[alsa-devel] snd-hda-intel overly loud when using OSS interface

[Takashi Iwai]

At Sat, 4 Oct 2008 08:52:16 -0400 (EDT),
Jan Engelhardt wrote:
> 
> Hi,
> 
> 
> [don't forget to Cc me]
> 
> I've got a Dell Precision 390 workstation, onboard sound running with 
> snd-hda-intel module.
> 
> 00:1b.0 Audio device: Intel Corporation 82801G (ICH7 Family) High 
> Definition Audio Controller (rev 01)
> 00:1b.0 0403: 8086:27d8 (rev 01)
> 
> When audio is output using the OSS interface (mpg123 or mplayer -ao 
> oss), output is overly loud and the PCM mixer control has no effect.
> 
> Master tuned in to 13% (alsamixer says dB gain=-40.50) is about the 
> level as when using the ALSA interface running with Master 58% (dB 
> gain=-19.50) with PCM 63% (dB gain=-19.50).

The hardware has no real "PCM" volume control.  It's implemented as a
mixer element for alsa-lib softvol plugin, which is of course skipped
when you use kernel OSS emulation.

Note that PCM and master volume controls are different.  The former
influences only on the PCM stream while the latter is the control for
the total analog output from both PCM and loopback signals.


Takashi