mixerctl configuration file
is the configuration file for
. It allows the
user to specify settings for the audio mixer at system startup. The exact set
of variables available are largely dependent on the audio device driver, and
vary from device to device. The file is made up of variable assignments
with comments designated by a hash mark (‘#’).
Some audio devices have _sense variables which can help identify connectors. The
connectors' state will be one of plugged
, depending on whether a jack is
The connectors on audio cards are generally as follows:
- Microphone in. Used to record from a microphone.
- Line out. Used for stereo speakers or headphones.
- Line in. Used to record from an external source.
- Speaker out; subwoofer.
- Speaker out; rear speakers.
- Optical connector; TOSLink, RCA, or 1/8" mini
Most devices have a number of digital to analogue converters (DACs), used for
sound playback, and each DAC has a corresponding output mixer. The mixers are
labelled “mix” or “sel”. Each DAC represents two
channels of playback.
Verify that playback works by playing an audio file (see
) or CD (see
). Check that any relevant
inputs.* variables are unmuted and set to a high enough value to permit
playback. For example, if playing a CD,
for cd variables to
adjust. Check also that the variable governing the general audio level, such
, is set to a sufficiently high
Some cards are capable of multi-channel sound. In some cases _dir variables
detail the direction (input or output) of the various connectors. Check that
the direction of the corresponding connectors is set to
. Other devices may need to set _source
variables to work correctly. The maximum possible value of the
shows the number of channels
Most devices have a number of analogue to digital converters (ADCs), used for
recording sound, and each ADC has a corresponding input mixer. The mixers are
labelled “mix” or “sel”. Each ADC represents two
channels of recording.
Connect line in on the audio card to an audio source, such as an amplifier. Many
devices have an auxiliary connector (“aux”) available for
recording, or a headphone socket could be used.
Check that the variable that determines recording volume, such as
, is set high enough to provide a
high enough sound level, but not so high as to distort the sound being
recorded. It is also a good idea to mute any record.* variables not being used
for recording. Obviously the recording source itself will have to be unmuted.
A simple test that recording works may be done using
whilst playing back
audio from an external source. The example below creates a .wav file of any
audio being played. The file can then be played back to determine quality.
$ aucat -o test.wav
- Default audio mixing device.