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Software Vault: The Gold Collection
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1993-03-25
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FAX483 480 LINE FACSIMILE PROGRAM
Dr. Ralph E. Taggart WB8DQT
602 S. Jefferson
Mason, MI 48854
COPYRIGHT NOTICE
The FAX483 program is copyrighted by Dr. Ralph E. Taggart.
You are free to make copies of this software for your own use and
to distribute copies to others, provided that no charge is levied
for such distribution. ALL OTHER RIGHTS ARE RESERVED. You may not
incorporate any elements of this program into other programs
offered for commercial sale without written permission of the
author.
INTRODUCTION
Since the introduction of the 480 line amateur facsimile
standard in the February 1993 issue of QST, there were two
additional upgrades (distributed as FAX481 and FAX482) to the
original program code. These upgrades improved the overall
operation of the program and added display of 120 lpm HF WEFAX.
The FAX480 mode has proved to be very popular among those who
have tried it and I was approached to add similar capabilities to
the Pasokon SSTV interface. As part of that effort, I elected to
create a single program structure to support both the Pasokon and
ViewPort interfaces. The FAX483 program is the ViewPort version
while FAX480P will be the Pasokon version.
Creating the common software skeleton gave me an excuse to
upgrade several aspects of the program. If you have never used a
previous version of FAX480, the changes are not relevant to you
and you can move on in the documentation. What follows is
intended as an outline of the major changes for the benefit of
previous users of the program.
ON THE AIR
On-the-air use by an ever-increasing number of
individuals has proved VERY gratifying. In addition to the
enthusiasm for the more detailed images (everyone considers
them MOST impressive), the FAX 480 mode has proved to be VERY
resistant to the effects of noise and QRM. Stations running
barefoot with simple antennas are getting excellent results.
Situations ranging from mediocre to poor for conventional SSTV
are yielding excellent fax images. You don't have to be a
"big gun" to get good results. In addition, the images hold up
very well when relayed from station to station. In short, it
looks like the mode will be a winner.
DISTRIBUTION FILES
The following files are included in the FAX483.ZIP
distribution file:
FAX483.EXE - the operating program
FAX483.DOC - this documentation file
HOUSE.480 - a sample fax image file
CONVERT.EXE - a file conversion program that converts old
image files (ie. image.a and image.b) to the new single-file
format (image.480).
K4OVV.STV - a sample SSTV image file
VGACAP.COM - the Gozum SHAREWARE program for image screen
capture.
HARDWARE REQUIREMENTS
The following hardware requirements must be satisfied for
proper operation of the FAX483 program:
(1) An IBM PC/AT/PS1/PS2 or compatible with a 10 MHz or
faster clock speed and a minimum of 640K of RAM.
(2) A VGA display adapter that is bios-compatible with
the IBM VGA standard. Virtually all VGA adapters meet
this requirement.
(3) A monochrome or color analog VGA monitor.
(4) A minimum of two 360K floppy disk drives, or a single
1.2 meg 5.25 or 1.4 meg 3.5 inch floppy drive, or a
hard drive. The choice of drive options has no effect
on the operation of the program but does impact the
number of fax or SSTV images that can be stored as well
as the speed with which images can be saved or loaded
from disk. All things being equal, you will enjoy the
program more if you have a hard-drive (a statement true
for most software), but, if you lack one, there won't
be any limitations on what you can do.
(5) An A&A Engineering ViewPort VGA SSTV interface, modified
by the addition of a 4 MHz clock circuit as described
in the February, 1993 issue of QST.
(6) An available parallel printer port.
SOFTWARE LIMITATIONS
On slower computers or those with lethargic VGA cards, the
system has to run flat out to keep up with the image data.
ANYTHING that slows down such a computer may result in a
situation where the system falls behind on receive, resulting in
a "tilted" image, even if the interface clock is right on
frequency. There are lots of things than can bog-down your
system. I know of at least one case where one station with a 486
was unable to keep up with the data while other stations were
doing fine on a 10 MHz 286! A poorly-implemented WINDOWS
installation can slow your system. Properly implemented PIF files
can allow WINDOWS and FAX480 to coexist without impeding the
operation of the latter. Some TSR programs may also steal clock
cycles and result in unpredictable problems. If you have
problems, try operating the program under DOS with no TSRs and
see how things work. On a very complex system, it may be
difficult to avoid some of these "enhancements", since things can
be going on in your system even though you think you have
programs like WINDOWS completely disabled.
If you have unexplained difficulties, try preparing a floppy
boot disk for your A drive that will bring you system up under
DOS with no TSRs or other operating enhancements and see how the
program works. The present release does not make any great memory
demands on the system since the screen memory actually serves as
the image buffer. There is no need for elaborate memory
management and there is minimal chance that the program will
conflict with your system in terms of resources. The reverse is
not necessarily so, however.
INSTALLATION
Hardware
Installation is a simple matter of connecting the parallel
port cable between the interface and your computer and making the
needed audio connections. A shielded audio cable should be
connected between the receiver audio output and the SSTV IN jack
on the rear of the interface. A microphone is connected to the
MICROPHONE IN connector on the front panel while a cable connects
between the MICROPHONE OUT connector on the rear apron and your
transceiver's microphone input connector. The two microphone
connectors on the interface have the the following pin-outs:
Pin Function
1 Microphone audio
2 PTT "hot"
3 PTT return/ground
4 Microphone ground
A connector compatible with your transceiver input should be
installed at the transceiver end of the cable between the
interface and the rig. Consult the documentation for your
transceiver for the equivalent pins on your transceiver's
microphone connector. You can test the connections by operating
your rig with the interface either on or off. In either case, the
rig should key with normal microphone audio. The microphone
patches through the interface at all times unless the interface
is actually transmitting an image.
