[mythtv] BIG DVB PATCH V3.5 - Logical Channel Numbers

[John Pullan]

On Sun, 2005-01-09 at 23:23 +0800, Tim Davies wrote:
> John,
> 
> Not that I know *anything* about the Europe/UK LCNs, but to paraphrase some
> pertinent parts of the Australian spec (yawn!):

Do you have a link to this spec.

> - The LCN is found in the second descriptor loop of the NIT with tag 0x83.
> I think it is a reserved id, but that's good isn't it?  Reserved for Aussie
> LCNs ;-)
> 
> - Unlike Europe, Australia uses non contiguous LCNs and three digit LCNs.
> Are we using 10 bits, and you guys use 8 bits?

I think we also use 10 bits, at least this is what I gleaned looking at
scan.c in dvb-apps.

> 
> - There are some rules about what to do with a service that doesn't have an
> LCN.  This bit of the code might need to be un-Australianised.  I haven't
> yet seen a service here without an LCN anyway...  
> 
> - European standards say that services with the same original_network_id /
> service_id shall have the same LCN.  That way, regional variants of a
> service can have the same LCN.  Not so here!  In Australia the service is
> uniquely identified by original_network_id / transport_stream_id /
> service_id.  There are several networks (approx ten?) in Oz with unique
> original_network_ids.  Each transmitter has its own network_id, it seems.
>
> Not that most of it really matters too much.  I tried to write the patch so
> that if you get the 0x83 descriptor, it populates the LCN data without
> stomping on another descriptor's code that can also populate it.  Assuming
> of course, any other LCN descriptor just populates a service_id to LCN
> mapping.
> 
> It only falls down if the 0x83 descriptor is used for something else
> somewhere.
> 

That's my point really. I was quite amused/worried when I saw your patch
and realised it was doing the same thing as the UK version of the code.
We intend having a table of network ids to which we can map special
descriptor handling. Hence my request for your network ids.


-- 
John Pullan <jmp at tarantella.com>