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Text File | 1993-03-25 | 63KB | 1,331 lines

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 to specify the black threshold. If you already have plenty of pixels down at the black end of the range, simply key without moving the reference bar. Once you key , 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 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 ( 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!