[linux-dvb] Re: tzap status output - what does it all mean?

[Rob <rob-linuxtv@noblesque.org.uk>]

Rob wrote:

> So to my original question, what does it mean if snr=ffff, ber=0 and 
> unc is stuck at 0100?  I guess ber and unc ideally should both be 
> zero?  Should snr be a high value or low?  What's a good value for the 
> signal reading?  An snr of ffff looks like the maximum value, which 
> looks a bit bogus to me...?
I decided to "Use the source, Luke", and I notice in cx22702.c that "We
don't have a register for SNR, so we take the inverse of the BER
register".  So I'll ignore the SNR figure...

It looks like there's one byte for signal strength, so "signal 00ff " in
the tzap output would be maximum.

And it looks like there's a one byte count for uncorrectable blocks, but
it wraps around and the difference (modulo 256) is reported, so I'm
still a bit puzzled why I see so many 0x100 in the output.  Maybe the
8-bit register increases up to 0x100 times between reads, but then stops
to prevent wraparound errors in calculations?

So would I be right in guessing that when ber is 0 and unc is 0x100,
that probably means the signal is so bad that there are _lots_ of
uncorrectable errors, and therefore it wasn't possible to correct any
blocks?  If the signal gets a bit better, then I'll start to see ber
above zero?  In other words, if unc is 0x100, then ignore ber.

--
Rob