[linux-dvb] DVB-S2 / Multiproto and future modulation support

hermann pitton hermann-pitton at arcor.de
Thu Sep 11 00:46:41 CEST 2008


Hi Steve,

Am Mittwoch, den 10.09.2008, 14:39 -0400 schrieb Steven Toth:
> Janne Grunau wrote:
> > On Wednesday 10 September 2008 17:10:19 Christophe Thommeret wrote:
> >> Le Wednesday 10 September 2008 15:38:23 Steven Toth, vous avez écrit :
> >>>> Is this card able to deliver both S and T at the same time?
> >>> No, the hardware can do S/S2 or T.
> >>>
> >>> The driver in the S2API tree only has S/S2 enabled (for the time
> >>> being).
> >> So, maybe we have to think a bit about how to add support for this
> >> kind of device.
> >>
> >> Maybe a solution could be to have :
> >> - adapter0/frontend0 -> S/S2 tuner
> >> - adapter0/frontend1 -> T tuner
> >>
> >> So applications could know that these 2 frontends are exclusive.
> >> That would not require any API change, but would have to be a rule
> >> followed by all drivers.
> > 
> > The experimental HVR4000 does this already and we have at least initial 
> > support for that in mythtv.
> 
> Yes, I believe it was added sometime ago.
> 
> > 
> > I don't think this was the intended use of multiple frontends in the DVB 
> > API but AFAIK all dual tuners drivers uses multiple adapters.
> 
> It actually was intended for use, it came from patches based on 
> linuxtv.org/hg/~stoth/hvr3000 2 years ago, for this exact reason.
> 
> The idea died on the vine, except for a few die-hard people to 
> maintained their own spin-off/derivative.
> 
> > 
> > I like this approach.
> 
> So do I, it solves a lot of problems with multiple frontends on a single 
> transport bus. At the time I did not patch the 7134 framework with the 
> minor changes for it to comply, but if that's done then the 6-in-1 7134 
> Dual DVB-S/T/Analog card would also benefit greatly. Right now that card 
> only supports some functions in the kernel (IIRC).

just a note on it.

> It's been a very long time but this was also mentioned on the mailing list.

All efforts are welcome. 

It is sad, that it needed that step to come up with new solutions,
whereas multiproto could be in the kernel since long, but only now is
allowed to be there the first time.

We have again forced competition instead of cooperation and I don't like
such, but I know you had no other choice. I'm still naive enough to hope
to rescue as much as possible from both efforts ...

For that 6-in-1 one on the saa7134, since it has two different PCI
bridges on that special PCI slot, it are in fact only two 3-in-1, except
for the shared LNB supply with its issues for the second DVB-S device,
it is really fairly simple to handle.

You just have to choose what you like to have, two DVB-S, two DVB-T
frontends or a mix of it and that is all and kaffeine will deal with it.

The only real danger is analog inputs if DVB uses already the dma
engines. Only packed formats can come through then, planar can really
cause corruption and there is no protection against it.

In the current poor, but fully usable shape, on DVB-T and DVB-S you can
do nothing wrong and just use a workaround, loading a compatible DVB-T
card, to get all possible usage conditions.

It has a manual switch for the two tda8275ac1 hybrid tuners, so you
decide, if you want DVB-T or analog RF loopthrough to both or feed a
different signal on the second.

The enabled DVB-S loopthrough can be used on an external receiver,
if wanted.

It is simpler then on m$ stuff, since fully transparent and totally safe
and fully functional, except for switching to 13Volts on the second LNB,
but they seem to have given up on it on vista too.

Cheers,
Hermann











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