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

Klaus Schmidinger Klaus.Schmidinger at cadsoft.de
Thu Apr 13 23:02:11 CEST 2006


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.

Just my 2ct.

Klaus



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