[linux-dvb] Re: signal noise ratio and signal strength

[Alessio Sangalli <alesan@manoweb.com>]

Holger Waechtler wrote:
> Hi Alessio,
> 
> the current API defines signal strength and SNR as values in 10^-6 dB or 
> dBm. This was originally defined by Nokia but is not implemented by most 
> frontend drivers since the hardware delivers a value between 0...127, 
> 0...255 or 0...65536 and most doc's don't specify how these map onto the 
> logarithmic scale.

ja, I've released an experimental patch for vdr, and many users told 
they had very very strange values, depending on the revision of the 
card, etc...


> In most cases you want the limited range anyway. We are working on some 
> changes in the driver, I'm currently porting some of the frontend 
> drivers to a new API, where we defined both signal strength and SNR to 
> be kind of linear within 0...65536. I'll post a RFC about the frontend 
> and DiSEqC API changes next days on this list, but until the 
> implementations go into the public driver we still need some time.

oh, very interesting!! I would be glad to take part to the discussion.

> We can't simply change the API because it was submitted as part of the 
> LinuxTV standard definition; we'll probably have to release a version 2 
> of the API. Suggestions about changes are welcome.

ok, thank you
bye


Alessio Sangalli








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