[mythtv-users] PCTV 292e DVB-T2

[David Matthews]

On 26/11/2014 08:23, Mark Perkins wrote:
>
>
>> On 26 Nov 2014, at 3:44 pm, "Gary Buhrmaster"
>> <gary.buhrmaster at gmail.com> wrote:
>>
>>> On Wed, Nov 26, 2014 at 3:07 AM, Mark Perkins
>>> <perkins1724 at hotmail.com> wrote: ..... So MythTV is incorrectly
>>> trying to tune DVB-T2 channels as DVB-T, it's just in the past
>>> this was masked because if the tune failed the driver tried
>>> DVB-T2 anyway despite being asked (by MythTV) to tune as DVB-T?
>>
>> What does the driver advertise as far as capabilities? If it claims
>> support of various auto detect modes, it is responsible to do so.
>> Otherwise it should reject any request for auto detect with EINVAL
>> A driver can not have it both ways (claim support and then not
>> perform it). You should be able to write some test cases for your
>> device to determine if the driver is properly complaint. Likely a
>> good test harness would be useful to many.
>> _______________________________________________
>
> Just to clarify, I was asking a question not making a statement.
>
> As far as the driver is concerned, there is a note that auto
> detection is supported in hardware but not enabled in the driver
> (which leaves your question completely unanswered, sorry, but
> hopefully someone with one of these devices will test and respond
> back shortly). At face value if the driver (when queried) reports
> support for auto detection but then cannot auto detect then that
> would seem to be a driver bug. Do you suspect that as the failure
> mode here? Or just trying to narrow things down?

I suspect the problem is that the API does not provide a way to say that 
a driver or device auto-switches between DVB-T and DVB-T2 or to say that 
it should auto-switch if capable.  This is different from other 
properties.  Essentially, DVB-T/T2 switching is modelled on DVB-S/S2 
switching.  A driver can say it supports T2 (S2) with 
FE_CAN_2G_MODULATION.  There are FE_CAN_QAM_AUTO and 
FE_CAN_HIERARCHY_AUTO properties but there isn't a FE_CAN_2G_AUTO property.

In order to use DVB-S2 an application has to use DVB API version 5. 
This uses the FE_SET_PROPERTY ioctl to set a list of properties.  One of 
these can be DTV_DELIVERY_SYSTEM which takes as a parameter values from 
the fe_delivery_system_t enum.  This has values such as SYS_DVBS, 
SYS_DVBS2, SYS_DVBT and SYS_DVBT2.  There are no AUTO entries in the 
enum.  I guess if it was known that a driver auto-switched then maybe 
omitting the DTV_DELIVERY_SYSTEM from the property list might 
auto-switch but the difficulty is knowing if a driver can do that.

The good thing about all this is that MythTV already has the mechanism 
for DVB-S/S2 switching so the patches I've done simply extend that to 
DVB-T/T2 switching.

David