Marko Mäkelä wrote: > If the IC markings on the device are badly worn (like those on my box, I > guess they have a bad conveyor belt at the factory), then you cannot > easily reverse engineer the scan doubler circuit to add an RGB input. > The only viable solution would be to build an NTSC/PAL encoder for the RGB > signal. There are one-chip solutions from some manufacturers. A friend > of mine (who also got the Redant box) is going to build something. > Hopefully the picture quality won't be too bad when using S-video. I have a schematic of a (very low quality) scan doubler with built-in tv tuner and a composite input. It's okay to get the general idea how these devices work: there is a digital video processor that is able to digitize one of it's video inputs (either composite or s-video), a dual ported line buffer to store a scan line, and a video DAC to generate the RGB output from the line buffer's contents. The timing (aka scan doubling) is controlled by a custom programmed IC (so goodbye to cloning) and the whole control of the device is done with a 8031 type MCU with internal firmware (so also goodbye to cloning). The most interesting thing that I could see from the schematics is the way that the scan line is stored in the buffer: it is a 16 bit YUV format, with 8bit color and 8 bit luminance information. It would be pretty easy to interface the 4 bit RGB output of the C128 here to get the correct colors, but not in this box here, I'm sure. I got this box very cheaply and was very upset about the low resolution it produced with the composite output. A 40 column screen was almost unreadable. In the schematics I found an interface header for an optional teletext module that offered s-video (not available externally), but this input was only active if the teletext chip was detected on the I2C bus. I played with the idea to simulate the I2C registers of this chip with my C64 (got this idea during the I2C thread on this list), but luckily I found that my other (good quality) scan converter has the teletext option with exactly the right chip, so I interfaced this module into the other box and connected an external s-video input. Well, it turned out that the output was as unreadable as with the composite input :-( I ended up selling the box to my (then) girl friend very cheaply just for watching TV :-) BTW, this box is the well-known Proview TV-box that was available for many years from Conrad Electronics in Germany. I never read a bad review about it, but I heard complaints from its users. Since these boxes can be had very cheaply on online auctions sometimes, I decided to get one just to have myself a look at it. I payed about EUR 50 for my first box, a good one with TV tuner, teletext module, s-video, composite and RGB-passthrough, and maybe EUR 20 for the bad one :-) I'm also still playing with the idea to use an Amiga scandoubler/flickerfixer to double the C128 RGB output. Thanks to Pasi's document on hacking a C= 2320 into an A500 I'm almost sure it should work. That type of cards take a 18bit digital RGB input and a clock signal and put it out scandoubled as analog RGB. Nicolas Message was sent through the cbm-hackers mailing list
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