[mythtv] DVB/ATSC channels.conf import troubles

[Johnny Graettinger]

I'm running a recent svn copy patched with the changes Christiaan
discusses for importing channels.conf in cases of DVB/ATSC cards. To
that end, I've constructed a channels.conf via azap  & dvbtraffic
containing pid's for each in-the-clear channel, eg:

CBS:625781200:QAM_256:209:212

On a perhaps related tangent, you'll notice that the frequencies used
are non-standard. Comcast in baltimore uses HRC (harmonic resonance
something?) rather than standard cable transmissions, so QAM scanning
in mythtv has not worked for me, prompting a more manual approach.
Indeed, I only got this working by using the recently added
/util/scan/atsc/us-Cable-HRC-center-frequencies-QAM256 file within the
dvb-apps distribution as a baseline.

azap -r CBS; dvbtraffic; cat /dev/dvb/adapter0/dvr0 > foo.mpg 

works great, and resulting streams when viewed seem without error.

Sorry for all the background, now on to myth specifically:

Following Christiaan's lead, I rearranged channels.conf to follow the
modulation with just a program number in the transport stream, and
imported it into mythtv-setup. The import succeeds, but an effect I've
noticed is that, in a video source containing only the imported
transports, a full scan of existing transports immediately returns
with error, and an existing transport scan simply sits indefinetly
with the progress bar at 3%

However, not to be deterred, I gave mythbackend a try. Lo and behold,
it gets a lock on the default channel for my HD-3000 tuner. But
watching tv simply sits in a black screen for a while.

As a test, while it was sitting in such state I cat'd dvr0 to an mpg.
The resultant mpg did increase in size, indicating the tuner was tuned
to particular video and audio pid's, however was not playable (mpeg
header not found).

One last strange issue. Another experiment I've performed is to start
mythbackend so that it gets an initial signal lock on the default
channel for the tuner. I then run dvbtraffic to confirm the tune.
What I've found is that, per update, dvb traffic does occasionally
print the pid's and bitrates I'd expect for the stream, but most of
the time it prints out a large number of 1-4 kbit pid's, which I
understand to be indicitave of a dirty or poorly locked signal.
Further, if I leave the same instance of dvbtraffic running, and then
kill the mythbackend instance, dvbtraffic immediately sorts itself out
and prints the correct pid's/bitrates (no re-locking via azap
necessary).

Is it because the lock in mythtv is poor that it's having trouble
picking correct pid's for the stream? Or are these two completely
seperate issues? And of course, any idea what could be causing the
strange locking/dvbtraffic behavior? Or alternatively, how I might
mangle the code in order to fix QAM scanning so myth finds these
channels for itself?

Any help *much* appreciated

Johnny