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UAUDIO(4)                  Kernel Interfaces Manual                  UAUDIO(4)

     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
     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
        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

     audio(4), usb(4)

     USB Approved Class Specification Documents,

     The uaudio driver appeared in NetBSD 1.5.

     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.

NetBSD 7.1.2                  September 20, 2011                  NetBSD 7.1.2