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.
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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
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