USB Administration Guide

USB Audio Overview

This Solaris release provides USB audio support which is implemented by a pair of cooperating drivers, usb_ac and usb_as. The audio control driver, usb_ac, a USBA (Solaris USB Architecture) compliant client driver provides the controlling interface to user applications. The audio streaming driver, usb_as, is provided to process audio data messages during play and record and set sample frequency, precision, and encoding requests from the usb_ac drive.

Both drivers comply to the USB audio class 1.0 specification.

Solaris supports external USB audio devices that are play-only or record-only. Onboard USB audio devices are not supported. See the usb_ac man page for supported audio data formats.

The primary audio device is /dev/audio. You can verify that /dev/audio is pointing to USB audio by using the following command:

% mixerctl
Device /dev/audioctl:
  Name    = USB Audio
  Version = 1.0
  Config  = external

Audio mixer for /dev/audioctl is enabled

After you connect your USB audio devices, you access them with the audioplay and audiorecord command through the following files:


You can select a specific audio device by setting the AUDIODEV environment variable or by specifying the -d option to the audioplay and audiorecord commands. However, setting AUDIODEV does not work for applications that have /dev/audio hardcoded as the audio file.

When you plug in a USB audio device, it automatically becomes the primary audio device, /dev/audio, unless /dev/audio is in use. Refer to How to Change the Primary USB Audio Device and usb_ac(7D) for instructions on changing /dev/audio from onboard audio to USB audio and vice versa.

Hot-Plugging Multiple USB Audio Devices

If a USB audio device is plugged into a system, it becomes the primary audio device, /dev/audio. It remains the primary audio device even after the system is rebooted. If additional USB audio devices are plugged in, the last one becomes the primary audio device.

See usb_ac(7D) for additional information on troubleshooting USB audio device problems.

How to Add Hot-Pluggable USB Audio Devices

Use this procedure to add hot-pluggable USB audio devices.

  1. Plug in the USB speakers and microphone.

    The primary audio device, /dev/audio, usually points to the onboard audio. After you connect USB audio devices, /dev/audio points to the USB audio devices that are identified in the /dev/sound directory.

  2. Verify that the audio device files have been created.

    % ls /dev/sound
    0     0ctl  1     1ctl  2     2ctl
  3. Test the left and right USB speakers.

    % cd /usr/demo/SOUND/sounds
    % audioplay -d /dev/sound/1 -b 100
    % audioplay -d /dev/sound/1 -b -100
  4. Test the USB microphone.

    % cd $HOME/au
    % audiorecord -d /dev/sound/2 -p mic -t 30