sam-t2/devtools/v9/html/python/lib/audio-device-objects.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="lib.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python Documentation Index' />
<link rel="first" href="lib.html" title='Python Library Reference' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='index' href='genindex.html' title='Index' />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="prev" href="module-sunaudiodev.html" />
<link rel="parent" href="module-sunaudiodev.html" />
<link rel="next" href="module-sunaudiodev-constants.html" />
<meta name='aesop' content='information' />
<title>21.1.1 Audio Device Objects </title>
</head>
<body>
<DIV CLASS="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="21.1 sunaudiodev  "
  href="module-sunaudiodev.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="21.1 sunaudiodev  "
  href="module-sunaudiodev.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="21.2 SUNAUDIODEV  "
  href="module-sunaudiodev-constants.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="module-sunaudiodev.html">21.1 sunaudiodev  </A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="module-sunaudiodev.html">21.1 sunaudiodev  </A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="module-sunaudiodev-constants.html">21.2 SUNAUDIODEV  </A>
</div>
<hr /></div>
</DIV>
<!--End of Navigation Panel-->

<H2><A NAME="SECTION0023110000000000000000"></A><A NAME="audio-device-objects"></A>
<BR>
21.1.1 Audio Device Objects
</H2>

<P>
The audio device objects are returned by <tt class="function">open()</tt> define the
following methods (except <code>control</code> objects which only provide
<tt class="method">getinfo()</tt>, <tt class="method">setinfo()</tt>, <tt class="method">fileno()</tt>, and
<tt class="method">drain()</tt>):

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-5227' xml:id='l2h-5227' class="method">close</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
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.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-5228' xml:id='l2h-5228' class="method">fileno</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Returns the file descriptor associated with the device.  This can be
used to set up <code>SIGPOLL</code> notification, as described below.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-5229' xml:id='l2h-5229' class="method">drain</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
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.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-5230' xml:id='l2h-5230' class="method">flush</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
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).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-5231' xml:id='l2h-5231' class="method">getinfo</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
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
<code>&lt;sun/audioio.h&gt;</code> and in the <span class="manpage"><i>audio</i>(7I)</span>
manual page.  Member names
are slightly different from their C counterparts: a status object is
only a single structure. Members of the <tt class="cdata">play</tt> substructure have
"<tt class="samp">o_</tt>" prepended to their name and members of the <tt class="cdata">record</tt>
structure have "<tt class="samp">i_</tt>". So, the C member <tt class="cdata">play.sample_rate</tt> is
accessed as <tt class="member">o_sample_rate</tt>, <tt class="cdata">record.gain</tt> as <tt class="member">i_gain</tt>
and <tt class="cdata">monitor_gain</tt> plainly as <tt class="member">monitor_gain</tt>.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-5232' xml:id='l2h-5232' class="method">ibufcount</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
This method returns the number of samples that are buffered on the
recording side, i.e. the program will not block on a
<tt class="function">read()</tt> call of so many samples.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-5233' xml:id='l2h-5233' class="method">obufcount</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
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.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-5234' xml:id='l2h-5234' class="method">read</tt></b>(</nobr></td>
  <td><var>size</var>)</td></tr></table></dt>
<dd>
This method reads <var>size</var> samples from the audio input and returns
them as a Python string. The function blocks until enough data is available.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-5235' xml:id='l2h-5235' class="method">setinfo</tt></b>(</nobr></td>
  <td><var>status</var>)</td></tr></table></dt>
<dd>
This method sets the audio device status parameters. The <var>status</var>
parameter is an device status object as returned by <tt class="function">getinfo()</tt> and
possibly modified by the program.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-5236' xml:id='l2h-5236' class="method">write</tt></b>(</nobr></td>
  <td><var>samples</var>)</td></tr></table></dt>
<dd>
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.
</dl>

<P>
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:

<P>
<div class="verbatim"><pre>
def handle_sigpoll(signum, frame):
    print 'I got a SIGPOLL update'

import fcntl, signal, STROPTS

signal.signal(signal.SIGPOLL, handle_sigpoll)
fcntl.ioctl(audio_obj.fileno(), STROPTS.I_SETSIG, STROPTS.S_MSG)
</pre></div>

<P>

<DIV CLASS="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="21.1 sunaudiodev  "
  href="module-sunaudiodev.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="21.1 sunaudiodev  "
  href="module-sunaudiodev.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="21.2 SUNAUDIODEV  "
  href="module-sunaudiodev-constants.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="module-sunaudiodev.html">21.1 sunaudiodev  </A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="module-sunaudiodev.html">21.1 sunaudiodev  </A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="module-sunaudiodev-constants.html">21.2 SUNAUDIODEV  </A>
</div>
</div>
<hr />
<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
</DIV>
<!--End of Navigation Panel-->
<ADDRESS>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</ADDRESS>
</BODY>
</HTML>