Classic Computer Magazine Archive START VOL. 5 NO. 3 / NOVEMBER 1990


JRI'S Genlock Explored




The JRI Genlock System
John Russell Innovations Inc.
P.O. Box 5277
Pittsburgh, CA 94565
(415) 458-9577
Mega, television
A must-have for anyone who's
looking for professional-quality
video output.

The JRI Genlock System lets you combine computer-generated images with an external video source such as a VCR or a video camera. In addition to being a genlocking device, it's also an encoder that lets you run your ST on any television. But what makes this board so special is that it accomplishes the genlocking process entirely through hardware. This means that all your software is automatically compatible with it. Furthermore, when genlocked to an external video signal, the board delivers a broadcast-quality RS170A NTSC signal for the first time on an ST.

There are several reasons why the built-in encoder included on STFMs cannot produce a high-quality video output, which eliminates its ability to genlock. First, the ST's video bandwidth is higher than the standard NTSC's; it is not possible to synchronize those two signals. Second, the signals of built-in encoders found on STFMs and produced by hardware add-ons such as VideoKey do not adhere to NTSC standards, making it impossible to synchronize these signals with professional video equipment because none of them are "interlaced" (i.e., a way to increase video resolution by doubling the number of horizontal scan lines then rapidly displaying them alternately. NTSC-standard video is interlaced).

Two Parts

The Genlock consists of two parts, the board itself and the remote-control unit. It also comes with an instruction manual and a disk that includes demos. Also on the disk is a DESKTOP.INF file that sets the Desktop colors in such a way that when genlocked to external video, the Desktop is shown over the moving image. The board, contrary to early reports, does not make use of the Mega's internal bus port. Instead, it fits into the socket of the video-shifter chip. Installing the board is very easy for an experienced hacker, but I recommend that the installation be done by your dealer, or JRI will install it for you.

The Genlock adds five additional ports to your Mega: Composite Video In (RCA connector), Composite Video Out (RCA connector), Audio Out (RCA connector), RGB/Computer, RGB/Genlock (both RGB connectors are the standard Atari monitor connectors) and finally, Remote (DIN connector). Furthermore, the Genlock sports the following three adjustment knobs: horizontal position of the computer graphic, hue of the incoming video-signal and lock. Lock is for adjusting the Genlock's synchronization signal with that of incoming video. The only time you may need to use it is when you try to genlock with a poor sync signal (such as the one from a poor-quality tape) .

Internally, there are four additional adjustment knobs for burst, bright, chroma and contrast. This means you can adjust the Genlock (with the aid of a vectorscope) to provide the best possible signal.

Monitor Ports

The port labeled RGB/Computer shows a graphic as it is transmitted from the computer and is independent of the remote-control unit. The second port, RGB/Genlock, lets you see the combined signals of the computer and the external video. In real-time situations, such as on-line video titling, you can use the Computer port as a preview monitor prior to sending the signal out for broadcast.

The wired remote control contains three switches and a fader knob. The switches control several features: Genlock ON/OFF, Mode Color/Mono (it supports monochrome, though no genlocking is possible and you'll not see the ST's high resolution mode in a normal TV or monitor) and Keying On/Off. The fader is used to perform fast or slow fades. If the Keying switch is off, you'll fade from video to computer; if on, your graphics will lay over the video image.

When genlocking, keep in mind that the input signal must be of high quality in order to obtain the best results. A poor quality signal forces the video to shake, because the Genlock cannot sync correctly to the incoming signal. Transitions using the fader are smooth and keying is clean. By planning your animations with the capabilities of the Genlock, you can create great special effects.

Perfect For Professionals

JRI's Genlock is perfect for professional video producers, because they can record on high-quality Betacam, 3/4- and 1-inch videotape recorders, for results as close to the original as possible. Plain old VHS just can't do justice to computer graphics.

But for those mere mortals who can only afford a Super VHS (S-VHS) video cassette, JRI will have ready, by the time you read this, the Super VHS upgrade (about $100) which will provide one set of S-VHS input/ output jacks; the output signal will be much better due to the increased resolution offered by S-VHS.

Although expensive, the JRI Genlock is a necessity for anyone who wants to produce professional-quality video productions.


