[linux-dvb] DVB-T and zigzag scans question

[Andrew de Quincey <adq_dvb@lidskialf.net>]

With DVB-T, the zigzag scanning code chooses a step size as follows:

stepsize = fe->info->frequency_stepsize * 2;

frequency_stepsize for OFDM frontends seems to be set to 166667 usually, which 
means it zigzags using a stepsize of 333334.

Thing is, in my experience, frequency bending doesn't work for DVB-T either. 
Using a stepsize of 166667 for trying to lock on to a slightly displaced 
signal is way too large, let alone 333334.

My guess for the problems with the tda100045h is that it loses the lock, kicks 
off a zigzag scan, then never manages to tune again because the steps are so 
large.

Does zigzag scanning/frequency bending work for anyone with DVB-T cards? Or is 
it some quirk here in the UK that means it achieves nothing useful?

I notice for DVB-C cards, zigzag scanning is disabled: stepsize is hardcoded 
to 0. 



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