ftp.cdrom.com/pub/cdrom//cdrom.tar/cdrom/faq/faq_mm

Internet Message Format | 1992-07-17 | 30KB

From: [e-mail] (Philip Bailey)
Newsgroups: comp.multimedia
Subject: Comp.Multimedia FAQ
Keywords: FAQ
Message-ID: <[e-mail]>
Date: 25 Jun 92 18:25:41 GMT
Sender: [e-mail] (News system)
Distribution: comp.multimedia
Organization: Center for Educational Computing Initiatives, at MIT
Lines: 738
Nntp-Posting-Host: abelard.mit.edu

There have been a number requests for the Frequently Asked Questions
file in comp.multimedia, I have been following the group for at least
6 months and do not believe one has ever been posted.  Some of the
requests have even come from our organization.  With this in mind and
the understanding that the information will be of use to The Center
for Educational Computing Initiatives at MIT, I am willing to compile
& distribute the comp.multimedia FAQ.

I can be reached via email at:
    pbailey.ceci.mit.edu    ( Philip H. Bailey )

A mail account for the comp.multimedia FAQ has been set up for FAQ specific
communications.

If you have questions and/or answers that you would like added, please
send mail to:
    [e-mail]

The following is a compilation of various articles I have collected,
I will try & credit sources.  I will be adding more topics as I have the time.

Please let me know what you think of the FAQ, are the entries to long, any
comments etc. Should I even be doing this?

---  comp.multimedia FAQ  ---

This message is automatically posted on a regular schedule in an
effort to cut down on repetitive questions in comp.multimedia.  It
was last changed on 25june92.

This information has not been confirmed, and all disclaimers apply.
Neither The Center for Educational Computing Initiatives or Philip H.
Bailey is responsible for the accuracy of the information.

If you have questions and/or answers that you would like added, please
send e-mail to:
    [e-mail]

  If you don't want to see this posting every week, please add the
subject line to your kill file.  Thank you.


I can be reached via e-mail at:
    pbailey.ceci.mit.edu    ( Philip H. Bailey )

---
- - - - - - - - - -

Contents:

 1) Goals of this FAQ
 2) Interactive Multimedia Protocol- what is it?
 3) General references for graphics, from Jef Poskanzer's comp.graphics FAQ
 4) Are there any source codes avail for FLI players
 5) P*64 Video -- H.261
 6) Microsoft's RIFF & MCI formats
 7) Information on Touch Screen Technology

There exist FAQ's in the following groups which may be of interest for
multimedia resources:
    alt.binaries.pictures
    alt.cd-rom
    alt.graphics.pixutils
    alt.hypertext
    comp.graphics
    comp.ivideodisc

--------------------
 1) Goals of this FAQ

The goal of this FAQ is not to duplicate information available via
other news groups, but to deal with the issues specific to multimedia.
This does not mean that questions about CD-ROMs will not be included,
but that questions about which CD-ROM to buy, might be better served
in the alt.cd-rom FAQ.

--------------------
 2) IMA Standard

>From: [e-mail] (Walt Thode)
Subject: Re: IMP: Interactive Multimedia Protocol- what is it?
Keywords: IMP
Date: 19 Feb 92 00:41:50 GMT
References: <[e-mail]>
Sender: [e-mail]
Reply-To: [e-mail] (Walt Thode)
Distribution: comp
Organization: Navy Personnel R&D Center, San Diego
Lines: 62

In article <[e-mail]> [e-mail] (Flint Pellett) writes:
>I recently got ahold of a fragment of a document that I was told
>was written by an Interactive Multimedia Steering Committee that
>is working on developing a Mil Std 1379d (if I got that right), and in
>it they refer to a "Chinatown Group report" that states the following:
>
>"Howard Mirowitz (Mitsubishi) reported that three trial implementations
>of the Chinatown Interactive Multimedia Protocol (IMP) are underway.
>The implementations are for X Windows, the Macintosh, and Microsoft
>Windows."

