[pulseaudio-discuss] Per-app flat volume adjustment is highly unintuitive, if mathematically consistent.

[Colin Guthrie]

'Twas brillig, and Jud Craft at 27/05/09 04:06 did gyre and gimble:
> Actually, wait.  There is one last thing that might clue me in.
> 
> Let's say I have, relative to each other, Firefox/youTube set to 100%
> and Banshee set to 80%.
> 
> Now, imagine I'm listening to Banshee and my volume is 100%.  Does
> flat volume mean that if I start to play a Firefox video...that
> Firefox will be at 100% and that Pulse will intelligently drop Banshee
> to 80%?
> 
> In essence...applying my per-app ratios automatically on the fly,
> whenever something comes up?  I'll be honest, I didn't really think of
> it like -that-.  That sounds awesome enough that I might need to give
> it another chance.

Yes!

The way I understand it, and apologies if I'm wrong here, is that 
Banshess want's 80% and it's the only app playing. In order to achieve 
that result, pulse does not scale the stream at all but sets the 
underlying hardware volume to 80% (but in dB's yada yada!). So the net 
result is I get sound at the right volume.

Then another stream joins that wants 100% So, pulse with start scaling 
the Banshee stream to ensure it is scaled in software to 80%, and turn 
up the underlying hardware volume to 100%. Net result is that Banshee 
continues playing at the same level and sounds the same but the new 
stream can be louder.

Essentially, whenever possible pulse is off-loading the scaling to the 
h/w, meaning less work in software = less load, and better quality audio 
due to the use of the full range of the DAC.

Hope that's right!

Col


-- 

Colin Guthrie
gmane(at)colin.guthr.ie
http://colin.guthr.ie/

Day Job:
   Tribalogic Limited [http://www.tribalogic.net/]
Open Source:
   Mandriva Linux Contributor [http://www.mandriva.com/]
   PulseAudio Hacker [http://www.pulseaudio.org/]
   Trac Hacker [http://trac.edgewall.org/]