[mythtv-users] known issues related to DVB-T in Australia (was: Channel tuning broken in 0.24)

[Igor Cicimov]

Hi Karl,

Thanks a lot for the email mate you saved me lots of time of googling and
collecting information about this issue! And is good to know that I'm not
going nuts and that channel tuning is well known problem in Australia.

I'm at work atm and the stupid IT security policy here doesn't allow me to
open the links you sent me so will have to wait until I get home
tonight. The news about broken import of channels.conf
is particularly upsetting for me since that was the next thing I wanted to
try *sigh*.

The tuner was happily working for 4 years on mythtv 0.20 and mythbuntu 8.04
although the cx88xx module was not recognizing the card properly and needed
little bit of help. After the upgrade to 0.23 all looked good as well but
when I moved to 0.24 the problems started. I guess there have been some
file and database changes during the process that ruined the fun for me. As
you mentioned the frequencies stored in the DB are not exactly correct so
wonder if I can fix this manually by editing the transponders in the
backend config or maybe strait in the database?

At least the channel 10 reception works good so my wife can record her
Masterchef thing and she's not that angry at me like she was 2 days ago :(

Cheers,
Igor

On Sun, Jun 3, 2012 at 6:38 PM, Karl Dietz <dekarl at spaetfruehstuecken.org>wrote:

> Hi Igor,
>
> I'll write together the issues that I'm aware of for DVB-T in Australia
> in case you or other Australians are ready for some patch testing or
> even looking for some code hacking to do :-)
>
> As you are on Mythbuntu you can build your own patched packages and even
> setup a PPA to share them with fellow testers very easily, see
> http://www.mythbuntu.org/wiki/**recipes<http://www.mythbuntu.org/wiki/recipes>
>
> On 31.05.2012 03:45, Igor Cicimov wrote:
>
>> Before rolling back to 0.23 I'll try to check the card performance
>> outside Mythtv. In meantime, any suggestions to solve this highly
>> appreciated.
>>
>
> There is at least two known issues with MythTV and DVB-T in AU.
>
> One is that the channel scanner stores the center frequency instead of
> the offset frequency of the transports which makes successful tuning
> harder depend on the quality of your DVB-T frontend.
> http://code.mythtv.org/trac/**ticket/9777<http://code.mythtv.org/trac/ticket/9777>
>
> Another is that the channel table in MythTV only contains the +125kHz
> offset but some transmitters seem to use a +167kHz offset.
> https://github.com/MythTV/**mythtv/blob/master/mythtv/**libs/libmythtv/**
> frequencytables.cpp#L336<https://github.com/MythTV/mythtv/blob/master/mythtv/libs/libmythtv/frequencytables.cpp#L336>
> changing the two instances of
> DTVModulation::**kModulationQAMAuto, 125000, 0);
> into
> DTVModulation::**kModulationQAMAuto, 125000, 167000);
> or
> DTVModulation::**kModulationQAMAuto, 125000, 166667);
> might help with that. (A user wanted to test it and report back on IRC
> earlier)
>
>
> With general DVB there was some issue with channel scan that got fixed
> for 0.25.
>
> The scanner didn't work well with segmented PAT/SDT tables. This fix has
> improved channel scans alot for me on DVB-C.
> http://code.mythtv.org/trac/**ticket/10054<http://code.mythtv.org/trac/ticket/10054>
>
>
> Some unfixed issues with EIT have patches that you could try.
>
> The scanner sometimes not finding the ONID/TSID has already been
> mentioned.
> http://code.mythtv.org/trac/**ticket/10217<http://code.mythtv.org/trac/ticket/10217>
> To get at least EIT, should you use that, you can try the patch from
> http://code.mythtv.org/trac/**ticket/10784<http://code.mythtv.org/trac/ticket/10784>
> To improve the quality of the EIT data you can also try
> http://code.mythtv.org/trac/**ticket/10098<http://code.mythtv.org/trac/ticket/10098>
>
>
> And I already worked on the broken channel.conf import, but didn't get
> it working and moved on to higher up stuff on my list.
>
> The channel.conf import is known broken for DVB due to not importing
> the ONID and TSID.
> I have attached a work in progress patch to that ticket, but sadly its
> still not working. Might be a starting point for someone who wants to
> fix the channel.conf import.
> http://code.mythtv.org/trac/**ticket/7701<http://code.mythtv.org/trac/ticket/7701>
>
>
> Regards,
> Karl
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