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<?xml version="1.0" encoding="UTF-8"?>
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<title>Qt 4.8: QAudioOutput Class Reference</title>
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<a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
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<li><a href="modules.html">Modules</a></li>
<li><a href="qtmultimedia.html">QtMultimedia</a></li>
<li>QAudioOutput</li>
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<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#public-functions">Public Functions</a></li>
<li class="level1"><a href="#signals">Signals</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
</ul>
</div>
<h1 class="title">QAudioOutput Class Reference</h1>
<!-- $$$QAudioOutput-brief -->
<p>The QAudioOutput class provides an interface for sending audio data to an audio output device. <a href="#details">More...</a></p>
<!-- @@@QAudioOutput -->
<pre class="cpp"> <span class="preprocessor">#include <QAudioOutput></span></pre><p><b>Inherits: </b><a href="qobject.html">QObject</a>.</p>
<p>This class was introduced in Qt 4.6.</p>
<ul>
<li><a href="qaudiooutput-members.html">List of all members, including inherited members</a></li>
</ul>
<a name="public-functions"></a>
<h2>Public Functions</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#QAudioOutput">QAudioOutput</a></b> ( const QAudioFormat & <i>format</i> = QAudioFormat(), QObject * <i>parent</i> = 0 )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#QAudioOutput-2">QAudioOutput</a></b> ( const QAudioDeviceInfo & <i>audioDevice</i>, const QAudioFormat & <i>format</i> = QAudioFormat(), QObject * <i>parent</i> = 0 )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#dtor.QAudioOutput">~QAudioOutput</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#bufferSize">bufferSize</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#bytesFree">bytesFree</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> qint64 </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#elapsedUSecs">elapsedUSecs</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QAudio::Error </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#error">error</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QAudioFormat </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#format">format</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#notifyInterval">notifyInterval</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#periodSize">periodSize</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> qint64 </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#processedUSecs">processedUSecs</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#reset">reset</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#resume">resume</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#setBufferSize">setBufferSize</a></b> ( int <i>value</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#setNotifyInterval">setNotifyInterval</a></b> ( int <i>ms</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#start">start</a></b> ( QIODevice * <i>device</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QIODevice * </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#start-2">start</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QAudio::State </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#state">state</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#stop">stop</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#suspend">suspend</a></b> ()</td></tr>
</table>
<ul>
<li class="fn">29 public functions inherited from <a href="qobject.html#public-functions">QObject</a></li>
</ul>
<a name="signals"></a>
<h2>Signals</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#notify">notify</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qaudiooutput.html#stateChanged">stateChanged</a></b> ( QAudio::State <i>state</i> )</td></tr>
</table>
<ul>
<li class="fn">1 signal inherited from <a href="qobject.html#signals">QObject</a></li>
</ul>
<h3>Additional Inherited Members</h3>
<ul>
<li class="fn">1 property inherited from <a href="qobject.html#properties">QObject</a></li>
<li class="fn">1 public slot inherited from <a href="qobject.html#public-slots">QObject</a></li>
<li class="fn">7 static public members inherited from <a href="qobject.html#static-public-members">QObject</a></li>
<li class="fn">8 protected functions inherited from <a href="qobject.html#protected-functions">QObject</a></li>
</ul>
<a name="details"></a>
<!-- $$$QAudioOutput-description -->
<div class="descr">
<h2>Detailed Description</h2>
<p>The QAudioOutput class provides an interface for sending audio data to an audio output device.</p>
<p>You can construct an audio output with the system's <a href="qaudiodeviceinfo.html#defaultOutputDevice">default audio output device</a>. It is also possible to create QAudioOutput with a specific <a href="qaudiodeviceinfo.html">QAudioDeviceInfo</a>. When you create the audio output, you should also send in the <a href="qaudioformat.html">QAudioFormat</a> to be used for the playback (see the <a href="qaudioformat.html">QAudioFormat</a> class description for details).</p>
<p>To play a file:</p>
<p>Starting to play an audio stream is simply a matter of calling <a href="qaudiooutput.html#start">start</a>() with a <a href="qiodevice.html">QIODevice</a>. QAudioOutput will then fetch the data it needs from the io device. So playing back an audio file is as simple as:</p>
<pre class="cpp"> <span class="type"><a href="qfile.html">QFile</a></span> inputFile; <span class="comment">// class member.</span>
<span class="type">QAudioOutput</span> <span class="operator">*</span>audioOutput; <span class="comment">// class member.</span>
...
