[linux-dvb] Some thoughts and questions

Manu Abraham abraham.manu at gmail.com
Mon Oct 8 20:18:10 CEST 2007


Wolfgang Wegner wrote:
> Hi,
> 
> On Sat, Sep 29, 2007 at 01:01:31PM +0200, Felix Domke wrote:
> [...]
>> I don't know if broadcasters are required to send non-inverted signals.
>> I just know (read: remember) that some do. I might be wrong, so second
>> opinions are welcome.
> 
> sorry for the delay...
> 
> Finally I checked again and it is really a transponder on turksat
> that uses inverted spectrum:
> 42°East, 10.956 GHz V SR 5859 FEC 5/6
> 
> This is also mentioned here: (Turksat 1C)
> http://www.satundkabel.de/print.php?sid=11988
> 
> And I just checked it with an old STV0299 frontend.
> There may be others, too, but as of now I can state that one as confirmed. ;-)
> 

Thanks for verifying it. I couldn't make out anything from that page. ;-) 
But anyway not much of a concern if you have verified the same.

I really wonder the cause whether it is really a broadcaster having a wrongly 
wired modulator. Don't see any reason why there should be inversion in that 
case of Ku band.

Anyway that doesn't matter for many/most demods to do a flip-flop in software, 
as they can detect an inversion. I guess device specifics should have been 
hidden in the specific devices only (ie not being able to find many devices 
that _cannot_ detect an inversion) Though not a big issue, as we have a 
workaround such that those ones can avoid that unnecessary flip-flop

(Usually we do things to make devices that do not work resort to workarounds, 
but here we have a logic inversion, in this case)

It is just that we have to resort to some workarounds, to avoid those funky 
things being done for all devices, because some really few devices cannot 
do those.

Regards,
Manu



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