11641 spelling mistakes in section 7d of the manual

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   6 .TH AUDIO 7D "Jan 10, 2020"
   7 .SH NAME
   8 audio \- common audio framework

  10 The \fBaudio\fR driver provides common support routines for audio devices in
  11 Solaris.
  12 .sp
  13 .LP
  14 The audio framework supports multiple \fBpersonalities\fR, allowing for devices
  15 to be accessed with different programming interfaces.
  16 .sp
  17 .LP
  18 The audio framework also provides a number of facilities, such as mixing of
  19 audio streams, and data format and sample rate conversion.
  20 .SS "Overview"

  21 The audio framework provides a software mixing engine (audio mixer) for all
  22 audio devices, allowing more than one process to play or record audio at the
  23 same time.
  24 .SS "Multi-Stream Codecs"

  25 The audio mixer supports multi-stream Codecs. These devices have DSP engines
  26 that provide  sample rate conversion, hardware mixing, and other features. The
  27 use of such hardware features is opaque to applications.
  28 .SS "Backward Compatibility"

  29 It is not possible to disable the mixing function. Applications must not assume
  30 that they have exclusive access to the audio device.
  31 .SS "Audio Formats"

  32 Digital audio data represents a quantized approximation of an analog audio
  33 signal waveform. In the simplest case, these quantized numbers represent the
  34 amplitude of the input waveform at particular sampling intervals. To achieve
  35 the best approximation of an input signal, the highest possible sampling
  36 frequency and precision should be used. However, increased accuracy comes at a
  37 cost of increased data storage requirements. For instance, one minute of
  38 monaural audio recorded in u-Law format (pronounced \fBmew-law\fR) at 8 KHz
  39 requires nearly 0.5 megabytes of storage, while the standard Compact Disc audio
  40 format (stereo 16-bit linear PCM data sampled at 44.1 KHz) requires
  41 approximately 10 megabytes per minute.
  42 .sp
  43 .LP
  44 An audio data format is characterized in the audio driver by four parameters:
  45 sample Rate, encoding, precision, and channels. Refer to the device-specific
  46 manual pages for a list of the audio formats that each device supports. In
  47 addition to the formats that the audio device supports directly, other formats
  48 provide higher data compression. Applications can convert audio data to and
  49 from these formats when playing or recording.
  50 .SS "Sample Rate"

  51 Sample rate is a number that represents the sampling frequency (in samples per
  52 second) of the audio data.
  53 .sp
  54 .LP
  55 The audio mixer always configures the hardware for the highest possible sample
  56 rate for both play and record. This ensures that none of the audio streams
  57 require compute-intensive low pass filtering. The result is that high sample
  58 rate audio streams are not degraded by filtering.
  59 .sp
  60 .LP
  61 Sample rate conversion can be a compute-intensive operation, depending on the
  62 number of channels and a device's sample rate. For example, an 8KHz signal can
  63 be easily converted to 48KHz, requiring a low cost up sampling by 6. However,
  64 converting from 44.1KHz to 48KHz is computer intensive because it must be up
  65 sampled by 160 and then down sampled by 147. This is only done using integer
  66 multipliers.
  67 .sp
  68 .LP
  69 Applications can greatly reduce the impact of sample rate conversion by
  70 carefully picking the sample rate. Applications should always use the highest
  71 sample rate the device supports. An application can also do its own sample rate
  72 conversion (to take advantage of floating point and accelerated instructions)
  73 or use small integers for up and down sampling.
  74 .sp
  75 .LP
  76 All modern audio devices run at 48 kHz or a multiple thereof, hence just using
  77 48 kHz can be a reasonable compromise if the application is not prepared to
  78 select higher sample rates.
  79 .SS "Encodings"

  80 An encoding parameter specifies the audiodata representation. u-Law encoding
  81 corresponds to CCITT G.711, and is the standard for voice data used by
  82 telephone companies in the United States, Canada, and Japan. A-Law encoding is
  83 also part of CCITT G.711 and is the standard encoding for telephony elsewhere
  84 in the world. A-Law and u-Law audio data are sampled at a rate of 8000 samples
  85 per second with 12-bit precision, with the data compressed to 8-bit samples.
  86 The resulting audio data quality is equivalent to that of stan dard analog
  87 telephone service.
  88 .sp
  89 .LP
  90 Linear Pulse Code Modulation (PCM) is an uncompressed, signed audio format in
  91 which sample values are directly proportional to audio signal voltages. Each
  92 sample is a 2's complement number that represents a positive or negative
  93 amplitude.
  94 .SS "Precision"

  95 Precision indicates the number of bits used to store each audio sample. For
  96 instance, u-Law and A-Law data are stored with 8-bit precision. PCM data can be
  97 stored at various precisions, though 16-bit is the most common.
  98 .SS "Channels"

  99 Multiple channels of audio can be interleaved at sample boundaries. A sample
 100 frame consists of a single sample from each active channel. For example, a
 101 sample frame of stereo 16-bit PCM data consists of 2 16-bit samples,
 102 corresponding to the left and right channel data. The audio mixer sets the
 103 hardware to the maximum number of channels supported. If a mono signal is
 104 played or recorded, it is mixed on the first two (usually the left and right)
 105 channel only. Silence is mixed on the remaining channels.
 106 .SS "Supported Formats"

 107 The audio mixer supports the following audio formats:
 108 .sp
 109 .in +2
 110 .nf
 111 Encoding            Precision  Channels
 112 Signed Linear PCM   32-bit     Mono or Stereo
 113 Signed Linear PCM   16-bit     Mono or Stereo
 114 Signed Linear PCM   8-bit      Mono or Stereo
 115 u-Law               8-bit      Mono or Stereo
 116 A-Law               8-bit      Mono or Stereo
 117 .fi
 118 .in -2
 119 .sp
 121 .sp
 122 .LP
 123 The audio mixer converts all audio streams to 24-bit Linear PCM before mixing.
 124 After mixing, conversion is made to the best possible Codec format. The
 125 conversion process is not compute intensive and audio applications can choose
 126 the encoding format that best meets their needs.
 127 .sp
 128 .LP
 129 The mixer discards the low order 8 bits of 32-bit Signed Linear PCM in order to
 130 perform mixing. (This is done to allow for possible overflows to fit into
 131 32-bits when mixing multiple streams together.) Hence, the maximum effective
 132 precision is 24-bits.
 133 .SH FILES

 134 .ne 2
 135 .na

 136 \fB\fB/kernel/drv/amd64/audio\fR\fR
 137 .ad
 138 .RS 29n
 139 Device driver (x86)
 140 .RE
 142 .sp
 143 .ne 2
 144 .na
 145 \fB\fB/kernel/drv/sparcv9/audio\fR\fR
 146 .ad
 147 .RS 29n
 148 Device driver (SPARC)
 149 .RE
 151 .sp
 152 .ne 2
 153 .na
 154 \fB\fB/kernel/drv/audio.conf\fR\fR
 155 .ad
 156 .RS 29n
 157 Driver configuration file
 158 .RE

 161 See \fBattributes\fR(5) for a description of the following attributes:
 162 .sp
 164 .sp
 165 .TS
 166 box;
 167 l | l
 168 l | l .
 170 _
 171 Architecture    SPARC, x86
 172 _
 173 Interface Stability     Uncommitted
 174 .TE

 177 \fBioctl\fR(2), \fBattributes\fR(5), \fBaudio\fR(7I), \fBdsp\fR(7I)
--- EOF ---