[vdr] Re: vdr-1.3.4 autopid and DVB-T

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

Marcel Wiesweg wrote:
> 
> Am Mittwoch, 11. Februar 2004 18:41 schrieb Koen De Vleeschauwer:
> > While playing around with vdr-1.3.4 and the "autopid" feature, I
> > noticed that sometimes vdr changes channels to values which seem wrong.
> >
> > Questions:
> > - Is my analysis correct?
> > - If it's correct, has this been solved already?
> > - If it hasn't been solved already, does anyone have code for vdr-1.3.4
> > which dumps all PSI information?
> >
> > thanks.
> >
> >
> > When tuning to a DVB-T transponder which emits multiple NIT's, vdr seems to
> > sometimes select the wrong NIT. As a result, when you're tuned to one
> > transponder vdr may changes parameters of other transponders to values
> > which correspond to a different location than the one you're in.
> >
> > Here I have three transponders. One (834 MHz) is part of a SFN, a single
> > frequency network. The same frequency is used throughout the country.
> > The transponder does emit 13 NIT's, corresponding to 13 geographic regions,
> > but all NIT's include a transponder at 834 Mhz (since it's a single
> > frequency network). Right now vdr checks whether the NIT contains the
> > frequency we're tuned to. But since the frequency is the same in all 13
> > regions, this test is always true. So vdr chooses one NIT more or less at
> > random, and starts changing transponders based upon that choice.
> >
> 
> It seems that the SI mechanisms used for DVB-T are more complex than DVB-S/C
> and non-trivial to implement.
> A complete solution will probably have to use some descriptors among Service
> Availability Descriptor, Cell frequency link descriptor, Cell list
> descriptor,  Frequency list descriptor,  Linkage Descriprot (linkage_type ==
> 0x08) with knowledge about the longitude/latitude of the current position :-)

I don't believe that an STB needs to know the longitude/latitude of the current position.
If you buy any commercial DVB-T STB and turn it on, it also has to be able
to get the correct channels, without knownig where it is - or does it?

Klaus


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