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 1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374 
  1. <HTML>

  2. <HEAD>

  3. <TITLE>The RtAudio Home Page</TITLE>

  4. <LINK HREF="doxygen.css" REL="stylesheet" TYPE="text/css">

  5. <LINK REL="SHORTCUT ICON" HREF="http://www.music.mcgill.ca/~gary/favicon.ico">

  6. </HEAD>

  7. <BODY BGCOLOR="#FFFFFF">

  8. <CENTER>

  9. <a class="qindex" href="index.html">Home</a> &nbsp; <a class="qindex" href="annotated.html">Class/Enum List</a> &nbsp; <a class="qindex" href="files.html">File List</a> &nbsp; <a class="qindex" href="functions.html">Compound Members</a> &nbsp; </CENTER>

  10. <HR>

  11. <!-- Generated by Doxygen 1.6.2 -->

  12. <div class="contents">

  13. 

  14. 

  15. <h1><a class="anchor" id="probe">Probing Device Capabilities </a></h1><p>A programmer may wish to query the available audio device capabilities before deciding which to use. The following example outlines how this can be done.</p>

  16. <div class="fragment"><pre class="fragment"><span class="comment">// audioprobe.cpp</span>

  17. 

  18. <span class="preprocessor">#include &lt;iostream&gt;</span>

  19. <span class="preprocessor">#include &quot;<a class="code" href="RtAudio_8h.html">RtAudio.h</a>&quot;</span>

  20. 

  21. <span class="keywordtype">int</span> main()

  22. {

  23.   <a class="code" href="classRtAudio.html" title="Realtime audio i/o C++ classes.">RtAudio</a> audio;

  24. 

  25.   <span class="comment">// Determine the number of devices available</span>

  26.   <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> devices = audio.<a class="code" href="classRtAudio.html#a747ce2d73803641bbb66d6e78092aa1a" title="A public function that queries for the number of audio devices available.">getDeviceCount</a>();

  27. 

  28.   <span class="comment">// Scan through devices for various capabilities</span>

  29.   <a class="code" href="structRtAudio_1_1DeviceInfo.html" title="The public device information structure for returning queried values.">RtAudio::DeviceInfo</a> info;

  30.   <span class="keywordflow">for</span> ( <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> i=0; i&lt;=devices; i++ ) {

  31. 

  32.     info = audio.<a class="code" href="classRtAudio.html#a02d7ff44ad1d7eae22283a052f3dfda8" title="Return an RtAudio::DeviceInfo structure for a specified device number.">getDeviceInfo</a>( i );

  33. 

  34.     <span class="keywordflow">if</span> ( info.<a class="code" href="structRtAudio_1_1DeviceInfo.html#a97573717ccb1e75a834a0a108cd6982d">probed</a> == <span class="keyword">true</span> ) {

  35.       <span class="comment">// Print, for example, the maximum number of output channels for each device</span>

  36.       std::cout &lt;&lt; <span class="stringliteral">&quot;device = &quot;</span> &lt;&lt; i;

  37.       std::cout &lt;&lt; <span class="stringliteral">&quot;: maximum output channels = &quot;</span> &lt;&lt; info.<a class="code" href="structRtAudio_1_1DeviceInfo.html#a81aaf488f8158ef55b1bb678f66feb7d">outputChannels</a> &lt;&lt; <span class="stringliteral">&quot;\n&quot;</span>;

  38.     }

  39.   }

  40. 

  41.   <span class="keywordflow">return</span> 0;

  42. }

  43. </pre></div><p>The <a class="el" href="structRtAudio_1_1DeviceInfo.html" title="The public device information structure for returning queried values.">RtAudio::DeviceInfo</a> structure is defined in <a class="el" href="RtAudio_8h.html">RtAudio.h</a> and provides a variety of information useful in assessing the capabilities of a device:</p>

  44. <div class="fragment"><pre class="fragment">  <span class="keyword">typedef</span> <span class="keyword">struct </span><a class="code" href="structRtAudio_1_1DeviceInfo.html" title="The public device information structure for returning queried values.">RtAudio::DeviceInfo</a> {

  45.     <span class="keywordtype">bool</span> <a class="code" href="structRtAudio_1_1DeviceInfo.html#a97573717ccb1e75a834a0a108cd6982d">probed</a>;                           <span class="comment">// true if the device capabilities were successfully probed.</span>

  46.     std::string <a class="code" href="structRtAudio_1_1DeviceInfo.html#a24df596ab8d54f2eb540c7cf16212b3b">name</a>;                      <span class="comment">// Character string device identifier.</span>

  47.     <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> <a class="code" href="structRtAudio_1_1DeviceInfo.html#a81aaf488f8158ef55b1bb678f66feb7d">outputChannels</a>;           <span class="comment">// Maximum output channels supported by device.</span>

