AUDIO(3)                                                 AUDIO(3)

     NAME
          audio - digital audio input and output

     SYNOPSIS
          bind -a #A /dev

          /dev/audio
          /dev/volume

     DESCRIPTION
          The audio device serves a one-level directory, giving access
          to the stereo audio ports.  Audio is the data file, which
          can be read or written to use the port.  Audio data is a
          sequence of stereo samples, left sample first.  Each sample
          is a 16 bit little-endian two's complement integer; the
          default sampling rate is 44.1 kHz.  Some implementations
          only support audio output and return a zero length when
          read.

          Volume is the control file associated with the audio port.
          Each input and output source has an associated stereo volume
          control, ranging from 0 (quiet) to 100 (loud).  In addition,
          there are controls for the sampling rate of the D/A and A/D
          converters and for any tone controls.  Reads return lines of
          the form

               source in left value right value out left value right
               value

          possibly abbreviated if the values are shared or non-
          existent.  For example, if all of the values are shared, the
          form degenerates to `source value'. Valid sources depend on
          the particular audio device, though all devices have a audio
          stereo source, which controls the output volume from the D/A
          converter connected to audio.

          Writes accept the same format with same abbreviations.
          Writing the string reset sets all of the attributes to their
          default value, and if no attribute is supplied, audio is
          assumed.

          The Sound Blaster 16 (or MCD) is half-duplex and has the
          following controls.

          audio out
               Data written to audio.

          synth in out
               MIDI synthesizer.

     Page 1                       Plan 9             (printed 3/29/24)

     AUDIO(3)                                                 AUDIO(3)

          cd in out
               CD player.

          line in out
               Line-level input.

          mic in out
               Monaural microphone input.

          speaker in out
               Monaural internal speaker connection.

          treb out
               Stereo treble tone control.  Values less than 50
               decrease the treble, those greater increase it.

          bass out
               Stereo bass tone control.

          speed in out
               Sampling rate for the D/A and A/D converters, expressed
               in Hz.  Defaults to 44100.

          Indigo audio is full-duplex and has the following controls.

          audio out
               Data written to audio.

          line in out
               Line-level input.

          mic in out
               Microphone input.

          aes in out
               Digital input.

          Nextstation audio is output only and has the following con-
          trols.

          audio
               Data written to audio.

          deemp
               A value of zero turns off the stereo de-emphasis fil-
               ter, any other value turns it on.

     SOURCE
          /sys/src/9/*/devaudio.c

     Page 2                       Plan 9             (printed 3/29/24)