[vdr] Re: Minimum initial info for autotuning

[Holger Waechtler <holger@convergence.de>]

Lauri Tischler wrote:
 > I was wondering what is minimum info required to begin autotuning ?
 >
 > On DVB-T nothing is required as uhf-channels are well-known.
 > Of cource tuning is faster if only active channels are defined.
 >
 > How about DVB-S then, is it possible to start with absolutely nothing
 > and then go thru all combinations of frequency, polarization, 
symbolrate etc.
 > .. or does the bloody thing crash or take about two weeks to scan all..
 >


The common approach is to have a list of common known frequencies to 
test for NIT's and when they all fail then start a linear frequency 
search for signal level peaks. When you found one you try different 
parameter sets and if none works you assume an analog transponder and 
continue your scan.

For DVB-S and DVB-T you should search in steps of the common UHF/VHF 
bands for the region you live in (here in europe mostly 8MHz steps, in 
UK with +/-166kHz offset for every frequency).

As soon you found a NIT you only continue the scan in holes of the 
transponder table (NIT's are not always complete nor error-free: here in 
Berlin the DVB-C FTA transponders don't transmit the NIT for encrypted 
channels and vice versa).

hope this helps,

Holger