This is an unusual question since I'll answer it right away because it was a truly unique device and there is absolutely nothing about the technology it used on the internet. I spoke with the hardware designer, and for the first time we can understand how it worked.
The DCTV is a hardware device from Digital Creations that connects to both the video port and the parallel port of an Amiga.
It is able to output a picture with full color video composite quality and also digitize a composite video signal.
It was released in 1991 for $495 in the USA.
The specs are as follows:
DCTV - Digital Composite Television - turns digital data from the RGB port to composite television signal uses the RGB port as an I/O port for sending compressed video information:
- the information is encoded into special Amiga display screens that DCTV recognises by a signature in the upper-left corner
- these screens contain the digitized and compressed form of the analogue waveform data required to create the composite display
the resulting composite image quality is far better and much worse than a normal Amiga RGB display:
- for pictures that contain a lot of color changes (like photographic materials) the quality is as good as everyday television
- in case of pictures with a lot of detail (like text) the display is blurry
uses the Amiga RAM as framebuffer - requires at least 1 MB of memory for functioning
- supports resolutions from 640×200 to 736×482/566 (NTSC/PAL) in 24 bit
- slow scan video digitizer - captures a still video frame in 6 to 10 seconds
- the parallel port is used for sending digitized images to the Amiga
- composite (RCA) input and output
- DB23 RGB connector passthrough for connecting two monitors at the same time - one for the Amiga (RGB) and one for the DCTV (composite)
- although DCTV does not interfere with normal genlock operation, its output cannot be fed into a genlock without the DCTV RGB Converter
Here is the device:
The pass-through connector would go on the video output port and the monitor cable would go on the other side, while the second connector would go on the parallel port.
There is a YouTube video showing it in action.
It would take the regular frame buffer output, displayed as is from the Amiga, in which you could kind of see the shape of the final picture, and turn it into a full color image. The onscreen display was spectacular, but I could never figure out how it was working.