Moderators: Dave Moll, Andrew Davie, Steve Anderson
Steve Anderson wrote:Well, Harry, as usual, you've managed something I wouldn't even attempt! How in the heck you get these things going is beyond me.
Right, the next thing is 1) getting it locked to a source of 405...do you have a source? 405 as far as I'm aware was not used in Australia.
Second 2) will be retrace blanking, i.e. cutting off the beam during retrace. Then, combined with the previous, adding the video modulation. I'm also in a non-405 country, where I might get some source material is a good question....
Pondering upon it a 'simple' 625 to 405 converter shouldn't be that difficult. OK, it'll never meet the standards required by the BBC (God bless 'em) But to get something on a screen it's not an impossible task....I've got a feeling I may have started something along these lines years ago...
I also recall the UK IBA published a 'guide' to standards conversion, sometime in the early 80s? Maybe before...time for a deep dig...not only 625 to 405, but 525-625 in both directions. All monochrome though. Adding colour though a nuisance isn't too onerous, just a hassle.
Of course, something like the WC-01 is a benchmark for classic standards conversion. Its flexibility is unquestioned, however how often do you need all those various modes? Not that often probably. If I were looking for a standards converter where would I place my money? For the moment let's forget colour.
1) 525-625 (A luxury)
2) 625-525 (Ditto)
3) 405-625
4) Maybe 625-405, a real 'maybe'.
5) 625-'Standard' to NBTV (32/12.5)
6) NBTV (32/12.5) to 625
Whilst about it throw in a few SSTV modes as well...maybe...but that's just me, not a major application.
Then add in to the mix some VGA output modes too...Oh heck! See what I mean? How the WC-01 came to fruition is amazing, considering the complexity of its remit.
Steve A.
Steve Anderson wrote:I haven't looked into this in detail, but a 405-to-625 convertor wouldn't be that difficult if you're OK with the 405 source only taking up around 65% of the 625 frame (both horizontally and vertically). So it would be viewable, just somewhat smaller...bearing in mind TVs of the 405 era had smaller screens than what we are used to these days.
Then there is the small problem of source material, after a while a test-card becomes a tad boring. There is a case for a 625-405 version.
A revision of the SSTV-625 convertor I made a few years ago may be in order....the output side (625 read mode) is already done and shouldn't require any modification (I think). The input side (now 405 write) would require significant work, both in hardware and software. A small plus-point is there's no requirement for a demodulator, simply baseband 405 in.
Steve A.
Maybe just a 625-405 down-convertor is actually all that's needed? Do we need to convert 405 to 625? In other words, for those that own a WC-01 what is its primary use? For those that would like to own one, what major use would you use it for?
As ever, specifying a suitable video A-D is a hurdle....but as mentioned elsewhere/previously, the TLC5540 appears suitable....though not available in a DIL package, only SO (useable...just) or TSSOP (unusable).
Harry Dalek wrote:I don't know of the TLC5540 are you planning a systems converter around this IC ? the idea of this is always interesting .
Return to Construction Diaries - Electronic Televisions
Users browsing this forum: No registered users and 8 guests