The information above is essentially correct.  There is a Military
Standard, MIL-STD-1379D, titled "Military Training Programs," that
provides standard guidance to military personnel.  Appendix D of this
document was adopted from the Interactive Multimedia Association's
"Recommended Practices for Multimedia Portability," and describes a
standard virtual device interface that sits between interactive
courseware and the hardware it runs on.  The general idea is to
facilitate portability of applications in general.  The DoD is interested
in it because it facilitates portability of its interactive courseware
both within the DoD and between the DoD and the commercial/industrial/
educational marketplace.  The specification of the current version of
this interface was begun some years ago; thus, it currently applies to
what might be called the "interactive videodisc" world.

More recently, the IMA has begun work on extensions and revisions to the
interface described above.  It currently has a wide range of focus groups
dealing with areas where multimedia standards might be beneficial to the
industry in general.  The "Chinatown Group" (the name did indeed come
from the habit of the members, who represented many of the Silicon Valley
"biggies," of meeting in various San Francisco Chinatown restaurants) was
working independently on a more complete, object-oriented version of a
standard interface.  The "Chinatown Group" was subsequently incorporated
as one of the focus groups within this new IMA compatibility effort.

>Obvious next questions:
>
>1. Has anyone heard of or seen this IMP in action, or is it vapor?
>2. If it doesn't exist yet and is still in development, what dates
>   are targeted?
>3. If you have seen it used, what does it do for you?
>4. Is it possible to see it somewhere, or even better yet, get a copy
>   of some implementation of it from somewhere?

For more information about the specifics of the trial implementations of
the IMP, contact Howard Mirowitz (Mitsubishi Electric) at [phone]
or as [e-mail].

For more information about the IMA's Compatibility Project, contact its
headquarters at [phone].  Philip Dodds, the head of the effort,
can be reached as [e-mail].

For more information about the interactive video version of the IMA
standard interface, contact Scott Lewis, the chair of the IVPC Special
Interest Group.  His phone number is [phone], and he can be
reached as [e-mail].

For more information about the DoD's adoption and mandating of
MIL-STD-1379D Appendix D, contact me at [phone].

--Walt Thode   Internet:  [e-mail]
                   UUCP:  {everywhere_else}!ucsd!nprdc!thode

----------------------------
3) General references for graphics questions:

The following is from Jef Poskanzer's comp.graphics FAQ of 19may91
Check the latest version for more details, the `*` entries are repeated
here for convenience.

Contents:

*    1-) General references for graphics questions.
     2-) Drawing three-dimensional objects on a two-dimensional screen.
     3-) Quantizing 24 bit images down to 8 bits.
     4-) Converting color into grayscale.
     5-) Quantizing grayscale to black&white.
     6-) Rotating a raster image by an arbitrary angle.
*    7-) Free image manipulation software.
     8-) Format documents for GIF, TIFF, IFF, BIFF, NFF, OFF, etc.
     9-) Converting between vector formats.
     10-) How to get Pixar films.
     11-) How do I draw a circle as a Bezier (or B-spline) curve?
*    12-) How to order standards documents.
     13-) How to FTP by email.
     14-) How to tell whether a point is within a planar polygon.
     15-) How to tesselate a sphere.


1-)
    Computer Graphics: Principles and Practice (2nd Ed.), J.D. Foley,
      A. van Dam, S.K. Feiner, J.F. Hughes, Addison-Wesley 1990, ISBN
      0-201-12110-7
    Principles of Interactive Computer Graphics (2nd Ed.), Newman and
      Sproull, McGraw Hill, ISBN 0-07-046338-7
    Procedural Elements for Computer Graphics, David F. Rogers, McGraw
      Hill, ISBN 0-07-053534-5
    Mathematical Elements for Computer Graphics 2nd Ed., David F. Rogers
      and J. Alan Adams, McGraw Hill, ISBN 0-07-053530-2
    Applied Concepts in Microcomputer Graphics, Bruce Artwick, Prentice-Hall,
      ISBN 0-13-039322-3
    Digital Picture Processing, vols. 1&2, Azriel Rosenfeld and Avi Kak,
      Academic Press 1976
    Three Dimensional Computer Graphics, Alan Watt, Addison-Wesley, ISBN
      0-201-15442-0
    An Introduction to Ray Tracing, Andrew Glassner (ed.), Academic Press
      1989, ISBN 0-12-286160-4
    Graphics Gems, Andrew Glassner (ed.), Acedemic Press 1990, ISBN
      0-12-286165-5