The cable used to connect the parallel port of the computer
with the DB-25 connector on the rear apron of the interface is a
double-male and is usually sold as a "parallel cable". Such
cables will have all connector pins wired. Similar-appearing
cable, usually marked "serial cable", will not be fully-wired and
will NOT function with the interface.
Software
If you have a hard drive, the best results will be obtained
by operating the software from the hard disk. From your root
directory, create a FAX subdirectory by typing:
md\fax <ENTER>
Switch to the new directory:
cd\fax <ENTER>
Now copy ALL the distribution files into this directory.
Assuming the files were on a disk in the A drive, you would type:
copy a:*.* <ENTER>
In operation, you would enter the FAX subdirectory to execute
the program and all image files would be stored in the
same subdirectory. Image file capacity is limited only by
available hard-disk storage.
The FAX483 program can be operated from a floppy drive
without any penalty other than the number of file images that can
be stored on a single floppy disk. Copy the programs noted above
on to a formatted disk for the drive in question. Operating from
a floppy drive would normally involve booting the software from
your program disk, after which you can remove the program disk
and insert formatted disks for image file storage. Each fax image
file requires 128K of available disk storage while SSTV image
files use 64K, so you will have the following image capacity for
various floppy drive configurations:
Drive Fax Images SSTV Images
360K 2 5
720K 5 11
1.2 meg 9 18
1.44 meg 11 22
These figures assume that no other files are stored on the disks
in question.
MAJOR CHANGES FROM PREVIOUS RELEASES
The following is a summary of the changes in the program
from previous versions (FAX480-FAX482). If you have never used
the FAX480 program before, simply move ahead to the OPERATION
section. The next two sections are intended for previous FAX480
users.
(1) Simplified image file structure. In previous releases,
each fax image was broken down into two 64K files. In the current
release, images are stored as single 128K files. This makes it
much easier to keep track of your images and maintain your image
files. This does mean however that previous users will have to
convert their "two-piece" image files for use in the new version.
A program, CONVERT.EXE, is included in the distribution .ZIP file
to accomplish this and it is very quick. See the following
section on IMAGE FILE CONVERSION before you attempt to use the
software for the first time.
(2) Faster screen writes. When loading or recalling an
image, it could take up to 30-40 seconds to "paint" the screen if
you had a slow CPU or VGA card. Those operations now take only 2-
3 seconds with the new software.
(3) Elimination of the printing option. It seems that few
people were using this option so I dropped it from this release.
If you really want it, I will incorporate it into a utility that
will print directly from your image files.
(4) Major improvement of the 307K screen-capture file
conversion. This option is now called directly from the Main Menu
and posts the image to the screen as conversion proceeds. In
addition to providing visual feedback, the routine now takes just
30 seconds on my 386 system instead of the 5+ minutes that used
to be required! It also incorporates complete control over which
portion of the original 640x480 image you include in the 512x480
fax image file.
(5) Simplify the Calibration Tone option on fax. This
function now results in the automatic transmission of 5 seconds
of black tone (1500 Hz), making it more convenient to use. Since
it only takes about 2 seconds to recall an image, I expect that
more stations will be making use of the Tuning Indicator and
Calibration Tone options. Operation of this option on SSTV has
not changed, since other stations vary in terms of the alignment
tones they may need for tuning.
(6) Fast (a few seconds) on-screen contrast enhancement of
displayed fax images. If you like the result, you can save it
using the original file name (thus replacing the original file),
or you can save it to a new name. Of course you can quit without
making any changes or saves if you desire.
(6) Fast FAX to SSTV conversion. Now that I have greatly
speeded up the conversion of screen capture files to FAX, the FAX
image files are now treated as the primary image files. The SSTV
file conversion option now consists of a routine that quickly (10
seconds or so) creates an SSTV file from a FAX image file. Given
the speed of conversion, interesting FAX images can be converted
on the fly for re-transmission on SSTV for the benefit of
stations that do not have fax capability. This should contribute
to peaceful coexistence.
New Users can bypass the next section but those of you who
have used previous versions should read the next section prior to
using the program for the first time.
CONVERTING IMAGE FILES
A program to convert the two-piece image files of previous
releases into the single image file used by the new program is
included in the distribution .ZIP file (CONVERT.EXE). This
program converts the original image files and then deletes them
once conversion is complete. Since you probably are very
protective of your previous image files, I would suggest that you
back them up to a floppy prior to conversion. In this way, in the
unlikely event that you don't like the new program, you can
recover the files in their original format. Alternatively, if you
have set up a FAX directory, as indicated under software
installation, you can copy image files you want to convert from
your old FAX480 directory. You can also copy over any SSTV images
you wish. In this way, all your old setup is retained until you
decide you want to stay with the new program.
Assuming that CONVERT.EXE is in your working directory,
simply boot the program:
convert <ENTER>
You will see a menu of the available image files and you
will be requested to input the file you wish to convert (no
extension). At that point the program will display the familiar
FAX480 display screen and the file will be loaded and the image
will scroll down the screen in the normal fashion. When the image
has been displayed, it will quickly (a few seconds) be converted
to the new format, the screen will clear, and you have the chance
to convert another file. You will note that the file you have
just converted is now missing from the directory listing. To quit
the conversion program, simply input <Q> in place of a filename
and you will be returned to DOS.
When you have converted the last file in the directory, you
will be unceremoniously dropped back to DOS via an error message.
I didn't think that an elaborate error handling routine was
required for a one-time event!
If you now type:
dir *.480 <ENTER>
you will see all your old files listed, but they are now single
128K (131,000+ bytes) files with a *.480 extension.
OPERATION
Booting the Program
Normal operation would involve switching to the FAX480
directory, at which point you would boot the software:
fax483 <ENTER>
If you want to use the call-insertion function provided with SSTV
transmission, you boot by inserting your call after the program
name:
fax483 urcall <ENTER>
It doesn't matter if you enter your call in upper or lower case -
it will be converted to upper-case for storage.
