The Display Cards 8*24 and 8*24 GC do not use software for switching to the
NTSC interlaced mode. To put the Display Card 8*24 GC into the NTSC mode, a
properly configured cable is all that is required. For more information,
search under "NTSC output without converter".
To acquire a color NTSC signal from any Apple Macintosh display card, an
RGB-to-NTSC converter will be required.
RasterOps and Truevision both have RGB-to-NTSC converters. RasterOps' Video
Expander and Truevision's VIDI/O Box accept the RS-170-A output of the Display
Card 8/24 and 8/24 GC and generate a full color NTSC interlaced video signal.
Both of these interface boxes also provide S-Video (also known as Y/C component
video) output via the standard 4-pin mini-DIN connector. S-Video connections
are used by S-VHS, HiBand 8mm, and ED Beta video devices.
Another device for RGB-to-NTSC conversion is ComputerVideo's Video NTSC
Encoder. This was designed for the older Macintosh video card; however, it
should work with the new display cards when the correct cable is used (see
above).
For cable requirements for these interface devices, please check with the
appropriate interface manufacturer.
For 8-bit video, Apple's convolution provides one of the finest methods for
eliminating the single-pixel flicker that NTSC produces. When using 24-bit
color, a different approach is required to address the NTSC flicker issue,
since Apple convolution works only to the 8-bit level. Scan converters, like
RGB/Videolink 600A, have been used for many years in the professional computer
graphics companies to address NTSC flicker.
Scan converters would be used for television broadcast-quality 24-bit images.
Scan converters not only convert the RGB signal to NTSC, they also eliminate
the flicker associated with horizontal single-pixel lines and provide
aspect-ratio conversion, color-bar generation, video transitions, freeze frame,
and video mixing.
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