Doc/lib/libsunaudio.tex

   1 \section{\module{sunaudiodev} ---
   2          Access to Sun audio hardware.}
   3
   4 \declaremodule{builtin}{sunaudiodev}
   5   \platform{SunOS}
   6 \modulesynopsis{Access to Sun audio hardware.}
   7
   8
   9 This module allows you to access the Sun audio interface. The Sun
  10 audio hardware is capable of recording and playing back audio data
  11 in u-LAW\index{u-LAW} format with a sample rate of 8K per second. A
  12 full description can be found in the \manpage{audio}{7I} manual page.
  13
  14 The module defines the following variables and functions:
  15
  16 \begin{excdesc}{error}
  17 This exception is raised on all errors. The argument is a string
  18 describing what went wrong.
  19 \end{excdesc}
  20
  21 \begin{funcdesc}{open}{mode}
  22 This function opens the audio device and returns a Sun audio device
  23 object. This object can then be used to do I/O on. The \var{mode} parameter
  24 is one of \code{'r'} for record-only access, \code{'w'} for play-only
  25 access, \code{'rw'} for both and \code{'control'} for access to the
  26 control device. Since only one process is allowed to have the recorder
  27 or player open at the same time it is a good idea to open the device
  28 only for the activity needed. See \manpage{audio}{7I} for details.
  29
  30 As per the manpage, this module first looks in the environment
  31 variable \code{AUDIODEV} for the base audio device filename.  If not
  32 found, it falls back to \file{/dev/audio}.  The control device is
  33 calculated by appending ``ctl'' to the base audio device.
  34 \end{funcdesc}
  35
  36
  37 \subsection{Audio Device Objects}
  38 \label{audio-device-objects}
  39
  40 The audio device objects are returned by \function{open()} define the
  41 following methods (except \code{control} objects which only provide
  42 \method{getinfo()}, \method{setinfo()}, \method{fileno()}, and
  43 \method{drain()}):
  44
  45 \begin{methoddesc}[audio device]{close}{}
  46 This method explicitly closes the device. It is useful in situations
  47 where deleting the object does not immediately close it since there
  48 are other references to it. A closed device should not be used again.
  49 \end{methoddesc}
  50
  51 \begin{methoddesc}[audio device]{fileno}{}
  52 Returns the file descriptor associated with the device.  This can be
  53 used to set up \code{SIGPOLL} notification, as described below.
  54 \end{methoddesc}
  55
  56 \begin{methoddesc}[audio device]{drain}{}
  57 This method waits until all pending output is processed and then returns.
  58 Calling this method is often not necessary: destroying the object will
  59 automatically close the audio device and this will do an implicit drain.
  60 \end{methoddesc}
  61
  62 \begin{methoddesc}[audio device]{flush}{}
  63 This method discards all pending output. It can be used avoid the
  64 slow response to a user's stop request (due to buffering of up to one
  65 second of sound).
  66 \end{methoddesc}
  67
  68 \begin{methoddesc}[audio device]{getinfo}{}
  69 This method retrieves status information like input and output volume,
  70 etc. and returns it in the form of
  71 an audio status object. This object has no methods but it contains a
  72 number of attributes describing the current device status. The names
  73 and meanings of the attributes are described in
  74 \file{/usr/include/sun/audioio.h} and in the \manpage{audio}{7I}
  75 manual page.  Member names
  76 are slightly different from their \C{} counterparts: a status object is
  77 only a single structure. Members of the \cdata{play} substructure have
  78 \samp{o_} prepended to their name and members of the \cdata{record}
  79 structure have \samp{i_}. So, the \C{} member \cdata{play.sample_rate} is
  80 accessed as \member{o_sample_rate}, \cdata{record.gain} as \member{i_gain}
  81 and \cdata{monitor_gain} plainly as \member{monitor_gain}.
  82 \end{methoddesc}
  83
  84 \begin{methoddesc}[audio device]{ibufcount}{}
  85 This method returns the number of samples that are buffered on the
  86 recording side, i.e.\ the program will not block on a
  87 \function{read()} call of so many samples.
  88 \end{methoddesc}
  89
  90 \begin{methoddesc}[audio device]{obufcount}{}
  91 This method returns the number of samples buffered on the playback
  92 side. Unfortunately, this number cannot be used to determine a number
  93 of samples that can be written without blocking since the kernel
  94 output queue length seems to be variable.
  95 \end{methoddesc}
  96
  97 \begin{methoddesc}[audio device]{read}{size}
  98 This method reads \var{size} samples from the audio input and returns
  99 them as a Python string. The function blocks until enough data is available.
 100 \end{methoddesc}
 101
 102 \begin{methoddesc}[audio device]{setinfo}{status}
 103 This method sets the audio device status parameters. The \var{status}
 104 parameter is an device status object as returned by \function{getinfo()} and
 105 possibly modified by the program.
 106 \end{methoddesc}
 107
 108 \begin{methoddesc}[audio device]{write}{samples}
 109 Write is passed a Python string containing audio samples to be played.
 110 If there is enough buffer space free it will immediately return,
 111 otherwise it will block.
 112 \end{methoddesc}
 113
 114 There is a companion module,
 115 \module{SUNAUDIODEV}\refstmodindex{SUNAUDIODEV}, which defines useful
 116 symbolic constants like \constant{MIN_GAIN}, \constant{MAX_GAIN},
 117 \constant{SPEAKER}, etc. The names of the constants are the same names
 118 as used in the \C{} include file \code{<sun/audioio.h>}, with the
 119 leading string \samp{AUDIO_} stripped.
 120
 121 The audio device supports asynchronous notification of various events,
 122 through the SIGPOLL signal.  Here's an example of how you might enable
 123 this in Python:
 124
 125 \begin{verbatim}
 126 def handle_sigpoll(signum, frame):
 127     print 'I got a SIGPOLL update'
 128 pp
 129 import fcntl, signal, STROPTS
 130
 131 signal.signal(signal.SIGPOLL, handle_sigpoll)
 132 fcntl.ioctl(audio_obj.fileno(), STROPTS.I_SETSIG, STROPTS.S_MSG)
 133 \end{verbatim}