From: Phillip Gawlowski Date: 2011-07-19T09:45:46+09:00 Subject: Re: Ruby + USB + CCTV Camera Driver? On Tue, Jul 19, 2011 at 2:20 AM, Bob Carpenter. wrote: > > It's not clear whether you guys think a software ADC is impractical or > whether it's impossible. It's not impossible. It's just so very impractical that it might as well be. > If you're saying it's impractical, is it due to performance - takes too > long to convert analog voltages to digital values? Yes. > If it's impossible, is it because reading voltages at USB pins cannot be > done in software? That, too, more or less. The third problem is that USB isn't even capable of *reading* different voltages, much less a waveform! It can read an on state and an off state. Analog signals are "composites" of different wave lengths--you have electrical power as carrier wave, on top of which you modulate all your other waves carrying actual data--which a digital connection just can't handle (after all, that's what ADC/DAC chips are for ;). > I have not found any reasonably priced digital cameras - reasonable > being in the range of $50/unit for quantities of 100. Please let me know > if you have seen any. If the problem is digitizing the video signal: Get or build a DVR, and pull the already-encoded video from that. It's cheaper and less headache-y that way. You'll probably need that anyway, since CCTV usually means "surveillance", and *that* again means "recording evidence for the police / court". -- Phillip Gawlowski phgaw.posterous.com | twitter.com/phgaw | gplus.to/phgaw A method of solution is perfect if we can forsee from the start, and even prove, that following that method we shall attain our aim.               -- Leibniz