2010/8/30 Takashi Iwai tiwai@suse.de
At Sat, 28 Aug 2010 06:58:20 +0800, Raymond Yau wrote:
2010/8/28 David Henningsson david.henningsson@canonical.com
2010-08-27 17:43, Clemens Ladisch skrev:
David Henningsson wrote:
So I've discovered that my sound card has a "PCM Playback Volume" control, but changing that control does not alter the volume.
Interestingly enough, this control does not come from the HDA
parser, it
is added by alsactl at boot time...!
This control was created by the software volume plugin. When not
using
this plugin, the control does not have any effect.
To get rid of it, delete its entry from /etc/asound.state.
Hmm, I wonder if this is an Ubuntu-specific bug then? Because when I
run
Maverick (the upcoming Ubuntu release) from a Live-CD, the "PCM
Playback
Volume" control is still there (and there is no asound.state, neither
in
/etc or in /var/lib/alsa). When I use the plughw interface, the "PCM Playback Volume" does not affect volume output. Should I use another device string to test the softvol plugin, to see if it's there or not?
The softvol plugin it is defined in "front" device in /usr/share/alsa/cards/HDA-Intel.conf
reason is some HDA codec does not has any hardware volume control
(analog)
this user-defined control only effective when the application use "front" device
Hm, but if PA opens the device with SND_PCM_NO_SOFTVOL flag, the softvol should be skipped.
AFAIK, PA did not use SND_PCM_NO_SOFTVOL and in "analog stereo duplex" profile , PA open "front" device for playback and capture which access the same "PCM Playback volume" control concurrently
You can see the output of snd_pcm_dump() in the pulseraudio log still contain soffvol which is an indiication that PA did not use SND_PCM_NO_SOFTVOL
the softvol control can only be distinguished using snd_ctl_elem_info_is_user() and there is no snd_mixer_* function to find out the softvol control since PA server use simple mixer api