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<H2><A NAME="SECTION00161120000000000000000"></A><A NAME="mixer-device-objects"></A>
<BR>
14.11.2 Mixer Device Objects 
</H2>

<P>
The mixer object provides two file-like methods:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4792' xml:id='l2h-4792' class="method">close</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
This method closes the open mixer device file.  Any further attempts to
use the mixer after this file is closed will raise an IOError.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4793' xml:id='l2h-4793' class="method">fileno</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Returns the file handle number of the open mixer device file.
</dl>

<P>
The remaining methods are specific to audio mixing:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4794' xml:id='l2h-4794' class="method">controls</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
This method returns a bitmask specifying the available mixer controls
(``Control'' being a specific mixable ``channel'', such as
<tt class="constant">SOUND_MIXER_PCM</tt> or <tt class="constant">SOUND_MIXER_SYNTH</tt>).  This
bitmask indicates a subset of all available mixer controls--the
<tt class="constant">SOUND_MIXER_*</tt> constants defined at module level.  To determine if,
for example, the current mixer object supports a PCM mixer, use the
following Python code:

<P>
<div class="verbatim"><pre>
mixer=ossaudiodev.openmixer()
if mixer.controls() &amp; (1 &lt;&lt; ossaudiodev.SOUND_MIXER_PCM):
    # PCM is supported
    ... code ...
</pre></div>

<P>
For most purposes, the <tt class="constant">SOUND_MIXER_VOLUME</tt> (master volume) and
<tt class="constant">SOUND_MIXER_PCM</tt> controls should suffice--but code that uses the
mixer should be flexible when it comes to choosing mixer controls.  On
the Gravis Ultrasound, for example, <tt class="constant">SOUND_MIXER_VOLUME</tt> does not
exist.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4795' xml:id='l2h-4795' class="method">stereocontrols</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Returns a bitmask indicating stereo mixer controls.  If a bit is set,
the corresponding control is stereo; if it is unset, the control is
either monophonic or not supported by the mixer (use in combination with
<tt class="method">controls()</tt> to determine which).

<P>
See the code example for the <tt class="method">controls()</tt> function for an example
of getting data from a bitmask.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4796' xml:id='l2h-4796' class="method">reccontrols</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Returns a bitmask specifying the mixer controls that may be used to
record.  See the code example for <tt class="method">controls()</tt> for an example of
reading from a bitmask.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4797' xml:id='l2h-4797' class="method">get</tt></b>(</nobr></td>
  <td><var>control</var>)</td></tr></table></dt>
<dd>
Returns the volume of a given mixer control.  The returned volume is a
2-tuple <code>(left_volume,right_volume)</code>.  Volumes are specified as
numbers from 0 (silent) to 100 (full volume).  If the control is
monophonic, a 2-tuple is still returned, but both volumes are
the same.

<P>
Raises <tt class="exception">OSSAudioError</tt> if an invalid control was is specified,
or <tt class="exception">IOError</tt> if an unsupported control is specified.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4798' xml:id='l2h-4798' class="method">set</tt></b>(</nobr></td>
  <td><var>control, (left, right)</var>)</td></tr></table></dt>
<dd>
Sets the volume for a given mixer control to <code>(left,right)</code>.
<code>left</code> and <code>right</code> must be ints and between 0 (silent) and 100
(full volume).  On success, the new volume is returned as a 2-tuple.
Note that this may not be exactly the same as the volume specified,
because of the limited resolution of some soundcard's mixers.

<P>
Raises <tt class="exception">OSSAudioError</tt> if an invalid mixer control was
specified, or if the specified volumes were out-of-range.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4799' xml:id='l2h-4799' class="method">get_recsrc</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
This method returns a bitmask indicating which control(s) are
currently being used as a recording source.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4800' xml:id='l2h-4800' class="method">set_recsrc</tt></b>(</nobr></td>
  <td><var>bitmask</var>)</td></tr></table></dt>
<dd>
Call this function to specify a recording source.  Returns a bitmask
indicating the new recording source (or sources) if successful; raises
<tt class="exception">IOError</tt> if an invalid source was specified.  To set the current
recording source to the microphone input:

<P>
<div class="verbatim"><pre>
mixer.setrecsrc (1 &lt;&lt; ossaudiodev.SOUND_MIXER_MIC)
</pre></div>
</dl>

