[mythtv-users] channel musical chairs

[Gary Buhrmaster]

On Sun, Nov 19, 2023 at 12:12 AM Ross Boylan
<rossboylan at stanfordalumni.org> wrote:

> All subchannels for 4 used to be on the same frequency, I think, but
> now they aren't.  Some of them have changed callsign as well.

This sounds like a reshuffle to provide for an
ATSC 3.0 lighthouse.  The (soon to be) lighthouse
transmitter will arrange to migrate their existing
subchannels to other station owners transmitter
(sometimes having various subchannels on
different transmitters in order to share the
coverage and/or bandwidth).

> I'm concerned about how this will interact with
> 1. SchedulesDirect: do I need a new xmltvid for the new channel?  Is
> that automatically updated from SD, or do I need to do something?

"It depends".  The upstream of SD will sometimes
reuse the same XMLTV, and sometimes assign a
new one.  It will depend, among other things, on
how the station owner is dealing with the change,
and how the (likely) new transmitter is marking
their subchannels (the FCC has some regs about
certain characteristics which can be a forcing
function).

> 2. Existing Recordings: If I delete a virtual channel, like 44.5, or
> change the callsign I assume the old recordings will either have
> nowhere to point for the channel or will have the wrong idea about the
> callsign (and icon) of the station.

In the current releases MythTV will retain existing
channels as long as there is a reference (as long
as you do not try to directly modify the database
outside of the MythTV programs themselves which
can disrupt the business logic).  While this retention
can be good, it can also be a bit confusing as the
old WZZZ and the new WZZZ may not be exactly
the same in certain characteristics, even if they
both seem to be WZZZ.  For most use cases you
will probably not notice/care, but most does not
mean all.

As you watch and then delete your time shifted
content the lingering issues will naturally
disappear (as will, as I recall, those existing
retained channel definitions marked as deleted).

> 3. Existing Recording Rules: what happens to them?  People have
> reported that, at least for rules that are "record on this channel"
> things may stop working.

Correct.  Record on "this" channel means exactly
that, *this* channel.  The match (as I recall) is based
on callsign (so if the callsign changes as it might it
will no longer match).  In general one should try to
avoid using this channel filters when possible (for
some programs, selecting record only new episodes
or record all episodes and retain a small number,
may work better presuming your source guide data
is good and you are consuming it appropriately
with current versions of MythTV).  I removed
"this channel" filters from all my rules some time
ago (although my content consumption is going
to be different from yours, so you may still want
or need "this channel").

> Like others I have found rescanning from mythtv-setup to be pretty
> cumbersome; in particular I recall it tends to recreate many channels
> I deliberately deleted.

For some use cases, marking them not visible
may be better than deleting (as depending on what
options you use when loading guide data they
can end up coming back).

In some cases if you are in the US (where
trying to record multiple muxes is rare) and
are using only recent HDHRs and Schedules Direct
one can do a bit better by using a 3rd party
application to update the stations based on
the SD data (if you are also using the grabber
that provides the get-lineup data) and then
tune using virtual channel number(s).  This
may require SD to update their lineup when
things change (although the HDHR itself
can be asked to detect channels and find
the new frequency/program for channel 4.1),
which may require opening a ticket with them
if no one else gets there first, and to disable
mythfilldatabase from adding/deleting
stations (two cooks will always spoil the stew).