[alsa-devel] What does 0dB refer to? (Logitech USB Speakers)
rene.herman at keyaccess.nl
Tue Apr 15 16:33:28 CEST 2008
On 15-04-08 15:12, John Rigg wrote:
> The dB setting in a mixer refers to gain, not level. Expecting the same
> absolute level from pro and consumer sound cards at the same gain setting
> is a little ridiculous. If I set a control at 0dB I want just that: 0dB
There is still the issue that we probably don't so much want a distribution
to have to decide if it's speaking to a pro or consumer card and that there
are differences between (cheap consumer only I gather?) cards as well, which
might be classified hardware bugs but which exist nonetheless.
Attempt to summarize:
1. ALSA mutes everything by default which as discussed is the only possibly
sane thing to do especially in a pro environment (although I myself think
that headphone using consumers and expensive gear using pros have a very
similar need here: to avoid heart attacks).
2. Distributions have been set up to save and restore the levels over driver
uses but since they obviously can't expect those poor, poor consumer users
to be able to find a volume slider upon not hearing sound come out they want
to unmute/init first time even -- which seems a somewhat flimsy motivation
for having this discussion, but oh well.
3. Other than muted, 0 dB is the other potentially sane default value with
it being defined as the no gain point. At least one (USB) driver has been
identified as not producing 0 dB gain at the 0 dB ALSA slider setting; it
gets the scale information from the hardware and the hardware is evidently
buggy. Fixing this in the driver through model specific quirks would be the
most sensible here as then the "0 dB" actually could start to mean what it
should mean again.
4. Personally, I'd actually like to have a complete set of "unmuted default"
controls on a per card basis. ALSA could distribute state files for those
cards that like to be inited to anything other than all mute/minimal. Bit of
a maintenance chore, and the usefulness depends on how much level variation
there actually is generally. Are we in essence only talking about Lennart's
buggy USB crap or is this more involved?
More information about the Alsa-devel