PDC

Having just bought a new DVD recorder (a hard-drive one is so much better!) I noticed it had PDC. I've known about it for a while - I know a lot of VCRs from the late 90s have it but why, at a time when baby digital was being born, was this technology coming out? Considering it only works on analogue it seems like an absolute waste. Why on earth is there no digital equivalent? Thanks to Sky's Personal Planner I can set the DVDR to start/stop recording but I assume that if a programme is set 10pm-10.30pm if it overruns the recording will just stop? In this day and age is seems bizarre.

My parents have a DVDR with the clunky Guideplus, a nice idea but the other day they missed the end of a film because it overran (They've now found the extend time either side feature!) But it still poses the question why has no suitable system been found for digital. Why can't an analogue teletext signal just be broadcast on Sky?

I hope you're not suggesting that there are problems with the amazing digital future? It's perfect. The BBC has told me so since 1997

No reason that I know of - in fact the BBC have a placeholder page on teletext to tell you to press the red button, and at least the BBC and ITV still have subtitles on 888 (which is handy because using the Help menu to active them via the Sky box crashes my box).

David

Anything is technically possible, but you'd need some sort of industry/broadcaster standard like PDC was, which there presumably isn't.

Those with PVRs in digiboxes could presumably use the EPG; some broadcasters do trigger the Now/Next info dynamically to match what is going out on air



It can and many stations do broadcast traditional teletext on satellite and cable - but it has to be sent seperately and encoded onto the video signal in the digibox because teletext cannot be broadcast on DVB.

PDC isn't teletext so it would depend on whether Sky Digiboxes are set up to do it. But then that would be no good for terrestrial viewers because no recent DTT boxes have encoders

PDC can only work on recorder with internal tuners - as when the timer is set and the device is waiting to record, the tuner in the recorder is effectively cycling through all the channels it is scheduled to record, checking the PDC codes for the shows it is going to record, and then seeing if they are still on-time! This is potentially possible with an internal Freeview tuner - but not really viable with an external set top box unless it is dedicated to the recorder and not used for other things.

Both the Freeview EPG and the Sky EPG that drives the Sky personal planner incorporate technology that allows up-to-the second recording - as long as the infrastructure and broadcaster support them.

AIUI the Freeview system is still partially based around the OnDigital legacy EPG data distribution systems - and may not update quickly.

However the Sky EPG does update very quickly - but only if the broadcasters do this reliably. The BBC are one of the few Sky broadcasters who use this functionality - but just as the BBC's PDC implementation is far from perfect, so their Sky EPG updating is not perfect. However it is better than other broadcasters who don't bother.

(BBC News 24 is a different kettle of fish - as it doesn't have a presentation dept. - so EPG updates only happen if someone takes the time to e-mail the EPG team when a schedule change is made)

So - BBC Personal Planner entries on Sky should work if the show over runs or is re-scheduled, however ITV, C4 and many Sky channels may not update dynamically.

PDC is encoded within the same data structure as teletext - it uses packets encoded in the same data stream I believe. However for PDC to effectively function it needs full control of the tuner to be able to sit and flip between channels checking for schedule changes - and this is much more of a challenge with set top boxes - especially if they are being watched at the time...