To make booting the software even move convenient in the
future, you might consider using your word processor (in the non-
document or ASCI mode) to create a batch file (FAX.BAT) in
your root directory. This file would have the following format:
cd\fax480
fax483 urcall
cd\
with the batch file installed, simply typing:
fax <ENTER>
from the root directory and you will move automatically to the
FAX480 subdirectory and boot the software with your call. When
you exit the program, you will be back in the root directory.
As the program boots, a "CHECKING PARALLEL PORTS..." message
will be posted as the computer checks the three possible parallel
port addresses looking for the interface. The interface unit
should be connected and turned on PRIOR to booting the software.
If the program doesn't find the interface unit, an error message
will be posted, outlining the possible problems. You can continue
at this point (type <C>) or exit the program (type <Q>). If you
continue, all image file functions will be available to you but
the program will not let you use the receive modes or transmit
modes, since, lacking a connection to the interface, the program
would "hang up" and require a keyboard or hard reset to get back
on line. If the problem was a lack of power to the interface or
failure to connect or switch the parallel port cable, simply
hit the <T> key to repeat the port test. If you don't intend to
use the interface for a particular operating session, hit <C> to
continue. Almost all program functions will be available to you
in such a case, except that the system will not let you display
or transmit images. Typing <Q> will cause you to exit the program
if your problem requires more in the way of thought or action.
MAIN MENU
This menu is the crossroads of the FAX483 program and
gives you access to all operating functions.
Fax functions are organized into three columns -
CRYSTAL-LOCKED, LINE TRIGGERED, and MISC. OPTIONS and this
organization will be followed in the functional descriptions
which follow. Also note that a 16-step grayscale is posted at the
bottom of the display screen. The brightness and contrast
controls of your monitor should be adjusted to clearly resolve
each of the steps.
The Main Menu incorporates a screen-saver routine that will
blank the display after 5 minutes with no keyboard activity.
Hitting ANY key on the keyboard will instantly restore the menu
display.
CRYSTAL-LOCKED Options
These options represent the preferred display modes since
they use the crystal-clock reference that gives the mode its
extreme noise immunity. Your options here are as follows:
<1> FAX480 Auto-start
This is the preferred receiving mode since image loading is
initiated by the start tone and controlled by the crystal clock
circuit, providing the maximum in noise immunity. This mode is
used to display transmissions from other stations where the image
is transmitted directly from the other computer ("live").
Although you can initiate display at any time prior to the
start of image transmission, the best results will be obtained if
you key <1> as soon as you hear the distinctive 5 second start
tone. When you key <1> the image display screen will appear
and the ** ACTIVE ** message will be posted to let you know
that the system is attempting to load an image. The start
routine is EXTREMELY reliable, even under VERY poor band
conditions. BE PATIENT as nothing will happen immediately. In
order to reserve the screen for useful image display, the auto-
start routine bypasses the 5 second start tone and most of th 5
second phasing interval that follows before it begins to display.
Do NOT expect to see anything for about 8 seconds after you have
keyed <1>!! If you have problems with auto-start, it is probably
a result of mis-tuning on the station you wish to receive. Check
out the <T>une Display option under MISC. OPTIONS for how to
assure that you are accurately tuned on receive.
If you entered the mode by accident, you missed the start
tone, or there was a problem with the transmitting station,
simply hit the <A> key to exit. The ** ACTIVE ** message will be
replaced by ** COMMAND **, at which point you can key <Q> to
return to the Main Menu. See <3> below for how to display an
image when you have missed the image start tone.
Assuming image transmission proceeds normally, the received
picture will be displayed, line by line, in the 512 x 480 display
window. Reception can be aborted at any time by hitting the <A>
key, at which point the ** ACTIVE ** message will be replaced by
** COMMAND ** and you can use <Q> to exit back to the Main Menu.
Assuming the transmission proceeds to completion, when the
display window is filled with image data, the ** ACTIVE **
message will be replaced by ** COMMAND **. At this point, the
received image will be retained and you have three options, as
indicated by the menu on the left side of the screen:
<S>ave Image
<T>ransmit
<C>ontrast
<Q>uit
See the FAX POST-DISPLAY options for the use of these functions.
<3> FAX480 Manual Start
If you missed the start tone for any reason, or the display
did not auto-start, you can display the image by keying <3>. In
all other respects, the option is identical to the preferred
auto-start routine.
<5> 120 LPM HF WEFAX
This is the 120 line/minute HF WEFAX display routine.
Display will require that you be accurately tuned to the fax
station, a requirement which is complicated by the fact
that there is no voice transmission to use as a guide. See
the discussion on the use of the tuning indicator for advice on
how to tune a fax signal. To start display, key <5> AFTER the
distinctive image start tone. Once display is complete, you have
the same options available as for the 480 line receive
options. If you select the TRANSMIT option, the image will be
transmitted in the 480 line format - NOT 120 lpm.
LINE-TRIGGERED Options
The ONLY reason for use of this option is to display images
that you have recorded on audio tape. These options do NOT have
the noise immunity of the crystal-locked options since each line
is triggered by a received sync pulse, which can be disrupted by
noise or interference.
<2> FAX480 Auto-start
The operation of this option is identical to that described
for FAX480 Auto-start under the CRYSTAL-LOCKED options.
<4> FAX480 Manual Start
This option functions identically to the FAX480 Manual Start
option under the CRYSTAL-LOCKED options.
