[mythtv] Ticket #2811: BBC Series link patch

David Matthews dm at prolingua.co.uk
Tue Jan 16 16:49:19 UTC 2007


MythTV wrote:
> #2811: BBC Series link patch
> Comment:
> 
>  With the default authority, is this used in a similar way to EIT data with
>  the EITa being the "authoritive" source for that mux, or is the
>  information
>  used to form the fully qualified CRID and that info is broadcast
>  consistently
>  across the muxes?

I'm not sure I've understood your question so rather than start a 
discussion on trac I'm replying to mythtv-dev.

The full form of a CRID from ETSI TS 102 323 is a URI of the form
crid://<CRIDAuthority>/<data>
e.g.
crid://fp.bbc.co.uk/ABC123
To save space in the EIT when sending the episode and series IDs it is 
only necessary to send the data part beginning with a slash ("/ABC123"). 
  The full CRID is created by adding the "default authority" (and 
"crid://" to be strictly accurate).  The default authority can be 
transmitted in any of NIT, BAT or SDT.  Currently it is transmitted on 
the SDT but it seems they will be transmitting it on the NIT in the 
future.  I assume that the default authority to be used for the episode 
or series ID for a particular programme is the default authority for the 
channel on which the programme will appear, rather than for the 
transport on which the EIT data is being transmitted.

At present the only place that CRIDs are transmitted are in the EIT and 
they are always transmitted just as the data part.  There may be 
circumstances in which the full CRID could appear in the future.  More 
importantly, though, it is quite possible that two different 
broadcasters might both use "/ABC123" but to refer to different 
programmes.  If we want to use programID to look for duplicates we need 
to add the default authority to make a globally unique identifier.  Note 
that when the BBC repeat an episode on a different BBC channel they use 
the same episode ID so the default authority is the same for all BBC 
channels.

I've included below a list of the default authorities last time I 
scanned using the patch that puts the default authority in the xmltvid.

 >
 >  This works well when the EPG monkeys actually get the information right.
 >

Using the programID has proved to be much better at avoiding duplicate 
recordings than text comparison.  Often there are small differences in 
the subtitle or description that would result in a recording being 
repeated.  I suspect that the text is retyped manually whereas the IDs 
are obtained from some BBC source directly.  They still need to get this 
right for radio, though.  There are repeats on BBC7 that have different 
episode IDs.

The only concern I have is that the broadcasters might reuse CRIDs after 
some period so a programme would fail to record because it had the same 
programID as something in the oldrecorded table.

David.

mysql> select name,xmltvid from channel where xmltvid != "";
+------------------+----------------------+
| name             | xmltvid              |
+------------------+----------------------+
| The HITS         | bds.tv               |
| TMF              | bds.tv               |
| UKTV Br'tIdeas   | bds.tv               |
| f tn             | bds.tv               |
| Ideal World      | bds.tv               |
| Kiss             | bds.tv               |
| Smash Hits!      | bds.tv               |
| Kerrang!         | bds.tv               |
| smooth fm        | bds.tv               |
| BBC World Sv.    | fp.bbc.co.uk         |
| The Hits Radio   | bds.tv               |
| Magic            | bds.tv               |
| Q                | bds.tv               |
| BBC FOUR         | fp.bbc.co.uk         |
| CBeebies         | fp.bbc.co.uk         |
| Community        | communitychannel.org |
| BBC R n Gaidheal | fp.bbc.co.uk         |
| BBC Radio 1      | fp.bbc.co.uk         |
| BBC Radio 2      | fp.bbc.co.uk         |
| BBC Radio 3      | fp.bbc.co.uk         |
| BBC Radio 4      | fp.bbc.co.uk         |
| heat             | bds.tv               |
| MOJO             | bds.tv               |
| 305              | fp.bbc.co.uk         |
| BBC R5 Live      | fp.bbc.co.uk         |
| BBC 5L SportsX   | fp.bbc.co.uk         |
| BBC 6 Music      | fp.bbc.co.uk         |
| BBC 7            | fp.bbc.co.uk         |
| 1Xtra BBC        | fp.bbc.co.uk         |
| BBC Asian Net.   | fp.bbc.co.uk         |
| 301              | fp.bbc.co.uk         |
| 302              | fp.bbc.co.uk         |
| 303              | fp.bbc.co.uk         |
| BBC ONE Scot     | fp.bbc.co.uk         |
| BBC TWO Scot     | fp.bbc.co.uk         |
| BBC THREE        | fp.bbc.co.uk         |
| BBC NEWS 24      | fp.bbc.co.uk         |
| BBCi             | fp.bbc.co.uk         |
| CBBC Channel     | fp.bbc.co.uk         |
| BBC R Scotland   | fp.bbc.co.uk         |
| UKTV History     | bds.tv               |
| smileTV          | bds.tv               |
| Premier Radio    | bds.tv               |
| BBC Parliament   | fp.bbc.co.uk         |
+------------------+----------------------+


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