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

Oliver Endriss o.endriss at gmx.de
Fri Apr 11 23:29:47 CEST 2008


hermann pitton wrote:
> 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.

Are you saying that you did not have any problems without the patch,
and is works with the patch, too?

I do not expect a big difference for common symbol rates like 22 MSPS
or 27.5 MSPS, but it will probably make a difference for high or low
symbol rates.

CU
Oliver

-- 
----------------------------------------------------------------
VDR Remote Plugin 0.4.0: http://www.escape-edv.de/endriss/vdr/
----------------------------------------------------------------



More information about the linux-dvb mailing list