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