NAME
uaudio —
USB audio device driver
SYNOPSIS
uaudio* at uhub?
audio* at audiobus?
DESCRIPTION
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
audio(4)) interface:
- 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 input.
- 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 indicates 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,
outputs.speaker.treble, outputs.speaker.mute, outputs.speaker, or
likewise.
- processing
- A processing unit does one of a number of audio processing
functions (e.g., channel up-down mixing, Dolby ProLogic, or chorus
effects). The name of the on-off control is
proN.M-enable, where N is a
number that identifies 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
processing 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 reading.
SEE ALSO
audio(4),
usb(4)
USB Approved Class Specification
Documents,
http://www.usb.org/developers/docs/devclass_docs/.
HISTORY
The
uaudio driver appeared in
NetBSD
1.5.
BUGS
Releases 1.0 and 2.0 of the USB Audio class specification are not mutually
compatible. The
uaudio driver only supports devices
compliant with Release 1.0.
There is no support for multiple-endpoints audio stream, adaptive recording,
async playback, and TYPE-II/III formats.
There is the possibility that a device has multiple mixer items which have the
same name.