[mythtv] DisEqC and dvbchannel-v5.patch

Allan Stirling Dibblahmythml0015 at pendor.org
Thu Sep 8 09:51:24 UTC 2005

Daniel Kristjansson wrote:
> On Tue, 2005-08-30 at 11:06 +0100, Allan Stirling wrote:
>>Daniel Kristjansson wrote:
>>>I've been waiting on confirmation from someone with DisEqC before
>>>applying this patch. It seems to help OFDM and ATSC users, but it
>>>significantly changes how DisEqC works so I'd really like someone
>>>to confirm that it actually works...
>>Doesn't seem work with DVB-s. Specific problems (which also appear to be 
>>slightly different, but still present) are:
>>Frequency is calculated incorrectly when input from "Full Scan (Tuned)". 
>>Specifically, looking at the FE_GET_FRONTEND from a hacked femon shows:
>>Looking at the code, shouldn't the stuff compensating for the LOF be 
>>outside the retry loop in handle_diseq? Also, should the code in 
>>CheckOptions not be removed or special-cased for when handle_diseqc is 
>>doing it?
> Can you try the latest code?
Will do very soon.

> Also, you may be right about CheckOptions(). It should also probably
> be located in Tune() not in TuneMultiplex() and SetChannelByString().
> And it shouldn't be doing the LOF stuff.
> BTW Would anyone use LOF frequency shifting and not use DisEqC?

Yes. It's used by Universal LNBs - which are all those used in Europe, 
pretty much. There are other LNB types, though, which may use this, with 
differing switching frequencies.

Just in case you're interested in what's going on here:
The low/high "switch" is (together with the tone Hor/Vert switch) is 
inside the LNB. The LNB converts the frequency from the satellite (which 
wouldn't travel very far on normal cables) to something transportable. 
The amount it reduces the frequency is the Local Oscillator Frequency. 
The value of the LOF is selected by the DVB-s card setting the LNB 
supply voltage to 18 or 13 volts.

> Maybe I can just rip it out of CheckOptions() altogether?
Tried that - Doesn't work. The code is somewhat spaghettiish there, 
however, so I don't understand why not :(



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