[vdr] Re: Experiences with patched VDR 1.2.x (was Re: [PATCH] Old descriptorh

["Martin Holst" <holstm@gmx.de>]

Dr. Werner Fink wrote:
> [...]
> > The "video data stream broken" occur on my machine (and on another with
> > 2* DVB-s 1.3) since vdr 1.0.x on (only) the secondary card. So I don't
> > know, how to track this in the source code. 
> 
> Let's read a comment within dvb_frontend.c:
> 
> [...]
> /**
>  *  if 2 tuners are located side by side you can get interferences when
>  *  they try to tune to the same frequency, so both lose sync.
>  *  We will slightly mistune in this case. The AFC of the demodulator
>  *  should make it still possible to receive the requested transponder 
>  *  on both tuners...
>  */
> static
> void dvb_bend_frequency (struct dvb_frontend_data *this_fe, int recursive)
> [...]
> 
> > What is the difference between the primary and the secondary
> > device-handling within VDR? I don't believe that the driver himself 
> > handle the cards in a different way. 
> 
> I's suppose that it could be that if two cards tune to the same frequency
> you'll may see "video data stream broken" ... maybe the workaround
> in dvb_frontend.c isn't good enough.   IMHO VDR should avoid to tune
> two cards onto the same frequency/transponder.

No let us assume that someone have 4 cards. With your idea, this guy
wouldn't be able to tune to 3 transponders in live view. Maybe it is possible to
start a transfer mode whenever a transponder is needed, to which one of card 2-4
is switched. But what about recording? 

Hmm, I think we should track this error on its root. I'd a look in DVB-CVS
and noticed that in mid-june 2002 there was a change in the mentioned
function. Maybe we should try the older version of that function?

Until now, we've no idea, why this error occur only on the secondary card.
When I understand the text above correctly, this behaviour should occur on
both cards at the same time. But this isn't the case. 
And why is it impossible to tune to any channel on the secondary card, when
this behaviour occur? Only a restart of the driver helped.

> On the other side. How the two cards are connected to the LNB. Is
> a multiswitch used?  Then the question rises: which multiswitches
> may cause such interferences which results to wrong frequencies
> (Schwebung, Seitenbaender).  Are there multiswitches which do
> _not_ show this behaviour?

I've a Philips quattro LNB and two Conrad Multiswitches, which are connected
to the LNB via four splitters. With a Dual-Receiver (analog), I've no
problems. And I've no problems with all the other receivers. So this shouldn't be a
problem with our sat-dish or multiswitch. But whether this is a vdr-related
problem or within the DVB-driver... I don't know.
 
Martin

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