79 lines
1.9 KiB
Text
79 lines
1.9 KiB
Text
.TH AUDIO 3
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.SH NAME
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audio \- audio device
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.SH SYNOPSIS
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.nf
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.B bind -a #A /dev
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.sp 0.3v
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.B /dev/audio
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.B /dev/audioctl
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.B /dev/audiostat
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.B /dev/volume
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.fi
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.SH DESCRIPTION
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The audio device serves a one-level directory,
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giving access to the stereo audio ports.
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.B Audio
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is the data file, which can be written for audio playback.
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Audio data is a sequence of stereo samples, left sample first.
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Each sample is a 16 bit little-endian two's complement integer;
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the default sampling rate is 44.1 kHz.
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.PP
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The length of the
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.B audio
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file as returned by
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.IR stat (2)
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represents the number of bytes buffered for output.
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.PP
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.B Audioctl
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is driver specific control file and left undocumented here.
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.PP
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.B Audiostat
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is a read only status file. The first line has a length of 32 bytes
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including the newline and starts with the string
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.B bufsize
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followed by the preferred write unit (in bytes) and the string
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.B buffered
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followed by the number of bytes currently queued for output. The
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numbers are decimal and right-padded with spaces to fit.
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After this fixed header, the contents of the file is driver specific.
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.PP
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.B Volume
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is the control file associated with the audio port. Each source has
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an associated stereo volume control,
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ranging from 0 (quiet) to 100 (loud).
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In addition, there are controls for the sampling rate,
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latency control and for any tone controls.
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Reads
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return lines of the form
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.IP
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.I source
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.I left
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.I right
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.PP
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or
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.IP
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.I source
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.I value
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.PP
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Valid sources depend on the particular audio device,
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though all devices have an
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.B audio
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stereo source, which controls the output volume from the D/A converter.
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Values for
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.B speed
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set the sampling frequency of the audio device and
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.B delay
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limits the audio data output buffering to a number of samples.
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.PP
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Writes accept the same format except that for stereo sources
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.I left
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and
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.I right
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can be abbreviated to a single
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.I value
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if both should be set the same.
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.SH SOURCE
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.B /sys/src/9/port/devaudio.c
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.SH SEE ALSO
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.IR nusb (4)
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