[mythtv-users] Tuning issues
Tony Sauri
hoiho.nz at gmail.com
Sun Dec 15 23:03:20 UTC 2013
On 16/12/13 11:01, Jean-Yves Avenard wrote:
> Hi there.
>
> something very weird here...
>
> I upgraded a mate's machine last thursday from ubuntu 10.04 (with myth
> 0.25) to 12.04 and 0.27.
>
> It was all working perfectly before that
> Since then all the recordings to one channels have failed (SBS).
>
> I made him do a full channel scan, and he can't receive that one
> channel anymore.
>
> The other weird thing I had personally never experienced is that when
> scanning for channels, it gives a message about finding conflicts
> (this is after deleting all channels and rescanning) and asking to
> enter channel numbers. That's for the now missing channel.
>
>
> Any ideas what would cause reception level to drop after only
> upgrading the OS? I don't believe there's been much change to the
> dvb-t card drivers (it's a DVICO Dual Digital 4 card)
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>
I am currently running up a test 027 mythtv system to replace
my ageing 024 system that still runs extremely well.
I am right now noticing something similar to what you report and have
been documenting what I think may be sub-optimal processing by
mythtv-setup during a channel scan and channel editing set-up.
In my case I get good signals from 2 sources:
A) The main regional transmitter with perfect line of sight and about 12
km distant.
B) The back lobe of an infill transmitter ... again perfect line of
sight but about 1.5 km distant.
It is further noted that the angular separation of these transmitters is
less than 30 degrees.
The transmitters carry the same signals (3 multiplexes) on different
frequencies:
Trans 1 Mux 1 Chan 32 Freq 562000000 Hz
Trans 2 Mux 1 Chan 33 Freq 570000000 Hz
Trans 1 Mux 2 Chan 34 Freq 578000000 Hz
Trans 2 Mux 2 Chan 35 Freq 586000000 Hz
Trans 1 Mux 3 Chan 36 Freq 594000000 Hz
Trans 2 Mux 3 Chan 37 Freq 602000000 Hz
So when I do a delete all capture card and re-add them and do a full
scan I end up with twice as many potential channels as I need.
Now when I go through the channel editor I have no way of discriminating
between the real or phantom channel records or to put it another way of
associating a channel record with a particular mux frequency.
I have found that if you decide to just use the first channel record
presented and add the xmltvid type stuff when you save it is rejected
because of a duplicate channelids.
So then it becomes a dance to make sure both phantom and real channel
record have different chanids before being able to save a channel record
successfully.
The only way I have found to stay sane is to resort to a little sql. :-)
In your friends case I would suggest the transmission signals have
changed meaning that he now has 2 SBS mux's available.
In passing I will also note that all of the scan methods available
eg Full Scan
Full Scan (Tuned)
Import Existing Scan
Scan of all existing Transports
Scan of Single Existing Transports
have issues in my particular use-case.
I have partially documented these issues and will submit them as bugs
or post here for comment shortly but at the moment (This Time of Year)
my wife seems to think I should spend my time in other ways.
Regards
Tony
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