db volume scaling

[Tim Blechmann]

>>> It means that the volume of the audio stream Amarok is pushing through
>>> the sound system scales from 20% of its maximum level to 40% of its
>>> maximum level to 60% of its maximum level.  Not sure why this is
>>> difficult to figure out.
>> fortunately this is not the case.
>> i suppose phonon internally represents the audio data as 32-bit floats
>> in the range from -1 to 1.
> 
> No idea.  There are many ways you can represent it.  0 to 1.  0 to 10. 
> -123 to -38.  The range doesn't really matter.

well, it doesn't matter for volume scaling, it does matter for signal
processing applications, though ... but well, then for amarok it doesn't
matter, since it doesn't provide any kinds of filters or eqs ...

>> but back to psychoacoustics: afaict, amarok uses phonom to create a
>> linear loudness scale, where a logarithmic loudness scale would be more
>> appropriate for the human ear (at least for mine).
>>
>> but i would suggest, you try my patch yourself, preferably in an
>> audiophile setup (quiet room, good speakers).
> 
> No need.  I've used programs with logarithmic volume sliders before.  I
> dislike them.  So do, I would imagine, the vast majority of users (many of
> whom might not understand such a scale, much less like it).

well, then can you explain, why mixing boards and amplifiers all over
the world use a logarithmic volume scale?

> If you're an audiophile, I imagine you have an external speaker and/or
> headphone amplifier.  Why not just use the line out of your computer and
> adjust the audio from your amplifier?  Why is this Amarok's problem?

actually, i am not using an external amplifier, but my rme hdsp audio
interface is directly connected to my genelec 1030 studio monitors. they
are active speakers, without a possibility to adjust the volume.

still, a few questions:
- when i want to reduce the volume by 6 db in the decibel scale, how
much do i have to reduce the volume in amarok's percent scale?
- when setup A is 10 db louder than setup B (setup A may be the studio,
setup B the living room). how much do i have to increase the volume in
amarok's percent scale to get the same sound pressure level, if my
default playback volume is (a) 20% or (b) 50%?

cheers, tim

-- 
tim at klingt.org
http://tim.klingt.org

Happiness is a byproduct of function, purpose, and conflict; those who
seek happiness for itself seek victory without war.
  William S. Burroughs

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 197 bytes
Desc: OpenPGP digital signature
URL: <http://mail.kde.org/pipermail/amarok/attachments/20090609/0afc1e3e/attachment.sig>