Using USB Audio Devices (Task Map)

Using USB Audio Devices

This Solaris release provides USB audio support that is implemented by a pair of cooperating drivers, usb_ac and usb_as. The audio control driver, usb_ac, is a USBA (Solaris USB Architecture) compliant client driver that provides the controlling interface to user applications. The audio streaming driver, usb_as, is provided to process audio data messages during play and record. It sets sample frequency and precision, and encodes requests from the usb_ac driver. Both drivers comply to the USB audio class 1.0 specification.

Some audio devices can set volume under software control. A STREAMS module, usb_ah, is pushed on top of the HID driver for managing this function.

Solaris supports USB audio devices that are play-only, record-only, or record and play. Hot-plugging of USB audio devices is supported.

• USB audio devices are supported on SPARC Ultra and x86 platforms that have USB connectors.

• USB audio devices that are supported in the Solaris 8 10/01, Solaris 8 2/02, or Solaris 9 or 10 release must support a fixed 44100 or 48000 Hz sampling frequency to play or record.

• USB audio devices that are supported in the Solaris 10 release must support a 48000 Hz sample rate to play or record.

• For fully supported audio data format information, see usb_ac(7D).

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 /dev/sound/N device links.

Note that the /dev/audio and /dev/sound/N devices can refer to speakers, microphones, or combo devices. If you refer to the incorrect device type, the command will fail. For example, the audioplay command will fail if you try to use it with a microphone.

You can select a specific default audio device for most Sun audio applications, such as audioplay and audiorecord, by setting the AUDIODEV shell variable or by specifying the -d option for these commands. However, setting AUDIODEV does not work for third-party 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. For instructions on changing /dev/audio from onboard audio to USB audio and vice versa, refer to How to Change the Primary USB Audio Device, and usb_ac(7D).

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.

For additional information on troubleshooting USB audio device problems, see usb_ac(7D).

How to Add USB Audio Devices

Use the following procedure to add 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/share/audio/samples/au % audioplay -d /dev/sound/1 -b 100 spacemusic.au % audioplay -d /dev/sound/1 -b -100 spacemusic.au

   
   

4. Test the USB microphone.

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

   
   

How to Identify Your System's Primary Audio Device

This procedure assumes that you have already connected USB audio devices.

1. Identify the state of your current audio device links.

   For example:

   % ls -lt /dev/audio* lrwxrwxrwx 1 root root 7 Jul 23 15:41 /dev/audio -> sound/0 lrwxrwxrwx 1 root root 10 Jul 23 15:41 /dev/audioctl -> sound/0ctl % ls -lt /dev/sound/* lrwxrwxrwx 1 root other 66 Jul 23 14:21 /dev/sound/0 -> ../../devices/pci@1f,4000/ebus@1/SUNW,CS4231@14,200000:sound,audio lrwxrwxrwx 1 root other 69 Jul 23 14:21 /dev/sound/0ctl -> ../../devices/pci@1f,4000/ebus@1/SUNW,CS4231@14,200000:sound,audioctl %

   
   

   The primary audio device, /dev/audio, is currently pointing to the onboard audio, which is /dev/sound/0.

2. (Optional) Add a new USB audio device.

3. Examine your system's new audio links.

   For example:

   % ls -lt /dev/audio* lrwxrwxrwx 1 root root 7 Jul 23 15:46 /dev/audio -> sound/1 lrwxrwxrwx 1 root root 10 Jul 23 15:46 /dev/audioctl -> sound/1ctl % ls -lt /dev/sound/* lrwxrwxrwx 1 root root 74 Jul 23 15:46 /dev/sound/1 -> ../../devices/pci@1f,4000/usb@5/hub@1/device@3/sound-control@0:sound,... lrwxrwxrwx 1 root root 77 Jul 23 15:46 /dev/sound/1ctl -> ../../devices/pci@1f,4000/usb@5/hub@1/device@3/sound-control@0:sound,... lrwxrwxrwx 1 root other 66 Jul 23 14:21 /dev/sound/0 -> ../../devices/pci@1f,4000/ebus@1/SUNW,CS4231@14,200000:sound,audio lrwxrwxrwx 1 root other 69 Jul 23 14:21 /dev/sound/0ctl -> ../../devices/pci@1f,4000/ebus@1/SUNW,CS4231@14,200000:sound,audioctl %

   
   

   Notice that the primary audio device, /dev/audio, is pointing to the newly plugged in USB audio device, /dev/sound/1.

   If you remove the USB audio device now, the primary audio device, /dev/audio, does not revert back to the onboard audio. See the following procedure for instructions on changing the primary audio device back to the system's onboard audio.

   You can also examine your system's USB audio devices with the prtconf command and look for the USB device information.

   % prtconf . . . usb, instance #0 hub, instance #0 mouse, instance #0 keyboard, instance #1 device, instance #0 sound-control, instance #0 sound, instance #0 input, instance #0 . . .