[mythtv-users] How to limit 2xDVB-S (+DiSEqC) to 1 LNB at a time?

Simon Hobson linux at thehobsons.co.uk
Mon Apr 27 12:21:12 UTC 2009

Mike Perkins wrote:

>>The reason is that unlike terrestrial where you just feed a load of 
>>signal down a cable and the tuner picks out what it wants, with 
>>sat, the LNB does some of the conversion. In a basic single sat 
>>system, signals sent up the cable will typically select high or low 
>>band, and horizontal or vertical polarisation - thus selecting one 
>>of four sets of signals. Since only one of the four sets of signals 
>>can be sent down the cable at once, that puts limitations on what 
>>signals can be tuned if you split the signal and run multiple 
>>tuners off it - ie the separate tuners can only access signals that 
>>are in the same band and on the same polarisation.
>Interesting. Perhaps there's a case for a feature similar to 
>multi-rec here? Where the tuner(s) can select channels from the 
>subset which the LNB has chosen?

Could get 'complicated' to say the least - though I believe one of 
the new HD freesat PVRs does have that ability if you tell it that 
the second input is actually a feedthrough from the first. I never 
got an answer, but a while ago I did ask if DVB-S uses multiplexes 
like DVB-T - because if it does, then not only would you have the 
complication of having one tuner have to follow another in it's band 
selection, but you could have multi-rec as well as.

I wouldn't like to sit down and work out the scheduling logic for that !

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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