[mythtv-users] digital cable channel scan incomplete

R. G. Newbury newbury at mandamus.org
Thu Dec 4 23:19:25 UTC 2008

matt lutz wrote:
> On Thu, Dec 4, 2008 at 3:44 PM, R. G. Newbury <newbury at mandamus.org> wrote:
>>  matt lutz wrote:
>>> All,
>>> I've recently switched from DirecTV/OTA to digital cable.  I have a
>>> HDHomeRun that I wanted to tune the ATSC channels with.  I've
>> successfully
>>> set up the new listings, the HDHR, and scanned for the channels.  I get
>> the
>>> local networks in HD, and some other odd news channels, but I don't get a
>>> decent amount of the available content.  I've been able to map all of the
>>> channels it does find to the proper channel # and xmltv ID, but the big
>>> problem is the missing channels.
>>> If I use the HDHR windows app, I get all of them.  here is my listings
>> page:
>> http://www.silicondust.com/hdhomerun/lineupui?Cmd=LocationProgramsWeb&Country=US&Postcode=22302
>>> Mythtv doesn't find anything with a 'program' number of over 100 for some
>>> reason.  I've searched all over the place on how to add new channels to
>> the
>>> database, and I've done what I think should be correct, but myth can't
>> get a
>>> good channel lock on the new channel I add to the db.
>>> Like I said, I know the HDHR can tune the channel, because I can get it
>> on
>>> my windows laptop using the HDHR software.  Does anyone have any ideas on
>>> what could be wrong in my myth setup?
>> It's not clear what you are actually adding to the db. What you need to
>> add are: a) the frequency to dtv_multiplex and b) the channel info to
>> the channel table.
>> The *number* which 'everyone' uses for a channel now means basically
>> nothing. And there actually are NO channel frequencies with a number
>> over 100: those are just for convenience.
>> There is page here:
>> http://www.mythtv.org/wiki/index.php/Adding_Digital_Cable_Channels_(For_ATSC/QAM_Tuner_Cards_--_USA/Canada)
>> which discusses this in some detail,
>> If your hdhr can see it, then it can produce output which you can use to
>>  set up your database. You really want to install the dvb-apps package
>> to  start with. It's in Fedora 'Everything' but available elsewhere of
>> course. Among other things it provides files listing frequencies and
>> channel numbers:
>> /usr/share/dvb-apps/atsc/us-ATSC-center-frequencies-8VSB
>> /usr/share/dvb-apps/atsc/us-Cable-Standard-center-frequencies-QAM256
>> Since these are ATSC OTA channels, you would use the first page and the
>> azap program to scan for channels. Or you could just create entries in
>> dtv_multiplex with numbers and frequencies.
>> THEN you have to find the digital streams, and set up the PID and other
>> info in the channels table. The wiki page describes this, and how to
>> test using azap and mplayer.
>> I suspect that you are trying to push into the database, the number
>> which you would use in casual talk to describe a station, when its
>> actual channel and PID are quite different due to the digital shift. The
>> 3 networks in Buffalo used to be '2,4 and 7' and they still call
>> themselves that, but those are NOT the tuning frequency channels they use.
>> Finally, if you can tune some unknown channel in mythtv, and recognize
>> it by its content against the guide you can use the on-screen editor to
>> set the Name (WABC-DT) and XMLTVID, to match you Schedules Direct
>> lineup. (But note: the xlmtvid is the definitive identifier at the
>> SchedulesDirect end, but a tv station (or cable provider) and (and they
>> do) change the frequency and/or PID of the digital stream whenever they
>> damn well please!
>> Geoff
> Geoff,
> Thanks for the reply.  Sorry - I misspoke when I said 'ATSC', I really meant
> qam256.  I do know the feqid and muliplex ID.  referenceing the hdhomerun
> listings data, I'm trying to tune feqid 91, multiplex 108.  These are the
> fields that I've entered into a new row in the database.  via mythtv, I
> can't get a lock on it.  That goes for any channel that has a multiplex id
> of over 100.  I'm not sure if that's just a coincidence or not...
> I should also add that I'm running mythbuntu 8.04 w/ mythtv 0.21, and I'm
> trying to tune Comcast digital cable.

OK. If your dtv_multiplex table has 108 entries, it has some duplicates: 
There are not than many actual frequencies...85 or 87 IIRC.

Run Mythtv-setup  and delete ALL tuners on the second page to get back 
to zero. And use mysql if necessary to delete all entries in the 
dtv_multiplex table.

Install dvb-apps and use azap and mplayer (its in the readme and the 
wiki) to scan your channels. You can also use the hdhr. For the hdhr you 
  can directly tune the unit with something like:

  hdhomerun_config 1010ea43 set /tuner0/channelmap us-bcast
   hdhomerun_config 1010ea43 set /tuner0/channel 8vsb:$1
   hdhomerun_config 1010ea43 set /tuner0/program $2
   wxvlc udp://@

In your case it will be the cable channel-map and qam256 not 8vsb. This 
is part of a script I wrote and $1 is the channel by frequency number in 
the list, and $2 is the program PID. If you have vlc (wxvlc) installed 
you can watch tv with this.

When you have a good list, use mythtv-setup to do a scan. Then adjust 
the information in light of what the hdhr has found. You need only 
ensure that the channel table has the correct dtv_multiplex frequency 
reference, and the correct PID (plus a couple of other settings, 
discussed on the wiki page).  The name and XMLTVID must match what 
SchedulesDirect uses for that channel per your setup at SD.


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