[mythtv-users] "Tuner 5 has an error"

[Mike Bibbings]

On 25/04/2019 05:06, mythtv at kosowsky.org wrote:
> I am using mythtv 29.1 under Ubuntu 18.04 running under kernel 5.0.9.
>
> I initially installed a Hauppauge WinTV-quadHD PC Express card that
> provides 4 dvb inputs:
> 	 /dev/dvb/adapter0/frontend0
>   	 /dev/dvb/adapter1/frontend0
>   	 /dev/dvb/adapter2/frontend0
>   	 /dev/dvb/adapter3/frontend0
>
> The Frontend ID for all is: LGDT3306A VSB/QAM Frontend.
>
> I then added a Hauppauge WinTV-HVR-955Q (aka Hauppauge Digital TV
> Tuner for Xbox One) USB tuner.
>
> That tuner is recognized by Linux as /dev/dvb/adapter4/frontend4.
> It works fine with VLC.
>
> Mythtv recognis the card appropriately as /dev/dvb/adapter4/frontend4
> with Frontend ID also LGDT3306A VSB/QAM Frontend.
>
> Everything seems fine, but I can't switch to the card input on LiveTV.
> System info says "Tuner 5 has an error" with details:
>         Tuner 4 [DVB: /dev/dvb/adapter4/frontend0] has an error
> (Note numbering is off because I name them Tuner 0 through 4 whereas
> System info seems to count them 1 to 5,
>
> The mythtv-setup configuration for the tuner is the exact same as the
> other 4.
>
> When I cycle through the tuners on Live TV, I go from Tuner 0 to 1 to
> 2 to 3 and back to 0.
> (Note that when I type M->Source, I get only the first 3 tuners...)
>
> The syslog shows for each tuner switch (but no errors for the 'skipped' Tuner 4):
> Apr 24 23:49:03 consult kernel: [83954.235912] dvb_frontend: dvb_frontend_get_frequency_limits: frequency interval: tuner: 42000000...870000000, frontend: 54000000...858000000
> Apr 24 23:49:03 consult kernel: [83959.284003] dvb_frontend: dvb_frontend_get_frequency_limits: frequency interval: tuner: 42000000...870000000, frontend: 54000000...858000000
>
> Any hints on how to track down the 'error' for the last tuner.
> _______________________________________________

You can safely ignore the "dvb_frontend: 
dvb_frontend_get_frequency_limits: ..." messages (they are due to an 
omission in a V4L update, where they should only be output under debug 
conditions, but the debug check line is missing).


 From a clean boot the output "dmesg | grep frontend" from a terminal 
session will show the order of detection and allocation to 
adapter<x>/frontend<y>


Assuming that all required firmware files are in /lib/firmware/, my 
initial guess (without seeing mythbackend.log) is that USB Tuner is not 
completely initialised at mythtv-backend startup, so mythtv gives the 
error message.

A quick check to see if this is the problem is to stop and start 
mythtv-backend as follows in a terminal session:

sudo systemctl stop mythtv-backend

sudo systemctl start mythtv-backend

now using mythfrontend try LiveTV, If the error is no longer present it 
means a race condition at startup

A quick and dirty fix, as an interim only, is to delay mythtv-backend 
startup by a fixed time:

In a terminal on the machine running mythtv backend:

sudo systemctl edit mythtv-backend.service and add the following two lines:

[Service]
ExecStartPre=/bin/sleep 20

Then exit from the edit screen (it uses nano by default, so Ctrl+x, then
y, then Return key) then  reboot the machine

The real fix is more complicated, if the startup delay resolves your 
issue there is more information at 
https://www.mythtv.org/wiki/Systemd_mythbackend_Configuration

see section on Delay starting the backend until tuners have initialized


Mike