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Problem tuning Channel 9

Posted: Sun Jan 29, 2023 2:34 am
by gpw928
I have two MythTV servers in slightly different locations on the far south coast of NSW. One is at Merimbula, the other near Bega.

In both cases the MythTV server is running on Debian GNU/Linux 10 (buster), both patched every few weeks.

The MythTV build dates back to 2019, and was cloned from:

Code: Select all

git clone -b fixes/30
I realise that I need to update, but it's been mostly reliable for a long time, and I have a specific new problem that has recently materialised in Merimbula, but not in Bega.

The local TV broadcasters are ABC, SBS, Seven, Nine, and Ten.

My DVB-T tuners are similar on both servers, with a pair of USB tuners on each host, and network connected HD Homeruns. They have all performed flawlessly for many years.

My new problem is that I can't use MythTV to tune anything from Channel 9 at Merimbula, no matter which tuner I select. I have no such problem at Bega (different signal source).

However, when I use the tuner in the TV set, I have no problems. Channel 9 is fine!

My signal is excellent typically 90 to 96%.

I have re-scanned the spectrum from the backend setup on the server several times. There is no problem identifying Nine with the scanning process.

When I try to watch anything from Nine, the text at the bottom of the screen will say:

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Signal 91% | BE 0 | (TLMs) Partial Lock
and that's where it stops. The problem is identified by the lower case "s" in "TLMs". When tuning works, you get "TLMS".

I'm thinking that there is is issue with the broadcast signal for Nine at Merimbula.

My next step is to upgrade MythTV, but I'd like to see if I can understand the nature of the problem before making any more changes.

Does anyone have any insight into the problem?

Re: Problem tuning Channel 9

Posted: Sun Jan 29, 2023 4:01 pm
by kmdewaal
It could be, as you indicate, that a modulation parameter may have been changed. In version 30 this is not picked-up when doing a rescan of existing transports. Even deleting all channels and then doing full scan does not fix this because the transports are not deleted and the modulation parameters in the database are only written when a new transport is found, not when an existing transport is found.

You can create a new video source, connect the capture cards to the new video source and do a full scan.
It could just be that it then all works.

N.B. This will leave your existing/old channel table intact and you can always go back by connecting the capture cards again to the old video source.

Channel scanning has been improved a lot in version 31 and 32 and the problem of not picking-up a change in transport stream multiplex parameters on a rescan should have been fixed there. However, the procedure described above (creating a new video source) should work in version 30.

Re: Problem tuning Channel 9

Posted: Sun Jan 29, 2023 9:29 pm
by gpw928
I'll create a new video source and test at the next opportunity (next weekend). I'll report the outcome.

Your assistance is greatly appreciated. Thank you.

[Resolved] Re: Problem tuning Channel 9

Posted: Fri Feb 03, 2023 6:13 am
by gpw928
I just created a new video source, attached the tuners to it, and re-scanned.

Channel Nine now works. Problem solved.

Thanks for the assistance!

Re: Problem tuning Channel 9

Posted: Wed Oct 25, 2023 11:36 am
by valen
Thank you both very much.
I had this issue on my mothers instance in Merimbula. It also hit SBS. Mother in law in bega has been fine too.
Golly it's a small world to have the exact same locations lol.

All working now.

Re: Problem tuning Channel 9

Posted: Wed Oct 25, 2023 8:37 pm
by gpw928
Yes, the same problem hit SBS in Bega and Merimbulalast week. Same solution...