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

Mark Brown broonie at opensource.wolfsonmicro.com
Wed Feb 17 01:43:08 CET 2010

On Wed, Feb 17, 2010 at 01:10:47AM +0100, Lennart Poettering wrote:
> On Wed, 17.02.10 12:47, Eliot Blennerhassett (linux at audioscience.com) wrote:

> > For our cards this is adjustable, but lets say for consumer cards it is
> > fixed.  This information is not currently available via the ALSA
> > API.

> I wonder how realistic it would even be to add an API for
> this. i.e. can we even know the refernce level? On many cards most
> likely not. For example, for my integrated USB speakers speaking of a
> reference voltage would already be misleading...

Like you say even where we know the actual level it's not practically
useful unless it's physically exposed somewhere the user can see it.

For things like line jacks where it is relevant these things do actually
get documented relatively often, and obviously measurements are possible
where they aren't.  I'm not sure how interesting it is unless the system
also supports configuration, though.

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