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The switchover to digital TV here in the UK is in trouble. One of the problems is the shortsighted design of the required set top box. The thing only has one video output, so you can't watch one channel while recording another on your VCR (unless one of the channels is an old fashioned analog signal).
Why
not have a set top box which decodes the digital signal, then outputs an RF signal modulated with all the channels? You just feed this into the aerial socket of the VCR, daisy chain the TV, and retune both to the new channels (if they're not smart enough to do it themselves). You don't even need a remote for the box, as all channel changing is done with the tuners in the existing equipment.
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ditto cable and satellite set top boxes. |
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As I run an aerial coax lead from my sitting room to my computer, I would find this extremely useful - no more arguing about channels with the housemates, no more having to go in the other room to change channels. |
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I guess the reason why companies don't want to do this is that they won't get the chance to sell you a second set top box for an exorbitant fee. b*st&rds. |
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No, the reason they don't do this is because it would no longer fit in a set top box if they did. It would take up a crate big enough for your widescreen TV to look like a decoder-top box. And the price tag would be equally impressive. They can make those boxes so small and affordable (I won't lie and say they're cheap) because they have exactly one modulator circuit which is tuned to the lowest frequency channel in the band, and exactly one digital decoder, and exactly one demodulator which can be tuned to any of the incoming channels. |
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An N-channel capable box would need all of the following:
a) A distribution amplifier capable of driving N demodulators, so that the cable doesn't see too heavy of a load.
b) N demodulators equipped with N local oscillators for tuning to each of the different channels.
c) N digital decoders.
d) N modulators with N more local oscillators to produce each of the output channels.
e) A wideband summing amplifier to combine all the channels into one signal.
f) Another distribution amplifier to drive all those TVs and VCRs that might possibly get connected to this decoder box. |
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That's some serious equipment you're asking for. You could start your own cable company with it. |
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Well I'm with Mickey, I think it's really annoying, and it seems to me to be a fairly basic requirement. Croissant, even if it is technically impractical. |
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That load of equipment is only necessary because of the way that cable TV is actually delivered. Given a broadband digital cable, there's no reason you couldn't feed channels down it digitally, and just have something along the lines of a network hub delivering them to the different ports. |
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The local cable hub could get delivered all the channels, and only feed through those that anybody is actually watching, as fed up the wire at extremely low bandwidth. |
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Each TV output port (ie coax) would still need to analogized and decoded in either hardware or software, but there only need be one of these - if the other three ports are pointed at TiVos and computers, the signal could just be fed through. |
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It would need minimal processing power, no more than a $20 ethernet hub. |
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Or is that beyond the capabilities of the sort of company we're dealing with? |
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In view of the practical problems rasied by BB, let me modify: No RF output (so no modulators), N (where N may = 2) video outputs (SCART) driven by N decoders. You send one O/P to the TV, one to the VCR. You channel flip at the set top box. Still lets you use your existing kit (assuming they have video inputs). |
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Back before the age of digital video signals, one concept I thought of would be to frequency modulate groups of channels up and down by a few MHz every few ms. There would be one fixed-frequency channel which contained data which, when unscrambled, would indicate the necessary frequency adjustments for the other channels. |
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The one limitation of this method would be that between groups of channels that were purchased as a unit there would have to be an unused channel. Otherwise, though, this method would allow groups of channels to be scrambled/unscrambled as groups, allowing for TV-set selection of the particular channel to view. |
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You can find two things you want to watch at at the same time, wow. |
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Yeah, but they're the only two things that are on all week... |
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[Mickey the Fish]: The only way to get away with a simple "network hub" arrangement is if all the TVs and VCRs have digital-capable tuners and decoders built in. If that were the case, there would be no cable box at all! As it is, you need one cable box for each device that you want to tune separately. Even if you combined just a few converters into a single enclosure, you'd have N complete cable boxes (as you know them today) inside there. You'd be no better off with one super-sized (and super-priced) box than with N separate boxes. In fact you'd be worse off because you cannot separate the contents of the super-box and install them in separate rooms. |
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Just solve the problem by doing away with digital TV altogether. Sinking millions of pounds of tax payers money into developing 300 channels of crap is not my idea of a bargain. |
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I exaggerated for the sake of effect. All the best ad agencies do it. |
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