  48.     <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> <a class="code" href="structRtAudio_1_1DeviceInfo.html#a56247b458a937ae84d98ca9c4b243275">inputChannels</a>;            <span class="comment">// Maximum input channels supported by device.</span>

  49.     <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> <a class="code" href="structRtAudio_1_1DeviceInfo.html#a3e8ad34c2d14e24293a0beafc26186e7">duplexChannels</a>;           <span class="comment">// Maximum simultaneous input/output channels supported by device.</span>

  50.     <span class="keywordtype">bool</span> <a class="code" href="structRtAudio_1_1DeviceInfo.html#a5365245e73ffe29a05734de4474acd58">isDefaultOutput</a>;                  <span class="comment">// true if this is the default output device.</span>

  51.     <span class="keywordtype">bool</span> <a class="code" href="structRtAudio_1_1DeviceInfo.html#a7c8aca084bd908799b6be5954b80def2">isDefaultInput</a>;                   <span class="comment">// true if this is the default input device.</span>

  52.     std::vector&lt;unsigned int&gt; <a class="code" href="structRtAudio_1_1DeviceInfo.html#afa65f5f92f66ce7aacd3ff35e11b230f">sampleRates</a>; <span class="comment">// Supported sample rates.</span>

  53.     <a class="code" href="RtAudio_8h.html#aafca92882d25915560018873221e44b8" title="RtAudio data format type.">RtAudioFormat</a> <a class="code" href="structRtAudio_1_1DeviceInfo.html#a23251b549b89b2fe04a57fcd7cb76ea4">nativeFormats</a>;           <span class="comment">// Bit mask of supported data formats.</span>

  54.   };

  55. </pre></div><p>The following data formats are defined and fully supported by <a class="el" href="classRtAudio.html" title="Realtime audio i/o C++ classes.">RtAudio</a>:</p>

  56. <div class="fragment"><pre class="fragment">  <span class="keyword">typedef</span> <span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> <a class="code" href="RtAudio_8h.html#aafca92882d25915560018873221e44b8" title="RtAudio data format type.">RtAudioFormat</a>;

  57.   <span class="keyword">static</span> <span class="keyword">const</span> RtAudioFormat  RTAUDIO_SINT8;   <span class="comment">// Signed 8-bit integer</span>

  58.   <span class="keyword">static</span> <span class="keyword">const</span> RtAudioFormat  RTAUDIO_SINT16;  <span class="comment">// Signed 16-bit integer</span>

  59.   <span class="keyword">static</span> <span class="keyword">const</span> RtAudioFormat  RTAUDIO_SINT24;  <span class="comment">// Signed 24-bit integer (lower 3 bytes of 32-bit signed integer.)</span>

  60.   <span class="keyword">static</span> <span class="keyword">const</span> RtAudioFormat  RTAUDIO_SINT32;  <span class="comment">// Signed 32-bit integer</span>

  61.   <span class="keyword">static</span> <span class="keyword">const</span> RtAudioFormat  RTAUDIO_FLOAT32; <span class="comment">// 32-bit float normalized between +/- 1.0</span>

  62.   <span class="keyword">static</span> <span class="keyword">const</span> RtAudioFormat  RTAUDIO_FLOAT64; <span class="comment">// 64-bit double normalized between +/- 1.0</span>

  63. </pre></div><p>The <code>nativeFormats</code> member of the <a class="el" href="structRtAudio_1_1DeviceInfo.html" title="The public device information structure for returning queried values.">RtAudio::DeviceInfo</a> structure is a bit mask of the above formats which are natively supported by the device. However, <a class="el" href="classRtAudio.html" title="Realtime audio i/o C++ classes.">RtAudio</a> will automatically provide format conversion if a particular format is not natively supported. When the <code>probed</code> member of the <a class="el" href="structRtAudio_1_1DeviceInfo.html" title="The public device information structure for returning queried values.">RtAudio::DeviceInfo</a> structure is false, the remaining structure members are undefined and the device is probably unusable.</p>

  64. <p>Some audio devices may require a minimum channel value greater than one. <a class="el" href="classRtAudio.html" title="Realtime audio i/o C++ classes.">RtAudio</a> will provide automatic channel number compensation when the number of channels set by the user is less than that required by the device. Channel compensation is <em>NOT</em> possible when the number of channels set by the user is greater than that supported by the device.</p>

  65. <p>It should be noted that the capabilities reported by a device driver or underlying audio API are not always accurate and/or may be dependent on a combination of device settings. For this reason, <a class="el" href="classRtAudio.html" title="Realtime audio i/o C++ classes.">RtAudio</a> does not rely on the queried values when attempting to open a stream. </p>

  66. </div>

  67. <HR>

  68. 

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  70.   <td>&copy;2001-2012 Gary P. Scavone, McGill University. All Rights Reserved.<br>Maintained by <a href="http://www.music.mcgill.ca/~gary/">Gary P. Scavone</a>.</td></tr>

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