[linux-dvb] Re: Newstruct and DVB-C with QAM_256

[Sergei Haller <Sergei.Haller@math.uni-giessen.de>]

On Thu, 4 Jul 2002, Holger Waechtler (HW) wrote:

HW> >
HW> > Holger,
HW> >     In the above output, both signal and snr are unusual 16-bit
HW> > values in that they each appear to have identical most significant
HW> > and least significant bytes.  Is this coincidence or are they really
HW> > just duplicated 8-bit values?
HW> >
HW>
HW> Some frontends supply the AGC gain as 8bit values, so we duplicate in
HW> order to allow values in the full range [0x0000...0xffff]. If we would
HW> scale them only by 256, the range would be [0x0000...0xff00].

So why don't you scale by 257: [0x00...0xFF]*257 = [0x0000...0xFFFF]

... but wait, 257 = 0x101, so 0xXY * 0x101 = 0xXYXY ...

so scaling by 257 is the same as duplicating the 8 bit values...


c ya
        Sergei
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