[mythtv-users] Fwd: Re: channel4 hd has no eit - cross-eit

Mike Perkins mikep at randomtraveller.org.uk
Sun Sep 5 10:18:07 UTC 2021

On 05/09/2021 11:06, UB40D via mythtv-users wrote:
> On Sun, 5 Sept 2021 at 10:25, Stephen Worthington <stephen_agent at jsw.gen.nz>
> wrote:
>>> BTW is there any significance to the fact that chanid and channum are not
>>> the same? Should they be? What's the difference between the two?
>> Chanid is an internal database index number generated automatically by
>> the channel scanning process.  It is required to be unique.  Channum
>> is the channel number used by the user to change to a channel in live
>> TV or the guide.  There can be multiple channels with different chanid
>> values that have the same channum.  For example, you may get the same
>> channel in HD from a DVB-T2 source, in SD from DVB-T and also from a
>> satellite or cable service.  To distinguish between the different
>> channels with the same channum, the highest priority one will be used
>> first.  You can set priority in quite complex ways, but usually you
>> will have higher priority for the HD versions of channels, either by
>> setting the channel table priority entry or by giving the DVB-T2
>> source higher priority.
> Thank you: this clarifies things a bit.
> I'm still not quite sure I understand why I would want to assign channums
> by myself. Is it so that (e.g.) BBC1 is number 1, BBC2 is number 2 and so
> forth, instead of having to deal with five-digit chanids?
> Also, I can't quite understand why I might want to retain several copies of
> the same channel under the same channum. Wouldn't it be simpler and less
> confusing to delete all of them except the HD one?
Normally the channum is (in the UK, at least) taken from the on-air data. For Freeview it gives 
repeatable low numbers which remain (mostly) the same even when the channel moves.

You might need more than one version of the channel for when you get scheduling conflicts: If a 
transport is is use, say, which is recording from another channel (eg BBC 4 HD) and blocking the HD 
version of Channel 4 HD then it will use the priority list to determine if there is an alternative 
so that both recordings can progress. If not, it will look at the /program/ priorities and schedule 
the lower one at a later time - if it can.


Mike Perkins

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