![]() Instead of a frame of 736x483 pixels of 16 colors, we got an effective resolution of about 368x483 pixels of full NTSC type color. 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. When converted to analog and added sync and so on the resulting signal was a full color composite signal that looked surprisingly good. The resultant data stream was at 14.318MHz and contained Y+(B-Y), Y+(R-Y), Y-(B-Y), Y-(R-Y), etc. The final value was created by adding these values together. 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. So every line would contain every other raw sample for an NTSC composite video signal. , logically shifted by half a 7.159MHz sample. Odd lines stored data as Y + (B-Y), Y - (B-Y), etc. Even (I think) lines stored data as Y + (R-Y), Y - (R-Y), etc. We combined alternate pixels so that we had 8-bits per pixel at half the rate. We used that mode, but re-interpreted the data. In more detail: Amiga had a frame buffer mode that displayed 736x483 pixels, but only 4-bits per pixel (16 colors). ![]() I will describe in more detail below, but it assumes some familiarity with NTSC composite video signals. I know that is pretty ambiguous, but it is a general description. 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 didn't really remember! Luckily I still have all the lab books and design notes from those days filed away. The onscreen display was spectacular, but I could never figure out how it was working.Īfter some research, I found the hardware engineer that built the DCTV and we exchanged some messages where he explained the system. ![]() 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. There is a YouTube video showing it in action. 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. although DCTV does not interfere with normal genlock operation, its output cannot be fed into a genlock without the DCTV RGB Converter.DB23 RGB connector passthrough for connecting two monitors at the same time - one for the Amiga (RGB) and one for the DCTV (composite).the parallel port is used for sending digitized images to the Amiga. ![]() slow scan video digitizer - captures a still video frame in 6 to 10 seconds.Uses the Amiga RAM as framebuffer - requires at least 1 MB of memory for functioning in case of pictures with a lot of detail (like text) the display is blurry.for pictures that contain a lot of color changes (like photographic materials) the quality is as good as everyday television.The resulting composite image quality is far better and much worse than a normal Amiga RGB display: these screens contain the digitized and compressed form of the analogue waveform data required to create the composite display.the information is encoded into special Amiga display screens that DCTV recognises by a signature in the upper-left corner.Uses the RGB port as an I/O port for sending compressed video information: It was released in 1991 for $495 in the USA.ĭCTV - Digital Composite Television - turns digital data from the RGB port to composite television signal It is able to output a picture with full color video composite quality and also digitize a composite video signal. The DCTV is a hardware device from Digital Creations that connects to both the video port and the parallel port of an Amiga. I spoke with the hardware designer, and for the first time we can understand how it worked. 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.
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