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| 54 | <H2><A NAME="SECTION0023110000000000000000"></A><A NAME="audio-device-objects"></A> |
| 55 | <BR> |
| 56 | 21.1.1 Audio Device Objects |
| 57 | </H2> |
| 58 | |
| 59 | <P> |
| 60 | The audio device objects are returned by <tt class="function">open()</tt> define the |
| 61 | following methods (except <code>control</code> objects which only provide |
| 62 | <tt class="method">getinfo()</tt>, <tt class="method">setinfo()</tt>, <tt class="method">fileno()</tt>, and |
| 63 | <tt class="method">drain()</tt>): |
| 64 | |
| 65 | <P> |
| 66 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 67 | <td><nobr><b><tt id='l2h-5227' xml:id='l2h-5227' class="method">close</tt></b>(</nobr></td> |
| 68 | <td><var></var>)</td></tr></table></dt> |
| 69 | <dd> |
| 70 | This method explicitly closes the device. It is useful in situations |
| 71 | where deleting the object does not immediately close it since there |
| 72 | are other references to it. A closed device should not be used again. |
| 73 | </dl> |
| 74 | |
| 75 | <P> |
| 76 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 77 | <td><nobr><b><tt id='l2h-5228' xml:id='l2h-5228' class="method">fileno</tt></b>(</nobr></td> |
| 78 | <td><var></var>)</td></tr></table></dt> |
| 79 | <dd> |
| 80 | Returns the file descriptor associated with the device. This can be |
| 81 | used to set up <code>SIGPOLL</code> notification, as described below. |
| 82 | </dl> |
| 83 | |
| 84 | <P> |
| 85 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 86 | <td><nobr><b><tt id='l2h-5229' xml:id='l2h-5229' class="method">drain</tt></b>(</nobr></td> |
| 87 | <td><var></var>)</td></tr></table></dt> |
| 88 | <dd> |
| 89 | This method waits until all pending output is processed and then returns. |
| 90 | Calling this method is often not necessary: destroying the object will |
| 91 | automatically close the audio device and this will do an implicit drain. |
| 92 | </dl> |
| 93 | |
| 94 | <P> |
| 95 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 96 | <td><nobr><b><tt id='l2h-5230' xml:id='l2h-5230' class="method">flush</tt></b>(</nobr></td> |
| 97 | <td><var></var>)</td></tr></table></dt> |
| 98 | <dd> |
| 99 | This method discards all pending output. It can be used avoid the |
| 100 | slow response to a user's stop request (due to buffering of up to one |
| 101 | second of sound). |
| 102 | </dl> |
| 103 | |
| 104 | <P> |
| 105 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 106 | <td><nobr><b><tt id='l2h-5231' xml:id='l2h-5231' class="method">getinfo</tt></b>(</nobr></td> |
| 107 | <td><var></var>)</td></tr></table></dt> |
| 108 | <dd> |
| 109 | This method retrieves status information like input and output volume, |
| 110 | etc. and returns it in the form of |
| 111 | an audio status object. This object has no methods but it contains a |
| 112 | number of attributes describing the current device status. The names |
| 113 | and meanings of the attributes are described in |
| 114 | <code><sun/audioio.h></code> and in the <span class="manpage"><i>audio</i>(7I)</span> |
| 115 | manual page. Member names |
| 116 | are slightly different from their C counterparts: a status object is |
| 117 | only a single structure. Members of the <tt class="cdata">play</tt> substructure have |
| 118 | "<tt class="samp">o_</tt>" prepended to their name and members of the <tt class="cdata">record</tt> |
| 119 | structure have "<tt class="samp">i_</tt>". So, the C member <tt class="cdata">play.sample_rate</tt> is |
| 120 | accessed as <tt class="member">o_sample_rate</tt>, <tt class="cdata">record.gain</tt> as <tt class="member">i_gain</tt> |
| 121 | and <tt class="cdata">monitor_gain</tt> plainly as <tt class="member">monitor_gain</tt>. |
| 122 | </dl> |
| 123 | |
| 124 | <P> |
| 125 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 126 | <td><nobr><b><tt id='l2h-5232' xml:id='l2h-5232' class="method">ibufcount</tt></b>(</nobr></td> |
| 127 | <td><var></var>)</td></tr></table></dt> |
| 128 | <dd> |
| 129 | This method returns the number of samples that are buffered on the |
| 130 | recording side, i.e. the program will not block on a |
| 131 | <tt class="function">read()</tt> call of so many samples. |
| 132 | </dl> |
| 133 | |
| 134 | <P> |
| 135 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 136 | <td><nobr><b><tt id='l2h-5233' xml:id='l2h-5233' class="method">obufcount</tt></b>(</nobr></td> |
| 137 | <td><var></var>)</td></tr></table></dt> |
| 138 | <dd> |
| 139 | This method returns the number of samples buffered on the playback |
| 140 | side. Unfortunately, this number cannot be used to determine a number |
| 141 | of samples that can be written without blocking since the kernel |
| 142 | output queue length seems to be variable. |
| 143 | </dl> |
| 144 | |
| 145 | <P> |
| 146 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 147 | <td><nobr><b><tt id='l2h-5234' xml:id='l2h-5234' class="method">read</tt></b>(</nobr></td> |
| 148 | <td><var>size</var>)</td></tr></table></dt> |
| 149 | <dd> |
| 150 | This method reads <var>size</var> samples from the audio input and returns |
| 151 | them as a Python string. The function blocks until enough data is available. |
| 152 | </dl> |
| 153 | |
| 154 | <P> |
| 155 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 156 | <td><nobr><b><tt id='l2h-5235' xml:id='l2h-5235' class="method">setinfo</tt></b>(</nobr></td> |
| 157 | <td><var>status</var>)</td></tr></table></dt> |
| 158 | <dd> |
| 159 | This method sets the audio device status parameters. The <var>status</var> |
| 160 | parameter is an device status object as returned by <tt class="function">getinfo()</tt> and |
| 161 | possibly modified by the program. |
| 162 | </dl> |
| 163 | |
| 164 | <P> |
| 165 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 166 | <td><nobr><b><tt id='l2h-5236' xml:id='l2h-5236' class="method">write</tt></b>(</nobr></td> |
| 167 | <td><var>samples</var>)</td></tr></table></dt> |
| 168 | <dd> |
| 169 | Write is passed a Python string containing audio samples to be played. |
| 170 | If there is enough buffer space free it will immediately return, |
| 171 | otherwise it will block. |
| 172 | </dl> |
| 173 | |
| 174 | <P> |
| 175 | The audio device supports asynchronous notification of various events, |
| 176 | through the SIGPOLL signal. Here's an example of how you might enable |
| 177 | this in Python: |
| 178 | |
| 179 | <P> |
| 180 | <div class="verbatim"><pre> |
| 181 | def handle_sigpoll(signum, frame): |
| 182 | print 'I got a SIGPOLL update' |
| 183 | |
| 184 | import fcntl, signal, STROPTS |
| 185 | |
| 186 | signal.signal(signal.SIGPOLL, handle_sigpoll) |
| 187 | fcntl.ioctl(audio_obj.fileno(), STROPTS.I_SETSIG, STROPTS.S_MSG) |
| 188 | </pre></div> |
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