Moderators: Dave Moll, Steve Anderson
Steve Anderson wrote:But 'cross-standard' isn't quite so easy, i.e. 525 to 12.5Hz or 625 to 15Hz. Not impossible, but quite a complex device would result. Quite a challenge really...similar to the conversion in years past between 405, 525 and 625 in any combination or direction, with or without colour...
Steve A.
Steve Anderson wrote:My thinking is to do a 525 to 32-line/15fps standards convertor as I have a source of US standard 525 signals, a small 'board' camera. Assuming that works it should be a relatively simple exercise to adapt it to a 625/12.5 version, though the only source of 625 I have is an output on our set-top box in the living room. Somewhat inconvenient as it's on a different floor to my workshop/office and the cable-run would be awkward and around 25m. I'll think of a solution.
One component issue could be the A-D required. The CA3306 has been the device of choice for decades but it's hard to find these days and probably expensive [1]. An alternative is the AD7822 which is 8-bit as opposed to the 6-bit CA3306 and just capable of the sample rate required. However, I bought some years ago in DIL packaging, now you may have to shop around as most suppliers only have them in SMD versions. An alternative needs to be found, and at a sane price!
Steve A.
[1] Though I do have a local (Thailand) source of the CA3306 in DIL packaging, around 60 in stock at around GBP3.00 each, made by Harris, Intersil or RCA. I think, once gone, that's it!
[/quote]Another chip that's getting harder to find in DIL packaging is the LM1881 sync separator, Cricklewood (UK) have them now, but how many? The same Thai supplier mentioned above has 1000+ in stock if UK sources dry up. Around GBP2.20 each in one-off quantities. The LM1881 has been superseded by the LMH1980 which handles HD and SD, but SMD (VSSOP) only.
Harry Dalek wrote:Well perhaps on the 625 line an old camera or VCR ,there are old PC video cards that output it i think i still have one in my draw and as in my project my gaming PC video card that is one of the many it can output.
"Steve Anderson"
Nope, no other sources of 625 here except the set-top box, no VCR, no Camcorder, no DVD player, nothing. They all died (as expected) years ago, I'm not sure the TV/monitor in the living room has a 625 input, though I know the TV in my office/workshop does, both 525 and 625, PAL or NTSC.
I could make a static 625 source using a PIC device, a crude Test Card type of thing. A modified version of the SPG used in the SSTV-625 up-convertor. It's monochrome only, but that's all I'm interested in anyway. Also, most test cards were monochrome except for the centre circle (BBC style, Test Card F) and maybe some primary and complimentary coulours around the edge. Quite easy to do in component video (YUV, Y,Pb,Pr etc.), but coding properly into PAL or NTSC is another thing! Especially considering how little it would be used.
Steve A.
Users browsing this forum: No registered users and 21 guests