[linux-dvb] Lost lock problems over extended periods of time

Andrew de Quincey adq_dvb at lidskialf.net
Tue Jun 7 15:50:16 CEST 2005


On Tuesday 07 June 2005 14:30, Manu Abraham wrote:
> Andrew de Quincey wrote:
> > Hi, I've been having (another :) problem with the DVB drivers. Basically,
> > at certain sites and with certain channels, cards seem to lose the lock
> > after a while.... the average is about 10 hours, so I think its unlikely
> > to be that multiswitch incompatability with certain TT DVB-S cards.
> >
> > This doesn't affect all sites or all channels or all cards - the same
> > channels at another site can be rock solid with no issues for months.
> >
> > The driver is supposed to launch a zigzag scan if it loses lock. However
> > this doesn't ever seem to regain the lock with this problem. Simply
> > restarting our streaming software (without a reboot) however, _does_
> > regain the lock (only to lose it again after a while).
> >
> > Snooping with dvbsnoop shows that the signal has been lost, but it does
> > appear to be zigzagging to try and require it, but failing (I see the
> > lock status varying between SIGNAL and SIGNAL|CARRIER|VITERBI, but never
> > above that).
> >
> > The difference between locking initially and losing a lock after a while
> > seems to be the call to dvb_frontend_init(). I'm going to try adding a
> > call to this in to the dvb_frontend_thread() loop if it loses the lock
> > after a while.
> >
> > I'm wondering if anyone else sees this? It seems to plague us constantly.
>
> I had that problem sometime back on the Twinhan cards, that time i
> thought it was because the tuners getting too hot.. As a temporary
> arrangement i tried a huge blower on the cards. This kept the 3 tuners
> cool.
>
> This never had any effect, whether the tuner was hot/cold.

Yeah - I can't test the temperature directly as I'm over 400 miles away from 
that machine - but I did read the HDD temperature with SMART, and it was 26C. 
I'm informed the site is air conditioned, and there is loads of open space. I 
really don't think this is temperature related either.

> The periods used to vary, don't know what exactly caused them to vary
> either. The variations used to happen something like what you said 10 ~
> 12 hours or sometime it was 48 hours. But 72 hours seemed the maximum
> that it would go many times.

Interesting - thats exactly it.. so its across completely different card 
architectures!? (I assume you're still talking about the twinhan cards here)

> Somebody at one of the universities in prague who was streaming in the
> unversity campus also had the same problems....

I seem to remember hearing from them as well, but we didn't manage to find a 
resolution.

> > I suppose these cards are really meant as consumer grade ones for zapping
> > channels, and not really designed for 24x7 reception on a single channel.
>
> I don't think it was the hardware, as the drivers from the manufacturer
> worked fine, eventhough they had their own share of the problems and
> bugs.. :-(

I wonder whether those drivers lose the lock and retune quickly, or if they 
don't lose the lock at all?

I'm hoping we can at least retune so its not such a big hassle - obviously 
some data is going to be lost, but its better than nothing (certainly better 
than it going down completely + irate clients etc).




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