Hartmut Hackmann wrote: > Hi, > > Oliver Endriss schrieb: > > 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 intended to do the same. If I had been aware of that, I would have done something else. ;-) My time is rather limited these days... > Since I have a patch for tda10086 which needs public testing as well, i > would like to propose this: > I do a static check and integrate the patch in my repository together > with my patch and ask for public testing. > Hope this will not overstress the few testers we have ;-) Ok. Since I don't have the hardware I ran the code with common symbol rates. The results looked ok. 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
