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

Trent Piepho xyzzy at speakeasy.org
Fri Apr 14 05:26:02 CEST 2006


On Thu, 13 Apr 2006, Klaus Schmidinger wrote:
> 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 bar graph would be a lot more professional if it was labeled in dB.

> 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.

This hasn't been my experience.  All my STBs have reported SNR in dB on their
diagnostic page.  Same with my cable modems, SNR, downstream, and upstream
signal level were in dB.  My DVD player reports the bitrate in mbits/sec, not
'high' or 'low'.  My thermometer is in degrees (Fahrenheit!), not 'hot' or
'cold'.

Suppose my driver says signal level is 0xb48c, is that good?  Sometimes there
are glitches, is it signal level?  Should I buy an amp, or an attenuator?  The
hardware can tell me this, but all I'm getting is 0xb48c, that tells me
nothing.

If you look at on the web for help, you'll find sites about what you should
look for in signal level and SNR, and they all use dB.  Now if I knew my
signal level was at +25 dB, that would be real information.  It's much too
high, I should remove an amp or buy an attenuator.



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