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

[Klaas de Waal]

On Thu, 5 Mar 2020 at 20:17, John Pilkington <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.
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