How reliable is PDC?

Discussion in 'Blu-ray & DVD Players & Recorders' started by bobones, Oct 9, 2003.

  1. bobones

    bobones
    Active Member

    Joined:
    Jan 15, 2002
    Messages:
    453
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +7
    In my second day with the E50 and so far it's been a pleasure to use. However, I've been playing with videoplus and PDC tonight, and two programs on timed record (both on BBC1 analogue) failed to start recording. I had to manually switch off PDC before the machine would kick into life.

    What's the problem here? Is the E50's PDC implementation poor, or does the BBC fail to transmit these codes? What's everyone elses opinion/experiences with PDC on the E50?

    Also, the recorded programs had gibberish inserted for their titles. Any ideas what's wrong?
     
  2. PhilipL

    PhilipL
    Well-known Member

    Joined:
    Jan 18, 2002
    Messages:
    3,787
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    103
    Ratings:
    +421
    Hi

    There are problems with PDC due to historical reasons (a "lite" version was first introduced and a lot equipment is built with that in mind and now gets confused by the fuller spec being used.) The BBC also has some failures, and if you complain they sometimes come back with saying "Sorry we got that program wrong". Does the E50 turn on then straight off again? I expect if you receive PDC on the ITV channel where you are this appears to work perfectly?

    A tip, when using PDC always make sure you set the times exactly as published, and set the timer to weekly. For example, something to record today (Thursday 9th) change to Weekly every Thursday instead and see if this resolves your problems. There is a valid technical explanation as to why this might help.

    Regards

    Philip
     
  3. bobones

    bobones
    Active Member

    Joined:
    Jan 15, 2002
    Messages:
    453
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +7
    Thanks Philip. My initial problem was that the recordings just never started in the first place, not starting and immediately stopping.

    I've just checked my recorder again, and a non-PDC timed recording failed to stop at the given time! Yes, non-PDC! This together with the corrupt program names, makes me suspect that there's something amiss in the recorder. My theory is that the Smartlink data from my Sony tv has corrupted something somewhere.

    In an attempt to correct things, I've reset to factory condition and retuned without using smartlink. My first attempt at PDC recording since then appears to have worked, so fingers crossed.

    The only other thing I noticed is that the recorder seems to think that CH4 doesn't do PDC. Perhaps this is to do with the "lite" version you mentioned.

    If I persist in having problems, I'll try your "weekly" tip. Failing that, the machine is going back if I can't rely on it to stop and start recordings with or without PDC!
     
  4. nwgarratt

    nwgarratt
    Distinguished Member

    Joined:
    May 5, 2002
    Messages:
    26,437
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Ratings:
    +2,871
    I have a E50 and I just use the standrard timer and videoplus and put a few extra minutes on the start and end.

    I have never liked PDC and it has never worked for me on any VCR I have had in the past.

    I wouldn't take it back just beause the PDC doesn' t work properly. It is probably the transmission that is causing the problem.

    Try doing a normal timer recording wihtout PDC and see what happens.
     
  5. fozzybear

    fozzybear
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Yup, nothing but trouble with PDC. Never use it anymore either, it's just not reliable.


    nwgarratt: I'm not stalking you, honest! :)
     
  6. Northerner

    Northerner
    Standard Member

    Joined:
    Aug 12, 2003
    Messages:
    112
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    19
    Location:
    The land where The Macallan is distilled
    Ratings:
    +0
    Now here's my tuppence worth!

    My experience with PDC is that it is only "fully" supported by the independent channels. BBC has always been a hit or a miss so just don't use it.

    As for the garbled titling, my E50 pulls the titles in with no problem.

    Do some tests without PDC - Videoplus should be OK - before you rush back and complain. ;)
     
  7. bobones

    bobones
    Active Member

    Joined:
    Jan 15, 2002
    Messages:
    453
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +7
    Northerner, the garbled titles and PDC seem to be working fine since I reset to factory condition and retuned without using smartlink.
     
