Mixed Signals
Any sufficiently advanced information is indistinguishable from noise
Tuesday 12 August 2008, 11:56 PM
Ridiculously high frequencies for Olympic HD
It's nice to see broadcasting revive a little of one of its less-appreciated traditions – pushing the development of radio technology. Over at the Olympics, Tech-On reports that Japanese TV networks Fuji and NTT are collaborating on an experimental digital link that chunters along for a kilometer at 120GHz. Even today, that's a fabulously high frequency to be dealing with – the highest radio frequencies you'll encounter in everyday gadgetry will be five, rarely ten, GHz. At 120GHz, the signal has a wavelength of around two and a half millimetres; given that everything which deals with that signal will have to be precisely made to within a tenth of that, this is serious stuff.
Why bother? At those frequencies, there is a lot of bandwidth. Fuji and NTT are talking about passing 11 Gbps through this system – which can contain multiple channels of uncompressed HD video. Lesser systems can handle compressed HD with its far less stringent demands, but it takes at least half a second from camera to control room to compress and decompress the signal. For live events with a local commentator, that severely limits their banter with the anchor. You can see why Fuji and NTT are down at the games. They say that proper, instantaneous links like these are much in demand in sport.
That I don't doubt – and anything that encourages ever more crazed dashes into the blue yonder of extreme wireless gets my vote – but I think I see a simpler solution. Compress the HD as before – but multiplex in a single 'good enough' low-def feed, with some compression optimised for low latency. There'll never be anything in the HD that'll affect fast back-and-forth conversations; "Goodness, Motty, that's a particularly subtle shade of vermillion I can see on that young woman over in the stands". The gallery can cut to the good-enough feed and the anchor work from it, the HD getting edited without anyone having to look at it.
That way you can use existing, cheaper link technology at the cost of a little extra DSP.
I say this in the full authority of a chap who once wired an old vidicon to a valve colour TV set, and nearly killed himself in the process, not someone who tames 120GHz in the afternoon before going home for their tea. You choose.
Why bother? At those frequencies, there is a lot of bandwidth. Fuji and NTT are talking about passing 11 Gbps through this system – which can contain multiple channels of uncompressed HD video. Lesser systems can handle compressed HD with its far less stringent demands, but it takes at least half a second from camera to control room to compress and decompress the signal. For live events with a local commentator, that severely limits their banter with the anchor. You can see why Fuji and NTT are down at the games. They say that proper, instantaneous links like these are much in demand in sport.
That I don't doubt – and anything that encourages ever more crazed dashes into the blue yonder of extreme wireless gets my vote – but I think I see a simpler solution. Compress the HD as before – but multiplex in a single 'good enough' low-def feed, with some compression optimised for low latency. There'll never be anything in the HD that'll affect fast back-and-forth conversations; "Goodness, Motty, that's a particularly subtle shade of vermillion I can see on that young woman over in the stands". The gallery can cut to the good-enough feed and the anchor work from it, the HD getting edited without anyone having to look at it.
That way you can use existing, cheaper link technology at the cost of a little extra DSP.
I say this in the full authority of a chap who once wired an old vidicon to a valve colour TV set, and nearly killed himself in the process, not someone who tames 120GHz in the afternoon before going home for their tea. You choose.
Previous
