[vdr] AW: AW: Re: AW: Re: DVB-c channel tuning/locking does not work 100% since VDR 1.1.19

["just4all" <just4all@gmx.de>]

Hi all,

i found a simple workaround for my problem. I double checked what the
dvb_frontend.c reports when tuning channels and of course there is an
offset off -0.250 MHz. Then I changed the LNB Drift part to the
following:

/**
	 *  let's start a zigzag scan to compensate LNB drift...
	 */
	{
		int j = fe->lost_sync_count;
		int stepsize;
		
		if (fe->info->type == FE_QPSK)
			stepsize = fe->parameters.u.qpsk.symbol_rate /
16000;
		else
			stepsize = fe->info->frequency_stepsize * 1;

		if (j % 32 == 0) {
			fe->lnb_drift = 0;
		} else {
			fe->lnb_drift = -fe->lnb_drift;
			if (j % 1)
				fe->lnb_drift += stepsize;
		}

		dvb_frontend_set_parameters (fe, &fe->parameters, 0);
	}

	dvb_frontend_internal_ioctl (&fe->frontend, FE_RESET, NULL);
}

That causes that the step size keeps 0 continuously. So if the channel
did not lock right for the first time it stays at the right frequency
(of course I had to change my channels.conf and correct the offsets)
instead of doing a zigzag scan till +- 2.000 MHz. I noticed that once
the zigzag scan is started it sometimes never gets the channel locked
and if so sometimes VDR does not show a picture at all. Perhaps the
receiver thread timed out or something like that.

Thank you all for your help.

-----Ursprüngliche Nachricht-----
Von: vdr-bounce@linuxtv.org [mailto:vdr-bounce@linuxtv.org] Im Auftrag
von just4all
Gesendet: Montag, 30. Dezember 2002 15:22
An: vdr@linuxtv.org
Betreff: [vdr] AW: Re: AW: Re: DVB-c channel tuning/locking does not
work 100% since VDR 1.1.19

Jaakko,

There are no frequencies which finally do lock EVERY time! 
There seem to be NO offset also. The Problem just appears when tuning to
another frequency/transponder. In Germany just QAM64 is used but you are
right QAM128 is harder to tune.
It seems that my DVB-c needs a little longer to tune a channel and the
driver does not like this.
I will go on testing also an report @ dvb-linux ml.

Thx for your help

-----Ursprüngliche Nachricht-----
Von: vdr-bounce@linuxtv.org [mailto:vdr-bounce@linuxtv.org] Im Auftrag
von Jaakko Hyvätti
Gesendet: Sonntag, 29. Dezember 2002 23:27
An: vdr@linuxtv.org
Betreff: [vdr] Re: AW: Re: DVB-c channel tuning/locking does not work
100% since VDR 1.1.19


  David,

  What kind of pattern is there on the frequencies that finally do lock?
Can you see any consistent freq offset?  Are there some channels/QAM
values that consistently lock easily and some that do not?  I guess
QAM_128 channels are harder to tune, am I right?

  I am right now trying to read the AFC register in ves1820, and for
QAM64
channels it stays pretty much constant at 0.02 MHz or something if I
tune
it carefully to a frequency that gives the smallest AFC.  QAM128
channels
fluctuate between -0.5 MHz and +0.7 MHz.  There is a lot to do with
QAM128!

  Hmph.  Opening and closing the device too often also makes the machine
hang every now and then.  How frustrating.  I'll continue testing this
in
a couple of weeks and discuss the results in the linux-dvb mailing list,
which is maybe more appropriate place for driver problems.

Jaakko

-- 
Foreca Ltd
Jaakko.Hyvatti@foreca.com
Pursimiehenkatu 29-31 B, FIN-00150 Helsinki, Finland
http://www.foreca.com


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