[mythtv-users] channel scan missing channels

Steven Adeff adeffs.mythtv at gmail.com
Tue Dec 14 23:06:12 UTC 2010

On Tue, Dec 14, 2010 at 3:06 PM, Michael T. Dean
<mtdean at thirdcontact.com> wrote:
>  On 12/14/2010 01:50 PM, Steven Adeff wrote:
>>>>  On 12/13/2010 04:54 PM, Steven Adeff wrote:
>>>>> In doing a channel scan on my parents new mythbackend we've noticed
>>>>> that Myth isn't finding all the channels that we find using the
>>>>> digital tuner in their HDTV. I've done full scans of "Cable", "Cable
>>>>> IRC" and "Cable HRC" at QAM-64, 128 and 256. I just can't seem to get
>>>>> Myth to see the channels. I need to try to create the channel by hand
>>>>> to see if Myth can tune them, but I'm wondering if anyone else has run
>>>>> into this before?
>> anyone have any ideas? there's a few channel's Myth just won't find
>> that the digital tuners they have *do* find, and they are HD channels
>> so it would be nice if I could get Myth to tune them.
> Have you tried to see if any other application using the exact same hardware
> (the PC and the PC tuners) can find them?  Something like dvbscan?
>  http://www.mythtv.org/wiki/Dvbscan
> Could well be tuner sensitivity/interference, etc., so we need to prove that
> it's actually the software--meaning we need to see some other software that
> uses the same hardware find those channels.

I have tried other channel scanners, the problem is, none of them give
me a usable output since they just show frequencies and sub channels,
but not the "virtual" channel shown by Myth or the TV's digital tuner.
On top of that, the mplexid value, which is basically the "channel" to
the service value's sub channel is not the number shown as the channel
on the digital tuner. So it makes it basically impossible to figure
out how to use something like dvbscan/scan to manipulate Myth's
channel database.
here's the output from scan,
I created the link so as I figure out what channels are what I can put
them there and hopefully help any others in that area.

I've tried scanning multiple times, but there are just certain channel
frequencies that Myth doesn't find/add.

The cable line has plenty of signal strength and a strong S/N ratio.
One of the digital tuners doing the scanning uses an output from the
same splitter that goes to Myth (for the time being as we set Myth up)
and has no trouble finding these channels.

And Robert, yes, thank you for your channel scanner work, along with
whomever helped. I remember trying to add QAM channels to Myth
compared to doing things the old manual way 4 or 5 years ago, and it
was not fun. I recently had to rescan my channels due to Comcast
moving things around and I was up and running almost immediately with
a proper channel mapping. I just wish Time Warner where my parents
are, and whom this is for, was as easy...

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