developers' Kit.  The worst part is that it can
take "up to 300 milliseconds"(!) to make the change.  This is probably
a misprint, as it happens much faster on my card.

> You can switch rapidly between ADC and DAC, but the result is pretty
> awful, though it did work. After that I gave up, along with giving
> up on my ultra-optimised 8 bit FIR fiter routines for the PC. I'll
> wait/pay for a soundcard which is a bit less limited!
> Antony. (deanaj@elec.canterbury.ac.nz) 

BTW, does anyone know of a lower-end PC soundcard that CAN do
simultaneous ADC/DAC?  Most of the common ones can't seem to.

-Steve

Steve Haehnichen
shaehnic@ucsd.edu
Newsgroups: comp.dsp
From: gints@roadkill.esd.sgi.com (Gints Klimanis)
Subject: Re: A simple question
Organization: Silicon Graphics, Inc.
Distribution: usa
Date: Fri, 2 Oct 1992 21:55:28 GMT

In article <1992Oct2.203621.5649@tamsun.tamu.edu>, mchung@ee.tamu.edu
(Maranatha Chung) writes:
|> Why is an odd order FIR filter better than an even order FIR filter?
Given impulse response is symmetric about its center, the group delay
is
(filter length - 1)/2.  For an odd length filter, the group delay would
be an integer.  For an even length filter, the group delay would be
fractional.

Some applications in image processing need to know where to chop off the
convolution header and tail so as to preserve pixel dimensions.  Linear
phase and an integer group delay make it easy to truncate the larger,
convolved image.  
Newsgroups: comp.dsp
From: tohall@ariel.lerc.nasa.gov (Dave Hall (Sverdrup))
Subject: Re: FFT in 2D
News-Software: VAX/VMS VNEWS 1.41    
Organization: NASA Lewis Research Center
Date: 28 Sep 1992 14:06 EST  

In article <1992Sep22.163256.15935@versyss.com>, keithd@versyss.UUCP (Keith Doyle) writes...
>I'm interested in using FFT for noise reduction of images, and while I
>have worked with FFT in 1D (for audio) and have an assortment of FFT
>source code for 1D, I don't really know how to apply it to the 2D case.
>Is it simply an FFT of all the rows combined with an FFT of all the columns
>of pixels in the image?  

    Here is the basic idea: Start with a 2-d array (matrix) of pixels. First,
take the 1-d FFT of each row vector, forming an intermdiate matrix from the 
result. Now take the 1-d FFT of each column vector in this matrix. The columns
of the final output matrix are formed from these transforms. Therefore, the
calculation of a 2-d FFT for an NxN matrix requires calculation of N^2 1-D
FFT's.


                  Hope this is useful info,


                                Dave Hall



Xref: sparky comp.dsp:2252 comp.sys.ibm.pc.soundcard:2199
From: na0s+@andrew.cmu.edu (Nicolas Alejandro Arauz)
Newsgroups: comp.dsp,comp.sys.ibm.pc.soundcard
Subject: realtime dsp with soundcards
Date: 28 Sep 92 14:26:24 GMT
Organization: Carnegie Mellon, Pittsburgh, PA

Maybe someone can answer this question for me:

> 
> I had been thinking about trying to write an effects program like you
> did in your archive, only using the SoundBlaster card, or the PAS-16 or
> the new Gravis card.  It seems as if you obviously know something about
> this, so I'll ask you.  My question that I wasn't sure about was whether
> or not ANY of these cards would all simultaneous input/output from the
> ADC/DAC do do digital effects?  Or perhaps even switch so fast that you
> wouldn't notice a lag.  Have you done any work with the commercial
> soundcards?  I haven't gotten your archive yet but I will take a look at
> it now.  It seems like you're possibly using high-sample rate DACs/ADCs
> from reading your message.  Thanks f or your help!
> 
Dear Nicolas,


I do not have the details about the commercial soundcards you would like
to know. Maybe it is a good question to ask as a followup to my posting
in the alt.dsp or comp.music newsgroup. 


Best regards,
Jos Groot
Newsgroups: comp.dsp
From: tavat@iastate.edu (Sanjeev Tavathia)
Subject: DIGITAL TRANSMITTER
Summary: Want to build a digital transmitter
Organization: Iowa State University, Ames IA
Date: Sat, 26 Sep 1992 16:06:13 GMT

Hi. I am thinkin' of makin' a digital transmitter which could work on wide
frequency range with channel selction option. I am comfortable with digital
modulation part but don't have enough idea of the antenna interface with
the circuit. What power signal should be fed to the antenna to make it 
receivable within 20 meters radius. What type of antena should I use.
Any suggestions??

