Re: Details about DVB frontend API

[Jean Delvare <khali@linux-fr.org>]

On Thu, 22 Oct 2009 21:13:30 +0200, Jean Delvare wrote:
> For example, the signal strength. All I know so far is that this is a
> 16-bit value. But then what? Do greater values represent stronger
> signal or weaker signal? Are 0x0000 and 0xffff special values? Is the
> returned value meaningful even when FE_HAS_SIGNAL is 0? When
> FE_HAS_LOCK is 0? Is the scale linear, or do some values have
> well-defined meanings, or is it arbitrary and each driver can have its
> own scale? What are the typical use cases by user-space application for
> this value?

To close the chapter on signal strength... I understand now that we
don't have strict rules about the exact values. But do we have at least
a common agreement that greater values mean stronger signal? I am
asking because the DVB-T adapter model I have here behaves very
strangely in this respect. I get values of:
* 0xffff when there's no signal at all
* 0x2828 to 0x2e2e when signal is OK
* greater values as signal weakens (I have an amplified antenna with
  manual gain control) up to 0x7272

I would have expected it the other way around: 0x0000 for no signal and
greater values as signal strengthens. I think the frontend driver
(cx22702) needs to be fixed.

-- 
Jean Delvare