Common Video Terminology


ADO (Ampex Digital Opticals): The trademark for a device used in TV stations and post-production houses to accomplish image transitions and special effects (page turns, mosaics, flips, rotations, size variations, etc.) with video.

Aliasing: A common display problem with computer graphics in which an image is displayed with jagged or stair-stepped edges (better known as jaggies) on diagonal lines, due to low pixel resolution.

Anti-Aliasing: A technique used to hide or smooth jagged edges in computer graphics by softening the transition between the foreground and background by interpolating intermediate shades of color between the two.

Cel: A single frame of an animation. The term originated in cartooning when the artist drew each image on a sheet of celluloid film.

Character Generator (or CG): A dedicated hardware device that creates text for use in video.

Chroma: The portion of a composite video signal providing color.

Chroma Keying: A widely used process in film and video production in which a subject is filmed or taped in front of a blue or green screen. When the film is processed the blue (or green) area is eliminated, leaving only the subject. The film can then be combined with another background creating a singular composed image.

Color 0: The color that was previously specified to become transparent when the computer graphics are overlayed on a video signal via a genlock. Everywhere in the image that color 0 appeared is now replaced with the video signal.

Composite Video: A single signal composed of chroma, luminance and a sync signal. It is currently the U.S. standard for television.

Digitizer: A hardware device that takes the analog video signal from a camera or VCR and converts it into digitally-defined pixels that a computer can display and modify.

Encoder: A hardware device that takes the individual components of an RGB signal and adds both horizontal and vertical sync signals to create a composite-video signal. The 520STFM and 1040STFM both come with a built-in encoder; 520s and 1040s that do not carry an M in the model name and Megas do not.

Frame: A complete video picture made up of 525 scan lines that are redrawn every 1/30 of a second in a standard NTSC broadcast.

Genlock (generator locking): A hardware device that extracts synchronization signals from incoming video and locks the computer's sync generator with that of the incoming video's source. The word is also used as a verb to describe the syncing of video equipment.

Interlacing: A method of increasing video resolution in which the number of horizontal scan lines are doubled then refreshed (rapidly displayed) alternately. NTSC-standard video is interlaced.

Keyer: A device (usually part of a genlock system) that overlays the computer's graphics on a video image.

Luminance: The brightness portion of a composite signal

NTSC System: The National Television Standards Committee's television standard, used in the United States and Japan.

Overscan: A feature (of hardware and/or software) that lets a graphics program use the entire video display area, creating a borderless image.

Paint Box: A specialized hardware system that lets you use a mouse or drawing tablet to create images for video or print.

Resolution: The number of pixels that can be displayed horizontally and vertically on a video screen.

RGB (Red-Green-Blue): A computer's method of displaying colors as three separate signals instead of the combined signals found in composite video.

RS-170A: A video industry standard to insure proper synchronization and levels of video signals and components.

Tweening: Drawing the cels between the key frames of an animation sequence. Some programs use interpolation to do this automatically.

Switcher: A device through which multiple video signals are sent, manipulated and assigned.

Sync Generator: A device that generates various types of video- synchronization signals, which are used to genlock (sync) video equipment together.

Sync Signal: The portion of a composite video signal that coordinates the transmitter's signal with the receiver's display.

VTR (Video Tape Recorder): The professional counterpart of a consumer VCR.

Y/C: Used to describe the separation of luminance and sync from chroma. In the near future this method may replace composite video. This is the same technique used to achieve a slightly better and cleaner picture in ED-BETA and Super VHS (S-VHS).



The Anti-Aliaser, $19,95. Tom Hudson, P.O. Box 3374, Shawnee, KS 66203.

A desk accessory to anti-alias your CAD-3D/Cyber Control animations automatically in the rendering process.

The Cyber Family, Antic Software, 544 Second St., San Francisco, CA 94107, (800) 734-2001 in the U.S.; (415) 957-0886 in Canada.

Cyber Studio, includes CAD-3D 2.0 and Cybermate ($79.95). CAD-3D is the main program of what was once the most powerful 3D rendering system available for any microcomputer. Wish-list features such as 3D animation, full-perspective, shading and lighting let you draw and render objects such as robots, spaceships and skeletons.

