[linux-dvb] stv0297: improvement for qam256 modulated channels

Johann Friedrichs johann.friedrichs at web.de
Sat Nov 3 19:38:48 CET 2007


Hi Oliver,

I'm not sure if you missed my last statement, that the patch works now
fine in my environment. But I use the changed value not only for QAM256
but for every Modulationrate. In that case I can get rid of the
unofficial frequencyshifting in av7110.c, where I had to tune down every
frequency by -250000.

@Hartmut: Can you explain the connection with the frequency shift? Maybe
those people that didn't need the shifting had merely a better signal,
but vdr-portal tells of quite some that need the shifting. Maybe the
value can be parametrized with  module_param to make everybody happy.

Johann

Oliver Endriss schrieb:
> e9hack at googlemail.com wrote:
>> 2007/10/28, e9hack <e9hack at googlemail.com>:
>>> I've seen two different values for the carrier offset on Windows XP for a
>>> TT-C2300. Registers 20/21h
>>> are programmed with 3c0a or 3ba4 (carrier offset 6763 or 6718). The value
>>> depends on the driver
>>> revision. On a TT-C1500, this value is 4000 (carrier offset 7209). It may
>>> be possible, that the
>>> value is calculated from some other values. I know, that the patch has no
>>> effect for some testers.
>>> This is the first report with a failure. So it isn't possible to add the
>>> patch.
>>>
>>> In my case, I've some channels in the UHF range with a poor signal
>>> strength. Without the patch, I
>>> got ber ~3500h and unc >10h. With the patch, I get ber ~b00h and unc 0.
>> Sorry, 'carrier offset' should be 'initial demodulation frequency'.
> 
> What shall we do with this patch?
> I think we cannot apply it right now.
> 
> @e9hack:
> Could it be that the windows driver tries different settings,
> and uses the one with the lowest BER?
> (Some kind of zig-zag scan for this parameter.)
> 
> CU
> Oliver
> 




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