[mythtv-users] mythbackend Start-up issue - possible race with dvb device firmware loading

Stephen Worthington stephen_agent at jsw.gen.nz
Thu Nov 19 13:17:09 UTC 2020

On Thu, 19 Nov 2020 12:28:14 +0000, you wrote:

>I'm running FC32 and, as far as I can tell, the device firmware is only
>being loaded at startup.  It's possible that it's loaded again whenever a
>recording is started.  It's hard to tell because that tuner is the second
>in the list and is rarely used.

I have never heard of a tuner where the firmware is ever reloaded.  It
will likely be loading when mythbackend tests the tuner as it starts
up.  If the firmware is actually being loaded more than once, that is
an indication that the tuner reset itself and is probably faulty -
check dmesg or kern.log and you will probably find messages about the
USB device disconnecting and reconnecting.  Given that this is a USB
tuner, the usual rule applies - suspect the cable first.  Make sure it
fits tightly in the PC socket - loose fit means that the slightest
jiggle on the cable (even a gust of air caused by the door being
opened) can be enough to cause the tuner to fault.  Change to cable to
a better fitting one if necessary.  Cats, kids and vacuuming are all
very hazardous to USB cables too, and bumping the aerial cable can
move the USB cable and cause trouble.  One useful trick is to use a
longer cable and lay the tuner flat on a surface at the back of the PC
and tape it down over the cables on both sides to that surface, so
that the USB and aerial cables are not able to move the tuner around
and jiggle things.

I used to have one USB DVB-T tuner that caused me endless problems
like that, and I finally managed to make it reasonably reliable by
using a different cable that was a very tight fit.  But even then, it
would still fail every few months, and just unplugging it an plugging
it in again made it start working again.  So eventually, because of
that and also because I wanted more tuners, I bought an 8 tuner DVB-T2
PCIe card (TBS6209).  That solved the problem!

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