[mythtv-users] Intermittent MythTV failure

[David Watkins]

> Excuse my ignorance, but I don't know what I'm looking at with logs at
> the moment. Which bits in particular make you question the dvb card? If
> I get a feel for what to look for, then I can try the cards one at a
> time and see if the problems persist.

It was all this sort of stuff.  I've no idea what it means, but it
doesn't look healthy and I don't get it in my backend log.

<snip>
[dvbsub @ 0xb71ea2e8]Junk in packet
[dvbsub @ 0xb71ea2e8]Invalid clut depth 0x13!
[dvbsub @ 0xb71ea2e8]Junk in packet
[dvbsub @ 0xb71ea2e8]Invalid y position!
[dvbsub @ 0xb71ea2e8]Invalid object location!
2007-08-20 10:58:30.284 AFD Error: Unknown decoding error
[dvbsub @ 0xb71ea2e8]Junk in packet
[dvbsub @ 0xb71ea2e8]Invalid y position!
DVBSub error: line overflow
DVBSub error: line overflow
2007-08-20 10:58:31.713 AFD Error: Unknown decoding error
[dvbsub @ 0xb71ea2e8]Junk in packet
[dvbsub @ 0xb71ea2e8]Invalid y position!
[dvbsub @ 0xb71ea2e8]Invalid object location!
[dvbsub @ 0xb71ea2e8]Junk in packet
DVBSub error: line overflow
[dvbsub @ 0xb71ea2e8]Invalid object location!
2007-08-20 10:58:37.190 AFD Error: Unknown decoding error
2007-08-20 10:58:40.765 AFD Error: Unknown decoding error
</snip>



> The other possibility you mentioned is the antenna. I've not got this
> configured very well at the moment. It's just a standard antenna with a
> couple of signal boosters. Not great, but it works most of the time so I
> don't see why that should be causing these intermittent problems.

What do you mean by a standard antenna?  Most roof antennas designed
for analog reception work 'sort of' for dvb but may not work well
enough.  Signal boosters may or may not help depending on where they
are (If the signal's being lost in the 'noise' then amplifiying both
doesn't achieve much).  Also it's possible to boost the signal too
much; some amplifiers have a gain control that you can adjust.

There's really no subsititute for getting the correct aerial
professionally installed, but maybe you can fiddle around with what
you've got to see if you can improve things.  As a rule of thumb you
want signal boosters as close to the antenna as possible, and you want
the input to each card to be as identical as possible.  ie don't daisy
chain them but split the cable into identical feeds.

The myth log probably isn't the best way to monitor what's going on.
Do you have a Set Top Box, to see how that performs?  I don't know if
they produce signal quality stats, but if they do you want to be
looking for a very low 'bit-error-rate'  (BER).  Actually there's
probably linux software that will report BER directly from your cards
(I don't know).


Good Luck

D