audio(3): remove out of date information

sys/man/3/audio

@@ -1,6 +1,6 @@
 .TH AUDIO 3 
 .SH NAME
-audio \- SoundBlaster or ESS1688 audio controller
+audio \- audio device
 .SH SYNOPSIS
 .nf
 .B bind -a #A /dev
@@ -12,49 +12,23 @@ audio \- SoundBlaster or ESS1688 audio controller
 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.
-.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
-.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.
 .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.
+latency control and for any tone controls.
 Reads
 return lines of the form
 .IP
@@ -80,49 +54,6 @@ 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.
-.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.
 .SH SOURCE
 .B /sys/src/9/port/devaudio.c
 .SH SEE ALSO