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

Andrew de Quincey adq_dvb at lidskialf.net
Tue Jun 7 13:51:54 CEST 2005

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. 
There does not appear to be any discernable pattern - we have a wide 
selection of TT DVB-S card vintages, and it can happen on any one of them, 
from cards that were bought 2 or 3 years ago to cards that were bought 2 
months ago. :(

Does anyone have any ideas as to why it would be happening? The only thing I 
can come up with is that the frontends just lose the lock after a bit, so 
they need to be retuned to work around it.

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. 

More information about the linux-dvb mailing list