FAX POST-DISPLAY OPTIONS
Any of the fax display options (1-5) will provide the
following options when image display is complete:
<S>ave Image
<T>ransmit
<C>ontrast
<Q>uit
<S>ave Image
Keying <S> will switch you will be prompted to provide the
name to be used for the image save. This name can be any valid
DOS filename (8 characters max.) and should not incorporate any
extensions. If you are using a floppy drive, be sure a disk is in
the drive with enough capacity to hold the 128K image. Normally
the file will be created in the default drive/directory. You can
save to another drive/directory by including the appropriate path
data in the file name you provide. NOTE: Files save to another
drive/directory will NOT appear on the listing when you attempt
to load images from the fax menu. If you want access to the image
you have saved, the file must be transferred at a later time. See
the IMAGE FILES section before attempting to do so. The image
remains posted during and after the save operation (it takes just
a few seconds). If you want to return to the Main Menu after a
save, use the <Q> option described below.
<T>ransmit
Hitting the <T> key will key the interface and begin image
transmission. When you use this option for the first time, you
will need to adjust the MIKE GAIN control on the interface
for at RF output reading on your transceiver that is between
1/2 and 2/3 of the PEAK reading normally observed with voice
transmission. Keeping the audio level down will reduce
distortion and the possibility of over-driving the transmitter.
It is also important since fax transmission (like SSTV) involves
a 100% duty-cycle and you do not want to overheat your final
amplifier stage(s). Using a dummy load to make the gain
adjustment is highly recommended. The setting of the MIKE GAIN
control has no effect on normal microphone audio, which is
normally set by a level or gain control on your transceiver. If
you change this control, readjustment of the MIKE GAIN control
will probably be required.
Transmission can be aborted at any time by hitting the <A>
key, at which point the interface will drop out of the transmit
mode and the ** ACTIVE ** prompt will be replaced by **COMMAND**.
When transmission is completed (normally about 2 minutes
and 18 seconds, the interface will drop out of the transmit
mode and ** ACTIVE ** will be replaced by **COMMAND**.
<C>ontrast
Sometimes you will encounter situations where your file
image is less than optimum in terms of contrast. Some hand-
scanner files have this problem, some color to grayscale
conversions are a bit soft, or you may receive a lower-contrast
image due to mis-tuning or less than optimum image quality from
the transmitting station. Keying <C> will result in a simple and
fast on-screen contrast enhancement. If you like the result, you
can save the image (<S>) to the old file name (thus replacing the
original) or to a new name.
If you wish to use this option on a received image, save the
image first, and then do the enhancement.
<Q>uit
Keying <Q> will result in a return to the Main Menu. The
current displayed image is saved to a temporary disk file and can
be restored in about 2 seconds using the <R>ecall Last Image
option from the Main Menu.
MISC. OPTIONS
<L>oad from Disk
When you key <L> to invoke this function, the names of all
FAX483 image files on the default directory/drive will
be displayed. Each of these will have an ".480" extension (see
the section on FAX IMAGE FILES). Enter the name of the file to
load (less the .480 extension) and the image file will be
loaded, the system will switch to the image display screen,
and the image will be transferred to the screen, a process that
takes about 3 seconds. Any of the secondary functions (<S>ave,
<T>ransmit, or <Q>uit can be used if desired. Note that you can
save the image to the default directory/drive under a
different file name or you can save to another
directory/drive with the save or a different file name. This
provides a convenient way to copy interesting images to a floppy
for backup purposes or to another disk to provide to another
fax/SSTV operator.
<R>ecall Last Image
If you have previously received an image or loaded one from
disk, that image will be posted to the active window of the
display screen. At that point, you have the same options
available to you as described under the receive modes.
If you have not loaded or received an image since the
program was booted, a black screen will be displayed. IMPORTANT
NOTE: Although unlikely, if you do something that causes the
program to abort, the temporary disk buffer file will be
retained and you can recall the image when you re-boot.
<C>alibration Tone
Keying <C> from the Main Menu will cause the interface to
send a 5 second 1500 Hz (black) calibration tone, at which point
you will be returned to the Main Menu. You would normally use
this option if the other station requests a calibration tone to
assist them in accurately tuning your signal.
<T>une Display
Proper grayscale rendition requires accurate
tuning/carrier insertion at your receiver. Usually you can
achieve sufficient accuracy by tuning for natural voice quality,
but this can be ambiguous at times. The tune display
provides a graphic aid for precision tuning. Two
vertical, parallel lines define the range from 1200 Hz (Sync) at
the top of the display to 2300 Hz (White) at the bottom. If you
are uncertain about the accuracy of your tuning, request that the
transmitting station transmit a 1500 Hz (Black) calibration tone
prior to sending an image. Key <T> for the tone display and you
will note a horizontal line between the two vertical lines.
Carefully adjust the receiver tuning (use the RIT control in the
case of a transceiver) until the horizontal line is lined up with
the two arrows. These arrows are positioned at the 1500 Hz point
on the frequency display. When the line is properly aligned with
the arrows, your are precisely tuned for image reception.
WEFAX tuning presents a special problem as there is no
voice signal to use, nor are sync pulses transmitted. Your best
option is to wait for a start tone - this should produce two
horizontal bars on the tune display. Carefully tune (you
have about 5 seconds) to place one bar at black and the other
at white.
No matter what your tuning mode, hitting the <Q> key will
return you to the fax menu.
<F>ile Conversion
The file conversion option provides a means to convert 307K
screen-capture files to the disk/screen format used by the
FAX483 program. While the conversion routine itself is quite
simple, it is part of the larger question about sources of
images, image file formats and the like. For this reason, the
operation of the file conversion option is deferred to a wider
discussion of image file conversion at the end of the
documentation.
<S>STV
Keying <S> will route you to the SSTV menu.
<Q>uit FAX480
Keying <Q> will result in an exit to your operating system
(typically DOS). All temporary files are erased on exit to
conserve disk space. If you have previously displayed a fax image
that you want to keep, be sure to save it prior to exit or it
will be lost.