More specific technical references can be obtained from an ACM/SIGGRAPH
mail daemon.  Send a message to

    [e-mail]

Just place important keywords in the Subject: field of your mail message.
E.g.,

    Subject: ray traced musical spheres

Please be as specific as possible.  "Graphics" is too vague and would
only flood the mailer.  Additional keywords help.  Some of the complete
reference files are obtainable via anonymous ftp thru gatekeeper.dec.com
(pub/misc/graf-bib) [megabytes].  Additional years references will be
added over time.

An automatic mail handler at Brown University allows users of "Computer
Graphics: Principles and Practice," by Foley, van Dam, Feiner, and
Hughes, to obtain text errata and information on distribution of the
software packages described in the book.  Also, users can send the
authors feedback, to report text errors and software bugs, make
suggestions, and submit exercises.  To receive information describing
how you can use the mail handler, simply mail [e-mail]
and put the word "Help" in the Subject line.  Use the Subject line
"Software-Distribution" to receive information specifically concerning
the software packages SRGP and SPHIGS.

Finally, all C code from "Graphics Gems" is available via anonymous ftp
from weedeater.math.yale.edu.  Look in the directory pub/GraphicsGems/src,
and get the README file first.

7-) Free image manipulation software.

There are a number of toolkits for converting from one image format to
another, doing simple image manipulations such as size scaling, plus
the above-mentioned 24 -> 8, color -> gray, gray -> b&w conversions.
Here are pointers to some of them:

    PBMPLUS, by Jef Poskanzer.  Comprehensive format conversion and image
    manipulation package.  The latest version is always available via
    anonymous FTP as export.lcs.mit.edu:contrib/pbmplus.tar.Z and
    ftp.ee.lbl.gov:pbmplus.tar.Z.  The version of 22nov89 (which currently
    is still the latest version, except for the one official patch so far)
    was posted to comp.sources.misc, and is therefore accessible via mail
    to one of the archive servers.  This version is also available in the
    X11R4 release tape.

    IM Raster Toolkit, by Alan Paeth ([e-mail]).
    Provides a portable and efficient format and related toolkit.  The
    format is versatile in supporting pixels of arbitrary channels,
    components, and bit precisions while allowing compression and machine
    byte-order independence.  The kit contains more than 50 tools with
    extensive support of image manipulation, digital halftoning and format
    conversion.  Previously distributed on tape c/o the University of
    Waterloo, an FTP version will appear someday.

    Utah RLE Toolkit.  Conversion and manipulation package, similar to
    PBMPLUS.  Available via FTP as cs.utah.edu:pub/urt-*,
    weedeater.math.yale.edu:pub/urt-*, and freebie.engin.umich.edu:pub/urt-*.

    Fuzzy Pixmap Manipulation, by Michael Mauldin <[e-mail]>.
    Conversion and manipulation package, similar to PBMPLUS.  Version 1.0
    available via FTP as nl.cs.cmu.edu:/usr/mlm/ftp/fbm.tar.Z,
    uunet.uu.net:pub/fbm.tar.Z, and ucsd.edu:graphics/fbm.tar.Z.

    Img Software Set, by Paul Raveling <[e-mail]>.  Reads and
    writes its own image format, displays on an X11 screen, and does some
    image manipulations.  Version 1.3 is available via FTP as
    export.lcs.mit.edu:contrib/img_1.3.tar.Z, and
    venera.isi.edu:pub/img_1.3.tar.Z along with a large collection of color
    images.

