[mythtv-users] Signal strength now reporting 50% instead of 100%

[Paul Harrison]

On 09/05/2022 13:33, James Abernathy wrote:

>
>
> On Mon, May 9, 2022 at 7:41 AM Paul Harrison <mythtv at mythqml.net> wrote:
>
>     On 09/05/2022 11:41, James Abernathy wrote:
>
>>
>>
>>     On Sun, May 8, 2022 at 8:39 AM James Abernathy
>>     <jfabernathy at gmail.com> wrote:
>>
>>
>>         Results of my first test of the Hauppauge WinTV Quad HD in a
>>         new system with Ubuntu 20.04.3 LTS and mythtv v31.
>>
>>         I installed Ubuntu 20.04.3 minimal and added the apt
>>         repository for v31. The install was as expected and I setup
>>         the 4 tuners to correspond to the Quad tuner PCIe card.
>>
>>         I used a table top antenna in my lab since I didn't have a
>>         tap for the big attic antenna.  I could not get the PBS
>>         station 40 miles away as expected but the nearby stations all
>>         scanned.  While watching LiveTV, I noticed that the signal
>>         strength displayed was 80-100% instead of 40-50% in V32
>>         Ubuntu 22.04, my production backend.
>>
>>         I'll try later today or tomorrow to move the test PC to a
>>         room that can access the same 8-way splitter that all my
>>         other tuners and tvs are connected to.  At this point it's
>>         looking like the difference between v31 and v32 or Ubuntu
>>         20.04 and 22.04.
>>
>>         Where I'm located with respect to the TV towers you can get
>>         great signals with a coat hanger jammed into the F-connector.
>>
>>         Jim A
>>
>>
>>     I've narrowed down when the signal reporting gets changed. On my
>>     newly built test system with MythTV v31 on Ubuntu 20.04.3 LTS my
>>     signals were reported as ~100% on most of my channels using my
>>     Hauppauge WinTV quadTV as it had for years on my production backend.
>>
>>     I added the ppa:mythbuntu/32 repository and upgraded to v32. The
>>     system updated all 21 packages and everything was working as
>>     before but now on v32.
>>
>>     But when I use Watch Live TV all my reported signal strengths
>>     were between 40-50%.  So the change is MythTV v32 related and not
>>     the version of Ubuntu. The OS remained at Ubuntu 20.04 with
>>     latest patches without any package updates to Linux during this test.
>>
>>     Jim A
>>
>
>     Could be this commit which changed the signal strength range for
>     DVBv5 :-
>
>     https://github.com/MythTV/mythtv/commit/5d76841b8c1878
>
>
>     You could  try starting the backend with --dvbv3 to see what you
>     get with the old DVB v3 API.
>
>
>     Like other have said if it not causing you any problems then I
>     wouldn't worry to much about it.
>
>
>     Paul H.
>
> You are correct. Starting the mythtv-backend with --dvbv3 does restore 
> the signal strength to what I was seeing on v31.
>
> So what I'm hearing is by default in v32 the signal strength is based 
> on dbm instead of %. Are there any problems using --dvbv3 instead of 
> the default??
>
> Jim A
>
>

The value is still calculated as a percent in the range 0 to 100% it's 
just the range of values accepted from the driver has been increased.


It was   -100dBm to -20dBm it is now -100dBm to 0dBm. Previously any 
value between -20dBm and 0dBm was being rejected and I think it would 
fall back to the DVB v3 legacy driver and use the value from that which 
will be the same value you got by forcing the use of  DVBv3.


I think because you are in a very strong signal area the signal strength 
was probably outside the previous allowed range but is now inside the 
new range. I tried to find any documentation related to what the range 
should be but a quick Google didn't find anything so no idea which value 
is correct \0/ I recall there is a DVB tool called  femon that you can 
use to monitor the signal input which may be useful to compare the output.


Paul H.
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