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.

DCTV Advertising

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:

    1. the information is encoded into special Amiga display screens that DCTV recognises by a signature in the upper-left corner
    2. 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:

    1. for pictures that contain a lot of color changes (like photographic materials) the quality is as good as everyday television
    2. 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:

Photo of the DCTV 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.

  • 2
    +1 for digging up old memories of that device. I remember seeing it in Amiga magazines and wanting one really bad. I just couldn't imagine a computer showing images that good. I hadn't fully understood how my Amiga 500 could even display 4096 colors. All of my previous computers only had 16 colors. :-D – cbmeeks Feb 2 '17 at 14:18
  • yes, the images out of the DCTV were amazing, the colors were so vivid. – Thomas Feb 2 '17 at 17:42
  • 5
    I just created an account here. Sorry that I didn't get to it sooner, just been really busy. If anyone has other questions, I'll try to answer them. I could probably answer other questions related to Digital Creations / Progressive Image or Play, Inc. hardware products. – P. Greaves Feb 13 '17 at 21:26
  • Welcome to the site. You probably want to get familiar with how Stack Exchange sites work first. Make sure you take note of the highlights in the Tour: retrocomputing.stackexchange.com/tour. As it stands, this is not an answer to the question at hand. You can put biographical info in your account where others can see it, and you can always chat in The BBS chat widget for the site: chat.stackexchange.com/rooms/38597/the-bbs That being said, if you can come up with an answer to the question, feel free to edit your introduction with the answer info. – jdv Feb 13 '17 at 21:58
  • Welcome Paul! Everyone, Paul is the person that worked on the DCTV and gave the answers I posted above. – Thomas Feb 13 '17 at 22:00

After some research, I found the hardware engineer that built the DCTV and we exchanged some messages where he explained the system.

This is the unedited text:

Wow, it has been a long time... I didn't really remember! Luckily I still have all the lab books and design notes from those days filed away. We used a technique that encoded the data on two consecutive lines in the Amiga frame buffer in a way that we could reconstruct a composite video signal when run through some processing and combined with data from the previous line (delayed through a line memory). I know that is pretty ambiguous, but it is a general description. I will describe in more detail below, but it assumes some familiarity with NTSC composite video signals.

In more detail: Amiga had a frame buffer mode that displayed 736x483 pixels, but only 4-bits per pixel (16 colors). We used that mode, but re-interpreted the data. We combined alternate pixels so that we had 8-bits per pixel at half the rate. Even (I think) lines stored data as Y + (R-Y), Y - (R-Y), etc. [Luma +/- red color difference value, alternating] at a 7.159MHz sample rate. Odd lines stored data as Y + (B-Y), Y - (B-Y), etc. [Luma +/- blue color difference value, alternating], logically shifted by half a 7.159MHz sample. So every line would contain every other raw sample for an NTSC composite video signal. In order to reconstruct the missing data, it would generate the Y component by averaging the values left and right of the missing sample, and the chroma component by subtracting the two adjacent samples from the previous line. The final value was created by adding these values together. The resultant data stream was at 14.318MHz and contained Y+(B-Y), Y+(R-Y), Y-(B-Y), Y-(R-Y), etc. When converted to analog and added sync and so on the resulting signal was a full color composite signal that looked surprisingly good.

So it was really a way to get full color out of the Amiga frame buffer by applying some signal processing techniques to trade off spatial resolution for increased colors. Instead of a frame of 736x483 pixels of 16 colors, we got an effective resolution of about 368x483 pixels of full NTSC type color. Chroma resolution was less (as with any composite NTSC type signal), including somewhat less resolution vertically. But it looked pretty good by 1990 standards! We found that we could even stream data off a fast (for the time) hard drive in real time, and used to demo by playing back scenes from "Back to the Future" at trade shows. Fun times.

Actually we may have used the 704x483 graphics mode... I got he 736 number from Wikipedia, but I am not sure it is correct. 704 sounds more right.

Then me asking a bit more:

You have cleared a mystery that was popping back in my mind now and then! It is true that for the time, the output was very good! so you could probably fit the decoding logic in a cpld?

And he replied:

The decoding logic fit in a 3000 series Xilinx FPGA. The line memory was external, along with the D to A converter and a few other things like a PLL for the pixel clock. I think the final product had an A to D converter for grabbing images from an external video source as well...

I will let him know about this thread just in case there are more questions, to see if he wants to participate.

  • Thanks a lot for doing this; hopefully we can get an answer from an actual hardware developer! :-) – wizzwizz4 Jan 28 '17 at 19:39
  • This answer was posted less than a minute of the question being asked by the same person. – RonJohn May 10 at 19:52
  • yes, I explained that in the first line I wrote when I posted the question; through the years I've heard a few people asking about DCTV and since there is aboslutely nothing on the internet about it, I thought this would be a good format to get the information shared. – Thomas May 11 at 10:12

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