[linux-dvb] TDA10086 fails? DiSEqC bad? TT S-1401 Horizontal transponder fails

hermann pitton hermann-pitton at arcor.de
Fri Apr 11 01:33:17 CEST 2008


Hi,

Am Donnerstag, den 10.04.2008, 22:40 +0200 schrieb Oliver Endriss:
> Hi,
> 
> Manu Abraham wrote:
> > Oliver Endriss wrote:
> > ...
> > > Ok, some calculations according your formula
> > > 
> > >>>>> BW = (1 + RO) * SR/2 + 5) * 1.3
> > > 
> > > 45 MSPS:
> > > BW = ((1 + 0.35) * 45/2 + 5) * 1.3 = 46
> > > 
> > > -> cutoff 36 MHz (maximum value supported)
> > > 
> > > 27 MSPS:
> > > BW = ((1 + 0.35) * 27/2 + 5) * 1.3 = 30,2
> > > 
> > > -> cutoff 31 MHz
> > > 
> > > 22 MSPS:
> > > BW = ((1 + 0.35) * 22/2 + 5) * 1.3 = 25,8
> > > 
> > > -> cutoff 26 MHz
> > > 
> > > Are these calculations correct, or did I miss something here?
> > 
> > 
> > It looks fine, just round it off to the next integer. ie always round it
> > up, rather than rounding it down. For the cutoff at 36MHz, it is fine as
> > well, since at the last step, you will not need an offset, since it
> > would be the last step in the spectrum.
> > ...
> > > Afaics a simple pre-calculated lookup table with 32 entries should do
> > > the job. At least for the cut-off frequency.
> > 
> > That's possible, since you need only 32 precomputed entries, rather than
> > continuous values. That would be much better too, without any runtime
> > overheads. Just the table needs to be done nice.
> 
> Now I found some time to come back to this issue,
> 
> I prepared a small patch to set the cutoff according to Manu's formula.
> The calculation is simple enough for integer arithmetic, so it is not
> worth to prepare a lookup-table.
> 
> @ldvb:
> Please test and report whether it works for you.
> 
> CU
> Oliver
> 

I'm not asked, but give you a report anyway.

On Hotbird 13.0E it makes no difference for me.

Cheers,
Hermann





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