  8. PhilipL

    PhilipL
    Well-known Member

    Joined:
    Jan 18, 2002
    Messages:
    3,787
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    103
    Ratings:
    +421
    Hi

    The problems are due to the manufacturers, especially the Japanese ones as PDC is very much a European thing only.

    Since using a work around for particular problems with PDC I was experiencing it has been spot on for 10 months or more. There is something satisfying with DVD, to just press the Play button and have your recording start bang on. Other methods gets you rubbish at the beginning and the end and take no account for shifted schedules.

    The main problem with PDC is originally Channel 4, one of the first broadcasters of it in the UK, implemented it as a “lite” version and the Europeans only use the "lite" version called VPS.

    The BBC especially, use PDC in its more advanced form, but nowhere near as advanced as it could be, which would allow things like re-programming the timer if a program is rescheduled for another day, and even allowing the timer to swap channels, so if a program is moved from BBC1 to BBC2, say due to live sports coverage, your video will move also.

    The main problems seem to arise from the "lite" version using only one data-stream per TV channel, whereas the full version can use 4 data-streams per channel of PDC information (not really 4 streams as they are interleaved).

    The BBC currently use 2, so they can still be signalling a VCR to be recording the previous program, while they use the other stream to get other VCRs prepared for recording the next program. Because the "lite" version and VPS only uses one channel, a lot of VCRs get confused due to poor implementation by the manufacturer with telling one stream apart from another. The problem comes when your VCR starts recording a program, but the BBC is still sending a signal for the previous program. Your VCR wakes up as it sees its signal for its timer setting and off it goes, but a moment later a "stop" code is sent for the previous program. While a VCR should ignore this "stop" code as it relates to a different program, often they do not, and then stop recording the program you wanted after a few seconds or upto 2 minutes after seeing the stop code. This gives rise to intermittent problems as some times the stop code will have been sent before the start of the next program, so it will work, and other times it will over-lap and give you a failed recording. Users then think it is the BBC forgetting to send the PDC signal 50% of the time!

    Other reasons such as the way PDC creates a program ID from the exact time and day entered. If the schedule is published differently later, what time do you put in, the original one or the new one? The PDC spec’s say you should always use the original published time, but the broadcasters often use the new time, meaning if you used the original time your recording will not happen at all!

    Regards

    Philip
     
  9. mike5

    mike5
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    When I use PDC with video plus, its record fine, but at the end of the recording the timer Icon stays on, doesn"t do this on BBC 1 or BBC 2 just ITV and Channel 4. Means I have switch the E50 on with the time button and clear it manually after a recording, Which I can"t understand.
     
  10. PhilipL

    PhilipL
    Well-known Member

    Joined:
    Jan 18, 2002
    Messages:
    3,787
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    103
    Ratings:
    +421
    Hi

    This sounds quite likely. BBC1 and BBC2 transmit stop codes, this tells the VCR that the program has come to its end and is complete, the VCR then clears the timer setting as it feels happy having be told “Stop!”.

    Because ITV and Channel 4 use a "lite" version, they do not bother with a Stop code, instead they just change the PDC code to the next program. A VCR sees its PDC code for that program change and so stops recording. Because it never receives a specific stop code, the VCR keeps hold of the timer setting in case it comes back again.

    The PDC setting has a validity window from 0:00 to 3am the next day. The VCR should be prepared to start recording between those times. If the BBC timer settings are being removed immediately after recording, and not the next morning, then this isn't to spec. If the BBC interrupted the program for a news flash, they would broadcast a stop code, and after the news flash would transmit the same PDC code to restart recording, if the timer setting is removed straight away, the VCR has nothing to tell it to start again, as it thinks it has done its job!

    For those interested the actual PDC specifications can be got from the European Telecommunications Standards Institute document number ETS 300 231 (http://pda.etsi.org/pda/queryform.asp) free but need to register. You may be surprised at just how much the system can do, but this has never really been utilised to the full, and not likely to now we move to digital, even though the system will port over easily.

    Regards

    Philip
     

Share This Page

Loading...