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

[Johannes Stezenbach <js@convergence.de>]

Werner Johansson wrote:
> 
> What seems strange about these Twinhan sat cards is that the signal quality
> and strength indications seems very low compared to what I get on my two
> regular STBs (one Philips/Canal Digital branded box and one Viasat branded
> Thomson DSI-35TH). All the sat equipment is connected to a Thomson SWID 98 C
> multiswitch fed with 4x2 signals from two quad LNBs pointed at 1W and 5E.
> Having tried different ports on the multiswitch they all behave the same,
> tried different cabling as well with no difference.
> 
> Also I have sat cards from two batches (one card with serial # starting with
> 0312 and two consecutive numbered cards starting with 0401), both giving the
> same results (roughly signal ~ 0x3c00 - 0x3d00 and snr ~ 0x1500 - 0x1900),
> which seems really low compared to the 80-90% quality and strength I get
> from the STBs??

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.

On the driver level we don't bother, we just deliver raw register
values and let the application do scaling/interpretation. The
downside of this is that you cannot compare the numbers you get
from different frontend hardware.

> 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.

Johannes