mythtv vs. comcast

Hans Fugal hans at
Sun Mar 14 15:02:17 MDT 2010

On 3/14/10 10:24 , Brad Midgley wrote:
> Hey
> Is anyone else trying to get mythtv to play nice with unencrypted comcast?
> I found I could no longer do nondestructive scans after upgrading to
> mythtv 0.22. As a result I'm slowly losing channels as comcast shuffles
> their channels around.
> See
> I'm using plain ubuntu 9.10, maybe I need to finally transition to mythbuntu.

I have been very unimpressed by the channel scanning behavior in 0.22.
It's really messed up.

I have notes and I have been meaning to put up a blog post, but I
haven't, and so I'll dump some raw notes here: feel free to ask
questions if anything's unclear.

Channel scanning
Heavens what a mess.

- set up distinct video sources for analog vs digital even if they have
the same lineup

Analog Cable (PVR-150)
- if scanning for channels worked instead of hanging, you could do that
(you can still do it but not get the full listing)
- fetch lineup from schedulesdirect, but make sure you use the analog
lineup for this source or you'll have gobs of channels to delete
- delete channels you don't actually get (plug your cable into your tv
or use ivtv-tune to check)

Digital Cable (hdhomerun)
- don't scan for channels, it's a total waste. because comcast uses this
thing to map virtual channels to actual qam256 channels+programs. multiple
SCTE tables are present, you need to use the one with the right VCT ID, but
myth's scanner doesn't let you choose it just has a worthless sequence of
confusing dialogs about (non-)conflicting ATSC, MPEG, or SCTE channels.
- use scte65scan to generate a channels.conf. I had to play detective to
out my VCT ID (3058) from the all-VCTs text output, because I couldn't find
it in the set-top box diagnostics. look at the government access type
include -p when generating to get the ATSC channels
- but oops, mythtv-setup crashes on reading channels.conf. REALLY?
- oh well, make mytthv sql then. feed it to mysql -u mythtv -p
mythconverg (password in /etc/mythtv/mysql.txt)

After either/both, run mythfilldatabase --only-update-channels, then
check in mythweb.

In mythweb, match up callsigns for channels you get on both tuners that
might be slightly different, so the channel only shows up once in the
program guide.

ATSC channels over cable won't get their xmltv ids automatically. best
way i've found is to manually update them in mythweb based on the
mouseovers of the channels in the ATSC lineup from schedules direct.

Finally delete any channels that don't have an xmltv id, or figure out
the id if it's a channel you want (and report the discrepancy to


The key concepts here are do an SCTE (this is how comcast maps
frequencies to channels) and don't EVER run myth's scanner.

scte65scan will make SQL to update or create the db tables. I think I
had to hack it (the Makefile I think) to get it to compile in Mythbuntu,
but it works great and seems to be well-documented. Make a note of the
VCT ID once you figure it out because it's much faster to scan a single
VCT than the whole thing. Also make note of which frequency has the VCT
information to further speed up the subsequent scans.

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