			Thanks

							Sanjeev
From: lake@cwjcc.INS.CWRU.Edu (Dr. Robin Lake)
Newsgroups: comp.dsp
Subject: Re: FFT in 2D
Date: 29 Sep 1992 12:38:20 GMT
Organization: Case Western Reserve Univ. Cleveland, Ohio, (USA)
Reply-To: lake@po.CWRU.Edu
NNTP-Posting-Host: cwjcc.ins.cwru.edu

In article <1992Sep28.211714.17597@lmpsbbs.comm.mot.com> johna@comm.mot.com writes:

In article <1992Sep22.163256.15935@versyss.com>, keithd@versyss.UUCP (Keith Doyle) writes...
>I'm interested in using FFT for noise reduction of images, and while I
>have worked with FFT in 1D (for audio) and have an assortment of FFT
>source code for 1D, I don't really know how to apply it to the 2D case.
>Is it simply an FFT of all the rows combined with an FFT of all the columns
>of pixels in the image?  

>>    Here is the basic idea: Start with a 2-d array (matrix) of pixels. First,
>>take the 1-d FFT of each row vector, forming an intermdiate matrix from the 
>>result. Now take the 1-d FFT of each column vector in this matrix. The columns
>>of the final output matrix are formed from these transforms. Therefore, the
>>calculation of a 2-d FFT for an NxN matrix requires calculation of N^2 1-D
>>FFT's.

One thing to watch out for is where the DC component of the 2-D FFT ends
up in the result.  Very likely to be at the "corners" of the resulting
array, requiring some reorganization to move to the "center".

Rob Lake
BP Research
lake@rcwcl1.dnet.bp.com
Newsgroups: comp.dsp
From: johnf@scd.hp.com (John Flowers)
Subject: DSP amateur asks a question
Organization: Hewlett-Packard
X-Newsreader: Tin 1.1 PL3
Date: Tue, 6 Oct 1992 21:31:04 GMT

I am interested in taking a sampled audio segment and shifting
the pitch down, without losing the tempo.

What hardware or software algorithm exists for doing this well.

I would like to do at most 2 steps(musical notation) of shift.
This would be of music and not voice.

Thanks.
--
*********************************************************************
*   John P. Flowers            _\|/_______________________          *
*   johnf@scd.hp.com            /|\ We can tell how                 *
*   HP Santa Clara Division         far gone you are!               * 
*   Laser R&D                                                       *
*   q: What's the difference between hardware and software ?        *
*   a: You can't kick the software.....                             *
*********************************************************************
Newsgroups: comp.dsp
From: vpham@cs.ulowell.edu (Vinh Pham)
Subject: tektronix rtd710a
Organization: University of Massachusetts at Lowell Computer Science
Date: Thu, 1 Oct 1992 04:10:53 GMT

hi,
if you interface with the Tektronix RTD710A, would you drop me line?
I have a couple of simple questions to ask.
Thanks.
huy

Newsgroups: comp.dsp
From: mchung@ee.tamu.edu (Maranatha Chung)
Subject: A simple question
Organization: Texas A&M University
Distribution: usa
Date: Fri, 2 Oct 1992 20:36:21 GMT

Sorry if this has been asked before.

Why is an odd order FIR filter better than an even order FIR filter?
Thanks.

Maranatha
mchung@ee.tamu.edu
Newsgroups: comp.dsp
From: dak@kaa.informatik.rwth-aachen.de (David Kastrup)
Subject: Array organization. Was: FFT in 2D
Organization: Rechnerbetrieb Informatik  /  RWTH Aachen
Date: 30 Sep 92 08:25:19 GMT

lake@cwjcc.INS.CWRU.Edu (Dr. Robin Lake) writes:


>One thing to watch out for is where the DC component of the 2-D FFT ends
>up in the result.  Very likely to be at the "corners" of the resulting
>array, requiring some reorganization to move to the "center".

What's wrong with the left upper corner? Index (0,0) is where it belongs.
If you want to somehow have a "logical" order with 0 in the middle, remember
that a frequency component of -1/N Hz is ABSOLUTELY indestinguishable
from (N-1)/N Hz due to sampling aliasing. The transform is based on
that fact (at least the fast algorithms), and why mangle up the indexing?

