[linux-dvb] [Proposal] Meaningful reporting of SNR

Andrew de Quincey adq_dvb at lidskialf.net
Thu Apr 13 23:08:06 CEST 2006


On Thursday 13 April 2006 22:02, Klaus Schmidinger wrote:
> Hartmut Hackmann wrote:
> > A comment / question:
> >
> > Does it make sense to spend significant effort on computing an accurate
> > SNR value?
> > It might make sense for VSB and DVB-C / S, i cant tell.
> > But i am sure that for DVB-T, it doesn't.
> > A signal to noise ratio might be excellent but reception very poor due
> > to several (short) echoes.
> > For antenna optimization and comparison there (to my experience) are 2
> > useful values: signal strength (minor) and the raw bit error rate
> > (major). The raw ber can be normalized to the maximum correctable ber and
> > this would be a useful measure since this number tells about the real
> > safety margin.
> >
> > Just my opinion
> >    Hartmut
>
> An actual application (like  VDR, for instance) isn't interested in all
> the various signal parameters and their scaling and units etc, etc. All
> it needs is an idea about signal *strength* and *quality*. So I agree with
> Hartmut. I'd like to have a way of asking the driver for exactly these
> two values, both on a fixed scale from 0 to some maximum (which should
> be the same for all devices, since it's an abstract value). I guess only
> the particular device's driver can take all the various parameters to
> form a useful "strength" and "quality" value. That's what the application
> would finally present to the user in, say, the form of a bar graph.
>
> The average user doesn't care about "dB" or "BER" or whatever. He wants
> to know whether the signal is "strong" and "good". At least that's what
> the STBs I've seen show.

Its a pity we can't just add these to the dvb_frontend_info structure :(
Or at least I assume we can't since we cannot change the binary API.



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