[vdr] multiple non-independent frontends

Klaus Schmidinger Klaus.Schmidinger at tvdr.de
Wed Jan 6 15:52:27 CET 2010


On 06.01.2010 15:30, Manu Abraham wrote:
> On Wed, Jan 6, 2010 at 5:55 PM, Klaus Schmidinger
> <Klaus.Schmidinger at tvdr.de> wrote:
>> On 06.01.2010 14:22, Tomasz Bubel wrote:
>>> [...]
>>>> - Added support for DVB cards with multiple fontends. Note that this only
>>>>  works for DVB cards where each frontend can be used independently of all
>>>>  the others on the same adapter.
>>> [...]
>>> Any chance of using using DVB-T frontend on HVR-4000? This card have 2
>>> separate frontends. And as quoted on
>>> http://www.linuxtv.org/wiki/index.php/Hauppauge_WinTV-HVR-4000:
>>>
>>> "Multiple frontends are supported: DVB-S/S2 and DVB-T appear as
>>> /dev/dvb/adapterN/frontend0 and /dev/dvb/adapterN/frontend1
>>> respectively.
>>>
>>> Due to a hardware limitation, the two frontends cannot be used
>>> simultaneously. However they can be used sequentially within the same
>>> application. The driver handles the mutual exclusion appropriately."
>> Well, that's still a problem.
>> Is there a defined way (via the LinuxDVB driver API) through which VDR
>> can find out whether the frontends can be used independently?
> 
> Some more food for thought ..
> 
> There is also one more added problem: Say there are two adapters and
> two frontends. I will try to convey the thought as simplest as
> possible by me...
> 
> A case in which frontend0 is bound to adapter0 and frontend1 is bound
> to adapter 1
> 
> This would seem like a classical case of having 2 independent
> adapters. But let's analyze it a bit more deeply. The two adapters A0
> and A1 are on the same physical A (adapter) chip and can send you data
> simultaneously on both the devices. Likewise F0 and F1 can be on the
> same physical F (frontend) chip and can send you simultaneous data to
> both A0 and A1.
> 
> Now suppose that you are having F0 and F1 operational: The F chip
> would have a limitation on some parameter, which is based on a
> combination of F0 and F1. If the sum parameter is exceeded on the
> whole F chip, the entire F chip would crash and might need a Reset.
> 
> Likewise the same holds good for the A chip too ..
> 
> Another case is where you have A0, A1 and F0, F1 on the same chip
> while additionally providing F2 and F3 on virtual A0' and A1'.
> 
> But in all cases, the question remains the same. How would the
> application like to handle a situation, when a certain parameter will
> be exceed on the next operation on the next 'Fx' interface ? (If the
> application feels free and does the operation which might cause some
> parameter to exceed, the chip as a whole would not respond, unless
> reset again)
> 
> Operations like this might be common on cards having dual, quad and
> hex frontends. The card itself might be able to stream dual, quad and
> hex simultaneous streams.



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