    Xim, by Philip R. Thompson.  Reads and writes its own image format,
    displays on an X11 screen, and does some image manipulations.
    Available in your nearest X11R4 source tree as contrib/clients/xim.
    A more recent version is available via ftp from video.mit.edu.  It uses
    x11r4 and the OSF/Motif toolkit to provide basic interactive image
    manipulation and reads/writes GIF, xwd, xbm, tiff, rle, xim, and other
    formats.

    xloadimage, by Jim Frost <[e-mail]>.  Reads in images in various
    formats and displays them on an X11 screen.  Available via FTP as
    export.lcs.mit.edu:contrib/xloadimage*, and in your nearest comp.sources.x
    archive.

    TIFF Software, by Sam Leffler <[e-mail]>.  Nice
    portable library for reading and writing TIFF files, plus a few tools
    for manipulating them and reading other formats.  Available via FTP as
    ucbvax.berkeley.edu:pub/tiff/*.tar.Z or uunet.uu.net:graphics/tiff.tar.Z

    xtiff, an X11 tool for viewing a TIFF file.  It was written to handle
    as many different kinds of TIFF files as possible while remaining
    simple, portable and efficient.  xtiff illustrates some common problems
    with building pixmaps and using different visual classes.  It is
    distributed as part of Sam Leffler's libtiff package and it is also
    available on export.lcs.mit.edu, uunet.uu.net and comp.sources.x.
    xtiff 2.0 was announced in 4/91; it includes Xlib and Xt versions.

    ALV, a Sun-specific image toolkit.  Version 2.0.6 posted to
    comp.sources.sun on 11dec89.  Also available via email to
    [e-mail].

    popi, an image manipulation language.  Version 2.1 posted to
    comp.sources.misc on 12dec89.

    ImageMagick, an X11 package for display and interactive manipulation
    of images.  Uses its own format (MIFF), and includes some converters.
    Available via FTP as export.lcs.mit.edu:contrib/ImageMagick.tar.Z

    Khoros, a huge (~100 meg) graphical development environment based on
    X11R4.  Khoros components include a visual programming language, code
    generators for extending the visual language and adding new application
    packages to the system, an interactive user interface editor, an
    interactive image display package, an extensive library of image and
    signal processing routines, and 2D/3D plotting packages.  Available via
    FTP as pprg.unm.edu:pub/khoros/*.

Don't forget to set binary mode when you FTP tar files.  For you MILNET
folks who still don't have name servers, the IP addresses are:

    export.lcs.mit.edu        18.30.0.238
    ftp.ee.lbl.gov        128.3.254.68
    cs.utah.edu            128.110.4.21
    nl.cs.cmu.edu        128.2.222.56
    venera.isi.edu        128.9.0.32
    ucbvax.berkeley.edu        128.32.133.1
    weedeater.math.yale.edu    130.132.23.17
    freebie.engin.umich.edu    141.212.68.23
    pprg.unm.edu        129.24.13.10

Please do *not* post or mail messages saying "I can't FTP, could
someone mail this to me?"  There are a number of automated mail servers
that will send you things like this in response to a message.  See
item 13 below for details on some.

Also, the newsgroup alt.graphics.pixutils is specifically for discussion
of software like this.  You may find useful information there.


12-) How to order standards documents.

The American National Standards Institute sells ANSI standards, and also
ISO (international) standards.  Their sales office is at [phone],
mailing address is 1430 Broadway, NY NY 10018.  It helps if you have the
complete name and number.

Some useful numbers to know:

CGM (Computer Graphics Metafile) is ANSI X3.122-1986.  GKS (Graphical
Kernel System) is ANSI X3.124-1985.  PHIGS (Programmer's Hierarchical
Interactive Graphics System) is ANSI X3.144-1988.  IGES is ASME/ANSI
Y14.26M-1987.  Language bindings are often separate but related numbers;
for example, the GKS FORTRAN binding is X3.124.1-1985.

Standards-in-progress are made available at key milestones to solicit
comments from the graphical public (this includes you!).  ANSI can let
you know where to order them; most are available from Global Engineering
at 800/854-7179.