<span class="type">void</span> startPlaying()
{
inputFile<span class="operator">.</span>setFileName(<span class="string">"/tmp/test.raw"</span>);
inputFile<span class="operator">.</span>open(<span class="type"><a href="qiodevice.html">QIODevice</a></span><span class="operator">::</span>ReadOnly);
<span class="type"><a href="qaudioformat.html">QAudioFormat</a></span> format;
<span class="comment">// Set up the format, eg.</span>
format<span class="operator">.</span>setFrequency(<span class="number">8000</span>);
format<span class="operator">.</span>setChannels(<span class="number">1</span>);
format<span class="operator">.</span>setSampleSize(<span class="number">8</span>);
format<span class="operator">.</span>setCodec(<span class="string">"audio/pcm"</span>);
format<span class="operator">.</span>setByteOrder(<span class="type"><a href="qaudioformat.html">QAudioFormat</a></span><span class="operator">::</span>LittleEndian);
format<span class="operator">.</span>setSampleType(<span class="type"><a href="qaudioformat.html">QAudioFormat</a></span><span class="operator">::</span>UnSignedInt);
<span class="type"><a href="qaudiodeviceinfo.html">QAudioDeviceInfo</a></span> info(<span class="type"><a href="qaudiodeviceinfo.html">QAudioDeviceInfo</a></span><span class="operator">::</span>defaultOutputDevice());
<span class="keyword">if</span> (<span class="operator">!</span>info<span class="operator">.</span>isFormatSupported(format)) {
<a href="qtglobal.html#qWarning">qWarning</a>()<span class="operator"><</span><span class="operator"><</span><span class="string">"raw audio format not supported by backend, cannot play audio."</span>;
<span class="keyword">return</span>;
}
audioOutput <span class="operator">=</span> <span class="keyword">new</span> <span class="type">QAudioOutput</span>(format<span class="operator">,</span> <span class="keyword">this</span>);
connect(audioOutput<span class="operator">,</span>SIGNAL(stateChanged(<span class="type"><a href="qaudio.html">QAudio</a></span><span class="operator">::</span>State))<span class="operator">,</span>SLOT(finishedPlaying(<span class="type"><a href="qaudio.html">QAudio</a></span><span class="operator">::</span>State)));
audioOutput<span class="operator">-</span><span class="operator">></span>start(<span class="operator">&</span>inputFile);
}</pre>
<p>The file will start playing assuming that the audio system and output device support it. If you run out of luck, check what's up with the <a href="qaudiooutput.html#error">error</a>() function.</p>
<p>After the file has finished playing, we need to stop the device:</p>
<pre class="cpp"> <span class="type">void</span> finishedPlaying(<span class="type"><a href="qaudio.html">QAudio</a></span><span class="operator">::</span>State state)
{
<span class="keyword">if</span> (state <span class="operator">=</span><span class="operator">=</span> <span class="type"><a href="qaudio.html">QAudio</a></span><span class="operator">::</span>IdleState) {
audioOutput<span class="operator">-</span><span class="operator">></span>stop();
inputFile<span class="operator">.</span>close();
<span class="keyword">delete</span> audioOutput;
}
}</pre>
<p>At any given time, the QAudioOutput will be in one of four states: active, suspended, stopped, or idle. These states are described by the <a href="qaudio.html#State-enum">QAudio::State</a> enum. State changes are reported through the <a href="qaudiooutput.html#stateChanged">stateChanged</a>() signal. You can use this signal to, for instance, update the GUI of the application; the mundane example here being changing the state of a <tt>play/pause</tt> button. You request a state change directly with <a href="qaudiooutput.html#suspend">suspend</a>(), <a href="qaudiooutput.html#stop">stop</a>(), <a href="qaudiooutput.html#reset">reset</a>(), <a href="qaudiooutput.html#resume">resume</a>(), and <a href="qaudiooutput.html#start">start</a>().</p>
