[linux-dvb] Re: [RFC] Frontend API

[Holger Waechtler <holger@convergence.de>]

Alessio Sangalli wrote:
> Holger Waechtler wrote:
>
> [...] diseq stuff
> 
> I don't know a lot about diseq, I just use a diseq to switch between
> hotbird and astra, but I don't know for now the low-level things.

(I get the feeling that most people on this list have this problem;)
You can get the Spec from http://www.eutelsat.org/satellites/4_4_5.html.
If somebody is interested I may write a little posting next days about 
how this is implemented by hardware in DVB cards, adapters and STB's.



>  >  - FE_READ_SIGNAL_STRENGTH and FE_READ_SNR return values in the range of
>  >    0...65536 (0 means no signal, higher values good signals). We don't
>  > define
>  >    if the this range is mapped linear, logarithmic or whatever but
>  > recommend that
>  >    a value of about 70% (~45000) means a good signal
> 
> this is the most important feature I was waiting for. Today those calls
> are a mess, because some drivers answer with a value under 255, others
> until 64k and others always with 0.
> 
> Shouldn't be better if the map is defined to a precise scale, I mean
> that linear/logarithmic/whatever? A program that wants to be or have a
> 'diagnostic' feature should be aware of the mapping system to display,
> for example, a graphic bar or whatever...

We should not define this since most frontend specs don't provide the 
necessary information to implement this.
(This is the situation we have now: for shure it's a fine feature of an 
API to deliver absolute SNR values measured in dBm, but what sense does 
it makes if there is almost no implementaion of this API?)

- Holger



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