[mythtv-users] DVB-S2 scan fails (0.29)

Mike Bibbings mike.bibbings at gmail.com
Sat Dec 23 22:50:17 UTC 2017


On 23/12/17 11:02, UB40D wrote:
> I'm rebuilding a standalone mythtv machine with ubuntu 16.04 LTS and 
> mythtv 0.29.
>
> I successfully imported the database backup from the old machine that 
> had died a few months ago during a software upgrade and that I had 
> never found the time to resurrect.
>
> I would now like to make tv reception work again. I have a Freesat HD 
> (DVB-S2) setup. To be sure, in mythtv-setup I have deleted all capture 
> cards and deleted all video sources. I have then remade the two 
> capture cards of my TBS 6981 dual tuner, I have made an EIT video 
> source and I'm now stuck at the input connections and channel scan phase.
>
> [DVB: /dev/dvb/adapter0/frontend0] (DVBInput) -> EIT
>
> scan for channels
>
> tv, unencrypted, video source eit, input /dev/dvb/adapter0/frontend0, 
> scan type full scan (tuned)
>
> When I get to the "scan type" screen, I fill it up with the parameters 
> for dvb-s2 from the very useful page at 
> http://parker1.co.uk/mythtv_freesat.php , which has been my reference 
> for years:
>
> Freq: 10847000
> Polarity: Vertical
> Symbol rate: 23000000
> Mod Sys: DVB-S2
> FEC: 2/3
> Modulation: 8PSK
> Inversion: leave at auto
> Rolloff: leave at 0.35
>
> Now the first glitch: a number of times, when I exit this screen, the 
> settings I just entered are lost, and I can't figure out why.
>
> If I exit by "left arrow", then go back in with "right arrow", the 
> settings I entered are still there.
>
> If I exit by "ESC / Save then exit", then go back in with "scan / full 
> scan", then the settings I entered have disappeared, despite me having 
> selected "Save then exit". Uh??? WTF?
>
> I then patiently re-enter the parameters, carefully exit that screen 
> just with left-arrow, go down one item to "scan", press enter, nothing 
> happens for about 10 seconds and then I get a SCANNING screen with 
> "failed to find any channels".
>
> What am I doing wrong? Could it be that my reference page is obsolete 
> and that these frequencies are no longer used? Well, I checked on the 
> BBC's website too and finally found this
> https://downloads.bbc.co.uk/reception/pdfs/satellitefrequencies.pdf
> which has essentially the same data as above:
>
> DSAT 4
> Astra 2E (28.2° East)
> Transponder 50
> Frequency: 10.84700 GHz
> Vertical polarisation
> Modulation: DVB-S2, 8PSK
> Symbol rate: 23.0 Mbaud
> FEC 2/3
> Transport Stream ID: 2050
>
> What else is the problem? And by the way, why does "save then exit" 
> not save the parameters? Could there be some wrong permissions 
> somewhere, either in the file system or in the database? It is a 
> rebuilt system after all... I was already more than impressed that the 
> old database backup was restored at all notwithstanding having 
> upgraded myth to a newer version.
>
I am not near my setup at the moment so the following is from memory:

If you are using the built-in kernel drivers for the tbs 6981 (these are 
open source, as distinct from TBS drivers) you need some extra firmware 
in /lib/firmware/ see :
https://github.com/ljalves/linux_media/wiki/CX24117-firmware

Once the firmware is installed you  need to reboot.

As far as scanning is concerned I use for Freesat UK  (there is auto 
switching between DVS-S and DVB-S2)

Freq: 10714000
Polarity: Horizontal
Symbol rate: 22000000

You can leave all other values at default.

Before running mythtv-setup make sure mythbackend is not running i.e. 
sudo systemctl stop mythtv-backend.service

If  upgrading from 0.28 to 29 ppa you need to use sudo apt dist-upgrade 
(and not sudo apt upgrade as this will leave somethings not upgraded)

Mike


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