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UAUDIO(4) NetBSD Kernel Interfaces Manual UAUDIO(4)
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uaudio -- USB audio device driver
uaudio* at uhub?
audio* at audiobus?
The uaudio driver provides support for USB audio 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). The following types of units
are handled by the uaudio driver and are accessible via the mixer (see
mixer A mixer has a number of inputs and one output. Each
input has a control that determines its volume in the
output. The name of the control is mixN-S, where N is a
number that identifies which mixer it is and S which
selector A selector unit selects one of multiple audio sources
such as mic-in and line-in. The name of the control is
selN-S1S2S3..., where N is a number that identifies
which selector unit it is and the sequence of Sn indi-
cates candidate units for the audio source.
feature A feature unit changes the sound in some way, like bass,
treble, mute, or volume. The name of the control is
determined in a heuristic way. If the unit changes the
sound to a speaker output terminal, the names of the
controls may be outputs.speaker.bass, out-
puts.speaker.treble, outputs.speaker.mute, out-
puts.speaker, or likewise.
processing A processing unit does one of a number of audio process-
ing functions (e.g., channel up-down mixing, Dolby Pro-
Logic, or chorus effects). The name of the on-off con-
trol is proN.M-enable, where N is a number that identi-
fies which processing unit it is and M which kind.
Depending on the type of processing unit there may be
other controls as well.
extension An extension unit performs some unspecified audio pro-
cessing The name of the on-off control is extN-enable,
where N is a number that identifies which processing
unit it is.
For more information the USB Audio class specification is indispensable
USB Approved Class Specification Documents,
The uaudio driver appeared in NetBSD 1.5.
Releases 1.0 and 2.0 of the USB Audio class specification are not mutu-
ally compatible. The uaudio driver only supports devices compliant with
There is no support for multiple-endpoints audio stream, adaptive record-
ing, async playback, and TYPE-II/III formats.
There is the possibility that a device has multiple mixer items which
have the same name.
NetBSD 8.0 January 26, 2015 NetBSD 8.0