-------------
4) Are there any source codes avail for FLI players

>From: [e-mail] (Frank van der Hulst)
Subject: Re: FLI Format
Date: 21 Jun 92 02:23:07 GMT
Organization: Dept. of Comp. Sci., Victoria Uni. of Wellington, New Zealand.
Lines: 15

In article <[e-mail]> [e-mail] writes:
>Are there any source codes avail for FLI players, I'm trying to write one for
>both Macintoshes and Amigas...

There is a file called FLILIB.ZIP on Simtel (MSDOS.GRAPHICS I think) which
contains C source code for FLI encoders & players. Be warned that this is
somewhat machine-specific, particularly in terms of MS/LS byte first stuff.

It also contains some Intel 8086 assembler routines (not a lot).

I've ported part of this (the part which creates a FLI) to Unix, including
translating the assembler into C. You can find that in a file called
PVQUAN13.ZIP on garbo.uwasa.fi or Simtel.

Frank.

---------------------------
5) P*64 Video -- H.261

>From: [e-mail] (Richard Stephen)
Subject: Re: P*64 Information Request
Keywords: standard, video coding
Date: 4 May 92 10:13:12 GMT
Organization: Business Development, Telecom Corporation of New Zealand
Lines: 21

In article <[e-mail]> [e-mail] (Lawrence D'Oliveiro, Waikato University) writes:
>If it's any help, I have in front of me a photocopy of the article "Overview
>of the px64 kbit/s Video Coding Standard" by Ming Liou, published in
>Communications of the ACM, April 1991, Vol 34, No 4.

The definitive document is CCITT Recommendation H.261. It is only the
video coding algorithm. There may even be an equivalent ANSI document by
now. If you  want additionally the MUX/DEMUX arrangement of the
bit-streams within the 64 kb/s time-slots and where the video is
allowed to lie, read H.221.

regards
============================ Richard Stephen =============================
| Business Development              |  email: [e-mail]
| Corporate Strategy & Development  |  voice: [phone]
| Telecom Corporation of NZ Ltd     |    FAX: [phone]
| PO Box 570, Wellington, NZ        |


>From: [e-mail] (Thierry Turletti)
Subject: Re: P*64 Information Request
Keywords: H.261 CODEC
Date: 7 May 92 15:42:19 GMT
Organization: INRIA, Sophia-Antipolis (Fr)

We have implemented a software version of H.261 codec. It runs on top of UNIX
and X-Windows. The coder output is directed towards a standard TCP connection,
instead of the leased lines or switched circuits for which regular H.261
codecs are designed. This enable us to test video conferences over regular
internet connections.
The coder uses the simple video capture board "VideoPix" provided by SUN for
the SparcStation.
We have to polish it a bit, but the first release is now available by anonymous
ftp from avahi.inria.fr, in "/pub/h261.tar.Z".

The graphical user interface of the codec makes use of the Motif 1.1
toolkit. Therefore, you might experience some problems during
compilation if you have Motif release 1.0. In this case, you can use a
compiled version of the codec (the compilation was done on a
SparcStation IPX). It is available by anonymous ftp from
avahi.inria.fr in "/pub/h261_exe.tar.Z"


Thierry Turletti                    Project RODEO
e-mail: [e-mail]    INRIA Sophia-Antipolis
                                - FRANCE -

---------------------
6) RIFF & MCI

>From: [e-mail] (Matt Saettler)
Subject: Re: Compound File Formats, RIFF vs ODA
Date: 7 May 92 19:59:21 GMT
Organization: Microsoft Corporation

The RIFF format was developed by IBM and Microsoft.

Here is a copy of an article I posted many months ago...

With this posting, I'm announcing that I have uploaded the
IBM/Miscrosoft RIFF and MCI definition document to usenet.
Microsoft is making this document available for public download
from Compuserve, the MM Sys BBS, Microsoft Online,
and through anonymous ftp.

