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Text File | 1994-04-09 | 11.7 KB | 255 lines

MPATCH - The Monitor Patch Utility, V37.4 ========================================= WHY MPATCH? ----------- Some time ago, I upgraded my old A2000 with the latest Denise revision since I do a lot of writing and DTP on my AMIGA, and that 50 Hz PAL display started to hurt my eyes. The MULTISCAN mode was better, but my C1960 monitor seemed to have problems sync'ing on the 60 Hz signal: the picture was always stretched vertically, so I had to switch to MANUAL and adjust the vertical size manually. However, the PAL mode was then squeezed vertically, resulting in a very odd aspect ratio; so I had to switch from MANUAL to AUTO and back every time a program came up with a PAL screen. The EURO72 mode introduced with V38 was a bit better but its 640 x 400 screen tended to become quite crowded once I had one or two CLI windows and the SE window open on it. Also some older software, like the famous PowerPacker, would always open a 60 Hz Productivity screen - so it had to be Multiscan (and switching manually) again. Then, one day, I scanned my C include files in search of some struct definition, and came across the monitor.h file, spotted the word VSYNCTRUE somewhere, and the rest was history. I had already toyed with various sync settings on a graphics card, and so I knew that some monitors (like the C1960) use the polarity of the sync signals to determine the aspect of the video signals they receive. I just had no idea that the ECS chipset supports positive sync signals as well. All I had to do is to find out where the BeamCon0 values are stored, and then write this small program. As I tested it, I found some other goodies to include, and so MPATCH grew ... USAGE ----- MPATCH can only be run from the CLI or Shell. MPATCH <monitor-name> [HSYNCTRUE][VSYNCTRUE][SYNCTRUE][LOLDIS] [HSYNCDELAY <delay>][VSYNCDELAY <delay>] <monitor-name> is the name of the monitor to be patched, e.g. "multiscan.monitor". Note that the ".monitor" extension *MUST* be given. Upper/lowercase is also important. V38 (2.1) monitor names are all in lower case; the new modes introduced with V39 (3.0), however, are mixed case. You must type "DoublePAL" or "DoubleNTSC" in order that these names be recognized. HSYNCTRUE - changes the horizontal sync signal's polarity to positive, or "true" (1) logical level. By default, all monitors have their syncs set to negative, or "false" (0) logical level. VSYNCTRUE - changes the vertical sync signal's polarity to positive, or "true" (1) logical level. By default, all monitors have their syncs set to negative, or "false" (0) logical level. SYNCTRUE - this is just a shortcut for HSYNCTRUE VSYNCTRUE; so if you specify SYNCTRUE, both syncs are switched to "true" (see above for details) LOLDIS - means "LOng LIne DISable". By default, every second scanline is a "long line" due to DMA timing restrictions. (The exact length of a PAL video scanline would be 227.5 DMA cycles per line. Since 0.5 cycles are impossible, every second scanline is displayed with a length of 228 cycles, hence the name "long line") This flag is set by default for all nonstandard modes. It should be set for the NTSC mode on PAL AMIGAs as well, at least if you are using "BBlank" or a similar utility that enables border blanking; otherwise the right border might look a bit wobbly. The following options can only be used with VGA/Multiscan modes, and will be ignored if used with the PAL or NTSC modes. HSYNCDELAY <value> - Modifies the position of the horizontal sync pulse in the horizontal blanking period. Negative values will move the display to the right, positive values will move it to the left. Although any value may be given, only values between -6 and +8 are reasonable. However, specifying a value beyond this range can do no harm, but will set the values to their allowable minimum or maximum respectively. VSYNCDELAY <value> - Modifies the position of the sync pulse in the vertical blanking period. <value> is in scanlines. Positive values move the display "up", while negative values move it "down". Any value may be given, but any value beyond the limits of the specified monitor will be ignored and the timings will be set to their allowable minimum or maximum respectively. The MPATCH command will most likely find a place in your startup-sequence or user-startup file. It must be inserted after the monitor definitions have been added to the system's database; I recommend putting it somewhere at the top of your user-startup file. HOW TO FIND THE CORRECT SETTINGS FOR YOUR MONITOR ------------------------------------------------- Before you start patching around, you should select your "default" display mode and adjust the monitor's controls so that it fills most of the screen and is centered horizontally and vertically. If you own a monitor that has a ADD/NOR switch (might also be labeled differently on your monitor, so consult your manual), set it to ADD (or whatever it is labeled). Such switches are found on the C1960 and some older VGA/SVGA multiscans. If your monitor supports PAL or NTSC display, use one of these modes to adjust the picture position, since it is not possible to adjust the position of any video mode with MPATCH. DO NOT TOUCH any of the monitor's controls afterwards - you won't need to anyway. (Close the small trapdoor if the monitor has one!) Now, open a shell window and invoke the Overscan Preferences editor. Select the monitor you wish to patch. Click on the "Set Text Overscan" gadget. Note to which direction the display is offset. Note whether it appears vertically stretched or squeezed. Click "Cancel" (or press <ESCAPE>), and activate your shell window. Now type: "mpatch <monitor_name>", where <monitor_name> is the name of the monitor you selected in the Overscan editor. Add one or more switches following the guidelines below: * If a mode