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/ ---------------------------------------------------------------- _______________________________________________ linux-dvb mailing list linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
