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
The
USB
specifications can be found at:
http://www.usb.org/developers/docs.html
audio(4),
usb(4)
HISTORY
The
uaudio
driver
appeared in
NetBSD1.5.
BUGS
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.