[pulseaudio-discuss] [PATCH 2/3] alsa: Default to 30% in absence of sink hw volume

Tanu Kaskinen tanu.kaskinen at linux.intel.com
Mon Dec 1 06:03:10 PST 2014

On Sun, 2014-11-16 at 21:23 +0500, Alexander E. Patrakov wrote:
> 16.11.2014 13:10, Tanu Kaskinen wrote:
> > If a sound card has no hardware volume that we could query when
> > creating a sink, 30% is a better default volume than 100%. 100% is
> > likely to be far too loud.
> Please make sure this is not applied on digital outputs (i.e. SPDIF and 
> HDMI/DisplayPort). There, 100% is the correct default, especially 
> because volume is expected to be the same by default in the cases of 
> passthrough and normal playback.
> P.S. I have not read enough context, sorry if this code path is already 
> only ever executed for analog outputs.

The code path is executed for all outputs, so your feedback is very
valid, thanks!

You didn't explain very thoroughly why 100% would be the best default
for digital outputs. You mentioned that the volume should by default be
the same for passthrough and non-passthrough. That alone doesn't seem to
be a good enough reason to default to full volume, however, because if
the full volume is way too loud, then the full volume should be avoided
in any case. Passthrough is a special case that shouldn't drive the
design to the extent that the common cases become broken.

That said, I believe the digital outputs are typically associated with
another important property: the existence of an extra volume control
between the sound card output and the speakers. If that's the case, then
I think it's a good idea to default to 100%, because the extra volume
control is likely going to limit the output to a sane level. I have
extremely little personal experience of systems that use digital
outputs, but it seems to me that such systems are very likely to have a
separate volume control - I haven't heard of direct-to-speakers hardware
with digital input that wouldn't have volume control.

This "separate volume control" logic applies to analog outputs too in
theory, but in practice we never know with analog outputs whether
there's a separate volume control or not.


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