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<title>libao - function - ao_plugin_open</title>
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<td><p class=tiny>libao documentation</p></td>
<td align=right><p class=tiny>libao version 1.2.0 - 201401271</p></td>
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<h1>ao_plugin_open</h1>
<p><i>declared in "ao/plugin.h";</i></p>
<p>Open the device for playback. All of the device options will have
already been set by previous calls to <a
href="ao_plugin_set_option.html">ao_plugin_set_option()</a>. If this is a
file output driver, the file itself will have be already opened and a
pointer to a <tt>FILE</tt> structure stored in <tt>device->file</tt>.
<p>If the plugin wishes to support automatic channel mapping, but it
was not possible to set <tt>device->output_matrix</tt> in <a
href="ao_plugin_device_init.html">ao_plugin_device_init()</a>, the
plugin should now set <tt>device->inter_matrix</tt> to the channel
ordering that will be expected for buffers submitted to <a
href="ao_plugin_play.html">ao_plugin_play()</a>.
<p>Plugins should use <tt>device->output_channels</tt> to determine
the number of output channels to configure, not
<tt>format->channels</tt>. <tt>device->output_channels</tt> is the
number of channels libao will be submitting upon each call to <a
href="ao_plugin_play.html">ao_plugin_play()</a>. A plugin may alter
the value of <tt>device->output_channels</tt> to demand a different
number of channels if necessary (such as if a plugin is manufacturing
a channel mapping manually).
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<pre><b>
int ao_plugin_open(<a href="ao_device.html">ao_device</a> *device, <a href="ao_sample_format.html">ao_sample_format</a> *format);
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<h3>Parameters</h3>
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<dt><i>device</i></dt>
<dd>Pointer to pre-allocated device structure. The plugin should
set its desired byte format in <tt>device->driver_byte_format</tt>.</dd>
<dt><i>format</i></dt>
<dd>Output device sample format. <tt>format->byte_format</tt> should
be ignored as it is relevant only to the library core.
<tt>format->channels</tt> is relevant only if a plugin is constructing
a channel mapping manually; otherwise <tt>device->output</tt> should
be used as it is the actual number of channels that will be sent to <a
href="ao_plugin_play.html">ao_plugin_play()</a>.</dd>
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<h3>Return Values</h3>
<blockquote>
<li>1 indicates success.</li>
<li>0 indicates failure to open the device.
<a href="ao_plugin_device_clear.html">ao_plugin_device_clear()</a> should be
called to ensure the deallocate of all private data structures.</li>
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<td><p class=tiny>copyright © 2001-2003 Stan Seibert, 2010-2011 Monty</p></td>
<td align=right><p class=tiny><a href="http://www.xiph.org/">xiph.org</a><br><a href="mailto:monty@xiph.org">monty@xiph.org</a></p></td>
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<td><p class=tiny>libao documentation</p></td>
<td align=right><p class=tiny>libao version 1.2.0 - 201401271</p></td>
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