[alsa-devel] Latency of mixer reconfiguration

Lennart Poettering mznyfn at 0pointer.de
Fri Feb 19 16:03:30 CET 2010

On Fri, 19.02.10 09:54, Mark Brown (broonie at opensource.wolfsonmicro.com) wrote:

> > > I suspect that trying to offer additional resolution in this way is more
> > > trouble than it's worth if you're concerned about the artifacts that are
> > > introduced during updates.  Providing per-channel differentiation if the
> > > hardware has only mono control has much fewer problems, though.
> > The current logic is to not do any software adjustment if the hardware
> > adjustment is "close enough" to the total adjustment we want to do,
> > tested against a threshold. Which I think is quite a reasonable
> > approach because it enables/disables this feature not globally, but
> > looks at each case and enables this logic only if it really has a
> > benefit.
> That sounds reasonable, though it's kind of surprising to me that there
> is hardware out there which benefits from it - I'd have expected either
> adequate resolution or nothing at all there.

On my own hardware this mechanism proved useful in two cases: one card
had a single volume slider for both channels and with PA you can now
set their volume independantly. And one set of external USB speakers
has a volume slider that starts at a very high level, so that the
minimum volume setting is everything but silent. PA extends the scale
downwards so that this limitation of the hw does not become apparent.


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

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