The only problem MAY be that people find graphical representations
of convolution masks or transforms irritating. I can live with that.
If you want to,
DISPLAY it shifted by whatever you want, but do not mangle the data
structure, because that tends to COMPLICATE things instead of making
them easier, especially since all the theorems of DFT are usually
formulated for indexes 0..N-1.
Newsgroups: comp.dsp
From: lonachon@mehta.anu.edu.au (andrew longhorn )
Subject: Real-time pitch shifting
Reply-To: lonachon@mehta.anu.edu.au
Organization: Australian National University
Date: Wed, 30 Sep 92 22:29:08 GMT


Hi, I have just subscribed here as I am looking for algorithms or even some helpful
pointers on real-time pitch shifting using DSPs.

I having some specialist hardware built for a pet-project I have the input will be
a single guitar string sound wave (from a standard magnetic pickup).

What I need to know is:
- if I sample at x Khz and I may assume the frequency of the note, Is there an
  easy-ish way to bend this to any semi-tone to +/- 1 octave?
- does not knowing the frequency overly complicate the computation? (other than
  waiting for 1 cycle to determine it.
- can any algorithms handle doing this to a single note that varies in pitch over
  time (the result must vary accordingly, i.e. if I shift an A440 down 2 semitones
  then the pitch of the input goes up 2 semitones I get an A440).

Please post or mail ANY helpful hints and/or locations for sources and/or sources
(any language). I am a baby DSP programmer, hints are welcome.

Thank you for your time,
Andrew Longhorn.
Xref: sparky comp.next.misc:4 comp.sys.next:215 comp.sys.next.software:1990 comp.sys.next.misc:20567
From: szurek@vms.cis.pitt.edu (Joseph R Szurek)
Newsgroups: comp.next.misc,comp.sys.next,comp.sys.next.software,comp.sys.next.misc
Subject: Alternative to Projection ??
Date: 6 Oct 92 15:45:48 GMT
Followup-To: comp.next.misc
Distribution: na
Organization: University of Pittsburgh
Originator: szurek@unixd1.cis.pitt.edu

We have heard that there is software (in existence) which can be used on a 
network of NeXT machines that will enable you to open a window on each
machine, then by cutting and pasting into this window, it can be viewed at
each station.

Does anyone know of this?  Have you seen or used it?  What about cost?

We're thinking that this might provide a (cost effective) alternative to
projection in a classroom lab where each student has a station anyhow.
Newsgroups: comp.soft-sys.andrew
From: wyneken@sun1.ruf.uni-freiburg.de (Matthew Wyneken)
Subject: Annoying delay when loading fonts
Organization: Rechenzentrum der Universitaet Freiburg, Deutschland
Date: Mon, 5 Oct 92 13:09:05 GMT

I'm running ATK on Sparcstations under Openwindows 3 as well as
X11 R5. My problem is that I occasionally get eternally long
delays (up to 5 seconds :-) when viewing formatted text, such
as in the help files. The lags seem to come at font changes
in the text.

I at first thought that maybe fonts were being resized but then
I noticed that the delays also come for font sizes that have 
already been created and are in the font path.

Can anybody tell me what is causing the lags? Is there anything
I can do about it?

Thanks.

-------------------------------------------------------------------
Deutsches Seminar I          |   Tel.: ++49-761-2034897
Linguistische Informatik     |
Universitaet Freiburg        |   e-mail: 
Friedrichstr. 50             |   mpw@supreme.coling.uni-freiburg.de
W - 7800 Freiburg            |
Germany                      |
-------------------------------------------------------------------

-- 
Matthew Wyneken

Deutsches Seminar I          |   Tel.: ++49-761-2034897
Linguistische Informatik     |
From: rr2b+@ANDREW.CMU.EDU (Robert Andrew Ryan)
Newsgroups: comp.soft-sys.andrew
Subject: rcsid strings
Date: 29 Sep 92 16:59:15 GMT
Article-I.D.: andrew.Qem8hX200Woi95JkRK
Distribution: world
Organization: The Internet

We are evaluating our policies with regard to standard contents of
source files.  Our policy on the copyright notices shouldn't affect
anyone, but we are wondering if anyone uses the rcsid strings in object
files and executables.  If you do use them please send me mail.  Also,
should .ch files have static rcsid strings so that include file versions
can be gleaned from object files?  Is the run time space worth it?

Thanks for sharing your thoughts,
-Rob Ryan
Andrew Consortium
From: damon@csc.liv.ac.uk (Damon Chaplin)
Newsgroups: comp.soft-sys.andrew
Subject: Andrew version of refer
Date: 28 Sep 92 15:04:12 GMT
Organization: Computer Science, Liverpool University


Has anyone written a version of refer which works on Andrew documents?
If so, where can I get it?