FAX IMAGE FILES
All FAX480 images are stores as 128K disk files with a *.480
extension. These files can be erased, copied, or renamed just
like any other DOS file. If you rename a file, be sure to include
the *.480 extension or the file will NOT be displayed on the
image file directory when you go to load images. Images save to
another directory can be copied to the FAX480 directory, at which
point they are displayed on the image directory. You may wish to
copy over-the-air images to another directory (or to floppies)
for long-term storage, just to reduce the "clutter" on the image
directory display when you go to load images.
FILE CONVERSION MENU
Keying <F> from the Main Menu will invoke the file
conversion option. Some discussion of screen image capture,
sources of images, and image formats is appropriate prior to
looking at how you perform the image conversion.
SCREEN IMAGE CAPTURE
The key to the conversion option is the ability to
capture computer images from various sources into a form the
conversion routine can manipulate. This is accomplished with a
family of programs called "screen capture" software. As noted in
the original article on the fax standard, I prefer the VGACAP
shareware program, which I have included on the distribution
disk. This is a TSR program that you boot from its resident
directory:
vgacap <ENTER>
Aside from a short (and transient notice), you then proceed to
run your applications software in the normal manner. VGACAP sits
in the background until you have an image displayed, at which
point you invoke the "capture" by keying <Alt-F4). At this
point, VGACAP takes over and converts the screen image (without
altering it) to a binary data file. If the image was in the 640 x
480 x 16 format (suitable for fax), the result will be a 307K
binary file containing all the data for the screen image. This
file will reside in the current directory and will be named:
screenxx.raw
where xx is a number from 00 to 99, depending upon how many
screen captures you have executed since booting VGACAP and
whether there are other screenxx.raw files left on the disk from
previous conversions. There will also be a matching palette file
(screenxx.plt), which we do need. Other capture programs
will operate in a similar manner, but I would suggest
the use of VGACAP for the most predictable results.
VGACAP.COM is now bundled in the .ZIP distribution file. This
program is SHAREWARE and you should read the text associated
with it. The file conversion routine converts these 307K
screenxx.raw files to 480 line FAX483 files. In order that we
have a screen file that CAN be converted, we must execute the
capture under very specific conditions, within the context of a
viewing program.
IMAGE VIEWERS
Many image options (see below) will support full-screen
display of images they create, but if this is not the case, they
will support conversion of the images to one of several popular
formats (.GIF, .PCX, .TIF, .IMG, or .TGA). In such cases, you
need a viewing program that will import the image files and
provide the full-screen display needed for capture as noted
above. There are many programs that will do this, but one I have
had good success with is VUIMAGE, a shareware package available
on the DRIG BBS. This is an excellent program supporting .GIF,
.PCX, and .TIF display, a wide range of monitor modes, and a very
wide range of scaling options. Most of my images, from a variety
of sources, are displayed using VUIMAGE to execute the actual
screen capture. I set the mode to 640x480x16 for high resolution
images I intend to capture as fax files. By adjusting the
scale, I can get just the screen display I wish to capture,
gaining considerable control over the dimensions and coverage
of the ultimate image file.
SOURCES OF IMAGES
Hand scanners and flatbed scanners can also be used to
generate images and most of these devices come with programs that
support the 640 by 480 x 16 VGA mode. Programs such as VGACAP can
be used to capture the screen images as described above.
TV frame grabbers can be used if they support high
resolution image capture. Most inexpensive boards will only
capture 240-256 video lines. In such cases, it makes little
sense to transmit these as fax, since 240 line SSTV formats will
match the resolution of the captured images. A high quality
black and white camera will typically produce sharper
images than a comparable color camera. These high
resolution frame grabbers usually support 640 x 480 VGA display
so programs like VGACAP can capture the images.
Other sources, such as paint programs, image libraries, BBS
sources, etc. can all provide images suitable for conversion to
fax.
COLOR VS. MONOCHROME
Image conversion is quite predictable with monochrome images
and most unpredictable with color. B&W hand-scanners and TV image
capture boards generate such monochrome images automatically and
present no problems when used with viewers such as VUIMAGE.
Color images must be converted to monochrome prior to screen
capture is acceptable results are to be obtained. Many viewing
programs allow color images to be displayed with a monochrome
palette (VUIMAGE, despite its other useful qualities, does NOT!),
in which case you can screen grab with good results. Programs
such as Graphics Workshop can be used to clip, re-scale, and
perform color to monochrome conversion. It the image is in a 640
x 480 format with 16 colors, programs such as PC Paintbrush can
be used to convert color images to grayscale.
All of this sounds very complex to start with, but you can't
hurt anything by experimenting. Once you have played with
grabbers, viewers, and images for a bit, it will all become
second nature.
307K IMAGE CONVERSION
This routine will convert the 307K screen binary files to
FAX483 fax image files. You will be prompted to provide three
items of information:
(1) The name of the file to convert
This is going to be a numbered screen file that should be entered
with NO extension:
screen06 <ENTER>
If the screen file is not in the current directory, specify the
path (using normal DOS conventions) as part of the filename:
\vuimage\screen06 <ENTER>
It is VERY important that the designated screen file actually
exist, for if it does not, the program will created a 0K file of
that name and proceed to convert an all-black image. No harm
done, but it wastes time to no good purpose. If you want to abort
the file conversion, enter a <Q> in place of the screen filename.
(2) Name of the fax file
This can be any valid DOS filename (8 char. max.), entered with
NO extension:
alison <ENTER>
The routine will automatically append the .480 extension to the
final image file (ie. alison.480). Try to assure that your name
is NOT identical to that of an existing file or the old file will
be over-written with the new one. When in doubt, use a "dummy"
name (like <screen06>, for example, and rename the file later
under DOS.
(3) Starting pixel (0-128)
The converted file will represent a 512 x 480 subset of the
original 640 x 480 screen image. The starting pixel selection
controls the position of the fax image, relative to the original
screen display. Selecting <0> will result in the converted image
shifted to the extreme left of the displayed image, omitting the
last 128 pixels of every line. Set to <128>, the fax "window"
will be shifted to the extreme right, omitting the first 128
pixels of every line. If set to <64>, the fax image will be
centered on the display image.
