[mythtv-users] Mux-shifting. DVB-T retune

[John Pilkington]

On 05/03/2020 19:39, Klaas de Waal wrote:
> 
> 
> On Thu, 5 Mar 2020 at 20:17, John Pilkington <johnpilk222 at gmail.com 
> <mailto:johnpilk222 at gmail.com>> wrote:
> 
>     On 05/03/2020 10:42, John Pilkington wrote:
> 
>        After the retune the 'chanid' part of the
>      > filename for new recordings on some channels now has no obvious
>      > relationship to the 'public' logical channel number, or to the
>     channel
>      > scanning log.  For example, Channel 4 used to be 10004 and is now
>     44054.
>      >
>      > I know this link has not been guaranteed in the past and has been
>     broken
>      > when individual channels have moved, but now it's widespread.  A
>     quick
>      > search hasn't found much, although I remember parts of earlier
>     threads
>      > about it.  Can I do some sort of reset, or am I stuck with the
>     new numbers?
> 
>     I've just noticed that a helpful reply about this came off-list.
> 
>     'Delete all video sources' does it, but also deletes all Transports and
>     Channels.  Scanning didn't work for me with Transports defined in an
>     empty list by the Editor, so starting a 'Full scan' was needed
>     initially.  Inter-Transport links can be exploited later, and can help
>     if you receive from more than one transmitter.
> 
> What happens in master/v31 is that when channels are deleted they are 
> not really deleted but they remain in existence until there are no more 
> recordings that reference them. This means that after deleting the 
> channels and doing a new scan all channels that still have recordings 
> will get new chanid values because the old channels are still present in 
> the database and the old chanid values are still in use. This means that 
> in v31 you really cannot depend on the numeric value of the chanid 
> anymore and hence it is not a good idea to write scripts etc that depend 
> on it. In principle the chanid could be a random number.
> 
> For completeness, if you have more than one video source you can also 
> delete only one, you do not have to delete them all.
> 
> Also, it was the idea that a rescan would be sufficient even if the 
> allocation of channels across multiplexes was changed and the 
> multiplexes were moved to a different frequency. The chanid values and 
> all the user information added to the channel (xmltvid, iconpath, 
> visible) would then be preserved.
> This does apparently not work as expected. It would be interesting to 
> have a log of the scan done when the old database is still there and 
> with "-v chanscan,record --loglevel=debug" as options for mythtv-setup.
> 
> Groetjes,
> Klaas.

I'm sorry, I should have asked about useful logs before jumping into 
this.  I don't think I have a system in a known-working pre-retune state 
now and juggling databases to get back to one doesn't appeal.  Mostly 
the retune did work and the extra steps aimed at maintaining a simple 
relationship between LCN and chanid probably didn't make sense; it's 
just that I do still have scripts that require chanid as input and I'm 
still giving that manually.  Insert appropriate emoji here.

John