[pulseaudio-discuss] Mic input volume controls

[Kulikov, Vitaliy]

> -----Original Message-----
> From: pulseaudio-discuss-bounces at mail.0pointer.de 
> [mailto:pulseaudio-discuss-bounces at mail.0pointer.de] On 
> Behalf Of Colin Guthrie
> Sent: Thursday, December 09, 2010 3:27 PM
> To: pulseaudio-discuss at mail.0pointer.de
> Subject: Re: [pulseaudio-discuss] Mic input volume controls
> 
> '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.htm
> > l#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!

Yes, that's what I meant and my point was just to support David's
suggestions. And I was about to type that scenario above actually does
not work with the current PA but then saw your new response to David.

Another thing, if my memory does not fail me, I believe that somebody in
that same thread stated that 20 dB gain should be good enough for all
purposes but that is not what my experience tells me. It may be good
enough when someone has its mic close to the mouth but may be not good
enough for mic far on the desk. This is why all those mic boost controls
with the ranges of 30 or 40 dB gain are in the audio codecs.

Vitaliy

> 
> Col
> 
> -- 
> 
> Colin Guthrie
> gmane(at)colin.guthr.ie
> http://colin.guthr.ie/
> 
> 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/]
> 
> _______________________________________________
> pulseaudio-discuss mailing list
> pulseaudio-discuss at mail.0pointer.de
> https://tango.0pointer.de/mailman/listinfo/pulseaudio-discuss
>