Start an audio driver

Note: You must be root to start this manager.


io-audio [-d driver [opt[,opt...]]] [-m opt[,opt...]]
         [-o opt[,opt...]] [v[v]...]

Runs on:



-d driver [opt[,opt...]]
Load the specified driver and pass it the given driver options. The driver name is the name of the shared object without the deva-ctrl- prefix and the .so extension. For example, to load the shared object, specify 4dwave as the driver name.

All audio drivers support the following card options:

The card number to mount the driver as.
The device number that additional following options apply to.
The symbolic name to assign to the PCM playback device.
The symbolic name to assign to the PCM capture device.

For information on the drivers and any specific options, see the entries for the deva-ctrl-* shared objects.

-m opt[,opt...]
Memory options. The opt variable can be any of the following:
The size of the DMA memory pool to create, in KB.
The name of a shared memory object to map and use as DMA memory pool. This object must be physically contiguous memory.
-o opt[,opt...]
Global options. The opt variable can be any of the following:
The time in seconds after the last change before sound card settings are written to disk, (a value of -1 prevents the settings from ever being written).
The priority of the software mixer thread. The default is 25.
On cards that have only a single channel in hardware, don't use software techniques to increase the maximum number of playing channels.
Set the priority of the interrupt service threads. The default is 50.
The maximum size, in kilobytes, for the DMA buffer.
Set the method of selecting the sampling frequency used by the PCM software mixing device if the underlying hardware device supports multiple rates:
  • FAHQ (First Active High Quality) — select the highest HW-supported sample rate that best fits the first active clients requested rate (all subsequent subchannels will be locked to the active rate).
  • FA (First Active) — select the sample rate based on the First Active client's requested sample rate; all subsequent subchannels are locked to the active rate.
  • Lvalue — lock the sample rate to the rate specified by value, regardless of the client's requested rate.

The default is FAHQ.

Adjust the fragment size used by the software mixer to something other than the default of 2048 samples. Here's an example of how to calculate the value to pass in with this option:

sw_mixer_samples = samples_per_frag * (hardware_rate/requested_rate) * (hardware_voices/requested_voices)

Increase the level of verbose output.


The io-audio manager provides support for dynamically loaded audio-driver modules. This utility enables you to load the audio drivers specified by the -d options when you start io-audio.

  • You can start more than one driver by using multiple -d command-line options, but don't try to start more than one instance of io-audio.
  • Graphics drivers run at a higher priority than applications, but they shouldn't run at a higher priority than the audio, or else breaks in the audio occur. You can use the on command to adjust the priorities of the audio and graphics drivers.

Once io-audio has started, you can dynamically load and unload drivers using the mount and umount commands. E.g. this command:

io-audio -dvortex -daudiopci &

gives the same result as this sequence:

io-audio &
mount -T io-audio vortex
mount -T io-audio audiopci
Note: When searching for shared objects, the io-audio manager uses the LD_LIBRARY_PATH environment variable.

To unload a module, use a command like this:

umount /dev/snd/controlC0


Provide support for Aureal Vortex sound card:

io-audio -vv -d vortex &

Load the AudioPCI driver, specifying the size of the DMA memory pool as 500 KB:

io-audio -vv -m pool_size=500 -d audiopci &

Lock the sample rate to 8 KHz (if the hardware supports 8 KHz natively):

io-audio -o sw_mixer_rate=L8000 -d my_audio_driver &

Start an audio driver, specifying the card options:

io-audio -d my_audio_driver \

The /dev/snd directory will look something like this:

# ls -l /dev/snd
total 0
lrw-rw-rw-  1 root      root              0 May 31 11:11 capture -> pcmC0D0c
-rw-rw-rw-  1 root      root              0 May 31 11:11 controlC0
-rw-rw-rw-  1 root      root              0 May 31 11:11 mixerC0D0
-rw-rw-rw-  1 root      root              0 May 31 11:11 pcmC0D0c
-rw-rw-rw-  1 root      root              0 May 31 11:11 pcmC0D0p
-rw-rw-rw-  1 root      root              0 May 31 11:11 pcmC0D1p
lrw-rw-rw-  1 root      root              0 May 31 11:11 pcmPreferredc -> pcmC0D0c
lrw-rw-rw-  1 root      root              0 May 31 11:11 pcmPreferredp -> pcmC0D1p
lrw-rw-rw-  1 root      root              0 May 31 11:11 playback_pcm_mixer -> pcmC0D1p
lrw-rw-rw-  1 root      root              0 May 31 11:11 playback_hw -> pcmC0D0p


In addition to the deva-ctrl-* drivers, the io-audio command can load the following shared objects:
Mixer DLL for the AC97 codec.
Mixer DLL for the AK4531 codec.
Mixer DLL for High Definition Audio codecs.
Shared object used to restore an audio driver's state.