<p>While the stream is playing, you can set a notify interval in milliseconds with <a href="qaudiooutput.html#setNotifyInterval">setNotifyInterval</a>(). This interval specifies the time between two emissions of the <a href="qaudiooutput.html#notify">notify</a>() signal. This is relative to the position in the stream, i.e., if the QAudioOutput is in the SuspendedState or the IdleState, the <a href="qaudiooutput.html#notify">notify</a>() signal is not emitted. A typical use-case would be to update a <a href="qslider.html">slider</a> that allows seeking in the stream. If you want the time since playback started regardless of which states the audio output has been in, <a href="qaudiooutput.html#elapsedUSecs">elapsedUSecs</a>() is the function for you.</p>
<p>If an error occurs, you can fetch the <a href="qaudio.html#Error-enum">error type</a> with the <a href="qaudiooutput.html#error">error</a>() function. Please see the <a href="qaudio.html#Error-enum">QAudio::Error</a> enum for a description of the possible errors that are reported. When an error is encountered, the state changes to <a href="qaudio.html#State-enum">QAudio::StoppedState</a>. You can check for errors by connecting to the <a href="qaudiooutput.html#stateChanged">stateChanged</a>() signal:</p>
<pre class="cpp"> <span class="type">void</span> stateChanged(<span class="type"><a href="qaudio.html">QAudio</a></span><span class="operator">::</span>State newState)
{
<span class="keyword">switch</span> (newState) {
<span class="keyword">case</span> <span class="type"><a href="qaudio.html">QAudio</a></span><span class="operator">::</span>StoppedState:
<span class="keyword">if</span> (audioOutput<span class="operator">-</span><span class="operator">></span>error() <span class="operator">!</span><span class="operator">=</span> <span class="type"><a href="qaudio.html">QAudio</a></span><span class="operator">::</span>NoError) {
<span class="comment">// Perform error handling</span>
} <span class="keyword">else</span> {
<span class="comment">// Normal stop</span>
}
<span class="keyword">break</span>;</pre>
</div>
<p><b>See also </b><a href="qaudioinput.html">QAudioInput</a> and <a href="qaudiodeviceinfo.html">QAudioDeviceInfo</a>.</p>
<!-- @@@QAudioOutput -->
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QAudioOutput[overload1]$$$QAudioOutputconstQAudioFormat&QObject* -->
<h3 class="fn"><a name="QAudioOutput"></a>QAudioOutput::<span class="name">QAudioOutput</span> ( const <span class="type"><a href="qaudioformat.html">QAudioFormat</a></span> & <i>format</i> = QAudioFormat(), <span class="type"><a href="qobject.html">QObject</a></span> * <i>parent</i> = 0 )</h3>
<p>Construct a new audio output and attach it to <i>parent</i>. The default audio output device is used with the output <i>format</i> parameters.</p>
<!-- @@@QAudioOutput -->
<!-- $$$QAudioOutput$$$QAudioOutputconstQAudioDeviceInfo&constQAudioFormat&QObject* -->
<h3 class="fn"><a name="QAudioOutput-2"></a>QAudioOutput::<span class="name">QAudioOutput</span> ( const <span class="type"><a href="qaudiodeviceinfo.html">QAudioDeviceInfo</a></span> & <i>audioDevice</i>, const <span class="type"><a href="qaudioformat.html">QAudioFormat</a></span> & <i>format</i> = QAudioFormat(), <span class="type"><a href="qobject.html">QObject</a></span> * <i>parent</i> = 0 )</h3>
<p>Construct a new audio output and attach it to <i>parent</i>. The device referenced by <i>audioDevice</i> is used with the output <i>format</i> parameters.</p>
<!-- @@@QAudioOutput -->
<!-- $$$~QAudioOutput[overload1]$$$~QAudioOutput -->
<h3 class="fn"><a name="dtor.QAudioOutput"></a>QAudioOutput::<span class="name">~QAudioOutput</span> ()</h3>
<p>Destroys this audio output.</p>
