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|Looking for CoCo help? If you are trying to do something with your old Color Computer, read this quick reference. Want to contribute to this wiki? Be sure to read this first. This CoCo wiki project was started on October 29, 2004. --OS-9 Al|
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The DS-69 Digisector is a video digitizer for the Color Computer, the CoCo 2, or the CoCo 3. It was marketed by The Micro Works of Del Mar, California. It digitizes 5 or 16 levels of gray from an NTSC video signal at resolutions of 128 x 128 pixels, or 256 x 256 pixels. The DS-69B is capable of running at 2MHz, and adds a filter to remove unused color information from the video signal, producing an image with less noise.
Unlike frame grabbers, which can digitize an entire video frame in real time, the DS-69 samples only a portion of the video frame at a time, and must build up a complete image from samples of many consecutive video frames. For this reason, it cannot be used to grab good quality images of moving scenes in real time. If the picture changes before the DS-69 has finished sampling it, the resulting image will appear torn and distorted -- an effect which is usually not desired. The DS-69 can be used most effectively with video cameras to capture still lifes, portraits, or static scenes. Or it can be used with a VCR that has a high quality pause. DVD players and other video sources that can produce a stable, NTSC video signal should also work.
The DS-69 itself is a cartridge that plugs into the expansion slot on the Color Computer. In length it is between the ROM Paks and the full-length disk controllers, or Tandy's RS-232 pack. On the end is a single RCA jack into which an NTSC video source is plugged. The enclosure for the digitizer is made from black, vaccuum-formed plastic in two parts -- a box into which the PC board is snapped, and a separate lid glued on top.
The hardware came with C-SEE software for digitizing video, displaying the resulting image on the CoCo's screen, printing it, and saving it to tape or floppy disk. When used on a disk system, the DS-69 requires a MultiPak Interface or equivalent.
The 256 x 256 16-level images produced by the DS-69B can be of rather good quality, if they are derived from a good video source. In fact, even on the CoCo 3, which has a 16-color display mode, but only has 4 real shades of gray in its 64-color palette, these images must be dithered to approximate all 16 levels. When loaded into a graphics program like CoCoMax III, false-color images could be made by assigning non-gray colors to the different palette slots. This produced a picture that was clearly a digitized image, but had an interesting aesthetic quality.
The DS-69B could also be used to produce high-color images by taking separate red-, green-, and blue-filtered images of the same scene. This could be done with a black-and-white video camera and some appropriately colored gels or filters, but the subject and camera would need to be completely still for quite a long time as each of the three images was digitized and saved in turn. A more effective way to produce such an image was to use an electronic color splitter, available around the time the DS-69 was sold. These color splitters were intended for similar video digitizers used on the Commodore Amiga. They would take a color video signal, and output the red, green, and blue components of the video in turn, as selected by a switch on the outside of the unit. When combined with a camcorder with digital freeze frame, one could capture high-color images of any scene.
(As an interesting side note, the DS-69 owner's manual credits Tim Jenison as a contributor to both the hardware and software. Tim was the author of the original CoCoMax paint program, and later founded NewTek, which produced the DigiView video digitizer for the Commodore Amiga, which worked in a similar way to the DS-69, and had an optional automated color filter wheel for producing color images.)
Additional software is required to combine the three component images into a high-color picture. No provision for this was made in C-SEE. The Rascan digitizer, which came on the market a few years later, came with software for displaying such 4096-color images on the CoCo 3 by rapidly switching the display between the red, green, and blue component images, and relying on persistence of vision to mix the colors together in the viewer's perception. Programs like Roger Taylor's Projector 3, Sockmaster's Hicolor, and view 4.4 for OS-9 can display such high-color images, either directly, or after having been converted to another file format.
In addition to the C-SEE program, the DS-69 included a BASIC program called RANDAC (RANDACB for the DS-69B) that would poke in a machine language routine which could digitize in 64-levels of gray. A BASIC program called SLOWPIC could then be used to call the RANDAC routine and capture a 256 x 256 pixel 64-level image on disk. This image takes up 64K and is not directly displayable on the CoCo. Another incuded sample BASIC program called BURGLAR could check for movement in a room by sensing changes in a continually scanned image.