[mythtv-users] TuningSignalCheck: SignalMonitor failed ----- Wrong timeout

Stephen Worthington stephen_agent at jsw.gen.nz
Wed Sep 29 12:17:21 UTC 2021

On Wed, 29 Sep 2021 12:44:19 +0100, you wrote:

>I have recently resurrected a USB tuner (Hauppauge Dual HD) which 
>performs very well. However it is failing every few days with the 
>following error:-
>Three instances:-
>Sep 28 20:00:01 tv mythbackend: mythbackend[1523]: E TVRecEvent 
>tv_rec.cpp:3959 (TuningSignalCheck) TVRec[9]: TuningSignalCheck: 
>SignalMonitor failed
>Sep 19 20:00:01 tv mythbackend: mythbackend[4247]: E TVRecEvent 
>tv_rec.cpp:3959 (TuningSignalCheck) TVRec[9]: TuningSignalCheck: 
>SignalMonitor failed
>Sep 12 20:00:01 tv mythbackend: mythbackend[1854]: E TVRecEvent 
>tv_rec.cpp:3959 (TuningSignalCheck) TVRec[9]: TuningSignalCheck: 
>SignalMonitor failed
>EIT scanning is running on this mux.
>The fact that they all occur at the same time is pretty weird. The 
>backend boots up at 17:00 and does a couple of single recordings from 
>then until about 18:30. At 20:00 the main recording period starts. The 
>above failure is not fatal, later recordings on this mux do work.
>The fact that the timeout is only one second is strange as well - the 
>timeouts for the tuner are the defaults 3000 signal 6000 tune.
>Can anybody give any guidance on what logging is required to debug this 
>and I will raise it as a proper issue.

Here in New Zealand, we have one DVB-T channel ("Three") which
requires a much longer timeout for some reason.  So if the recordings
that fail are all on one channel, that is a likely cause.  Three takes
7000-8000 ms to tune normally, and sometimes even longer, so I have
set all my capturecard.channel_timeout values to 10000 ms and that
fixed the problem.  I have only 1000 ms for capturecard.signal_timeout
- I have never had any problem with that setting.

I had to make that change to my settings after one MythTV version
upgrade where the tuning was changed so that it does not automatically
retry and instead obeyed the timeouts.  Before that change, tuning of
Three worked, apparently by timing out and retrying on the same tuner,
but without restarting the tuning process completely.  So the tuner
got set to receive the mux containing Three and mythbackend started
receiving data, but failed to find the header packets for the Three
channel and timed out.  But it left the tuner running and restarted
looking for the header packets, and then found them on the second try,
before a second timeout happened.

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