[alsa-devel] TAS571x input mixer

[Petr Kulhavy]

Hi,

I'm implementing input mixer controls for the TAS571x amplifier driver.
The mixer register values are signed 3.23 fixed-point linear 
coefficients (i.e. numbers between -8.0 and +7.999), where the default 
value is 1.0

I would like to represent them as ALSA controls and have a few questions:

* The mixing coefficients are signed, i.e. using negative values can 
invert the signal polarity. Does it make sense to allow negative values 
at all?

* Does it make sense to allow values >1.0 i.e. allow digital 
amplification of the signal?

* What is the usual way of representing linear mixer coefficients in 
ALSA (most of the codecs use dB though)? Shall I try to convert them to 
dB? Are there such functions in ALSA?

Thanks
Petr