unixdev.net


Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (plan9)
Page:
Section:
Apropos / Subsearch:
optional field

AUDIO(3)                   Library Functions Manual                   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 writ-
       ten  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  sam-
       pling  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 out-
       put 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 con-
       trols.

       audio out
              Data written to audio.

       synth in out
              MIDI synthesizer.

       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 controls.

       audio  Data written to audio.

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

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



                                                                      AUDIO(3)