[alsa-devel] Verifying mixer dB data/Invalid dB data from USB cards, especially Aureon 5.1 MkII

Lennart Poettering mznyfn at 0pointer.de
Thu Feb 18 19:13:23 CET 2010

On Thu, 18.02.10 14:15, Raymond Yau (superquad.vortex2 at gmail.com) wrote:

> VLC media player has a slider from 0% to 300% , so the user are easily to
> know  100% is the point which there is no software gain and no software
> autentation
> How did PA expose these software amplication in the UI so that ordinary user
> can know that point ?

Depends on the UI program. gnome-volume-control currently only puts a
marker at the ALSA 0dB point, but not a second one where software amp

However, I have been talking to a couple of folks regarding presenting
that in a nicer way, i.e. colour slider ranges green/yellow/red:


Summary: green → all hw vol control where alsa reports < 0dB; yellow →
hw control where alsa reports > 0dB; and finally red → software volume

I think this color coding of the slider ranges is the best once can do
to represent the technical background of all of this in a way that
gives the right indication even for people with no technical background.

> For the Mic Boost +20dB case , how PA handle this +20dB switch in the "Flat
> Volume" model if you did not expost the Mic Boost switch to the user in the
> mixer control ?
> +20dB is quite significant in with the Capture Volume control

We currently don't cover boost switches, simply because tehre is no dB
data queriable for them.

I'd really prefer if those boost switches would be turned into binary
volume elements which carry normal dB information like any other
volume element. After all they are just a volume element, with only
two steps.


Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4

More information about the Alsa-devel mailing list