SND_UAUDIO(4)          FreeBSD Kernel Interfaces Manual          SND_UAUDIO(4)

NAME
     snd_uaudio - USB audio and MIDI device driver

SYNOPSIS
     To compile this driver into the kernel, place the following lines in your
     kernel configuration file:

           device sound
           device usb
           device snd_uaudio

     Alternatively, to load the driver as a module at boot time, place the
     following line in loader.conf(5):

           snd_uaudio_load="YES"

DESCRIPTION
     The snd_uaudio driver provides support for USB audio class devices and
     USB MIDI class devices.

     A USB audio device consists of a number of components: input terminals
     (e.g. USB digital input), output terminals (e.g. speakers), and a number
     of units in between (e.g. volume control).

     Refer to the `USB Audio Class Specification' for more information.

SEE ALSO
     sound(4), usb(4)

     USB Audio Class Specifications,
     http://www.usb.org/developers/docs/devclass_docs/.

HISTORY
     The snd_uaudio driver first appeared in FreeBSD 4.7.

AUTHORS
     This manual page was adopted from NetBSD 1.6 and modified for FreeBSD by
     Hiten Pandya <hmp@FreeBSD.org>.

BUGS
     The PCM framework in FreeBSD only supports synchronous device detach.
     That means all mixer and DSP character devices belonging to a given USB
     audio device must be closed when receiving an error on a DSP read, a DSP
     write or a DSP IOCTL request.  Else the USB audio driver will wait for
     this to happen, preventing enumeration of new devices on the parenting
     USB controller.

     Some USB audio devices might refuse to work properly unless the sample
     rate is configured the same for both recording and playback, even if only
     simplex is used.  See the dev.pcm.%d.[play|rec].vchanrate sysctls.

     The PCM framework in FreeBSD currently doesn't support the full set of
     USB audio mixer controls.  Some mixer controls are only available as
     dev.pcm.%d.mixer sysctls.

FreeBSD 13.1-RELEASE-p6        November 12, 2016       FreeBSD 13.1-RELEASE-p6