[mythtv-users] Rotor issues

[Peter Bienstman]

Hi,

"open on demand" was already on, I'm afraid.

However, I put a frontend on a laptop, so that I was able to keep an
eye on the rotor itself and the logs at the same time.

Some strange observations:

* upon startup, mythtv tunes to each capture card. Nothing problematic
per se, but I have 5 satellite positions defined, and rather than 5
rotor movements, there are 6 or sometimes 7.

* when looking at the logs scrolling by, it certainly sometimes happen
that tuning and waiting for a lock is already happening while the
motor is still turning

* I tried working around this by lowering the rotor speed in the
recording settings, in the hope that mythtv would wait longer before
it started tuning. That didn't help. Actually it seems the tuning
started a bit faster when mythtv thought the rotor was slower, but
this is probably just sampling bias.

The full logs are here, containing the startup with scanning all the
cards, and then manually selecting a channel on a different satellite,
resulting in a failed lock:

https://www.dropbox.com/s/bn7qkn0158jkkv8/backend.log.fast?dl=0 (speed
0.8 / 1.2, half of default value)
https://www.dropbox.com/s/0q5srfnvm5yppc1/backend.log.slow?dl=0 (speed
0.2 / 0.2)

So, it would seem the main problem is that mythtv does not wait for
the rotor to stop before it starts tuning and looking for a lock.

There's probably all sorts of ways these 2 operations could interfere.
I'm not an expert, but I could imagine problems from the fact that
both the LNB and the rotor make use of 18V vs 13V. Or perhaps, when
tuning while the rotor is still moving between satellites, the card
starts to explore nearby frequencies in order to get a lock, and then
fails to get back to the correct frequency when the rotor stopped
moving?

Cheers,

Peter

On Mon, May 23, 2016 at 4:34 PM, David Engel <david at istwok.net> wrote:
> On Sun, May 22, 2016 at 09:56:48PM +0200, Peter Bienstman wrote:
>> Hi,
>>
>> I have a satellite dish connected to a rotor. Switching channels
>> within a single satellite works without problems, but for turning to
>> another satellite, often I have to try several times before I get a
>> lock, e.g. by selecting a different channel in the new satellite, or
>> first switching to a different satellite altogether. Sometimes I have
>> to try this many times, or even reboot.
>>
>> I tried increasing all sorts of timeouts, disecq commands repeats,
>> played with the rotor turning speed settings, etc but without much
>> effect
>>
>> mythbackend -v channel --loglevel debug does not reveal anything
>> special. The correct commands seem to be sent, the channel gets tuned
>> to, but it's the locking phase that's problematic.
>>
>> I doubt it's a dish alignment problem, because once I have a lock, the
>> signal and SNR levels are good and I can keep watching without
>> problems.
>>
>> Any ideas on how to fix this?
>
> Please try turning on the "open on demand" option on each tuner.
>
> David
> --
> David Engel
> david at istwok.net
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