PDC Live


Here is a cleaned-up collection of some notes I made while trying to figure out what was going on. There is no definitive information here that isn't on one of the other pages. It is instructive to see what use (and abuse!) of the PDC system was occurring in July 1996.

Stream IDs

An illustration of BBC2's use of stream ID occurred while some portion of the late-night educational transmission "The Learning Zone" was being broadcast. This is billed as one item, running from 00:30 to 05:00, although it actually contains many Open University and other programmes. Here is an extract from the packet log as the programme changed, slightly prettified:
	01:24:43  s1 0 0 UNDEF  0 0  UK-BBC2 24/07 01:00 No info
	01:24:46  s0 0 0 UNDEF  0 0  UK-BBC2 24/07 00:59 No info
	01:24:47  s1 0 0 UNDEF  0 0  UK-BBC2 24/07 01:00 No info
	01:25:37  s0 0 0 UNDEF  0 0  UK-BBC2       RI/T  No info
	01:25:38  s2 0 0 UNDEF  0 0  UK-BBC2 24/07 01:24 No info
	01:25:38  s1 0 0 UNDEF  0 0  UK-BBC2 24/07 01:00 No info
I think this represents a programme that started at 01:00 running throughout on stream 1, a sub-segment which started at 00:59 stopping on stream 0, the stop being marked with the special date and time 00/15 30:63, and another segment starting at 1:24 on stream 2.

Special Flags in the Date and Time Fields

Occasionally you may notice that the date and time fields of the PDC transmission change from something sensible like 23/07 16:05 to some unlikely value, like 00/15 28:63. It is reported that these strange values are described in the EBU specification for PDC with some complexity. Certainly, the short descriptions I have received do not bear much resemblance to the use to which they are put:
	31:63    VCR obeys own timer
	30:63    Record Inhibit/Terminate
	29:63    Interrupt (pause) current recording
	28:63    Continue recording after interrupt
Without seeing the specification, it is not easy to determine what these actually do; it doesn't seem likely that the BBC2 could have had exactly the above interpretations in mind when they sent some of these:

More details or ideas appreciated.

BBC2 Regional Opt-Outs

BBC2 was supposed to use the timer flag during regional opt-outs until the service was properly set up, but that hasn't been my experience! For example, although there was supposed to be a regional variation at 23:15 on 23 July 1996 and the PDC packets broadcast by Wenvoe went:
    22:31:37-23:15:57 486  s0 0 0 UK-BBC2 23/07 22:30 Newsnight
    23:16:12-23:16:12   1  s0 0 0 UK-BBC2 00/15 RI/T
    23:19:32-23:58:09   9  s1 0 0 UK-BBC2 23/07 23:15 Double Exp.
    23:57:53-00:17:38  11  s0 0 0 UK-BBC2 23/07 23:55 Weatherview
    00:32:05-00:55:41  56  s0 0 0 UK-BBC2 24/07 00:30 Learning Zone
According to the TV listing, Wales was supposed to opt out from Double Exposure and broadcast two programmes, one at 23:15 and one at 23:45. Then they should have rejoined at 23:55 when Weatherview was supposed to be on for 5 minutes---but the Weatherview code kept going for 30 minutes!

The next night was really confusing, with no opt-out and two codes that don't match up with anything advertised (although the second one is in Learning Zone).

    22:33:29-23:16:47 466  s1 0 0 UK-BBC2 24/07 22:30 Newsnight
    00:00:17-00:00:17   1  s1 0 0 UK-BBC2 24/07 23:55 not scheduled!
    00:00:45-00:00:45   1  s0 0 0 UK-BBC2 24/07 23:15 Double Exp.
    00:31:00-00:31:15   2  s0 0 0 UK-BBC2 25/07 00:28 not scheduled!
However, in both cases note that I get hardly any packets for hours. This might therefore be the fault of my receiving program, which is trying to get the BBC Micro Teletext Adapter to do something occasionally it doesn't normally do at all. Note also that the BBC2 service is supposed to be properly regional now (or soon if not already), so this issue is perhaps a matter of short-lived interest.
This page was created on 22 July 1996. It was last updated 31 August 1996.
Please send comments to Robin O'Leary pdc at ro dot nu
Copyright (C)1996--2004 Robin O'Leary. All rights reserved.