[pulseaudio-discuss] [PATCH 2/2] volume: Add LFE balance API

[David Henningsson]

On 2015-09-18 15:17, Tanu Kaskinen wrote:
> On Fri, 2015-09-18 at 14:47 +0200, David Henningsson wrote:
>> The gnome/unity-control-center UIs have a master volume slider, and
>> three sub-sliders: balance, fade, and subwoofer. Balance and fade
>> use PA's set_balance and set_fade APIs accordingly, but the subwoofer
>> slider sometimes does unintuitive things.
>>
>> In order to make that slider behave better, let's add a LFE balance
>> API that these volume control UIs can use instead. With this API,
>> the UI can balance between "no subwoofer" and "only subwoofer" with
>> "equal balance" in the middle, which would make it more consistent
>> with the behaviour of the other sliders.
>>
>> BugLink: https://bugzilla.gnome.org/show_bug.cgi?id=753847
>>
>> Signed-off-by: David Henningsson <david.henningsson at canonical.com>
>
> As a user, I don't expect a subwoofer slider to mute other channels.

What you got with my patch (and one patch to -control-center to use the 
API) is three sliders. They're all adjusting the balance in the sense 
that in the middle, all channels are loud, and some channels are 
gradually weakening when you move a slider towards the edge.

I find that to be the most consistent.

> Have you got any support from other people for your proposed subwoofer
> slider behaviour?

FWIW, after I came up with the name "lfe balance" (just to see if there 
was another name for the same thing), the first hit is to some Apple 
program, which seems to be using the LFE balance the same way. [1]

> If I understand correctly, the bug is about strange relation between
> the overall volume slider and the subwoofer volume slider. I fully
> agree with Britt Yazel (comment #10). However, I don't know if the
> subwoofer slider can be made sane without an API that supports the
> "overall volume" concept properly (which pa_cvolume doesn't do).

...and is unlikely to do any time soon, so we need something else.

-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic

[1] https://support.apple.com/kb/PH12578?locale=sv_SE