[pulseaudio-discuss] [PATCH 0/5] volume: Decrease PA_VOLUME_MAX to be < 2^31

Colin Guthrie gmane at colin.guthr.ie
Sun Oct 10 05:03:48 PDT 2010

'Twas brillig, and Arun Raghavan at 10/10/10 11:30 did gyre and gimble:
> On Sun, 2010-10-10 at 10:46 +0100, Colin Guthrie wrote:
> [...]
>> I'd also like to expose a new constant in the headers called
>> PA_VOLUME_OVERDRIVE (or similarly named) that represents +11dB and
>> should be our generally recommended "overdrive" (aka software
>> amplification > 100%) amount for volume control UIs.
>> Currently gnome-volume-control allows up to PA_VOLUME_NORM*1.5 which is
>> ~= +11dB via current mappings, which is one reason why we previously
>> decided on +11dB as our overdrive amount. That said, other volume
>> control UIs (pavucontrol, kmix and, surprisingly,
>> gnome-volume-control-applet) only allow volumes up to PA_VOLUME_NORM, so
>> the idea would be to allow them to go right up to PA_VOLUME_OVERDRIVE,
>> and hopefully implement an appropriate use of colours and markers etc.
>> to make it clear to the user that they may not want to go >100% or risk
>> clipping.
>> http://pulseaudio.org/wiki/WritingVolumeControlUIs#Colouredvolumesliders
> Sounds reasonable. Although, independent of the rest of these changes,
> I'd also like to propose that the max. s/w gain (i.e. PA_VOLUME_MAX) be
> decreased from its current value (~289 dB now, ~271 dB with my change)
> to something more reasonable, like ~20 dB.
> I came to this conclusion the hard way - while testing these patches, I
> managed to turn up the volume high enough to temporarily damage my
> hearing (it was a sudden burst, and I got to the off switch in time, so
> no permanent damage done, I hope).

Urk! I'll try and type quietly...

> I understand that some overdrive is useful in general, but are there any
> objections to capping the max. to something like ~20 dB?

I think that imposing a more sensible limit probably makes sense. I
can't think of any practical reasons to push things to dB's > 20 ish so
on the whole I'd be in favour of a more sensible upper limit.

Quite what that limit should be however is perhaps debatable so other
opinions should maybe be canvassed to get the final 20dB upper limit.



Colin Guthrie

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