The files are available for anonymous ftp download from
the ~ftp/vendor/microsoft/multimedia directory on the
machine uunet.uu.net on the internet.

If you don't have anonymous ftp access, try Compu$erve
in the MULTIMEDIA or MSOPSYS forum, or Microsoft Online.

This document describes multimedia interfaces (MCI) and data
formats (RIFF).  IBM has committed to include support for these
in OS/2.  These interfaces are already supported in the Multimedia
Extensions for Windows (MME).  These extensions will be included
in Windows 3.1, and are in the current (final) beta.

Included in the RIFF file format is a waveform (audio) definition;
this format is the system standard for Windows and OS/2 (and, hence
a.b.s.d).

Here's the rmtxt.ztx.readme file:

This document is available in two forms: RTF and Text.

The source (compressed) files are:
Text:    RMTxt.zip(6 character) or RIFFMCIT.ZIP
RTF:    RMRTF.zip(6 character) or RIFFMCIR.ZIP

Documents are distributed to:
uunet.uu.net:     ~ftp/vendor/microsoft/multimedia
MM Sys BBS:    206 936-4082 9600,n,8,1
Compu$erve:    Go Multimedia, forum 6, go msopsys


The file formats and interfaces discussed here are supported in the
Multimedia Extensions to Windows.  In addition, IBM has stated that
they will support these formats and interfaces in OS/2

----------------------------------------------------------------------------
     Multimedia Programming Interface
     and Data Specifications 1.0

     Issued as a joint design by IBM Corporation and
     Microsoft Corporation

     August 1991

     This document describes the programming interfaces and
     data specifications for multimedia that are common to
     both OS/2 and Windows environments. These
     specifications may be enhanced to incorporate new
     technologies or modified based on customer feedback
     and, as such, specifications incorporated into any
     final product may vary.

     Microsoft is a registered trademark, and Windows is a
     trademark of Microsoft Corp.

     IBM and OS/2 are registered trademarks of International
     Business Machines Corporation.


Overview

     This document describes the file format and control
     interface specifications for multimedia. These
     specifications allow developers to use common file
     format and device control interfaces.


Resource Interchange File Format


     The Resource Interchange File Format (RIFF), a tagged
     file structure, is a general specification upon which
     many file formats can be defined. The main advantage of
     RIFF is its extensibility; file formats based on RIFF
     can be future-proofed, as format changes can be ignored
     by existing applications.

     The RIFF file format is suitable for the following
     multimedia tasks:

     o     Playing back multimedia data

     o     Recording multimedia data

     o     Exchanging multimedia data between applications
       and across platforms

     Chapter 2, Resource Interchange File Format,
     describes the RIFF format.


Multimedia File Formats


     A number of RIFF-based and non-RIFF file formats have
     been defined for the storage of multimedia data.
     Chapter 3, Multimedia File Formats, describes the
     following file formats:

     o     Bundle File Format

     o     Device-Independent Bitmap (DIB) and RIFF DIB file
       formats

     o     Musical Instrument Digital Interface (MIDI) and
       RIFF MIDI file formats

     o     Palette File Format

     o     Rich Text File Format

     o     Waveform Audio File Format


Media Control Interface


     The Media Control Interface (MCI) is a high-level
     control mechanism that provides a device-independent
     interface to multimedia devices and resource files.

     The Media Control Interface (MCI) provides a command
     set for playing and recording multimedia devices and
     resource files. Developers creating multimedia
     applications are encouraged to use this high-level
     command interface rather than the low-level functions
     specific to each platform. The MCI command set acts as
     a platform-independent layer that sits between
     multimedia applications and the underlying system
     software.

     The MCI command set is extensible in two ways:

     o     Developers can incorporate new multimedia devices
       and file formats in the MCI command set by creating
       new MCI drivers to interpret the commands.

     o     New commands and command options can be added to
       support special features or functions required by
       new multimedia devices or file formats.

