[mythtv-users] Mytv Unreliable

[Mike Perkins]

James Cummings wrote:
> On Tue, Mar 25, 2008 at 11:05 PM, Tim Sawyer <mythtv at calidris.co.uk> wrote:
>>  I haven't done a channel scan for ages, yet this problem has been intermittent
>>  for ages, seemingly on only one of the two tuners.
> 
> Given that your address is in the UK (where I am as well), I would
> strongly recommend doing a rescan of existing transports on a regular
> basis.  The small variations in channel line-ups and frequencies
> *always* cause problems on my box (with a Nova-T 500).  It will be
> recording fine for awhile, then suddenly not be able to find files for
> programs it believes it has recorded.  A rescan of existing transports
> always seems to solve this.  Whenever another freeview STB of mine
> announces that "There has been a change in channel line-up" (even if
> it doesn't turn out to be a visible), I always go into the lounge and
> rescan the mythtv box.  This seems to happen every few weeks.  This
> seems to solve the problem.  Perhaps it isn't the rescan of existing
> transports, but the stopping and restarting of the backend that one
> has to do to run the setup... but that is what seems to work for me.
> 
> I'm going to be upgrading the box from Ubuntu feisty to gutsy soon
> (in preparation to eventually upgrade to Hardy in a couple months or
> so)... I hope that doesn't mess things up too much.
> 
You can get some indication of channel changes by checking the backend log(s) on 
an occasional basis. I can't remember the exact message to look for, but if your 
logs suddenly start growing rapidly (you do use logrotate, don't you?) then it's 
worth a check, and then a rescan if necessary.

Another fun thing to watch out for is if your aerial is able to pick up from 
more than one transmitter. As the transmitters (people) are in the process of 
changing the transmitter (equipment) power levels you may find that channels 
which were in one multiplex suddenly move to another one and thus disappear from 
your lineup.

This link gives you the exact frequencies for each UK TV channel:
http://www.digitalspy.co.uk/terrestrial/tuning/
note that the DVB multiplexes use centre frequencies; the ones given above (I 
believe) are the lowest frequency in each channel band. Then use this link:
http://www.dtg.org.uk/retailer/transmitters.html
to find out which transmitters near you use which channels to send which 
multiplex. Use the Transport Editor screen in mythtv-setup to find out which 
multiplexes the full scan picked up, and work out which transmitters sent which. 
Delete ('D' key) the ones you don't want, then 'Rescan existing transports' to 
give you a clean channel line-up. This Link:
http://www.dtg.org.uk/retailer/dtt_channels.html
will tell you what digital channels are carried by which multiplex. * This list 
is the one which can (and does) change from month to month.

Incidentally, I use three K-World DVB-T 100 cards (£30 each from Maplin) to get 
my digital input, and have found no difference between the cards. They do take 
25-30 watts *each* power, so should only be used in a well-ventilated back end.

Hope this helps.

Mike Perkins