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  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 1.4.4 -->

  12. <h1><a class="anchor" name="probe">Probing Device Capabilities</a></h1>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>

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

  14. 

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

  16. <span class="preprocessor">#include "<a class="code" href="RtAudio_8h.html">RtAudio.h</a>"</span>

  17. 

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

  19. {

  20.   <a class="code" href="classRtAudio.html">RtAudio</a> audio;

  21. 

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

  23.   <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> devices = audio.<a class="code" href="classRtAudio.html#a3">getDeviceCount</a>();

  24. 

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

  26.   <a class="code" href="structRtAudio_1_1DeviceInfo.html">RtAudio::DeviceInfo</a> info;

  27.   <span class="keywordflow">for</span> ( <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> i=1; i&lt;=devices; i++ ) {

  28. 

  29.     info = audio.<a class="code" href="classRtAudio.html#a4">getDeviceInfo</a>( i );

  30. 

  31.     <span class="keywordflow">if</span> ( info.<a class="code" href="structRtAudio_1_1DeviceInfo.html#o0">probed</a> == <span class="keyword">true</span> ) {

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

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

  34.       std::cout &lt;&lt; <span class="stringliteral">": maximum output channels = "</span> &lt;&lt; info.<a class="code" href="structRtAudio_1_1DeviceInfo.html#o2">outputChannels</a> &lt;&lt; <span class="stringliteral">"\n"</span>;

  35.     }

  36.   }

  37. 

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

  39. }

  40. </pre></div><p>

  41. The <a class="el" href="structRtAudio_1_1DeviceInfo.html">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>

  42. <div class="fragment"><pre class="fragment">  <span class="keyword">typedef</span> <span class="keyword">struct </span><a class="code" href="structRtAudio_1_1DeviceInfo.html">RtAudio::DeviceInfo</a> {

  43.     <span class="keywordtype">bool</span> probed;                           <span class="comment">// true if the device capabilities were successfully probed.</span>

  44.     std::string name;                      <span class="comment">// Character string device identifier.</span>

  45.     <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> outputChannels;           <span class="comment">// Maximum output channels supported by device.</span>

  46.     <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> inputChannels;            <span class="comment">// Maximum input channels supported by device.</span>

  47.     <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> duplexChannels;           <span class="comment">// Maximum simultaneous input/output channels supported by device.</span>

  48.     <span class="keywordtype">bool</span> isDefaultOutput;                  <span class="comment">// true if this is the default output device.</span>

  49.     <span class="keywordtype">bool</span> isDefaultInput;                   <span class="comment">// true if this is the default input device.</span>

  50.     std::vector&lt;unsigned int&gt; sampleRates; <span class="comment">// Supported sample rates.</span>

  51.     <a class="code" href="RtAudio_8h.html#a1">RtAudioFormat</a> nativeFormats;           <span class="comment">// Bit mask of supported data formats.</span>

  52.   };

  53. </pre></div><p>

  54. The following data formats are defined and fully supported by <a class="el" href="classRtAudio.html">RtAudio</a>:<p>

  55. <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#a1">RtAudioFormat</a>;

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

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

  58.   <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>

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

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

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

  62. </pre></div><p>

  63. The <code>nativeFormats</code> member of the <a class="el" href="structRtAudio_1_1DeviceInfo.html">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">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">RtAudio::DeviceInfo</a> structure is false, the remaining structure members are undefined and the device is probably unusable.<p>

  64. Some audio devices may require a minimum channel value greater than one. <a class="el" href="classRtAudio.html">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. 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">RtAudio</a> does not rely on the queried values when attempting to open a stream. <HR>

  66. 

  67. <table><tr><td><img src="../images/mcgill.gif" width=165></td>

  68.   <td>&copy;2001-2008 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>

  69. </table>

  70. 

  71. </BODY>

  72. </HTML>