[pulseaudio-discuss] Mic input volume controls

Colin Guthrie gmane at colin.guthr.ie
Thu Dec 9 13:27:05 PST 2010

'Twas brillig, and Colin Guthrie at 09/12/10 16:12 did gyre and gimble:
> 'Twas brillig, and Kulikov, Vitaliy at 01/12/10 17:34 did gyre and gimble:
>> Hello everybody,
>> I would like to add more details for issue #1. Just changing order of
>> the capture and MIC volume controls in the path is not enough if those
>> volumes have gain only ranges and the reason is that, AFAIK, currently
>> PA adjusts requested volume to the higher HW volume step. But if we
>> change it to lower HW step it should work just fine. Here is the example
>> how that works. 
>> Let's say we have 22.5 dB gain only range with the 1.5 dB steps for
>> capture HW control and 40 dB gain only range with the 10 dB steps for
>> MIC boost control. Now, for all volumes between 0 and 10 dB PA will keep
>> MIC boost level at 0 dB (when it is first in the path) and set capture
>> level to 1.5, 3, 4.5 etc levels. And when level reaches 10 dB, then MIC
>> boost will be set at 10 dB and capture at 0 dB. For the requested levels
>> between 10 and 20 db, MIC boost will be kept at 10 dB and capture level
>> will take the difference and so on.
> What you describe above is how PA currently works with regards to volume
> changes. We use the alsa API with a +1 dir argument to various functions
> e.g.
> http://www.alsa-project.org/alsa-doc/alsa-lib/group___simple_mixer.html#gef9c6ce9deb46de7b5727dc9982dc6d6
> So we will use "accurate or first above" this means that less
> attenuation will be done if the accuracy cannot be performed exactly.
> So no need to worry about this.

I think I perhaps misunderstood your point. Perhaps you were talking
about volumes above 0dB, in which case the +1 direction is not really
appropriate. I kinda missed that distinction in David's original
messages but I saw sense in my latest reply!



Colin Guthrie

Day Job:
  Tribalogic Limited [http://www.tribalogic.net/]
Open Source:
  Mageia Contributor [http://www.mageia.org/]
  PulseAudio Hacker [http://www.pulseaudio.org/]
  Trac Hacker [http://trac.edgewall.org/]

More information about the pulseaudio-discuss mailing list