[mythtv-users] explain defaultinput field in capturecard table in mythconverg

[Stephen Worthington]

On Mon, 12 May 2014 15:24:22 +1000, you wrote:

>Hi,
>
>My first query is: what is the exact semantics of this field? I notice that in the past
>it defaulted to DVBInput but it now defaults to Television, so I have a mix of both.
>
>I assume that this field tells the backend which input the capture card should sample,
>and some cards do have multiple input sources (though I did not see where in the setup
>one can select this).
>
>On a more general subject, the way the kernel brings up DVB cards, they do not keep
>their device names (/dev/dvb/adapter?) across boots. This means that mythtv cannot really
>keep any parameters that are specific to one card but not to another. I have a mix of
>card types.
>
>Is this a problem, or does mythtv operate in a device agnostic way?
>If this is a problem then I will probably need to differentiate the cards for udev
>(or whatever assigns device names today).
>
>TIA

If you are using cards that are not interchangeable, then you do need
to fix the order the kernel enumerates them, or use udev to create
unchanging links to use in mythtv-setup.  A number of device drivers
will accept a parameter "adapter_nr" to fix the device number they
receive.  It goes in a .conf file /etc/modprobe.d in Mythbuntu.  For
example, I have these two lines in my /etc/modprobe.d/options-dvb.conf
file:

#Set adapter numbers for Nova-TD 500 DVB-T card (dual tuners), and
AverMedia AverTV DVB-T Volar USB tuner (they use the same driver).
options dvb_usb_dib0700 adapter_nr=0,1,2

That makes my three DVB-T tuners always on /dev/dvb/adapter0,
/dev/dvb/adapter1 and /dev/dvb/adapter2.  It does not particularly
matter to me which DVB-T tuner is on which number, as they are all
capable of receiving the same things.  But as far as I can tell, they
AverTV DVB-T Volar USB tuner always gets adapter0.  I may just be
lucky the AverTV tuner works in a way that means it is always on 0,
but I suspect that it has to do with how the driver works.  And the
dual tuners on the Nova-TD 500 DVB-T card are always 1 and 2 and they
are always guaranteed to be in the same order as the kernel always
enumerates sub-devices on one PCI bus card in the same order.

I also have these settings to lock down two my DVB-S2 tuners:

#Set adapter number for TurboSight TBS5922 QBOX S2 DVB-S2 USB tuner.
options dvb-usb-tbsqbox22 adapter_nr=3

#Set adapter number for TeVii S470 DVB-S2 PCIe x1 card.
options cx23885 adapter_nr=4

If your tuners have drivers that accept the adapter_nr option, that is
the easiest way to get the order right.  If not, then you have to
start trying to use udev rules.  Finding the driver name to use
adapter_nr with is not always easy - you often have to spend some time
reading through the log files to work out the correct driver name. But
it is usually easier than getting a udev rule that works.