Cyber Paint ($29.95) is powerful 2D and 2-1/2D animation software. It works as a post-production and touch-up program for CAD-3D drawings, as a video titler and as an excellent drawing program. Use Cyber Paint to create professional-looking animation sequences.

Cyber Control ($49.95) is a motion-control language that works in conjunction with CAD-3D. With this BASIC-like programming language, all the functions of CAD-3D can be controlled, Cyber Control also enhances CAD-3D with new capabilities, such as two additional "Cameras."

Cyber Sculpt ($89.95) and Cyber Texture ($49.95) are advanced modeling and texturing tools that complement CAD-3D, allowing for even more complex objects and scenes.

Several collections of objects rendered in CAD-3D for modification or to use as-is are available from Antic Software. These Design Disks ($29.95 each) include furniture, architecture, human beings, cartoons, microbots and video titles. Two 3D-font collections are also available.

DEGAS Elite, Discontinued. Electronic Arts.

Though DEGAS Elite is no longer available (Electronic Arts considers it dead and buried), it still deserves mention because it Includes absolutely everything a good drawing program should and its file format - .PI1 for low resolution, .PI2 for medium and .PI3 for high - is widely recognized as a standard. Its features run the gamut from simple free-hand drawing to sophisticated color-cycling animation and picture distortion functions. DEGAS Elite uses GDOS to make use of the different fonts available both commercially, and in the public domain.

NEOchrome, $39.95 Atari Corp., 1196 Borregas Ave., Sunnyvale, CA 94086, (408) 745-2000.

Atari's popular paint program shines with simple, straightforward menus, which belie powerful drawing program packed with features such as color cycling and block manipulation. NEOchrome has two features not found elsewhere: the "Jack Knife," which permits cutting and pasting of an irregular-shaped block, and the ability to access the ST's extended character set.

Spectrum 512, $69.95. Antic Software, 544 Second St., San Francisco, CA 94107, (800) 234-7001 (U.S.): (415) 957-0886 (Canada). The only program that permits the ST's 512 colors to be visible simultaneously, it sports sophisticated color manipulation tools which could be used, for example, to change the eye color on a digitized photo from brown to blue. An included anti-aliasing function uses an algorithm to soften the perception of jagged edges on diagonal lines. Spectrum 512 reads NEOchrome and DEGAS Elite files and can be used as a title page maker.

(Author's Note: Combine the strengths of DEGAS, NEOchrome and Spectrum 512 to create a great title page with fonts from the first, custom block-outs from the second and a 512-color gradient-fill background from the third.)

DigiSpec, $39.95. Trio Engineering, P.O. Box 332, Swampscott, MA 01907, (617) 964-1673.

Converts digitized images to Spectrum format.

Videotext, $125. Water Fountain Software, 13 17th St., 3rd Floor, New York, NY 10003, (212) 929-6204.

Powerful and versatile video titler that uses GDOS fonts.


JRI Genlock, John Russel Innovations, P.O. Box 5277, Pittsburg, CA 94565, (415) 458-9577.

Hardware device that lets you lay computer images over television images. (See the sidebar, "The Missing Link.") JRI's Genlock is available in the following incarnations:

JRI Genlock 520 External System, Call for price.

JRI Genlock 1040 External System, Call for price.

JRI Genlock Mega internal Normal System, $650.

JRI Genlock Mega internal High-Band System, $750.

JRI Genlock STE External System, Call for price.

Video Key, $99.95. Monitor Master, Practical Solutions, 1135 N. Jones Blvd.,Tucson, AZ 85716, (602) 322-6100. Video Key converts RGB signals to VCR color format which means you can use your television as a computer monitor. Monitor Master includes a video jack so you can easily hook your late-model 1040ST to your television. It also lets you switch between a color and monochrome monitor with the simple push of a button.

Video Wizard, $29.95 (plus shipping, and handling). IntraCorp Inc., 14160 SW 139th Court, Miami, FL 33186, (3(5) 252-9040.

Hardware device that lets you link your ST with your VCR.

Vidi-ST, $149.95. Computer Games Plus, 1839 E. Chapman Ave., Orange, CA 92667, (714) 639-8189.

"Grabs" video images in real-time. John Nagy reviewed it in the May 1990 issue of START.