MAN sezione 1 - Torna all'indice
MAN PAGE: ALSACTL(1)Contents
alsactl - advanced controls for ALSA soundcard driver
alsactl [options] [store|restore] <card #>
alsactl is used to control advanced settings for the ALSA
soundcard drivers. It supports multiple soundcards. If
your card has features that you can't seem to control from
a mixer application, you have come to the right place.
alsactl [options] [store|restore] <card #>
Commands
store saves the current driver setup for the selected
soundcard to the configuration file.
restore loads driver setup for the selected soundcard from
the configuration file.
If no soundcards are specified, setup for all cards will
be saved or loaded.
Options
-h, --help
Help: show available flags and commands.
-f, --f file
Select the configuration file to use. The default
is /etc/asound.conf
-d, --debug
Use debug mode: a bit more verbose.
-v, --version
Print alsactl version number.
/etc/asound.conf (or whatever file you specify with the -f
flag) is used to store current settings for your sound
cards. The settings include all the usual soundcard mixer
settings. More importantly, alsactl is capable of con
trolling other card-specific features that mixer apps
usually don't know about.
The configuration file is generated automatically by run
ning alsactl store. Editing the configuration file by hand
may be necessary for some soundcard features (e.g.
enabling/disabling automatic mic gain, digital output,
joystick/game ports, some future MIDI routing options,
etc).
Configuration File Syntax
There are some terms in the config file that bear explain
ing. The "capabilities" comments before each line tells
you some characteristics of each channel. This is purely
informational; these are not flags you can set. Capabili
ties are listed below.
hardware-mute
The soundcard itself is capable of muting the chan
nel. Otherwise, kernel midlevel code will set the
volume to minimum when an application requests mut
ing on this channel.
join-mute
Muting this channel can only be toggled for left
and right at the same time, not independently --
even if you can control the volumes for left and
right independently!
stereo The channel is stereo.
record The channel may be used as a recording source.
join-record
Recording from this channel can only be toggled for
both left and right at once; they cannot be toggled
independently.
record-by-mute
This channel can be recorded even if it's muted, so
you can avoid feeding your record source back to
the speakers.
external-input
The channel controls a signal from an external
input (like Line-In or CD). This serves to distin
guish external source channels from onboard source
channels (like OPL-3 synth).
digital
This channel is fed to an onboard digital mixer for
possible hardware processing (for instance, sur
round-sound processing if your card has it).
The configuration file also has boolean switches which are
used to toggle certain card-specific advanced features.
For example:
; Type is 'bool'.
switch( "MIC Gain", false )
This shows that my card has a switchable mic gain, and
that it's currently turned off. To turn it on, just change
"false" to "true," save the config file, and run alsactl
restore.
Let's say I have this entry in /etc/asound.conf for my PCM
output.
; Capabilities: stereo hardware-mute digital.
; Accepted channel range is from 0 to 63.
channel( "PCM", stereo( 40 mute, 50 mute ))
When alsactl restore is run, the PCM volume will be set to
40 for the left and 50 for the right, but both will be
muted. Since this card supports hardware-mute, muting will
be done by hardware rather than by zeroing the levels.
amixer(1), alsamixer(1), aplay(1)
None known.
alsactl is by Jaroslav Kysela <perex@suse.cz> This docu
ment is by Paul Winkler <zarmzarm@erols.com>.
25 Nov 1998 3 | 
