[mythtv-users] DVB-C problems

Rudy Zijlstra mythtv at edsons.demon.nl
Wed Jan 3 23:56:15 UTC 2007

R. G. Newbury wrote:

>Rudy Zijlstra wrote:
>>I've been trying to get my DVB-C card working, or rather, to get MythTv 
>>working with my cable operator. This means working around the assumption 
>>on Myth that all cable operators are fully standards compliant. Or 
>>rather, the assumption that all cable operators use DVB-C in the same 
>>manner. One of the assumptions here is that the NIT-Actual will describe 
>>the actual network layout. On DVB-C it is very common though, that 
>>several NIT-Other are present, which each describe the network layout 
>>for a particular geographical area. STB for these operators will present 
>>the user with a network-id choice, and the user has to type in the 
>>network id. The STB then searches for the NIT-Other with this 
>>network-id, and installs from there.
>>This goes against the MythTv assumptions.
>>I've tried to work around this by manual scanning, and taken the 
>>following steps:
>>- determine the frequencies used on my cable (dvbsnoop of frequency, and 
>>manual analysis of of relevant NIT-Other(s).
>>- enter found frequencies into dtv_multiplex
>>- let mythtv-setup perform scan of transports
>>- edit found channels to refer to correct transport stream instead of to 
>>incorrectly assumed transports from NIT-Actual
>>- delelete transports from NIT-Actual from dtv_multiplex, so they do not 
>>clutter the table (and cause confusion for me).
>>End result is that it still does not work, because siscanner will work 
>>from the NIT, and takes the NIT-Actual (judging from output from "-v 
>>As i am no coder, i would like pointers to continue this. I would very 
>>much like to be able to use my DVB-C card to record.
>You don't say what hardware you are using and what other problems have 
>forced you to take this route.
HW is working so not a problem, Read start of message closely and you 
will know what forced me.  Its actually stated there.

>What go you get when you do a channel scan from the second page of Input 
>Connections (in mythtv-setup) with the 'Unencrypted channels only' box 
Nothing. Almost all channels encrypted.... See other (later) messages. 
Also, because of NIT-Other usage the channel scan will actually find 
nothing, nada, niente. See above. This is DVB, not ATSC.

>That should get you a scan of every available digital stream which your 
>cable co sends down the wire...You may only want 30 out of the 450, but 
>they are all there..Then run mythfilldatabase (which will put garbage 
>into the junk channels). Then use Live TV to check the channels. You can 
>use 'e' to see the channel information on channels you can actually tune.
MythFilldabase in my situation for that input is a complete loss of time 
and effort. It actually does nothing for DVB-C based inputs (which have 
been defined as  EIT only), as are mine.

>Deleting channels is a bit of a pain. You have to go back into 
>mythtv-setup, OR, run mysql in a console and do a 'delete from channel 
>where channum = '84#2';' (or whatever the channel is)...(Or check all of 
And i am not in the US (so i am lucky as i do not have to care about 
ATSC and its idiocies (Sorry, once spend a year in a team adding ATSC 
support to a DVB system. The only good thing ATSC did was define the 
famous table for screen resolutions. Otherwise it was a big effort in 
"not invented here"). Not the only time i've seen politics have a big 
negative impact on technology. In this case ATSC basically defined a lot 
of tables to do what DVB was already doing. Functionally nothing was 
added. The good point of the resolution discussion was the discussion, 
as it defined the resolutions to be used. Support for the resolutions 
itself was already present in both MPEG as well as DVB. (yes, the much 
hyped: "ATSC supports High Definiton" is just that: Hype).

>the 84#x channels and delete using the mplexid). And checking the 
>channels will undoubtedly cause some lockups. Run the frontend in a 
>window, smaller than your screen space, leave the mouse on the close (x) 
>box at the top right, and use Alt-Tab to change windows, if you are 
>using a console window for mysql.

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