[mythtv] DVB Channel Changes

Taylor Jacob rtjacob at earthlink.net
Wed Apr 14 19:37:40 EDT 2004

> On Wednesday 14 April 2004 06:06, Taylor Jacob wrote:
>> > > This is my main goal.  It is really difficult to write a dvb scanner
>> > > when you have a database that does not represent the heirarchy of the
>> > > dvb channel strucutre (I.E. Source -> Transport -> Program).  A scanner
>> > > would be much easier to write if it could track the Transports (or
>> > > transponders in my case for DVB-S) and each Program that hangs off of
>> > > them..
> I don't get it. You can just select distinct rows matching on transport,
> network and provider id in conjunction with frequency, symbolrate and
> polarity. I would suggest enforcing the use of the transport, network,
> provider ids.

Here are my thoughts..

For starters it breaks a heiarchy that already exists, and screws up the relationship between
transport and channel. This makes manually adding channels a completly redundant.  Have you ever
tried this?  I was adding some services here and I don't know how many times I put in the same

If there was a scanning module (which I want to start working on, but need to get an idea whats
wrong with a re-work of the tables first) to traverse the DVB NIT tables to pull channel
information, transport information, etc you would have no way of knowing about transports that you
do not have a channel associated with.

Here is an example with the current setup:

You only are using fta channels and not encrypted channels from some satellite service.  Several
transponders only have encrypted signals when you set it up so there is no reference to the
transponders you are not currently tuning to.

You tell your myth to scan the transponders currently (from this distinct query) and unless they
happen to mention the other transponders existance in the tables you will not scan them, and miss
new fta channels in your scan..

To work around this with teh current setup you could put in dummy channels.

With the proposed setup:

You would pull the tables of transponders and add the new channels when something shows up on the
new transponders you don't have a channel for currently.

>> > Possibly.  However, the scanner is non-trivial and probably best donated
>> > to the wider community ?  Look at the "scan" app and see what needs
>> > improving on that, and then wrap the whole lot I think?
>> >
>> > Also look at VDR and see how they shoe-horn things there.  I'm not
>> > denying that it's a bit of a hack, but I think there is little
>> > motivation or willingness to make big changes to the code base, so in
>> > order to work this in I suggest that you look at minimising the amount
>> > of work/changes required as much as other stuff...
>> From what I have glanced at it appears that VDR just uses a special
>> channels.conf file. I don't know how this handles programs changing
>> location.  I also wonder if importing a channels.conf is really too much
>> of a hack job.  What really needs to be done is to parse through the
>> important DATA Tables and make parses for each of those.  You can download
>> the specs on all of the DVB descriptors from the ETIA.. I wrote a half *ssed
>> guide parser in an afternoon just based on that document, that I am sure
>> would end up being part of what I would do..
>> I agree that it is a huge task..  Maybe I can spark some interest in folks
>> and get some help in writing some of the Descriptor parsers.. :)
> What about bringing in the libsi from vdr? I have not looked very closely, but
> i belive it contains parsers for about every needed table/descriptor.

This might be an execellent idea.  I have used their code as a starting point for a few different
dvb tests ive done.

> Setting up MythTV is not anything like configuring a simple STB. One thing is
> that your 'always' setting up a remote box, or at least have to make it work
> in a remote setup. That gives you a lot of extra logic to deal with.

I mean that setting DVB is far more complicated than it should/needs to be.  There is no reason to
have to manually type in piles of channels when the dvb system is sending all of the information
you need to set it up already.

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