[mythtv-users] Entering USA Cable channels into the DVB tables

R. G. Newbury newbury at mandamus.org
Mon Jan 16 21:55:51 UTC 2006


Len Reed wrote:

>I'm using 0.18.2....
>
>There have been a number of posting on the DVB channel tables, but it 
>still isn't clear to me.  I've also looked at
>
>http://www.cuymedia.com/doxygen-dev-docs/html/group__db__schema.html
>
>Maybe with an example someone can clear it up.
>
>I have an HD5000 card connected to cable.  Here is a sample channel, as 
>seen by azap.  Using this information, I can use the DVB utils to 
>capture the signal and play it via mplayer. The following example is for 
>my local (Atlanta) FOX affiliate on Gwinnett Charter cable, for what 
>it's worth:
>
>FOX:669000000:QAM_256:2048:2049:2
>
>So, my dtv_multiplex table has an entry with
>mplexid=4, frequency=669000000, sourceid=qam_256, etc.
>  
>
Since digital channels are multiplexed into the same frequency, the 
mplexid is used to identify the frequency. So you can have 30 channels 
but only 6 or 7 frequencies. The sourceid is the lineup which relates to 
these digital channels...ie if you have analog cable to a PVR as lineup 
one, and digital cable to the HD3000 as lineup two at zap2it, then the 
sourceid will be '2'. The modulation will be qam_256. You can set that 
with update dtv_multiplex set modulation='qam_256' where sourceid'2';


>In the database, Fox digital is my chanid 3785.  So I assume I should
>
>update channel set freqid = 4 where chanid = 3785;
>
>where '4' is the mplexid from the dtv_multiplex table for 669Mhz.
>
>  
>
In my setup, the freqid is  the same as the channum, that is, the number 
in the EPG which you  'call' for the channel you want.

>I further guess that the channel table should get the serviceid (last 
>column of the azap line, "2"):
>
>update channel set serviceid = 2 where chanid = 3785;
>
>  
>
Yes.


>Where do I encode the video and audio pids (2048 and 2049 in hex, 8264 
>and 8265 in decimal)?
>
>  
>
There is no entry for these values. If you look at the output of 
dvbscan, there are no duplicate values. The PID is a unique identifier 
of the stream (although you can probably identify some audio only 
streams, where the vid is 0).


>Now, assuming that I can get this all working, do I then need an 
>additional rows in dtv_multiplex for the other channel on 669 MHz?
>
>CBS:669000000:QAM_256:2176:2177:1
>
>  
>

No. It is the same frequency and therefor the same mplexid as the other 
channel. What will be different will be the chanid, the channum, 
callsign etc. AND the serviceid... which together uniquely identify the 
channel and which piece of hardware are to be used. (The backend looks 
at the sourceid and then looks for the card (s) which are connected to 
that source.)

Kinda confusing, but precise as you could expect for a relational 
database...all information, but only once, (ignoring keys).  Mr. Codd 
would be happy.

Although I would love to know what atscsrcid is for and what value 
should/could go there!

Geoff



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