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

[Marcel Wiesweg <marcel.wiesweg@gmx.de>]

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 :-)

A quick solution might involve manually setting the NID or a translation 
source -- NID?

Marcel


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