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          --- old/usr/src/man/man7d/audio.7d
          +++ new/usr/src/man/man7d/audio.7d
   1    1  '\" te
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   6      -.TH AUDIO 7D "Aug 3, 2009"
        6 +.TH AUDIO 7D "Jan 10, 2020"
   7    7  .SH NAME
   8    8  audio \- common audio framework
   9    9  .SH DESCRIPTION
  10      -.sp
  11      -.LP
  12   10  The \fBaudio\fR driver provides common support routines for audio devices in
  13   11  Solaris.
  14   12  .sp
  15   13  .LP
  16   14  The audio framework supports multiple \fBpersonalities\fR, allowing for devices
  17   15  to be accessed with different programming interfaces.
  18   16  .sp
  19   17  .LP
  20   18  The audio framework also provides a number of facilities, such as mixing of
  21   19  audio streams, and data format and sample rate conversion.
  22   20  .SS "Overview"
  23      -.sp
  24      -.LP
  25   21  The audio framework provides a software mixing engine (audio mixer) for all
  26   22  audio devices, allowing more than one process to play or record audio at the
  27   23  same time.
  28   24  .SS "Multi-Stream Codecs"
  29      -.sp
  30      -.LP
  31   25  The audio mixer supports multi-stream Codecs. These devices have DSP engines
  32   26  that provide  sample rate conversion, hardware mixing, and other features. The
  33   27  use of such hardware features is opaque to applications.
  34   28  .SS "Backward Compatibility"
  35      -.sp
  36      -.LP
  37   29  It is not possible to disable the mixing function. Applications must not assume
  38   30  that they have exclusive access to the audio device.
  39   31  .SS "Audio Formats"
  40      -.sp
  41      -.LP
  42   32  Digital audio data represents a quantized approximation of an analog audio
  43   33  signal waveform. In the simplest case, these quantized numbers represent the
  44   34  amplitude of the input waveform at particular sampling intervals. To achieve
  45   35  the best approximation of an input signal, the highest possible sampling
  46   36  frequency and precision should be used. However, increased accuracy comes at a
  47   37  cost of increased data storage requirements. For instance, one minute of
  48   38  monaural audio recorded in u-Law format (pronounced \fBmew-law\fR) at 8 KHz
  49   39  requires nearly 0.5 megabytes of storage, while the standard Compact Disc audio
  50   40  format (stereo 16-bit linear PCM data sampled at 44.1 KHz) requires
  51   41  approximately 10 megabytes per minute.
  52   42  .sp
  53   43  .LP
  54   44  An audio data format is characterized in the audio driver by four parameters:
  55   45  sample Rate, encoding, precision, and channels. Refer to the device-specific
  56   46  manual pages for a list of the audio formats that each device supports. In
  57   47  addition to the formats that the audio device supports directly, other formats
  58   48  provide higher data compression. Applications can convert audio data to and
  59   49  from these formats when playing or recording.
  60   50  .SS "Sample Rate"
  61      -.sp
  62      -.LP
  63   51  Sample rate is a number that represents the sampling frequency (in samples per
  64   52  second) of the audio data.
  65   53  .sp
  66   54  .LP
  67   55  The audio mixer always configures the hardware for the highest possible sample
  68   56  rate for both play and record. This ensures that none of the audio streams
  69   57  require compute-intensive low pass filtering. The result is that high sample
  70   58  rate audio streams are not degraded by filtering.
  71   59  .sp
  72   60  .LP
  73      -Sample rate conversion can be a compute-intensive operation, dependingon the
       61 +Sample rate conversion can be a compute-intensive operation, depending on the
  74   62  number of channels and a device's sample rate. For example, an 8KHz signal can
  75   63  be easily converted to 48KHz, requiring a low cost up sampling by 6. However,
  76   64  converting from 44.1KHz to 48KHz is computer intensive because it must be up
  77   65  sampled by 160 and then down sampled by 147. This is only done using integer
  78   66  multipliers.
  79   67  .sp
  80   68  .LP
  81   69  Applications can greatly reduce the impact of sample rate conversion by
  82   70  carefully picking the sample rate. Applications should always use the highest
  83   71  sample rate the device supports. An application can also do its own sample rate
  84   72  conversion (to take advantage of floating point and accelerated instructions)
  85   73  or use small integers for up and down sampling.
  86   74  .sp
  87   75  .LP
  88   76  All modern audio devices run at 48 kHz or a multiple thereof, hence just using
  89   77  48 kHz can be a reasonable compromise if the application is not prepared to
  90   78  select higher sample rates.
