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

Uri Shkolnik urishk at yahoo.com
Thu Sep 11 07:48:27 CEST 2008




--- On Thu, 9/11/08, Steven Toth <stoth at linuxtv.org> wrote:

> From: Steven Toth <stoth at linuxtv.org>
> Subject: Re: [linux-dvb] DVB-S2 / Multiproto and future modulation support
> To: "Christophe Thommeret" <hftom at free.fr>
> Cc: linux-dvb at linuxtv.org
> Date: Thursday, September 11, 2008, 4:00 AM
> Christophe Thommeret wrote:
> > Le Thursday 11 September 2008 00:59:31 Andreas
> Oberritter, vous avez écrit :
> >> Hans Werner wrote:
> >>>> 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.
> >>> Yes, if we keep to that rule then only
> frontends which can operate truly
> >>> simultaneously should have a different adapter
> number.
> >> An adapter refers to a self-contained piece of
> hardware, whose parts can
> >> not be used by a second adapter (e.g.
> adapter0/demux0 can not access the
> >> data from adapter1/frontend1). In a commonly used
> setup it means that
> >> adapter0 is the first initialized PCI card and
> adapter1 is the second.
> >>
> >> Now, if you want a device with two tuners that can
> be accessed
> >> simultaneously to create a second adapter, then
> you would have to
> >> artificially divide its components so that it
> looks like two independant
> >> PCI cards. This might become very complicated and
> limits the functions
> >> of the hardware.
> >>
> >> However, on a setup with multiple accessible
> tuners you can expect at
> >> least the same amount of accessible demux devices
> on the same adapter
> >> (and also dvr devices for that matter). There is
> an ioctl to connect a
> >> frontend to a specific demux (DMX_SET_SOURCE).
> >>
> >> So, if there are demux0, frontend0 and frontend1,
> then the application
> >> knows that it can't use both frontends
> simultaneously. Otherwise, if 
> >> there are demux0, demux1, frontend0 and frontend1,
> then it can use both
> >> of them (by using both demux devices and
> connecting them to the
> >> frontends via the ioctl mentioned above).
> > 
> > Sounds logical. And that's why Kaffeine search for
> frontend/demux/dvr > 0 and 
> > uses demux1 with frontend1. (That was just a guess
> since i've never seen 
> > neither any such devices nor
> comments/recommendations/rules about such case).
> > 
> > However, all dual tuners devices drivers i know expose
> the 2 frontends as 
> > frontend0 in separate adapters. But all these devices
> seems to be USB.
> > 
> > The fact that Kaffeine works with the experimental
> hvr4000 driver indicates 
> > that this driver populates frontend1/demux1/dvr1 and
> then doesn't follow the 
> > way you describe (since the tuners can't be used
> at once).
> > I would like to hear from Steve on this point.
> > 
> > 
> 
> Correct, frontend1, demux1, dvr1 etc. All on the same
> adapter. The 
> driver and multi-frontend patches manage exclusive access
> to the single 
> internal resource.
> 
> - Steve
> 
> 
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I wrote about it in a previous post, it's not always so. What about diversity (two frontends, single demux (or non if it's not TS based content)?


      



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