[mythtv-users] DVB delivery systems

[Stuart Auchterlonie]

On 22/09/15 14:27, Devin Heitmueller wrote:
>>> [   12.267085] tda18271 6-0060: creating new instance
>>> [   12.271685] TDA18271HD/C2 detected @ 6-0060
>>> [   12.526085] tda18271 6-0060: attaching existing instance
>>> [   12.526096] DVB: registering new adapter (em28xx #0)
>>> [   12.526106] DVB: registering adapter 2 frontend 0 (Sony CXD2820R
>>> (DVB-T/T2))...
>>> [   12.526313] DVB: registering adapter 2 frontend 1 (Sony CXD2820R
>>> (DVB-C))...
>>> [   12.533764] em28xx #0: Successfully loaded em28xx-dvb
>>> [   12.533775] Em28xx: Initialized (Em28xx dvb Extension) extension
>>>
>>
>> This is good, and makes your life easier, however i thought i'd check
>> out my new PCTV 292e and it only presents a single frontend.
> 
> Sorry for the delayed reply.
> 
> Yeah, so on the 290e the kernel originally had it rigged up as two
> separate frontends due to the inability to switch the delivery system
> at runtime in the kernel API.  This functionality was later added to
> the kernel, and the various drivers were updated to only present a
> single frontend with the ability to toggle the delivery system at
> runtime.
> 
> In short, the inconsistencies you are seeing across different people's
> dmesg output is a result of the kernel version they are running.
> Newer kernels will show a single frontend, older kernels will show two
> frontends.
> 
> The reason there is now a single frontend is actually pretty sensible
> - it ensures that applications cannot attempt to use both frontend
> device nodes at the same time thinking they are separate tuners -
> which would lead to all sorts of crazy results (since both frontends
> were driving the same demodulator and tuner).  Having a single
> frontend with the ability to toggle its mode of operation allows us to
> do device locking properly and makes it more obvious to the
> application that there is only a single device.

Makes complete sense to me. For those older kernels where there are 2
frontends presented, if by some miracle someone has both cable and
terrestrial presented at the same time, then they will need to use
inputgroups to make the other frontend unavailable.

Regards
Stuart