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[linux-dvb] Re: Twinhan DST / TS204 and signal quality questions



Werner Johansson wrote:
> Johannes Stezenbach wrote:
> 
> >If a STB displays a weak signal, what happens? Right, people call the
> >support hotline and complain: "Why is my signal so bad? My Mom's
> >STB gets a much stronger signal!"
> >Solution from the marketing department: Adjust the scale of
> >the displayed signal strength so it is always >80% (unless the
> >signal is so bad that the picture suffers). Then both the
> >customers and the support people are happy.
> 
> :) Ah, I should have guessed... Never underestimate the power of the 
> marketing department! So that's why one should never use the signal 
> meters on a consumer STB to do LNB/dish alignment work...

Well, I was exaggerating a tiny bit, but you get the idea. You cannot
trust "signal quality" readings from consumer equipment.

(OTOH our frontend drivers could still be crap compared to some STB,
regardless what the "signal quality" readings say.)

> >>The TS204 flag, would that imply that the Reed-Solomon FEC has not been 
> >>done
> >>on the card itself, or are the last 16 bytes of data just junk from the
> >>correction process?
> >
> >
> >It's junk.
> 
> At least that's good news, but then the natural follow-up question - why 
> would the tuner output that junk if there's absolutely no need for it? 
> In the Twinhan case it's easy to get rid of it anyway by some DMA code 
> in the BT chip (and I guess that's how it's done in the driver?), but it 
> seems to be one stupid tuner! :)

It's not the fault of the frontend, which signals data/fec output
on a pin. But I guess Twinhan saved to decode this pin to make the
hardware cheaper. Which IMHO isn't a real problem.


Johannes




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