[mythtv] Current DVB problems rundown

Kenneth Aafløy lists at kenneth.aafloy.net
Sun Sep 11 02:04:54 UTC 2005

Lørdag 10 september 2005 08:04, skrev Daniel Kristjansson:
> On Sat, 2005-09-10 at 04:37 +0200, Kenneth Aafløy wrote:
> > IMHO, first of all we should store the frequency of the last succesfull
> > tuning event, so that this could be used in any later tunings.
> I don't like this, it violates the principle of least surprise.
> Normal everyday actions such as changing channels and making
> recordings should not mess with the transponder/multiplex table.

It should not modify the original value in the database, but either enter it 
into a separate field or as a list in the frequency field.

> > We must however support checking that the transponder/multiplex is the
> > one we want before storing the last good frequency!
> This capability is already present in DVBSignalMonitor... You just
> have to add the kDTVSigMon_WaitForMGT or kDTVSigMon_WaitForNIT flag,
> for ATSC or DVB, resp.

Hu, the NIT can take a huge time to get, why not SDT as that's transmitted 
more frequently, or event the PAT?

> > If something goes wrong with tuning the stored frequency, the original
> > could still be tried after some grace period.
> I don't expect this to swing widely very often. Even those
> mountain-top transmitters are serviced fairly often and are
> usually climate controlled, so the drift shouldn't be that bad.

Hmm, wonder if that reasoning applies here:

- My LNB sits on the sunny wall, like everyone elses, which would easily
  cause a very large temperature difference. Not to mention summer and winter.

- The LNB converts the frequency of the signal down about 1Ghz.

- The transmitter is located fairly far away, and definatly has no climate

> Most of the time the frequency will be wrong simply because the user
> used the wrong frequency table. Situations like John Poet's where
> a new antenna/transmitter is being tested will be the exception not
> the rule.

Right, nothing we can with keyboard problems, exept perhaps trying to
tune the parameters right away and emit a warning if it failed!


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