<!-- @@@~QAudioOutput -->
<!-- $$$bufferSize[overload1]$$$bufferSize -->
<h3 class="fn"><a name="bufferSize"></a><span class="type">int</span> QAudioOutput::<span class="name">bufferSize</span> () const</h3>
<p>Returns the audio buffer size in bytes.</p>
<p>If called before <a href="qaudiooutput.html#start">start</a>(), returns platform default value. If called before <a href="qaudiooutput.html#start">start</a>() but <a href="qaudiooutput.html#setBufferSize">setBufferSize</a>() was called prior, returns value set by <a href="qaudiooutput.html#setBufferSize">setBufferSize</a>(). If called after <a href="qaudiooutput.html#start">start</a>(), returns the actual buffer size being used. This may not be what was set previously by <a href="qaudiooutput.html#setBufferSize">setBufferSize</a>().</p>
<p><b>See also </b><a href="qaudiooutput.html#setBufferSize">setBufferSize</a>().</p>
<!-- @@@bufferSize -->
<!-- $$$bytesFree[overload1]$$$bytesFree -->
<h3 class="fn"><a name="bytesFree"></a><span class="type">int</span> QAudioOutput::<span class="name">bytesFree</span> () const</h3>
<p>Returns the free space available in bytes in the audio buffer.</p>
<p>NOTE: returned value is only valid while in <a href="qaudio.html#State-enum">QAudio::ActiveState</a> or <a href="qaudio.html#State-enum">QAudio::IdleState</a> state, otherwise returns zero.</p>
<!-- @@@bytesFree -->
<!-- $$$elapsedUSecs[overload1]$$$elapsedUSecs -->
<h3 class="fn"><a name="elapsedUSecs"></a><span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span> QAudioOutput::<span class="name">elapsedUSecs</span> () const</h3>
<p>Returns the microseconds since <a href="qaudiooutput.html#start">start</a>() was called, including time in Idle and Suspend states.</p>
<!-- @@@elapsedUSecs -->
<!-- $$$error[overload1]$$$error -->
<h3 class="fn"><a name="error"></a><span class="type"><a href="qaudio.html#Error-enum">QAudio::Error</a></span> QAudioOutput::<span class="name">error</span> () const</h3>
<p>Returns the error state.</p>
<!-- @@@error -->
<!-- $$$format[overload1]$$$format -->
<h3 class="fn"><a name="format"></a><span class="type"><a href="qaudioformat.html">QAudioFormat</a></span> QAudioOutput::<span class="name">format</span> () const</h3>
<p>Returns the <a href="qaudioformat.html">QAudioFormat</a> being used.</p>
<!-- @@@format -->
<!-- $$$notify[overload1]$$$notify -->
<h3 class="fn"><a name="notify"></a><span class="type">void</span> QAudioOutput::<span class="name">notify</span> ()<tt> [signal]</tt></h3>
<p>This signal is emitted when x ms of audio data has been processed the interval set by setNotifyInterval(x).</p>
<!-- @@@notify -->
<!-- $$$notifyInterval[overload1]$$$notifyInterval -->
<h3 class="fn"><a name="notifyInterval"></a><span class="type">int</span> QAudioOutput::<span class="name">notifyInterval</span> () const</h3>
<p>Returns the notify interval in milliseconds.</p>
<p><b>See also </b><a href="qaudiooutput.html#setNotifyInterval">setNotifyInterval</a>().</p>
<!-- @@@notifyInterval -->
<!-- $$$periodSize[overload1]$$$periodSize -->
<h3 class="fn"><a name="periodSize"></a><span class="type">int</span> QAudioOutput::<span class="name">periodSize</span> () const</h3>
<p>Returns the period size in bytes.</p>
<p>Note: This is the recommended write size in bytes.</p>
<!-- @@@periodSize -->
<!-- $$$processedUSecs[overload1]$$$processedUSecs -->
<h3 class="fn"><a name="processedUSecs"></a><span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span> QAudioOutput::<span class="name">processedUSecs</span> () const</h3>
<p>Returns the amount of audio data processed by the class since <a href="qaudiooutput.html#start">start</a>() was called in microseconds.</p>
<p>Note: The amount of audio data played can be determined by subtracting the microseconds of audio data still in the systems audio buffer.</p>