Once you have entered the required data, the display will
indicate that the image palette file is being re-ordered, after
which (a few seconds) the monitor will shift to the normal
display screen and the image will be posted as conversion
proceeds. When display is complete (about 30 seconds or so on my
386 system), the new image file will be written to disk and you
can use the <Q> key to escape to the Main Menu, you can transmit
the image (<T>), or you can save it to still another filename
(<S>).
At 307K per file, screenxx files eat up disk storage, so it
is usually a good idea to erase the .raw and .plt files that you
have successfully converted. This can be done individually:
delete screen06.*
which will simultaneous erase both files, or you can do a global
deletion:
delete screen*.*
which will eliminate ALL screen files (.raw and plt) in the
current directory.
SSTV OPTIONS
I originally added the SSTV options simply as a convenience,
since I felt that most ViewPort operators would be using John's
software. While they do, particularly those with 32K Hi-color
cards, I am amazed at the number of folks who are using the SSTV
option on a regular basis. In part, this is because the program
is so easy to use, but it also is the result of the fact that
good quality black and white pictures can be quite superior to
mediocre color, especially if you have a standard VGA display.
A factor I had not considered is the fact that the ability
to send and receive SSTV easily while operating the fax program
is a real plus in that the SSTV guys on frequency don't get as
restless if there is the opportunity to work slow scan as well as
fax. The ability, with this version, to make fast conversions, in
real-time, between fax files and SSTV files, helps as well, as a
received fax picture (or one of your own files) can be re-
transmitted on SSTV for the benefit of those without fax
capability.
RECEIVE FUNCTIONS
This column lists all the available slow-scan receive modes,
including Robot B&W and color modes, Scottie modes, and Amiga AVT
94. Each will briefly be described in the sections which follow.
Prior to this however, a few general notes about SSTV reception
are in order. When you key ANY of the modes listed below, the
program will post the SSTV display screen and proceed to display
the incoming picture. Since the SSTV display screen has lower
resolution than the fax screen, the additional information that
can be included is more limited.
For example, the fax receive modes post an ** ACTIVE **
prompt when displaying an image and a ** COMMAND ** prompt to
indicate that you can input commands. On SSTV, this function is
achieved with a white square that appears in the lower left of
the screen. When actively acquiring an image, this square is
displayed (equivalent to the ** ACTIVE ** prompt on fax). When
the square disappears (equivalent to ** COMMAND **), you can
initiate one of the post-display options to be discussed shortly.
While the square is posted and image data is being scrolled
onto the screen, the keyboard ignores ALL keyboard inputs EXCEPT
the <A> key for the abort function. If you need to abort display
for any reason, simply key <A> and the square will disappear,
allowing you to selection one of the post-display options. These
will be discussed under SSTV POST-DISPLAY OPTIONS in a later
section.
Proper tuning is essential for reliable SSTV display. You
will also note that, except for the synchronous 36 second option,
all the SSTV options will be far less immune to noise than a fax
station under the same conditions.
In all the modes that follow, you initiate display by simply
hitting the indicated key. In most cases, best results will be
achieved if you use the key just after you hear the image start.
Remember, although you can display images transmitted in the
various color formats listed below, they will be displayed as
high-quality (64 grayscale values) grayscale images. If you want
color, use the ViewPort VGA. Note that, if you have a standard
VGA adapter that will only handle 256 display colors, you may
prefer the quality of the monochrome images.
Robot B&W Modes
<1> 8/8.5 Second
Most stations will not be using the original 120/128 line
SSTV format (all the other modes produce 200/240 line images) but
there are operators out there using older equipment that cannot
transmit or receive 240 line pictures. Display will take about 8
seconds. Note that the image appears quite "coarse" as it is
scrolled on the screen, because of the small number of pixels.
Some software displays 8 second/120 line pictures in a smaller
format for this reason. FAX480 displays the image at normal size
and solves the resolution dilemma AFTER the image has been
scrolled onto the screen. You will note that just after the
screen is filled, the image suddenly looks softer and a good-deal
less "digital" in appearance. This is because the program does a
pixel averaging routine to produce a much better looking image on
the display.
Unlike many programs, you CAN re-transmit an 8 second image,
in either 8 seconds or 36 seconds. It will look just like the
original in the former case but will look even better in 36
seconds because of the processing used for the display.
While not indicated on the menu, this option will also prove
for display of Robot 12 second color images.
<2> 36 Second <S>
This is a nice mode because it provides full resolution but
without the time required for color display. It is the preferred
mode for SSTV operation between FAX480 stations. Note the <S>
that follows on the menu display. This provides for display of of
36 second transmissions using the crystal clock instead of the
normal line triggering. If you are exchanging 36 second pictures
with another FAX480 station, key <S> instead of <2> AFTER the
image starts. The result will be reception with essentially the
same noise immunity as fax. When conditions are poor, the <S>
option may be worth a try with other stations since some Robot
and Amiga units will produce a pretty straight picture.
Robot Color
<3> 36 Second
The 36 second Robot color mode (NOT the same thing as 36
second B&W) lets stations transmit 240 line color images in less
time. For many reasons, it is a compromise that will produce
results inferior to the use of the 72 second color mode.
<4> 72 Second
This is the "standard" mode for SSTV color transmission in
that virtually any system can receive and transmit in this
format. The mode is used a lot so you will become quite familiar
with the key location! This is the highest quality Robot color
mode and will produce excellent monochrome pictures.
Scottie Color Modes
Although the Scottie modes add a line sync pulse, they are
designed as synchronous modes, keyed to a crystal clock, much
like the FAX480 system (but with 240 lines of resolution). As
presently implemented, I use the sync pulse, so you will not see
any inherent noise immunity. NOTE: If someone can provide me with
PRECISE timing data for these modes, I would be happy to convert
the routines to synchronous operation.
