[Hardy LPIA LUM]: RealTek hda-intel volume remapping for non-linear volume scales

[Colin Ian King]

LP#249233 - sound volume too low.

for Hardy LPIA LUM.

The attached patch fixes a hardware volume scaling issue on a variety of
Realtek chips found on Atom based netbooks. The main issue is that
setting the volume at low levels is very low and does not scale
linearly. Also, at high volume levels one can get distortion. Hence
there is a requirement to keep the volume levels between a defined
minimum and maximum and also try and scale the provided volume levels to
produce a perceived linear scaling response.

One can select linear or parabolic volume remapping to scale (remap) a
volume level to physical volume level between a desired minimum
and maximum range. This allows adjustment if the volume is not audible
at low settings or distorts if set too high.

Linear mapping scales the volume linearly between a given low and high.

Parabolic mapping scales the volume between a given low and high
so that low volume levels are scaled more favourably (using an inverse
squared parabolic function) than high volume ranges to overcome
non-linear volume scaling found on Realtek model cw020 hardware.

The default is no mapping whatsoever.

Attached: The patch.

-- 
Colin King   <colin.king at canonical.com>
"Me transmitte sursum, caledoni" 
	
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