[pvrusb2] HVR 1900: How do I use analogue only (avoid using it for DVB ) ?

[Mike Isely]

On Wed, 8 Jul 2009, Martin Dauskardt wrote:

> > That would be an issue with the application -- not the driver.
> > 
> > This is *not* the first supported hybrid analog / digital device to
> > appear and be supported under linux.  There are many other devices
> > that allow analog and digital video reception, while only allowing one
> > at a time.
> > 
> > The application needs to treat the analog and digital interfaces as
> > two sides to a single device.
> > 
> > Regards,
> > 
> > Mike Krufky
> 
> This would be the perfect solution, but I know that Klaus Schmidinger has no 
> plans to support analogie devices - vdr is a DVB only application. The usage 
> with analogue devices (pvrinput plugin) is developed as a community project.
> 
> How does mythtv handle hybrid devices?
> 
> Maybe I can solve my problems with vdr's parameters:
> 
>   -D NUM,   --device=NUM   use only the given DVB device (NUM = 0, 1, 2...)
>                            there may be several -D options (default: all DVB
>                            devices will be used)
> 
> .. and with the existing pvrusb2 module parameters 
> 
> My idea:
> 
> modprobe pbrusb2 adapter_nr=9
> 
> vdr -D 0 -D 1 -D 2 -D 3 -Ppvrinput
> 
> This example should allow vdr using three DVB cards, while non of them would 
> be the HVR. I will test it as soon as my HVR 1900 arrives.
> 

Mike is right in that this unfortunately is a job for the app not the 
driver.  Honestly it never occurred to me that there would be any reason 
to _disable_ use of an interface.

As for how MythTV handles this:  Basically there you define two 
different devices but declare as part of your configuration that they 
are related.  Then MythTV will handle this by never trying to record 
from both at the same time.  Unfortunately this is not exactly a perfect 
solution - if you tell MythTV to scrap EPG data it will basically leave 
the DVB side permanently open thereby rendering the V4L side useless.  
But if you leave EPG gathering disabled then MythTV handles this pretty 
well.

In an ideal world (IMHO) it should be possible to open a single 
interface (be it V4L or DVB or something else) and to get full 
functionality of the device through that one interface.  If that were 
truly the case then things would make a lot more sense on the 
application side.  But the reality right now is quite different, owing 
to the differing histories of the those two subsystems (DVB and V4L) 
within Linux - including completely incompatible internal architectures, 
opposing API approaches, and generally differing design goals (digital 
video streaming for DVB vs analog uncompressed video capture for V4L).  
I'd love to see one common interface that cleanly handles all of this, 
but until / if that happens we're stuck with the current situation :-(

You mentioned before that by disabling DVB configuration that this works 
around the problem.  Well of course it does but it obviously is not a 
general solution.  I *suppose* I could add a module option to turn off 
specific interfaces for specific instances of a device.  But that smells 
like a giant hack, and I may have trouble getting it accepted upstream.  
Really the answer is what Krufky pointed out: that given the current API 
situation, the app should probably know enough to relate interfaces that 
map to a common device.  If there's something I can do in the driver to 
help *that*, then I'm open to suggestions.

  -Mike


-- 

Mike Isely
isely @ isely (dot) net
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