     Using MCI, an application can control multimedia
     devices using simple command strings like open, play,
     and close. The MCI command strings provide a generic
     interface to different multimedia devices, reducing the
     number of commands a developer needs to learn. A
     multimedia application might even accept MCI commands
     from an end user and pass them unchanged to the MCI
     driver, which parses the command and performs the
     appropriate action.

     Chapter 3, Media Control Interface, describes MCI and
     its command set in detail.


Registering Multimedia Formats


     This document discusses several multimedia codes and
     formats that require registration. These multimedia
     elements include the following:

     o     Compression techniques

     o     RIFF form types, chunk IDs, and list types

     o     Compound-file usage codes

     o     Waveform audio format codes

     To register these multimedia elements, request a
     Multimedia Developer Registration Kit from the
     following group:RIFF forms;registering

     Microsoft Corporation

       Multimedia Systems Group
       Product Marketing
       One Microsoft Way
       Redmond, WA 98052-6399

     The Multimedia Developer Registration Kit also lists
     currently defined multimedia elements.

Any detailed feedback or questions to [e-mail], please.

Matt Saettler, Microsoft Multimedia Systems Group

----------------
7)
>From: Haydn Huntley <[e-mail]>
Subject: Re: Brands of touch screen monitors?
Keywords: monitors touch screen
Organization: Indiana University, Bloomington
Date: Fri, 17 Apr 1992 10:33:27 -0500

In article <[e-mail]> [e-mail] (Tauren N Mills) writes:
>I'm looking for sources and brands of touch screen monitors.

I've also been researching touch screen monitors and touch screen
panels.  Elographics sells both kinds of devices, and Edmark sells
just the panels.  Elographics' panels install relatively permanently,
while Edmark's use velcro.  Elographics' are much more expensive ~$700
for just the panel, additional for the monitor.  Edmark charges about
$275.  The advantage of the Elographics panels is that they are pretty
durable, and would be suitable for a public access kiosk, while the
Edmark panels would be the kind of thing you'd place on PC's at home
or in a classroom.

Phone numbers:
Elographics [phone]
Edmark      [phone]


--Haydn

;;  *****************************************************
;;  *  Haydn Huntley    [e-mail]  *
;;  *****************************************************

>From: [e-mail] (Brad Steele)
Subject: Re: Information of Touch Screen Technology
Date: 23 Jun 92 13:24:15 GMT
Organization: Ericsson Network Systems, Inc.

Are you talking hardware or software?

I know how they work in hardware.  There are a row of lensed
LEDs along the top and right of the screen.  Along the bottom
and left there are a row of photodiodes.  They are aligned so
that each photodiode can only detect the LED directly opposite
it.  The LEDs are turned on and the output from the photodiodes
are scanned.  When you put your finger on the screen you will
block a vertical light path and a horizontal light path.  This
will give the scanning chip coordinates that it passes on to
the computer.  Just for grins, put two fingers on a screen at
once.  The screen will pick a square either above and to the
left or below and to the right depending on the direction it
scans.  Why can't you see it?.  The LEDs are near-infrared.

Regards,
Brad Steele

>From: [e-mail] (Rodney Radford)
Subject: Re: Information of Touch Screen Technology
Date: 23 Jun 92 14:33:55 GMT
Organization: SAS Institute Inc.

>I know how they work in hardware.  There are a row of lensed

         [ rest of followup deleted for space ]

Yes, that is one method of implementing touch screen systems, but not the
only method. I have an old terminal from the Plato educational system that
used very small wires arranged in grid across the screen. One half of the
wires (either the horizontal or vertical wires) are attached to a flexible
membrane, while the other set is attached to a hard surface under the membrane.
As you touch the screen, the wires touch, and simple scanning hardware/software
can determine the position of the touch (this is very similar to the membrane
keyboard on most calculators work). The system I have supports 16x16 touch
points on a 512x512 black/white graphics screen.

There are very possibly, even other methods. Anybody else have any ideas?

---
Rodney Radford          || Computer Graphics/Imaging
[e-mail]      || SAS Institute, Inc.
[phone] x7703    || Cary, NC  27513
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End of FAQ

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