  91   79  .SS "Encodings"
  92      -.sp
  93      -.LP
  94   80  An encoding parameter specifies the audiodata representation. u-Law encoding
  95   81  corresponds to CCITT G.711, and is the standard for voice data used by
  96   82  telephone companies in the United States, Canada, and Japan. A-Law encoding is
  97   83  also part of CCITT G.711 and is the standard encoding for telephony elsewhere
  98   84  in the world. A-Law and u-Law audio data are sampled at a rate of 8000 samples
  99   85  per second with 12-bit precision, with the data compressed to 8-bit samples.
 100   86  The resulting audio data quality is equivalent to that of stan dard analog
 101   87  telephone service.
 102   88  .sp
 103   89  .LP
 104   90  Linear Pulse Code Modulation (PCM) is an uncompressed, signed audio format in
 105   91  which sample values are directly proportional to audio signal voltages. Each
 106   92  sample is a 2's complement number that represents a positive or negative
 107   93  amplitude.
 108   94  .SS "Precision"
 109      -.sp
 110      -.LP
 111   95  Precision indicates the number of bits used to store each audio sample. For
 112   96  instance, u-Law and A-Law data are stored with 8-bit precision. PCM data can be
 113   97  stored at various precisions, though 16-bit is the most common.
 114   98  .SS "Channels"
 115      -.sp
 116      -.LP
 117   99  Multiple channels of audio can be interleaved at sample boundaries. A sample
 118  100  frame consists of a single sample from each active channel. For example, a
 119  101  sample frame of stereo 16-bit PCM data consists of 2 16-bit samples,
 120  102  corresponding to the left and right channel data. The audio mixer sets the
 121  103  hardware to the maximum number of channels supported. If a mono signal is
 122  104  played or recorded, it is mixed on the first two (usually the left and right)
 123  105  channel only. Silence is mixed on the remaining channels.
 124  106  .SS "Supported Formats"
 125      -.sp
 126      -.LP
 127  107  The audio mixer supports the following audio formats:
 128  108  .sp
 129  109  .in +2
 130  110  .nf
 131  111  Encoding            Precision  Channels
 132  112  Signed Linear PCM   32-bit     Mono or Stereo
 133  113  Signed Linear PCM   16-bit     Mono or Stereo
 134  114  Signed Linear PCM   8-bit      Mono or Stereo
 135  115  u-Law               8-bit      Mono or Stereo
 136  116  A-Law               8-bit      Mono or Stereo
↓ open down ↓ 7 lines elided ↑ open up ↑ 
 144  124  After mixing, conversion is made to the best possible Codec format. The
 145  125  conversion process is not compute intensive and audio applications can choose
 146  126  the encoding format that best meets their needs.
 147  127  .sp
 148  128  .LP
 149  129  The mixer discards the low order 8 bits of 32-bit Signed Linear PCM in order to
 150  130  perform mixing. (This is done to allow for possible overflows to fit into
 151  131  32-bits when mixing multiple streams together.) Hence, the maximum effective
 152  132  precision is 24-bits.
 153  133  .SH FILES
 154      -.sp
 155  134  .ne 2
 156  135  .na
 157      -\fB\fB/kernel/drv/audio\fR\fR
 158      -.ad
 159      -.RS 29n
 160      -32-bit kernel driver module
 161      -.RE
 162      -
 163      -.sp
 164      -.ne 2
 165      -.na
 166  136  \fB\fB/kernel/drv/amd64/audio\fR\fR
 167  137  .ad
 168  138  .RS 29n
 169      -64-bit x86 kernel driver module
      139 +Device driver (x86)
 170  140  .RE
 171  141  
 172  142  .sp
 173  143  .ne 2
 174  144  .na
 175  145  \fB\fB/kernel/drv/sparcv9/audio\fR\fR
 176  146  .ad
 177  147  .RS 29n
 178      -64-bit SPARC kernel driver module
      148 +Device driver (SPARC)
 179  149  .RE
 180  150  
 181  151  .sp
 182  152  .ne 2
 183  153  .na
 184  154  \fB\fB/kernel/drv/audio.conf\fR\fR
 185  155  .ad
 186  156  .RS 29n
 187      -\fBaudio\fR configuration file
      157 +Driver configuration file
 188  158  .RE
 189  159  
 190  160  .SH ATTRIBUTES
 191      -.sp
 192      -.LP
 193  161  See \fBattributes\fR(5) for a description of the following attributes:
 194  162  .sp
 195  163  
 196  164  .sp
 197  165  .TS
 198  166  box;
 199  167  l | l
 200  168  l | l .
 201  169  ATTRIBUTE TYPE  ATTRIBUTE VALUE
 202  170  _
 203  171  Architecture    SPARC, x86
 204  172  _
 205  173  Interface Stability     Uncommitted
 206  174  .TE
 207  175  
 208  176  .SH SEE ALSO
 209      -.sp
 210      -.LP
 211  177  \fBioctl\fR(2), \fBattributes\fR(5), \fBaudio\fR(7I), \fBdsp\fR(7I)
    
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