.TH AUDIO 3 .SH NAMEaudio \- SoundBlaster or ESS1688 audio controller.SH SYNOPSIS.nf.B bind -a #A /dev.sp 0.3v.B /dev/audio.B /dev/volume.fi.SH DESCRIPTIONThe audio device serves a one-level directory,giving access to the stereo audio ports..B Audiois 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 outputand return a zero length when read..PPThe length of the.B audiofile 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..PPThe file.B audiostatprovides additional timing and latency control.  When read, it returnslines of the form.IP.B "bufsize \f2s\fP buffered \f2b\fP offset \f2o\fP time \f2t\fP.PPreporting number of bytes.I sused for DMA operations (i.e., the minimum useful size for reads and writes),the number of bytes.I bcurrently buffered, and the time.I tat which offset.I owas reached.  Using.I tand.IR o ,it is possible to calculate at what time a byte with a different offset willbe recorded or played back..PP.B Volumeis 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 convertersand for any tone controls.Readsreturn lines of the form.IP.I source.B in left.I value .B right.I value.B out left.I value.B right.I value.PPpossibly 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 audiostereo source, which controls the output volume from the D/A converterconnected to.BR audio ..PPWrites accept the same format with same abbreviations.Writing the string.B resetsets all of the attributes to their default value,and if no attribute is supplied,.B audiois assumed..PPThe Sound Blaster 16 (or MCD) is half-duplex and accepts the following controls on its.B volumefile,in the format shown above for reads..TF "\fLspeaker in out".TP.B audio outData written to audio..TP.B synth in outMIDI synthesizer..TP.B cd in outCD player..TP.B line in outLine-level input..TP.B mic in outMonaural microphone input..TP.B speaker in outMonaural internal speaker connection..TP.B treb outStereo treble tone control.Values less than 50 decrease the treble,those greater increase it..TP.B bass outStereo bass tone control..TP.B speed in outSampling 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.IR usb (4)