.TH AUDIO 3
.SH NAME
-audio \- SoundBlaster or ESS1688 audio controller
+audio \- audio device
.SH SYNOPSIS
.nf
.B bind -a #A /dev
.sp 0.3v
.B /dev/audio
+.B /dev/audioctl
+.B /dev/audiostat
.B /dev/volume
.fi
.SH DESCRIPTION
The audio device serves a one-level directory,
giving access to the stereo audio ports.
.B Audio
-is the data file, which can be read or written to use the port.
+is the data file, which can be written for audio playback.
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.
.PP
The length of the
.B audio
file as returned by
.IR stat (2)
-represents the number of bytes buffered for input or output.
-This provides some control over record or playback latency.
+represents the number of bytes buffered for output.
.PP
-The file
-.B audiostat
-provides additional timing and latency control. When read, it returns
-lines of the form
-.IP
-.B "bufsize \f2s\fP buffered \f2b\fP offset \f2o\fP time \f2t\fP
+.B Audioctl
+is driver specific control file and left undocumented here.
.PP
-reporting number of bytes
-.I s
-used for DMA operations (i.e., the minimum useful size for reads and writes),
-the number of bytes
-.I b
-currently buffered, and the time
-.I t
-at which offset
-.I o
-was reached. Using
-.I t
-and
-.IR o ,
-it is possible to calculate at what time a byte with a different offset will
-be recorded or played back.
+.B Audiostat
+is a read only status file. The first line has a length of 32 bytes
+including the newline and starts with the string
+.B bufsize
+followed by the prefered write unit (in bytes) and the string
+.B buffered
+followed by the number of bytes currently queued for output. The
+numbers are decimal and right-padded with spaces to fit.
+After this fixed header, the contents of the file is driver specific.
.PP
.B 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.
+is the control file associated with the audio port. Each source has
+an associated stereo volume control,
+ranging from 0 (quiet) to 100 (loud).
+In addition, there are controls for the sampling rate,
+latency control and for any tone controls.
Reads
return lines of the form
.IP
.I source
-.B in left
-.I value
-.B right
-.I value
-.B out left
-.I value
-.B right
+.I left
+.I right
+.PP
+or
+.IP
+.I source
.I value
.PP
-possibly abbreviated if the values are shared or non-existent.
-For example, if all of the values are shared, the form degenerates to
-.RI ` source
-.IR value '.
Valid sources depend on the particular audio device,
though all devices have an
.B audio
-stereo source, which controls the output volume from the D/A converter
-connected to
-.BR audio .
-.PP
-Writes accept the same format with same abbreviations.
-Writing the string
-.B reset
-sets all of the attributes to their default value,
-and if no attribute is supplied,
-.B audio
-is assumed.
+stereo source, which controls the output volume from the D/A converter.
+Values for
+.B speed
+set the sampling frequency of the audio device and
+.B delay
+limits the audio data output buffering to a number of samples.
.PP
-The Sound Blaster 16 (or MCD) is half-duplex and accepts the following controls on its
-.B volume
-file,
-in the format shown above for reads.
-.TF "\fLspeaker in out"
-.TP
-.B audio out
-Data written to audio.
-.TP
-.B synth in out
-MIDI synthesizer.
-.TP
-.B cd in out
-CD player.
-.TP
-.B line in out
-Line-level input.
-.TP
-.B mic in out
-Monaural microphone input.
-.TP
-.B speaker in out
-Monaural internal speaker connection.
-.TP
-.B treb out
-Stereo treble tone control.
-Values less than 50 decrease the treble,
-those greater increase it.
-.TP
-.B bass out
-Stereo bass tone control.
-.TP
-.B speed in out
-Sampling rate for the D/A and A/D converters,
-expressed in Hz.
-Defaults to 44100.
+Writes accept the same format except that for stereo sources
+.I left
+and
+.I right
+can be abbreviated to a single
+.I value
+if both should be set the same.
.SH SOURCE
.B /sys/src/9/port/devaudio.c
.SH SEE ALSO
-.IR usb (4)
+.IR nusb (4)
projects / plan9front.git / blobdiff