<5> Mode 1
This mode provides optimum resolution and it gets used a lot
because it works better than Robot 72 under noisy conditions.
<6> Mode 2
Like Robot 36 color, Scottie 2 is a compromise in sending
240 line images in less time. Like the Robot 36 color mode, the
pictures lack the quality of the Scottie 1 mode, but they do take
less time and are MUCH better than 120 line images.
Amiga AVT Color
Although there are several AVT color modes, I support the
AVT 94 because it is the most widely used. Precision tuning is a
MUST for AVT display and if the display will not trigger, you are
probably slightly off frequency and should resort to the Tune
Display option.
<7> 94 Second
This is a synchronous mode and I have retained that in this
software (there are no sync pulses). When you key <7>, the white
"active" square will be posted as the software attempts to decode
the header. If it does so, display will begin just as you hear
the distinctive header replaced by the actual video data. If it
cannot decipher the header, the square will go away. There is no
way to restart display if this occurs. As noted above, the
problem is likely to be mis-tuning of your receiver. If you want
to try again, ask the other station to end an alignment tone and
use the Tune Display option.
SSTV POST-DISPLAY OPTIONS
When display of any SSTV mode is complete (the white square
at the lower-left disappears), you have several options,
indicated by the letters posted at the left side of the screen:
<S>
<T>
<C>
<R>
<Q>
These same options are visible if you have loaded an image file.
Each will be described below.
Save Image
Keying <S> will save the image currently on display. The
screen will clear and you will be asked to provide a name for the
image file. This can be ANY valid DOS filename (8 characters
maximum, no extension). If you use the name of an existing image
file, the old file will be over-written. Type the desired file
name and hit <ENTER> and the image will reappear for a moment, it
will be saved under the name you provided (with an .STV
extension), and you will be returned to the SSTV Menu. The
process takes just a second or two. If you want the image back,
key <R> from the SSTV Menu to recall it (discussed below).
Otherwise, you can get it back later using the Load Image from
Disk option.
Transmit
Keying <T> will cause the screen to clear and you will see
the following options:
<1> 8 Second
<2> 36 Second
<Q>uit
Keying <1> will transmit the displayed picture in the 8
second/120 line format, while <2> will send it in the 36
second/240 line format. The latter is obviously preferred unless
you are working someone with older gear, such as the Robot 400,
which cannot handle 240 line pictures. In either case, the image
will be re-posted, the interface will key, and the image will be
transmitted. When transmission is complete, the interface will
drop out of transmit and the image will remain posted. To
transmit again (in the same or another mode), simply key <T>.
If you need to abort transmission for any reason, use the
<A> key. If you are using your interface for the first time, see
the notes under the fax transmission section for how to set the
transmit audio level.
Contrast Expansion
Images may be received with less-than optimum contrast due
to slight mis-tuning or poor image setup at the transmitting end.
Always save such an image first, but you can then either load it
from disk (or recall it after the save) and perform a contrast
enhancement by keying <C>.
If you key <C>, the computer will BEEP to indicate the
command was received, but nothing else will seem to happen for a
minute or so while the computer does an analysis of the pixel
distribution of the image. The process takes about 55 seconds on
my 20 MHz 386. The computer will BEEP again when the analysis is
complete and the posted image will be cleared and a graph of
pixel brightness values will be displayed. The graph consists of
a horizontal bar where the extreme left is black and the extreme
right is white. The length of the vertical lines below the bar is
proportional to the number of pixels at various brightness
levels.
You must now specify what thresholds you would like for the
black and white ends of this range. For example, if the image
seemed too light, there will probably be a gap between the left
end of the bar and where you first see a significant clustering
of pixels. If the picture was too dark there will be a similar
gap at the right (white) end of the bar. A really "soft" picture
may have gaps at both ends! If this is all more than you want to
deal with, you can use <Q> to quit with no changes, but let's
forge ahead.
The first task is to specify the black threshold. If you
look carefully, you will se a sort vertical bar extending ABOVE
the bar at the extreme left. If you key <+> (use <SHIFT> and <+>
if your keyboard doesn't have a dedicated <+> key) to move this
bar to the right until you reach the first significant cluster of
pixels. If you over-shoot, the <-> key will move the bar back to
the left. When it is position where you want it, key <B> to
specify the black threshold. If you already have plenty of pixels
down at the black end of the range, simply key <B> without moving
the reference bar.
Once you key <B>, the bar will disappear and reappear at the
extreme right (white). Now use the <-> key, if needed, to move
the bar to the left until you reach the first significant cluster
of pixels (or <+> to move back if you over-shoot). When the bar
is positioned where you want it, key <W> to establish the white
threshold. You can key <W> right away if you already have
significant clustering at the white end of the contrast range.
Once you key <W>, the image will be re-posted and the
computer will scroll down through it, readjusting pixel values.
Unless you made only very minor threshold changes, the effect
should be fairly obvious. On my system, it takes about 1.5
minutes to scroll down and the computer will BEEP when the job is
finished.
If you like the altered picture more than the original, use
<S> to save it to the original filename. You can also save it
with another name if you wish. If you don't like the effect, you
can use <Q> to quit. If you want to experiment with other
threshold settings, load the original image from disk and try
again.
Repair
Noise, interference, or slight mis-tuning can result in line
trigger errors where lines are offset slightly to the right,
spoiling an otherwise nice image. If you have just received the
image, save it first (<S>) but then call it back. The defects can
be almost completely repaired by keying <R>. When you do so, a
small horizontal bar will appear just beyond the upper right edge
of the display. Use <U> or <D> to move the bar up or down until
it is opposite an offset line (look carefully). When it is, key
<A>, and the line in question will slide LEFT by exactly one
pixel. Key <A> as many times as required to properly position the
line. You can then reposition the bar (<U> or <D>) to repair
other lines. When you are done, use <D> to move the bar down to
the bottom image margin and the repaired image will be replaced
by a prompt, asking if you want to replace the image with the
repaired version. Key <Y> to replace or <N> to leave the original
intact.