appears stretched vertically (on my C1960, the MultiScan mode used to behave this way), try the SYNCTRUE switch. * If a mode appears squeezed vertically, try the VSYNCTRUE switch. * If a mode appears to be too far to the right, try the HSYNCDELAY option with a positive value. The effect of HSYNCDELAY is cumulative, so if you specify HSYNCDELAY 2, find the picture is still too far to the right, you must not type HSYNCDELAY 4, but HSYNCDELAY 2, since the old setting is still in effect. Typing HSYNCDELAY 4 would result in a total delay of 6! You may of course specify a negative value if you specified a value too large. Generally, monitors with a scan rate below 31.5 kHz tend to be too far to the right, such as the super72 or Double... modes * If a mode appears to be too far to the left, try the HSYNCDELAY option with a negative value. * If the right border appears to be somewhat instable, try the LOLDIS switch. Press <ENTER> and go back to the Overscan editor. Click "Set Text Overscan" again. The display should now be somewhat different. If you are satisfied, note all the switches you set and add a line at the top(!) of your "S:user-startup" file. If you wish to patch your workbench screen's monitor as well, you *MUST* insert the MPATCH command before any text is printed to the console window, or the changes will not affect the workbench screen. Repeat the above steps for all monitors you wish to patch. On my system, I have the following lines at the top of my "S:User-Startup" mpatch multiscan.monitor synctrue hsyncdelay -1 mpatch euro72.monitor hsyncdelay -1 mpatch super72.monitor vsynctrue hsyncdelay 8 mpatch DoublePAL.monitor synctrue hsyncdelay 4 mpatch DoubleNTSC.monitor synctrue hsyncdelay 4 With these settings, all modes(!) are perfectly centered on the screen, and the Super72 display fills the whole screen and has the correct aspect ratio. TECHNICAL DETAILS ----------------- A) SYNC POLARITY ---------------- Some monitors, especially the C1960 and most VGA Multiscans, use the polarity of the sync signals to determine the aspect of the picture they are displaying. The term "polarity", although frequently used in this context, is not fully accurate, because the sync signals are always standard TTL level (+5V) signals. A better description would be "active-low" and "active-high". By default, the sync signals are "active-low", meaning that the sync lines are always on high (or logical "1") level and go to low (or logical "0") level only at the end of a scan line (HSYNC) or frame (VSYNC). Setting HSYNCTRUE or VSYNCTRUE reverses this behaviour. Now the lines are by default on low level and go to high level only at the end of a scan line or frame. There are 4 possible combinations of sync polarity: HSYNC NEG, VSYNC NEG - standard setting HSYNC NEG, VSYNC POS - stretches the picture vertically (all modes) HSYNC POS, VSYNC NEG - ??? (no result on my monitor) HSYNC POS, VSYNC POS - squeezes display vertically (VGA/SVGA modes only) NOTE that this behaviour applies to the C1960 monitor. Your monitor might show a completely different behaviour or no reaction at all. B) SYNC DELAY AND PERIOD ------------------------ The HORIZONTAL blanking period starts at the end of each scan line and must be long enough for the beam to reach the left border before any data is being displayed. The horizontal sync signal must occur somewhere within this period. The "beam return" starts with the end of the sync pulse. Hence, the later the sync pulse occurs within the blanking interval, the more the picture will start to the left. NOTE that the sync/blanking counters are independent of display data fetch which is controlled by other register values, so it may well be possible to start scan line display before the beam has reached its leftmost position. MPATCH will not allow you to do so. The VERTICAL blanking period starts at the bottom of the frame and must be long enough for the beam to reach the top of the screen. The vertical sync signal must occur somewhere within this interval, and must be at least one scanline long in order to be recognized as a vertical sync signal by the monitor. The "beam return" starts with the end of the sync pulse. By modifying the position of the sync pulse within the vertical blanking interval it is possible to adjust the vertical picture position by a few scan lines. Specifying a positive delay will make the picture appear "higher", while specifying a negative delay will make the picture appear "lower". However, specifying a delay that is too great will result in a partially invisible display, as the beam needs some time to reach the top of the screen. MPATCH only modifies the sync signal's offset, not its length, since shorter syncs might result in some monitors not being able to catch the sync signals correctly. This is true for both the horizontal and vertical SYNCDELAY options. BUGS, COMMENTS, SUGGESTIONS: ---------------------------- MPatch has been successfully tested on an A2000 with ECS chipset, Kick/WB 3.0, 1 MB of chip memory and 9 MB of 32-Bit memory on my GVP GForce 030/25 board, and on a stock A1200 with nothing installed except a clock module, with a C1960 monitor attached to both of them. If you encounter any problems with MPatch, have some reasonable suggestions for improvements or find the program useful enough to send any money, feel free to write to the following address. I accept USD, DEM and ATS, but no credit cards :') You are also invited to contact me if you want to swap Japanese comic books, ANIME videotapes (Manga and others, VHS only) or disks with scanned japanese cartoon pictures. This is my private MsgPort address Gregor S. M. Kuhlmann Friedhofsallee 4/5 A-2451 Hof am Leithaberge AUSTRIA EUROPE from the end of July 1994, I can also be reached as Gregor S. M. Kuhlmann c/o Digital Sound & Vision Kauergasse 10/2 A-1150 VIENNA AUSTRIA EUROPE (sorry no email yet, but I'm working on it ...)