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Originally Posted by Kat Manton
I'd thought of doing just that but I can be something of a perfectionist - if Y is defined as 0.299R + 0.587G + 0.114B then so it shall be with my circuit. Also missing off colours might be ok for off-air pictures, but bits of the software's TV programme guide and menus might disappear or become less readable if I missed off a colour or two. I'm possibly going to have to re-skin it anyway once I've seen it in monochrome.
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Get it within 10% and that will be absolutely fine. Even with my reviewers hat on* I would be most unlikely to spot anything wrong.
*I have reviewed all the 405 line converters that have ever been commercially available for the
BVWS Bulletin or
405 Alive. I hope to be reviewing Darryl's new design soon. I may have a go at reviewing
KAT405 but strictly speaking this is not a commerically available product. It may need a postscript to the article I wrote about the history of 405 converters a few years ago. I'm happy to say that this passage may need updating:
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Some have suggested using computers or digital signal processors (DSP). Conceptually there is no problem. I’m a pretty lousy programmer and I could write you the conversion algorithms in a few lines of a high level language such as BASIC. These would take a 625 line image, already in the computer, and convert it to a 405 line image, also within the computer. And there’s the snag. You still need to get the picture in and out and you have to ensure that the computer can keep up with the data. Video comes at you continuously so real time means exactly that – you cannot put your hand up, take time out and catch up later. So when you say you have built a converter with a cast off 486 PC I won’t believe you. Modern DSP chips are entirely capable of doing the digital parts of the processing though you will still need to get the signals in and out. Maybe I'm prejudiced but I would rather use programmable logic than DSP for this job.
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