It takes a few minutes to "repair" and image but it may be
worth it to fix a valuable image marred by a few line offsets.
Quit
Keying <Q> will return you to the SSTV Menu. The last image
posted can be recalled at any time using the Recall Last Image
function to be discussed shortly.
OTHER FUNCTIONS
<R>ecall Last Image
If you have previously received an image or loaded one from
disk, that image will be posted to the active window of the
display screen. At that point, you have the same options
available to you as described under the receive modes.
IMPORTANT NOTE: Although unlikely, if you do something that
causes the program to abort, the temporary disk buffer file
will be retained and you can recall the image when you re-boot.
<L>oad Image from Disk
When you key <L> to invoke this function, the names of all
FAX483 SSTV image files on the default directory/drive will
be displayed. Each of these will have an ".STV" extension.
Enter the name of the file to load (less the .STV extension)
and the image file will be loaded, the system will switch to
the image display screen, and the image will be transferred to
the screen, a process that takes about a second. Any of the
secondary functions (<S>, <T>, <C>, <R>, or <Q>uit can be used
if desired. Note that you can save the image to the default
directory/drive under a different file name or you can
save to another directory/drive with the save or a different
file name. This provides a convenient way to copy interesting
images to a floppy for backup purposes or to another disk to
provide to another fax/SSTV operator.
<C>alibration Tone
Keying <C> from the SSTV Menu will post a menu where you
have the choice of transmitting a sync, black, or white tone or
using <Q> to quit. Make you choice on the basis of what the other
operator is expecting. In the case of FAX480 users, the best
choice is always black (1500 Hz). The interface will then key and
transit the desired tone until you hit the <Q> key, at which
point you will return to the SSTV Menu.
<T>une Display
Proper grayscale rendition requires accurate
tuning/carrier insertion at your receiver. Usually you can
achieve sufficient accuracy by tuning for natural voice quality,
but this can be ambiguous at times. The tune display
provides a graphic aid for precision tuning. Two
vertical, parallel lines define the range from 1200 Hz (Sync) at
the top of the display to 2300 Hz (White) at the bottom. If you
are uncertain about the accuracy of your tuning, request that the
transmitting station transmit a 1500 Hz (Black) calibration tone
prior to sending an image. Key <T> for the tone display and you
will note a horizontal line between the two vertical lines.
Carefully adjust the receiver tuning (use the RIT control in the
case of a transceiver) until the horizontal line is lined up with
the two arrows. These arrows are positioned at the 1500 Hz point
on the frequency display. When the line is properly aligned with
the arrows, your are precisely tuned for image reception. Other
SSTV system have different alignment options (sync, keyed sync
and black, etc., in which case you should tune appropriately.
No matter what your tuning mode, hitting the <Q> key will
return you to the SSTV menu.
<F>ile Conversion
Most FAX480 users will be using ViewPort VGA software for
their primary SSTV operations and this software supports file
inports in a number of formats. In deciding what type of file
conversion to support in the FAX480 SSTV module, I decided that
the best option was to provide a means to convert FAX480 files to
SSTV. Now that the new screen-capture file conversion is very
fast and much easier to use, operators will be accumulating a lot
of interesting fax files. If these files could be RAPIDLY
converted to SSTV, it would help to keep the no-fax SSTV
operators at bay when they start to get restless. This version
operates very fast (about 10 seconds on my 386), so it is quite
practical to create an SSTV file of a fax image that has just
been received and transmit it for the benefit of those on
frequency without fax capability.
When you key <F>, you will see a display of all of the
FAX480 image files (just like the fax Load from Disk option), and
you simply type the name of the file you want to convert (no
extension, as usual) and hit <ENTER>. The system will display the
480 line image (2-3 seconds) and will then proceed to make the
conversion, a process that will take another 6-8 seconds on most
systems. When conversion is complete, the SSTV image will be
posted VERY briefly as it is saved, and you will be back to the
file menu. You can proceed to convert another file or exit at any
time by using <Q>. The filename applied to the SSTV picture is
the same as that of the fax file, except that it has the .STV
slow scan extension instead of the .480 fax version.
In addition to being fast, the routine does an excellent job
of conversion because in employs a pixel averaging scheme that
increases the number of grayscale values even while reducing
resolution. The output is a very nice looking SSTV version of the
picture. The top and bottom 20 lines are clipped in the
conversion, but, other than that, the images are equivalent.
FAX480 OPTIONS ON OTHER SYSTEMS
When you operate FAX480 on the air, you will get questions
about the mode and how to implement it. Obviously, getting a
ViewPort is the simplest solution and quite economical. Most
FAX480 users will agree that this mode alone justifies the cost
of the interface. As long as an operator has the computer, the
ViewPort is a reasonable add-on, even if they don't plan to use
it for SSTV.
At least one station has developed software for the MFJ
interface running on a Mac (talk about a $100 saddle on a $10
horse), so a PC version may be practical. John Hoot of Software
Systems Consulting has modified the SSC PC-Fax program to handle
FAX480 so that is another option. I am working on a version for
the Pasokon, so it may not be long before we have most computer
bases covered. The Amiga is a problem because I don't know of
anyone programming for that system. If you know of anyone, have
them contact me, as the Amiga should be a resonavle platform in
its 640 x 400 mode.
That leaves the Robot folks and there is no way to implement
480 lines on that unit. You could sample the image but that
provides no advantage, other than looking in! I think the best
option for Robots connected to computers is to use the Robot as a
"dumb terminal" with the computer providing the actual display.
If I can get a Robot manual, I may work up such a program!