[pulseaudio-discuss] Mic input volume controls

Mark Brown broonie at sirena.org.uk
Thu Dec 2 02:56:17 PST 2010

On Thu, Dec 02, 2010 at 11:38:08AM +0100, David Henningsson wrote:

> Hmm. I remember Lennart's original approach would have been to maximize  
> signal quality (i e, move "Master" and let "PCM" stay at 0 dB). Moving  
> this analogy to the input case, what would be the highest quality for 20  
> dB - having "Mic Boost" at 20 dB and "Capture" at 0 dB, or "Mic Boost"  
> at 0 dB and "Capture" at 20 dB?

It's not going to make such an enormous difference if both are analogue,
but in general each analogue amplification stage will introduce noise so
you want to amplify as early as possible.  If Capture is digital (which
is possible) then it is vastly better to do the amplification in the
boost stage as you've discarded data in the ADC with the signal at the
low level it was at.

>> so perhaps best to leave that until UCM
>> can just tell us without probing).

> After having spoken to Mark Brown at Plumber's, he does not expect UCM  
> to handle HDA stuff in the near future, it will be something for the  
> embedded world primarily and we will still have to rely on PA's mixer  
> paths. So unfortunately, I wouldn't hope for UCM to be our great problem  
> solver.

Well, someone can always set up use cases for their system if they want
to.  I'd expect Pulse to be able to DTRT with PC hardware without any of
that most of the time, though.

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