<P>

<P>

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	54	<H2><A NAME="SECTION00161120000000000000000"></A><A NAME="mixer-device-objects"></A>
	55	<BR>
	56	14.11.2 Mixer Device Objects
	57	</H2>
	58
	59	<P>
	60	The mixer object provides two file-like methods:
	61
	62	<P>
	63	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
	64	<td><nobr><b><tt id='l2h-4792' xml:id='l2h-4792' class="method">close</tt></b>(</nobr></td>
65	<td><var></var>)</td></tr></table></dt>
66	<dd>
67	This method closes the open mixer device file. Any further attempts to
68	use the mixer after this file is closed will raise an IOError.
69	</dl>
70
71	<P>
72	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
73	<td><nobr><b><tt id='l2h-4793' xml:id='l2h-4793' class="method">fileno</tt></b>(</nobr></td>
74	<td><var></var>)</td></tr></table></dt>
75	<dd>
76	Returns the file handle number of the open mixer device file.
77	</dl>
78
79	<P>
80	The remaining methods are specific to audio mixing:
81
82	<P>
83	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
84	<td><nobr><b><tt id='l2h-4794' xml:id='l2h-4794' class="method">controls</tt></b>(</nobr></td>
85	<td><var></var>)</td></tr></table></dt>
86	<dd>
87	This method returns a bitmask specifying the available mixer controls
88	(``Control'' being a specific mixable ``channel'', such as
89	<tt class="constant">SOUND_MIXER_PCM</tt> or <tt class="constant">SOUND_MIXER_SYNTH</tt>). This
90	bitmask indicates a subset of all available mixer controls--the
91	<tt class="constant">SOUND_MIXER_*</tt> constants defined at module level. To determine if,
92	for example, the current mixer object supports a PCM mixer, use the
93	following Python code:
94
95	<P>
96	<div class="verbatim"><pre>
97	mixer=ossaudiodev.openmixer()
98	if mixer.controls() & (1 << ossaudiodev.SOUND_MIXER_PCM):
99	# PCM is supported
100	... code ...
101	</pre></div>
102
103	<P>
104	For most purposes, the <tt class="constant">SOUND_MIXER_VOLUME</tt> (master volume) and
105	<tt class="constant">SOUND_MIXER_PCM</tt> controls should suffice--but code that uses the
106	mixer should be flexible when it comes to choosing mixer controls. On
107	the Gravis Ultrasound, for example, <tt class="constant">SOUND_MIXER_VOLUME</tt> does not
108	exist.
109	</dl>
110
111	<P>
112	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
113	<td><nobr><b><tt id='l2h-4795' xml:id='l2h-4795' class="method">stereocontrols</tt></b>(</nobr></td>
114	<td><var></var>)</td></tr></table></dt>
115	<dd>
116	Returns a bitmask indicating stereo mixer controls. If a bit is set,
117	the corresponding control is stereo; if it is unset, the control is
118	either monophonic or not supported by the mixer (use in combination with
119	<tt class="method">controls()</tt> to determine which).
120
121	<P>
122	See the code example for the <tt class="method">controls()</tt> function for an example
123	of getting data from a bitmask.
124	</dl>
125
126	<P>
127	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
128	<td><nobr><b><tt id='l2h-4796' xml:id='l2h-4796' class="method">reccontrols</tt></b>(</nobr></td>
129	<td><var></var>)</td></tr></table></dt>
130	<dd>
131	Returns a bitmask specifying the mixer controls that may be used to
132	record. See the code example for <tt class="method">controls()</tt> for an example of
133	reading from a bitmask.
134	</dl>
135
136	<P>
137	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
138	<td><nobr><b><tt id='l2h-4797' xml:id='l2h-4797' class="method">get</tt></b>(</nobr></td>
139	<td><var>control</var>)</td></tr></table></dt>
140	<dd>
141	Returns the volume of a given mixer control. The returned volume is a
142	2-tuple <code>(left_volume,right_volume)</code>. Volumes are specified as
143	numbers from 0 (silent) to 100 (full volume). If the control is
144	monophonic, a 2-tuple is still returned, but both volumes are
145	the same.
146
147	<P>
148	Raises <tt class="exception">OSSAudioError</tt> if an invalid control was is specified,
149	or <tt class="exception">IOError</tt> if an unsupported control is specified.
150	</dl>
151
152	<P>
153	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
154	<td><nobr><b><tt id='l2h-4798' xml:id='l2h-4798' class="method">set</tt></b>(</nobr></td>
155	<td><var>control, (left, right)</var>)</td></tr></table></dt>
156	<dd>
157	Sets the volume for a given mixer control to <code>(left,right)</code>.
158	<code>left</code> and <code>right</code> must be ints and between 0 (silent) and 100
159	(full volume). On success, the new volume is returned as a 2-tuple.
160	Note that this may not be exactly the same as the volume specified,
161	because of the limited resolution of some soundcard's mixers.
162
163	<P>
164	Raises <tt class="exception">OSSAudioError</tt> if an invalid mixer control was
165	specified, or if the specified volumes were out-of-range.
166	</dl>
167
168	<P>
169	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
170	<td><nobr><b><tt id='l2h-4799' xml:id='l2h-4799' class="method">get_recsrc</tt></b>(</nobr></td>
171	<td><var></var>)</td></tr></table></dt>
172	<dd>
173	This method returns a bitmask indicating which control(s) are
174	currently being used as a recording source.
175	</dl>
176
177	<P>
178	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
179	<td><nobr><b><tt id='l2h-4800' xml:id='l2h-4800' class="method">set_recsrc</tt></b>(</nobr></td>
180	<td><var>bitmask</var>)</td></tr></table></dt>
181	<dd>
182	Call this function to specify a recording source. Returns a bitmask
183	indicating the new recording source (or sources) if successful; raises
184	<tt class="exception">IOError</tt> if an invalid source was specified. To set the current
185	recording source to the microphone input:
186
187	<P>
188	<div class="verbatim"><pre>
189	mixer.setrecsrc (1 << ossaudiodev.SOUND_MIXER_MIC)
190	</pre></div>
191	</dl>
192
193	<P>
194
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