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Journal of nicholas (3034)

Wednesday June 15, 2005
04:20 PM

digital TV

[ #25218 ]

My parents have just bought a digital terrestrial set top box, presumbly because my mum wants to be able to get all the extra Wimbledon coverage avaiable on digital. Digital TV. Fun. Generally it looks great. Except for the cross fade, where the MPEG encoder clearly couldn't cope with the transition from a roof to a blue sky, and pixelated slightly, much like watching a progressive image rendering in a web browser. I seem to remember from watching satellite some years back that fades to black don't work well either. Which is daft, given that in both cases the images didn't also contain a lot of motion, so the data rate should be high enough to make it work seamlessly, given a slightly more intelligent compression system.

For a simple box, it's a complex setup. The aerial signal goes from the wall to the STB. There's an onward connection for the signal from the STB to the video, and in turn the video has onwards RF to the TV. The STB has a Scart cable to the TV (which it uses to send its video signal, as it doesn't have an RF modulator). The STB also has a Scart cable to the video, which seems to be bi-directional (the can record the STB, and when playing back the STB relays the video's signal up the Scart connection to the TV). And the video does quite literally record the STB - on screen menus and all. (We could get more complex here if we wanted to, because the TV has a second Scart socket, as well as other audio/video in/out and itself can do a lot of switching. But lets not go there)

Anyway, the problem, which I can't figure out why, is that when the video records BBC2, the recording has a lot of herringbone intererence. There is no interference when recording other channels. Confusing. The video is recording off-air (ie using its demulator, getting RF signal from the daisychained aerial feed). I wonder what's special about BBC2. The only thing I can think of is that historically it has had the weakest signal strength, and maybe the video is getting confused by some signal reflected back from further along the cable. Whereas for the other stronger direct signals it is not. But that (reflected signal) ought to appear as ghosting. Confused. Any better suggestions?

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  • I think it's a miracle that most people get their TV/DVD/Video/Satellite/Tivo box combinations working at all. For "home electronics" it's waaaaay too complicated.


  • I've had a Sony DVB-T set top box for about a year now. I bought it for only one minor technical reason, but after purchasing it I learnt that it was supposed to have the best audio and video output anyway. What I was surprised to learn though, was that most digiboxes have a terrible reputation for complex and unhelpful GUI design, something my Sony is free from.

    It's not the price that is putting older people off, it's stupid design and over complex interface. Until TVs and PVRs all have their own DVB tun

    -- "It's not magic, it's work..."