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<div class="title">Duplex Mode </div>  </div>
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<div class="textblock"><p>Finally, it is easy to use <a class="el" href="classRtAudio.html" title="Realtime audio i/o C++ classes.">RtAudio</a> for simultaneous audio input/output, or duplex operation. In this example, we simply pass the input data back to the output.</p>
<div class="fragment"><div class="line"><span class="preprocessor">#include &quot;<a class="code" href="RtAudio_8h.html">RtAudio.h</a>&quot;</span></div>
<div class="line"><span class="preprocessor">#include &lt;iostream&gt;</span></div>
<div class="line"><span class="preprocessor">#include &lt;cstdlib&gt;</span></div>
<div class="line"><span class="preprocessor">#include &lt;cstring&gt;</span></div>
<div class="line"></div>
<div class="line"><span class="comment">// Pass-through function.</span></div>
<div class="line"><span class="keywordtype">int</span> inout( <span class="keywordtype">void</span> *outputBuffer, <span class="keywordtype">void</span> *inputBuffer, <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> nBufferFrames,</div>
<div class="line">           <span class="keywordtype">double</span> streamTime, <a class="code" href="RtAudio_8h.html#a80e306d363583da3b0a1b65d9b57c806" title="RtAudio stream status (over- or underflow) flags.">RtAudioStreamStatus</a> status, <span class="keywordtype">void</span> *data )</div>
<div class="line">{</div>
<div class="line">  <span class="comment">// Since the number of input and output channels is equal, we can do</span></div>
<div class="line">  <span class="comment">// a simple buffer copy operation here.</span></div>
<div class="line">  <span class="keywordflow">if</span> ( status ) std::cout &lt;&lt; <span class="stringliteral">&quot;Stream over/underflow detected.&quot;</span> &lt;&lt; std::endl;</div>
<div class="line"></div>
<div class="line">  <span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> *bytes = (<span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> *) data;</div>
<div class="line">  memcpy( outputBuffer, inputBuffer, *bytes );</div>
<div class="line">  <span class="keywordflow">return</span> 0;</div>
<div class="line">}</div>
<div class="line"></div>
<div class="line"><span class="keywordtype">int</span> main()</div>
<div class="line">{</div>
<div class="line"> <a class="code" href="classRtAudio.html" title="Realtime audio i/o C++ classes.">RtAudio</a> adac;</div>
<div class="line">  <span class="keywordflow">if</span> ( adac.<a class="code" href="classRtAudio.html#a747ce2d73803641bbb66d6e78092aa1a" title="A public function that queries for the number of audio devices available.">getDeviceCount</a>() &lt; 1 ) {</div>
<div class="line">    std::cout &lt;&lt; <span class="stringliteral">&quot;\nNo audio devices found!\n&quot;</span>;</div>
<div class="line">    exit( 0 );</div>
<div class="line">  }</div>
<div class="line"></div>
<div class="line">  <span class="comment">// Set the same number of channels for both input and output.</span></div>
<div class="line">  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> bufferBytes, bufferFrames = 512;</div>
<div class="line">  <a class="code" href="structRtAudio_1_1StreamParameters.html" title="The structure for specifying input or ouput stream parameters.">RtAudio::StreamParameters</a> iParams, oParams;</div>
<div class="line">  iParams.<a class="code" href="structRtAudio_1_1StreamParameters.html#ab3c72bcf3ef12149ae9a4fb597cc5489">deviceId</a> = 0; <span class="comment">// first available device</span></div>
<div class="line">  iParams.<a class="code" href="structRtAudio_1_1StreamParameters.html#a88a10091b6e284e21235cc6f25332ebd">nChannels</a> = 2;</div>
<div class="line">  oParams.<a class="code" href="structRtAudio_1_1StreamParameters.html#ab3c72bcf3ef12149ae9a4fb597cc5489">deviceId</a> = 0; <span class="comment">// first available device</span></div>
<div class="line">  oParams.<a class="code" href="structRtAudio_1_1StreamParameters.html#a88a10091b6e284e21235cc6f25332ebd">nChannels</a> = 2;</div>
<div class="line"></div>
<div class="line">  <span class="keywordflow">try</span> {</div>
<div class="line">    adac.<a class="code" href="classRtAudio.html#a6907539d2527775df778ebce32ef1e3b" title="A public function for opening a stream with the specified parameters.">openStream</a>( &amp;oParams, &amp;iParams, RTAUDIO_SINT32, 44100, &amp;bufferFrames, &amp;inout, (<span class="keywordtype">void</span> *)&amp;bufferBytes );</div>
<div class="line">  }</div>
<div class="line">  <span class="keywordflow">catch</span> ( <a class="code" href="classRtError.html" title="Exception handling class for RtAudio &amp; RtMidi.">RtError</a>&amp; e ) {</div>
<div class="line">    e.<a class="code" href="classRtError.html#a251dcdac396c998c91706dd2dd3b8bfc" title="Prints thrown error message to stderr.">printMessage</a>();</div>
<div class="line">    exit( 0 );</div>
<div class="line">  }</div>
<div class="line"></div>
<div class="line">  bufferBytes = bufferFrames * 2 * 4;</div>
<div class="line"></div>
<div class="line">  <span class="keywordflow">try</span> {</div>
<div class="line">    adac.<a class="code" href="classRtAudio.html#aec017a89629ccef66a90b60be22a2f80" title="A function that starts a stream.">startStream</a>();</div>
<div class="line"></div>
<div class="line">    <span class="keywordtype">char</span> input;</div>
<div class="line">    std::cout &lt;&lt; <span class="stringliteral">&quot;\nRunning ... press &lt;enter&gt; to quit.\n&quot;</span>;</div>
<div class="line">    std::cin.get(input);</div>
<div class="line"></div>
<div class="line">    <span class="comment">// Stop the stream.</span></div>
<div class="line">    adac.<a class="code" href="classRtAudio.html#af4c241ff86936ecc8108f0d9dfe3efdd" title="Stop a stream, allowing any samples remaining in the output queue to be played.">stopStream</a>();</div>
<div class="line">  }</div>
<div class="line">  <span class="keywordflow">catch</span> ( <a class="code" href="classRtError.html" title="Exception handling class for RtAudio &amp; RtMidi.">RtError</a>&amp; e ) {</div>
<div class="line">    e.<a class="code" href="classRtError.html#a251dcdac396c998c91706dd2dd3b8bfc" title="Prints thrown error message to stderr.">printMessage</a>();</div>
<div class="line">    <span class="keywordflow">goto</span> cleanup;</div>
<div class="line">  }</div>
<div class="line"></div>
<div class="line"> cleanup:</div>
<div class="line">  <span class="keywordflow">if</span> ( adac.<a class="code" href="classRtAudio.html#a3863e45ff81dbe97176de0ee7545917f" title="Returns true if a stream is open and false if not.">isStreamOpen</a>() ) adac.<a class="code" href="classRtAudio.html#a90d599002ad32cf250a4cb866f2cc93a" title="A function that closes a stream and frees any associated stream memory.">closeStream</a>();</div>
<div class="line"></div>
<div class="line">  <span class="keywordflow">return</span> 0;</div>
<div class="line">}</div>
</div><!-- fragment --><p>In this example, audio recorded by the stream input will be played out during the next round of audio processing.</p>
<p>Note that a duplex stream can make use of two different devices (except when using the Linux Jack and Windows ASIO APIs). However, this may cause timing problems due to possible device clock variations, unless a common external "sync" is provided. </p>
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