On 01/17/2013 07:16 PM, Manu Abraham wrote:
On Thu, Jan 17, 2013 at 3:03 PM, Antti Palosaari <crope@xxxxxx> wrote:
On 01/17/2013 05:40 AM, Manu Abraham wrote:
MB86A20 is not the only demodulator driver with the Linux DVB.
And not all devices can output in dB scale proposed by you, But any device
output can be scaled in a relative way. So I don't see any reason why
userspace has to deal with cumbersome controls to deal with redundant
statistics, which is nonsense.
What goes to these units in general, dB conversion is done by the driver
about always. It is quite hard or even impossible to find out that formula
unless you has adjustable test signal generator.
Also we could not offer always dBm as signal strength. This comes to fact
that only recent silicon RF-tuners are able to provide RF strength. More
traditionally that estimation is done by demod from IF/RF AGC, which leads
very, very, rough estimation.
What I am saying is that, rather than sticking to a dB scale, it would be
better to fit it into a relative scale, ie loose dB altogether and use only the
relative scale. With that approach any device can be fit into that convention.
Even with an unknown device, it makes it pretty easy for anyone to fit
into that
scale. All you need is a few trial runs to get maxima/minima. When there
exists only a single convention that is simple, it makes it more easier for
people to stick to that convention, rather than for people to not support it.
That is true. I don't have really clear opinion whether to force all to
one scale, or return dBm those which could and that dummy scale for the
others. Maybe I will still vote for both relative and dBm.
Shortly there is two possibilities:
1) support only relative scale
2) support both dBm and relative scale (with dBm priority)
[3) support only dBm is not possible]
regards
Antti
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http://palosaari.fi/
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