[mythtv] Problems with QAM scanning on Air2PC

[Taylor Jacob]

Quoting Jarod Wilson <jarod at wilsonet.com>:
> >  The dtv_multiplex table gets populated, but after the scan there are
> > simply no channels listed. As I mentioned on IRC, I have a standalone
> > samsung HDTV box, so I know that QAM is working on the cable.

> I'm in exactly the same boat. When I use azap w/the QAM256 channels.conf, it
> shows locks on all the channels I'd expect to see locks on (and then some),
> but when running a scan from Myth's setup util, just like thor, I repeatedly
> get this on the console:

>From what I can gather from non NDA OpenCable/ATSC documentation all of the SI
tables (System Information) for OpenCable is sent on a seperate QPSK Modulated
carrier (what your cable modem locks on to figure out what its supposed to
do).. This channel contains the entire channel lineup, list of frequencies used
for digital, and guide.. Sadly none of the current cards on the market can lock
onto a QPSK channel.. This is called an Out of Band channel I believe..

ATSC Cable channel tables (CVCT) are sent on multiplexes/transports that are Not
Encrpyted, but on multiplexes/transports that contain only encrypted channels
there are only Mpeg-TS level tables to know where the programs (virtual
channels) are at.. I don't use these for filling the channels table since they
contain no channel name, number, etc.. The Mpeg-TS tables are used for picking
the PIDs only..

I have found on my local cable system I can get a lock on something like 20-30
multiplexs, but only 6-7 of them contain a CVCT.. Its also possible that some
of the multiplexes/transports you get a lock on, but no channels are used for
cable modem downlink..

This is the best I can explain the issue.. The way the scaning loops work is
once it gets a lock it shoves that transport into the database, so later on
re-crawling what myth can lock onto can be a simple process.. If one day we get
a card that will do the QPSK multiplex cable scaning would be a MUCH MUCH faster
thing, and also could mean we could import whatever guide information the cable
company is sending since from what I can gather it is just ATSC style guide
that I already can parse and shove into the database..

Taylor