3 audio \- SoundBlaster or ESS1688 audio controller
12 The audio device serves a one-level directory,
13 giving access to the stereo audio ports.
15 is the data file, which can be read or written to use the port.
16 Audio data is a sequence of stereo samples, left sample first.
17 Each sample is a 16 bit little-endian two's complement integer;
18 the default sampling rate is 44.1 kHz.
19 Some implementations only support audio output
20 and return a zero length when read.
26 represents the number of bytes buffered for input or output.
27 This provides some control over record or playback latency.
31 provides additional timing and latency control. When read, it returns
34 .B "bufsize \f2s\fP buffered \f2b\fP offset \f2o\fP time \f2t\fP
36 reporting number of bytes
38 used for DMA operations (i.e., the minimum useful size for reads and writes),
41 currently buffered, and the time
49 it is possible to calculate at what time a byte with a different offset will
50 be recorded or played back.
53 is the control file associated with the audio port.
54 Each input and output source has an associated stereo volume control,
55 ranging from 0 (quiet) to 100 (loud).
56 In addition, there are controls for the sampling rate of the D/A and A/D converters
57 and for any tone controls.
59 return lines of the form
71 possibly abbreviated if the values are shared or non-existent.
72 For example, if all of the values are shared, the form degenerates to
75 Valid sources depend on the particular audio device,
76 though all devices have an
78 stereo source, which controls the output volume from the D/A converter
82 Writes accept the same format with same abbreviations.
85 sets all of the attributes to their default value,
86 and if no attribute is supplied,
90 The Sound Blaster 16 (or MCD) is half-duplex and accepts the following controls on its
93 in the format shown above for reads.
94 .TF "\fLspeaker in out"
97 Data written to audio.
109 Monaural microphone input.
112 Monaural internal speaker connection.
115 Stereo treble tone control.
116 Values less than 50 decrease the treble,
117 those greater increase it.
120 Stereo bass tone control.
123 Sampling rate for the D/A and A/D converters,
127 .B /sys/src/9/port/devaudio.c