[mythtv-users] DVB-T Problem Locking Signal

[Matthew McClement]

Ian Barton wrote:
> Thanks, but that didn't fix it for me. As an example on Channel 5 I
> get the following stats:
> 
> Signal strength 94% L_s
> 
> However, Myth can't get a lock with either card. Kaffeine has no
> problems.

I had a similar problem with a pair of Compro T200 cards in one of my
backends recently. A KWorld(cx88 based) worked fine, but MythTV refused
to get a lock when using any of the Compro cards(saa7134 based). Signal
strength was ~75%, but the OSD also reported a BER of 65535.

A channel scan under mythtv-setup would sometimes work, and other times
fail completely. However, using dvbscan to generate a channels.conf and
then using tzap worked fine, and the values for SNR and BER were
normal(not what MythTV's OSD reported).

I solved the problem in the end by generating a channels.conf using
dvbscan, sorting and finding all the multiplexes and then did a tuned
frequency scan using *exactly* the settings from the channels.conf for
that plex(inversion/guard/etc) and told it to ignore the signal timeout.
This resulted in a successful channel scan.

I'm still not entirely sure what the original problem is. I found a
utility called wscan(http://www.edafe.org/vdr/wscan.html) normally used
for VDR which also failed to find any channels however it did report
something interesting initially. The Kworld card supports
HIERARCHY_AUTO, while the Compro's don't. Gentle poking of the card with
scans where hierarchy is set to auto seems to kill its ability to tune
for the next ~15 minutes or a hard reboot. Whether that's really the
problem or just a broken driver I don't know and I'm loath to
investigate much further as it's working for now.

Matt