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/devclass_docs/.

HISTORY

The uaudio driver appeared in NetBSD 1.5.

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.