Thanks, Damon
From: janssen@parc.xerox.com (Bill Janssen)
Newsgroups: comp.soft-sys.andrew
Subject: Re: Proposed tree mods
Date: 29 Sep 92 18:49:28 GMT
Distribution: world
Organization: The Internet

Looks good to me.  Nice to admit that `zip' isn't real...

Bill
Newsgroups: comp.soft-sys.andrew
From: zstern@adobe.com (Zalman Stern)
Subject: Re: AFS dependencies in ez (Was:  building 5.1 on HP-UX)
Organization: Adobe Systems Incorporated
Date: Mon, 5 Oct 1992 03:31:54 GMT

In article <8enA9kAGf047QWi4Bo@athena.mit.edu> wdc@ATHENA.MIT.EDU (Bill  
Cattey) writes:
> At the risk of torching up another fire storm:  Isn't it about time
> we removed the AFS dependencies from AUIS?
> 
> Does anyone remember the reason why EZ needs to know about AFS?

1) File saving and restoring code calls vclose for final saves (not  
checkpoints) to ensure that the file really made it to the server.

2) The code that handles '?' at a filename completion prompt appeneds a  
slash ('/') to names depending on the least significant bit of the inode  
number. This is a gross ugly performance hack that made a lot of difference  
in user satisfaction.

3) The error messages that come up on an error return from a file system  
call were written with AFS in mind.

4) Ez checks the error return from close.

1 and 2 won't work without AFS. (And if I recall were #ifdef'ed  
appropriately from day one.) 3 is a user interface anomaly ("What's a file  
server?") and 4 is good programming practice no matter what. I carefully  
avoided building in any knowledge about access control lists for example.  
(Using "access" where needed.) It would be diffcult to do that for DCE since  
files can have ACL's. This corresponds to ez as it was originally written.  
Things have probably changed. My memory is also far from infallible.
--
Zalman Stern		   zalman@adobe.com		    (415) 962 3824
Adobe Systems, 1585 Charleston Rd., POB 7900, Mountain View, CA 94039-7900
  "Yeah. Ask 'em if they'll upgrade my shifters too." Bill Watterson
Newsgroups: comp.soft-sys.andrew
From: asherman@laser.fmrco.com (Aaron Sherman)
Subject: Request for FAQ
Reply-To: asherman@fmrco.COM
Organization: I-Kinetics, 19 Bishop-Allen Dr., Cambridge, MA
Date: Thu, 1 Oct 1992 15:19:47 GMT


If there is an FAQ for this group, could someone please send it to me?

Thanks.


			-AJS

PS: If there is none, could someone please send me whatever info would
    be useful to someone looking into this software (how to get, limitations,
    benefits, etc...)
--
--------
Disclaimer: I am solely responsible for the content of this message.
The views expressed here may not be the views of I-Kinetics, Fidelity,
any of the Fidelity-owned corporations or my mother.
Newsgroups: comp.soft-sys.andrew
From: marshall@cs.iastate.edu (Bill Marshall)
Subject: Monochrome Setup
Keywords: preferences
Organization: Iowa State University, Ames IA
Date: Mon, 5 Oct 1992 20:06:19 GMT

I used Andrew this summer at IBM Rochester (to anyone in Rochester:
nice setup!) so now I am trying to run Andrew from an HP750. It runs
fine, but I have a monochrome X-terminal and things are hard to read
to ez. (The background is shaded or the text is)

I have read through help on preferences and ez, but I can't get the
write items in my .preferences file. Here is what I have:

ez.background: 			white
ez.foreground: 			black
*.BackgroundColor: 		white
*.ForegroundColor: 		black
AMShome:cs.iastate.edu

Thanks,
Bill

--
			    Bill Marshall
		     Computer Science Department
			Iowa State University
		       marshall@cs.iastate.edu
From: wjh+@ANDREW.CMU.EDU (Fred Hansen)
Newsgroups: comp.soft-sys.andrew
Subject: Newsletter from Andrew Consortium
Date: 1 Oct 92 23:20:34 GMT
Distribution: world
Organization: The Internet

The September, 1992 edition of the Andrew View, newsletter of the Andrew
Consortium, is available for anonymous ftp from 

	emsworth.andrew.cmu.edu  (128.2.45.40)

as ./newsletters/92Sept.d.   Subdirectories ASCII and PostScript contain
versions for the ATK-deprived.

If you haven't got ftp access, please send mail to 
	info-andrew-request@andrew.cmu.edu

Fred Hansen
Director, Andrew Consortium

PS:  You can try AUIS remotely.  For instructions:
	finger help@atk.itc.cmu.edu
Newsgroups: comp.soft-sys.andrew