[mythtv] Re: [mythtv-commits] Re: Ticket #339: Simplify Tuning process

Daniel Kristjansson danielk at cuymedia.net
Thu Sep 22 15:01:35 UTC 2005

On Thu, 2005-09-22 at 10:42 -0400, Taylor Jacob wrote:
> Quoting Daniel Kristjansson <danielk at cuymedia.net>:
> <snip>
> > The whole tuning in RunTV is just busy waiting at the moment, but
> > I'm planning to use things like the signals from the SignalMonitor
> > to trigger trips through HandleTuning().
> I know we talked about this many times before.. Why are we relying on driver
> reported signal levels, they really mean nothing.. I always considered the only
> thing any driver reported usefully was FE_HAS_LOCK..
This is all we rely on for signal lock on DVB cards, the signal levels
are solely for the UI and antenna adjusting.

> All this means really is
> that the potential exists for obtaining useful data.. For example most of the
> ATSC cards I have (Air2pc, hd5000, and hd3k) seems to report FE_HAS_LOCK more
> as a carrier detected not a true lock on the data coming in..
Yep, this is why we look for data after we get a "Signal Lock".
BTW In the tuning changes patch I've renamed "Signal Lock" to
"Partial Lock", and "Channel Lock" to "Lock" ("Channel Lock"
means there is data and it matches what we are looking for).

> Many drivers just report arbitrary vaules that have no unit because the author
> did not have the datasheet, and this will not change.. Not even if all
> manufacturers of demodulators decide to support linux for some reason..
Quite a few I think. Some report a Signal of 100% when there
is a lock and 0% when there isn't, but report a valid S/N ratio
so we should probably validate the data for the UI and report
the more useful one.

> I recall talking to Isaac many months ago about the signal monitoring and in the
> end it made sense to just do all of the signal level monitoring based on if
> valid data was flowing or not.. Anything else really does not work, or has
> flaws..
Well for DVB I look for a FE_HAS_LOCK and then begin looking at the
data. I think FE_HAS_LOCK should be the minimal requirement for DVB

-- Daniel

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