unity-design team mailing list archive

[Martín Soto <donsoto@xxxxxxxxx>]

On Fri, May 7, 2010 at 3:58 PM, Matthew Paul Thomas <mpt@xxxxxxxxxxxxx>wrote:

> [...]
> It is awkward that we have separate system and application-specific
> volume settings, but I don't see how getting rid of the system volume
> setting would work.
>

PulseAudio has a solution for precisely this problem: the so-called flat
volumes [1, 2]. Basically, what they do is setting the global volume in such
a way that the original volumes defined for the various streams are kept
unaltered when mixed into the final, single stream (i.e., a high volume set
for one of the streams will result in a high overall volume.) This is
already implemented in PulseAudio, by the way, but inactive in Lucid. If you
want to activate it, though, it's as easy as changing the flat-volumes
setting in /etc/pulse/daemon.conf to "yes".

I suppose this feature is currently deactivated because it makes the main
volume slider behave in a very strange way. Actually, the right solution
when flat volumes are active would be to hide this slider completely, and
rather provide a slider that controls the currently sounding stream. I have
the impression that this would be a lot more intuitive to use for most
people.


> Ensuring the alert sounds are loud enough to be heard over other sounds
> - -- whether by making them temporarily louder, or making the other sounds
> temporarily softer -- is an interesting idea, but it seems out of scope
> for the sound menu itself.
>

I proposed the idea of automatically controlling the volume of (or around)
notification sounds as a way to eliminate one more aspect with which users
must currently fiddle. If we managed to implement this (I know it isn't so
easy) this would definitely simplify the user interface, which is one of the
main goals you stated.

My idea to implement this, by the way, would be to measure the perceptual
loudness [3] of the current stream using Replay Gain [4] or similar. The
resulting (instant) value would be used to set the volume for the
notification stream. This can probably be all done inside PulseAudio by
creating an appropriate module.

Since I'm not an expert in signal processing, however, I don't know how
difficult it would be to implement Replay Gain or a similar loudness measure
in a way that can be used for this purpose. I also wonder what the impact on
battery life would be. I'll try to look a bit more into these issues and
report here when/if I find some answers. Of course, any useful pointers will
be greatly appreciated.

Cheers,

M. S.

[1] http://0pointer.de/blog/projects/oh-nine-fifteen.html

[2] http://www.pulseaudio.org/wiki/WritingVolumeControlUIs (there's a
section called "Flat Volumes" down the page)

[3] http://en.wikipedia.org/wiki/Equal-loudness_contour

[4] http://en.wikipedia.org/wiki/Replay_gain