Bug 502057 - PulseAudio and ALSA volume misaligned
Summary: PulseAudio and ALSA volume misaligned
Keywords:
Status: CLOSED NOTABUG
Alias: None
Product: Fedora
Classification: Fedora
Component: pulseaudio
Version: rawhide
Hardware: i686
OS: Linux
low
low
Target Milestone: ---
Assignee: Lennart Poettering
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2009-05-21 16:54 UTC by Oliver Clark
Modified: 2009-05-23 21:07 UTC (History)
4 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2009-05-23 21:07:58 UTC
Type: ---
Embargoed:


Attachments (Terms of Use)
alsa-info (19.70 KB, text/plain)
2009-05-21 16:55 UTC, Oliver Clark
no flags Details

Description Oliver Clark 2009-05-21 16:54:45 UTC
Description of problem:
PulseAudio volume control and ALSA volume control not aligned.

Version-Release number of selected component (if applicable):
Name: pulseaudio
Arch: i586
Version: 0.9.15
Release: 11.fc11

How reproducible:
Always happens.

Steps to Reproduce:
1. Open ALSA mixer (alsamixer -c0) and PulseAudio's sound preferences or pavucontrol.
2. Reduce the volume using PulseAudio down to 0.
3. Watch the ALSA mixer get to -64 dB gain or 0% before PulseAudio.
  
Actual results:
Volumes from both ALSA mixer Master and the PA Output Device Internal Audio slider in pavucontrol:
PA 100, ALSA 100 (dB gain = -0)
PA 90, ALSA 88 (dB gain = -9)
PA 80, ALSA 72 (dB gain = -18)
PA 70, ALSA 58 (dB gain = -27)
PA 60, ALSA 45 (dB gain = -35)
PA 50, ALSA 30 (dB gain = -45)
PA 40, ALSA 17 (dB gain = -54)
PA 30, ALSA 2 (dB gain = -63) At this point there is 'almost no sound'
PA 20, ALSA 0 (dB gain = -64) 
PA 10, ALSA 0 (dB gain = -64)
PA 0, ALSA 0 (dB gain = -64)

Expected results:
PulseAudio and ALSA should both scale smoothly from -64 dB gain to 0.

Comment 1 Oliver Clark 2009-05-21 16:55:47 UTC
Created attachment 344991 [details]
alsa-info

Comment 2 Adam Williamson 2009-05-22 16:11:07 UTC
To be clear, here, the issue is really that when adjusting the volume with PA, you don't get a smooth scale from -64 to 0dB gain; the settings between 0 and 30% in PA are more or less useless.

Comment 3 Lennart Poettering 2009-05-23 21:07:58 UTC
PA 0.9.15 basically maps 0dB to 100% and -90dB to 0%. In between that the mapping from the 'percentages' to dB is 'linear'. At 16bit PCM resolution 'silence' is reached around -90dB. That's why the scale ends there.

Your sound card's schedule already ends at -64dB as it seems. To the effect that between -64dB and -90dB PA extends the attenuation range in software.

In the current git version of PA I changed the mapping between 'percentage' volumes and the gain. Now, the attenuation factor and the percentage have a cubic relation. This should give us a more 'natural' feeling of pixel distance on the screen and actual change in loudness.


Note You need to log in before you can comment on or make changes to this bug.