[mythtv-users] Possible to manually add QAM channel information?

Brian Merrill bmerrill at sfcn.org
Wed Jul 27 01:21:13 EDT 2005

Bruce Pennypacker wrote:

>bmerrill Merrill wrote:
>>I would like to get QAM working with MythTV.  I am able to watch QAM HDTV from my cable provider using a combination of dvb-apps, dvbtraffic and mplayer but scanning for the channels using the latest MythTV cvs doesn't seem to work, i.e. it doesn't detect the channels on the first pass and gets "stuck" on subsequent scanning of existing transports.  My understanding from the few scant threads I've been able to find on the subject seem to indicate that my cable provider is not transmitting certain information that Myth requires.  I have tried calling them and speaking to the engineers but have not been able to make much headway through the red tape, though my limited knowledge on what exactly is missing probably doesn't help either.
>>However, I was wondering, if I have collected all the relevant info from dvb-app such as Video PID, Audio PID, etc, would it be fairly straight forward to manually add that information directly into MySQL?  I am certainly no expert with MySQL but I think I could figure  out the relevant commands if someone could point me in the direction of the relevant table(s) that I would need to modify.  But of course if someone knows the actual command that would be very much appreciated as well.  Or is there perhaps an even easier way than modifying MySQL directly?  Or should I not waste my time trying, i.e. a fix is imminent?
>You can do this by modifying one of the tables in mysql.  Take a look at
>http://www.pchdtv.com/forum/viewtopic.php?t=882 for an idea of what
>you'll need to do.  You will need to know a bit about mysql commands. 
>Here's a rundown of what you'll need to do:
>$ mysql -u mythtv -p mythtv
>(login to mysql)
>mysql> use mythconverg;
>(all myth data is in the mythconverg database - do this before any of
>the following commands)
>mysql> describe channel;
>(displays the structure of the channel table - this is the one you need
>to modify)
>mysql> describe dtv_multiplex;
>(you'll need some data from this table as well)
>mysql> select mplexid,frequency from dtv_multiplex;
>(you might just want to cut & paste this into a file and/or print it out
>so you can refer back to it)
>mysql> select chanid,channum,freqid,mplexid,serviceid from channel;
>(shows all the necessary fields you'll care about in the channel table)
>The above commands, along with what's posted at that pchdtv.com url,
>should be enough for you to manually configure your QAM channels.  The
>only really tricky part is figuring out what you should use for the
>serviceid since that requires a bit of trial & error with the dvb-apps. 
>It's based on the audio/video PID's but it's just a sequence #, not the
>actual PID's...
>mythtv-users mailing list
>mythtv-users at mythtv.org
Thanks for the information and the link.  I haven't quite got it working 
yet, but I think I'm close.  I am guessing as you hypothesized that the 
serviceid might be the wild card that isn't properly set and preventing 
me from tuning the channel.  As I have it configured now, when I start 
up mythbackend I get the following output:
Starting up as the master server.
2005-07-26 22:58:29.947 mythbackend: MythBackend started as master server
2005-07-26 22:58:29.951 DVB#0 DVB SI Table Parser Started
2005-07-26 22:58:29.951 DVB#0 Using DVB card 0, with frontend pcHDTV 
HD3000 HDTV.
2005-07-26 22:58:29.953 New DB connection, total: 3
2005-07-26 22:58:30.217 DVB#0 DVB signal f998 | snr fc21 | ber    0 | 
unc    0
2005-07-26 22:58:30.217 DVB#0 Status: LOCK.
2005-07-26 22:58:30.217 DVB#0 Multiplex Locked
2005-07-26 22:58:36.221 DVB#0 Timeout Getting PMT
2005-07-26 22:58:36.221 DVB#0 ERROR - Tuning for channel #2_1 failed.
2005-07-26 22:58:36.221 Closing DVB channel

So I'm guessing that the "Timeout Getting PMT" error has to do with the 
serviceid and myth not being able to find the video and audio PIDs, but 
perhaps I'm wrong in that assumption and perhaps I have something 
misconfigured elsewhere?  If I run "azap -r c110" for example and then 
run dvbtraffic in another window, the video and audio pids appear to be 
in the second grouping which according to the pchdtv thread above would 
correspond to a serviceid value of 2, but I have tried setting the 
serviceid with a value from 0 all the way up to 10 with no luck.
A general rundow of what I have done so far:
1. Added a video source corresponding to HDTV over the air stations 
since these should be equivalent to HDTV cable without adding all of the 
analog cable channels that would just get in the way.
2. Tried running "Scan for channels" first with terrestrial then again 
with cable but it failed to add any channels, although it did add the 
3. Ran mythfilldatabase to at least initialize the channel table
4. In MySql, set the freqid obtained from dvb-apps:
    mysql> update channel set freqid=711000000 where channum="2_1";
5. Obtained the mplexid corresponding to freq 711000000 which was 6 in 
my case
    mysql> select mplexid,frequency from dtv_multiplex;
6. Set the mplexid in the channel table:
    mysql> update channel set mplexid=6 where channum="2_1";
7. Tried to set the serviceid based on information my dvbtraffic
    mysql> update channel set serviceid=2 where channum="2_1";

Is there I've missed or done wrong in the above steps?  Thank you very 
much for your help.


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