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. 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 ;-) Best regards Hartmut _______________________________________________ linux-dvb mailing list linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
