| ★ HARDWARE ★ VIDEO DIGITALISEUR ★ VIDI VIDEO DIGITISER (ROMBO PRODUCTION) ★ |
Caught in the act of digitising Chris Jenkins explains how a video digitiser can help you re-capture that special moment you captured on video As video equipment becomes more affordable, digitisers such as the Rombo Vidi become more popular. The Vidi will capture pictures from video tape, video cameras, or even other computers. The powerful image editing facilities make Vidi most useful if your intention is to produce a printed digitised image, or to incorporate black and white images into other programs. Indeed, AMS sells the Vidi digitiser with the Amstrad Pagemaker package, in order to produce digitised pictures for its desktop publishing programs. The Vidi comes with software on disc, or, for a small additional charge, on Rom. A ribbon cable connector and a video lead are also provided. The digitiser itself is a featureless black box; all picture control is through software. Control is available either through a system of menu bars, or using RSX commands in your own programs. The Vidi is a frame grabber rather than a slow scanner, able to capture up to six frames per second. This makes it possible to use a moving picture for your video source. Some digitisers can only cope with still pictures, and since the pause mode on many video machines creates "snow" and bands of interference on the picture, these are fairly useless.
Vidi images can be captured in three modes; Mode 2, which is high resolution but offers only two shades; Mode 1, medium resolution with four shades; or Mode 0, a special 16-shade limitation. Brightness, contrast, and picture alignment can be set before grabbing a frame, and saving it to disc or tape, printing it out to any Epson compatible printer or flipping to the previous frame. Each saved image can be assigned an individual filename, and "?" can be used for pattern matching. Files can also be deleted or catalogued from the Save menu. There are two separate types of file extension available; Bin is the normal screen only format, while the Art option gives two separate files, one the palette file Pal, containing the screen mode and colours, the other Scr which is the normal screen file. This option makes files compatible with Rainbird Art Studio files, meaning that your Vidi images can be further edited using this power graphics program. "Powerful image editing facilities make Vidi most useful if your intention is to incorporate black and white images into other programs" The print menu offers options to print the image horizontally or vertically, single or double strike, and with or without line feed. The control menu offers what control you have over screen colour; the ink, border and paper colour can be set to any of the CPC's available shades. In Mode 1, a different colour can be assigned to each of the four brightness levels. Also available is a Mode 0, which allows you to build up a 16-level image using successive shades of brightness. This obviously necessitates using a still image as your video source. The menu bar system is easy to use, but if you want to incorporate the Vidi into your own programs you will need some knowledge of Basic RSX programming. If you are using Basic 1.0 string variables have to be passed to the RSX routines, using commands such as A$="Picture":|View,@a$. Life is simpler with Basic 1.1, where you can use just | View, "Picture". The RSX commands include bank switching for 128K machines, ink, paper and border colour, brightness, contrast, clear window, copy screen, frame grab, convert to AMS Pagemaker format, compress image to quarter size, set frame position, and so forth. One of the most interesting RSX commands is VSprite. This allows you to copy a window from one part of the screen to another. The parameters are left, right, top and bottom of the source window, and X/Y coordinates of the top left hand corner of the destination. It's also possible to define a scan window in a similar way, so it should be possible to build up some interesting multi-image effects if you can handle the necessary RSX programming. The main opposition to the Vidi machine is the Electric Studio video digitiser, which was reviewed in Popular December 18, 1986. Though more expensive, this system comes with a built-in graphics manipulation program controlled by a light-pen (also provided). The colour control possibilities are much greater than those of the Vidi software, so this might be the better choice if you are interested in art for art's sake. Another slight catch to the Rombo system is that although the Rom software is available for £4.95, to use it you will need a £34.95 Rombox in which to mount the chip. Generously, though, Rombo will give you a free Vidi chip if you buy the Rombox. Unless you have some obscure technical application for a digitiser, the Vidi unit is probably of most use as part of desktop publishing system. If you are interested in digitised images in, for example, games programs, you will certainly need to use a graphics package such as Art Studio to get the best results. PCW |
|  |
