[linux-dvb] Signal, SNR, BER . .

Mac Michaels wmichaels1 at earthlink.net
Sat Jul 9 06:56:54 CEST 2005


On Friday 08 July 2005 11:03 pm, stonewall at inebraska.com 
wrote:
> Working with szap on a satellite multicast application,
> does anyone have documentation to the meaning or value of
> the bits set on the frontend read for the SNR (or also
> known as EbN0) and BER?
>
> The values from szap only are relational, but the tuner
> on these PCI cards are calculating absolutes.  For
> instance, a nominal SNR for the work I'm doing is around
> 15dB . . . but the report from szap, even if you convert
> to decimal, is 58,000 . . .

I think szap just returns whatever value the driver 
supplies.

The raw data for the lgdt3302 chip is noise. There is a 
formula to convert it to SNR in dB in the specifications. I 
coded that up but it produces a negative number when the 
noise is greater than the signal and a small value around 
15 dB for good signal. The DVB interface is an unsigned 
integer so a weak signal results is a large positive value 
and a good signal is a small positive value. Mythtv seems 
to expect the opposite so I changed the driver to return 
the raw data from the chip. 

> And with BER, this is normally a double precision number
> . . . with a good status of around 10e-6 or so.
>
> Thanks in advance for any assistance
>
> Stonewall
>
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