[mythtv-users] channel musical chairs

[Stephen Worthington]

On Sun, 26 Nov 2023 21:24:00 -0800, you wrote:

>This is a followup report on the effects of some changes.  I took a
>channel, 4.1 in San Francisco, that apparently had only a change in
>frequency and program #.  I had exactly one existing plex at the new
>frequency, and I changed mplexid in the relevant row of the channel
>table to point to it.
>
>This alone seems to have been enough so that myth could tune to the
>channel, which must mean it is either ignoring the program #, which I
>think is what channel.serviceid is, or looking harder if it seems not
>to work.
>
>And clearly having the correct freqid is not important, though I
>eventually changed it and the seriesid to match what I think are the
>right values (from the OTA scan of HDHR).
>
>The channel listings I'm getting seem to match what is broadcast.
>Although my last scan said the channel was KRON-TV, my listing seems
>to identify it as the CW.  The internet confirms the station is more
>or less owned by The CW.
>
>Ross

The freqid field is only used for analogue channels - it is completely
ignored for any digital channel.  I believe scans of digital sources
will now set it to NULL for new channels.  To find the frequency a
digital channel is on, you have to use SQL like this:

MariaDB [mythconverg]> select frequency from dtv_multiplex where
mplexid=(select mplexid from channel where callsign='TVNZ 1');
+-----------+
| frequency |
+-----------+
| 578000000 |
+-----------+
1 row in set (0.001 sec)

The serviceid values normally stay the same when a channel moves
frequency.  They are supposed to be unique across all the channels
that are able to be received at any site, and are usually unique
across an entire TV system.  So when moving a channel to another mux,
the serviceid normally does not need to be changed.  If a channel is
moving to a mux that already exists in dtv_multiplex, then yes, just
changing the mplexid is usually all that is required.

The serviceid is used to match EIT EPG data to a channel, so the
channel name in the scan data and the channel name in the EPG data (if
present) do not need to match, and occasionally are actually
different.  Matching of external EPG data is done on the xmltvid value
for the channel.  Often xmltvid values created automatically have the
serviceid as the first part, for example: 1275.dvb.guide.