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   <meta name="Description" content="Tutorial for PortAudio, a cross platform, open-source, audio I/O library.It provides a very simple API for recording and/or playing sound using a simple callback function.">
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<h1>
PortAudio Tutorial</h1></center>
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<h2>
Querying for Available Devices</h2>

<blockquote>There are often several different audio devices available in
a computer with different capabilities. They can differ in the sample rates
supported, bit widths, etc. PortAudio provides a simple way to query for
the available devices, and then pass the selected device to Pa_OpenStream().
For an example, see the file "pa_tests/pa_devs.c".
<p>To determine the number of devices:
<blockquote>
<pre>numDevices = Pa_CountDevices();</pre>
</blockquote>
You can then query each device in turn by calling Pa_GetDeviceInfo() with
an index.
<blockquote>
<pre>for( i=0; i&lt;numDevices; i++ ) {
&nbsp;&nbsp;&nbsp;&nbsp; pdi = Pa_GetDeviceInfo( i );</pre>
</blockquote>
It will return a pointer to a <tt>PaDeviceInfo</tt> structure which is
defined as:
<blockquote>
<pre>typedef struct{
&nbsp;&nbsp;&nbsp; int structVersion;&nbsp;
&nbsp;&nbsp;&nbsp; const char *name;
&nbsp;&nbsp;&nbsp; int maxInputChannels;
&nbsp;&nbsp;&nbsp; int maxOutputChannels;
/* Number of discrete rates, or -1 if range supported. */
&nbsp;&nbsp;&nbsp; int numSampleRates;
/* Array of supported sample rates, or {min,max} if range supported. */
&nbsp;&nbsp;&nbsp; const double *sampleRates;
&nbsp;&nbsp;&nbsp; PaSampleFormat nativeSampleFormat;
}PaDeviceInfo;</pre>
</blockquote>
If the device supports a continuous range of sample rates, then numSampleRates
will equal -1, and the sampleRates array will have two values, the minimum&nbsp;
and maximum rate.
<p>The device information is allocated by Pa_Initialize() and freed by
Pa_Terminate() so you do not have to free() the structure returned by Pa_GetDeviceInfo().</blockquote>
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