[linux-dvb] [PATCH]Fix a bug in scan, which outputs the wrong frequency if the current tuned transponder is scanned only

e9hack e9hack at googlemail.com
Tue Dec 2 20:22:41 CET 2008

Christoph Pfister schrieb:
> 2008/11/17 e9hack <e9hack at googlemail.com>:
>> Hi,
>> if the current tuned transponder is scanned only and the output needs the frequency of the
>> transponder, it is used the last frequency, which is found during the NIT scanning. This
>> is wrong. The attached patch will fix this problem.
> Any opinion about this patch? It seems ok from a quick look, so I'll
> apply it soon if nobody objects.

After some more investigation, my patch has some problems:

1)Usually the patch is only necessary for transponders, which transmits NIT data of other
transponders (DVB-C only?).

2)It will not work with DVB-S. On DVB-S the returned frequency from frontend is the
LNB-IF. It must be convert to the transponder frequency depend on the LNB configuration.
Scan can't read the LNB configuration from frontend. It must trust the given parameters.

3)On DVB-S, the reported frequency from frontend contains the offset from zigzag scan. If
the offset is greater than 2kHz, scan can't find the correct frequency within the NIT data.

3)The reported frequency from many frontends contains a measured offset. If the offset is
  greater than 2kHz, see above.

Depend on this 4 points, scan should not report any transponder infos, if the current
transponder is scanned only (scan does not tune itself) and if the output format must
contain the frequency of the transponder.


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