<pre class="cpp"> <span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span> bytesInBuffer <span class="operator">=</span> <a href="qaudiooutput.html#bufferSize">bufferSize</a>() <span class="operator">-</span> <a href="qaudiooutput.html#bytesFree">bytesFree</a>();
<span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span> usInBuffer <span class="operator">=</span> (<span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span>)(<span class="number">1000000</span>) <span class="operator">*</span> bytesInBuffer <span class="operator">/</span> ( channels() <span class="operator">*</span> sampleSize() <span class="operator">/</span> <span class="number">8</span> ) <span class="operator">/</span> frequency();
<span class="type"><a href="qtglobal.html#qint64-typedef">qint64</a></span> usPlayed <span class="operator">=</span> processedUSecs() <span class="operator">-</span> usInBuffer;</pre>
<!-- @@@processedUSecs -->
<!-- $$$reset[overload1]$$$reset -->
<h3 class="fn"><a name="reset"></a><span class="type">void</span> QAudioOutput::<span class="name">reset</span> ()</h3>
<p>Drops all audio data in the buffers, resets buffers to zero.</p>
<!-- @@@reset -->
<!-- $$$resume[overload1]$$$resume -->
<h3 class="fn"><a name="resume"></a><span class="type">void</span> QAudioOutput::<span class="name">resume</span> ()</h3>
<p>Resumes processing audio data after a <a href="qaudiooutput.html#suspend">suspend</a>().</p>
<p>Sets <a href="qaudiooutput.html#error">error</a>() to <a href="qaudio.html#Error-enum">QAudio::NoError</a>. Sets <a href="qaudiooutput.html#state">state</a>() to <a href="qaudio.html#State-enum">QAudio::ActiveState</a> if you previously called start(<a href="qiodevice.html">QIODevice</a>*). Sets <a href="qaudiooutput.html#state">state</a>() to <a href="qaudio.html#State-enum">QAudio::IdleState</a> if you previously called <a href="qaudiooutput.html#start">start</a>(). emits <a href="qaudiooutput.html#stateChanged">stateChanged</a>() signal.</p>
<p>Note: signal will always be emitted during execution of the resume() function.</p>
<!-- @@@resume -->
<!-- $$$setBufferSize[overload1]$$$setBufferSizeint -->
<h3 class="fn"><a name="setBufferSize"></a><span class="type">void</span> QAudioOutput::<span class="name">setBufferSize</span> ( <span class="type">int</span> <i>value</i> )</h3>
<p>Sets the audio buffer size to <i>value</i> in bytes.</p>
<p>Note: This function can be called anytime before <a href="qaudiooutput.html#start">start</a>(), calls to this are ignored after <a href="qaudiooutput.html#start">start</a>(). It should not be assumed that the buffer size set is the actual buffer size used, calling <a href="qaudiooutput.html#bufferSize">bufferSize</a>() anytime after <a href="qaudiooutput.html#start">start</a>() will return the actual buffer size being used.</p>
<p><b>See also </b><a href="qaudiooutput.html#bufferSize">bufferSize</a>().</p>
<!-- @@@setBufferSize -->
<!-- $$$setNotifyInterval[overload1]$$$setNotifyIntervalint -->
<h3 class="fn"><a name="setNotifyInterval"></a><span class="type">void</span> QAudioOutput::<span class="name">setNotifyInterval</span> ( <span class="type">int</span> <i>ms</i> )</h3>
<p>Sets the interval for <a href="qaudiooutput.html#notify">notify</a>() signal to be emitted. This is based on the <i>ms</i> of audio data processed not on actual real-time. The minimum resolution of the timer is platform specific and values should be checked with <a href="qaudiooutput.html#notifyInterval">notifyInterval</a>() to confirm actual value being used.</p>
<p><b>See also </b><a href="qaudiooutput.html#notifyInterval">notifyInterval</a>().</p>
<!-- @@@setNotifyInterval -->
<!-- $$$start[overload1]$$$startQIODevice* -->
<h3 class="fn"><a name="start"></a><span class="type">void</span> QAudioOutput::<span class="name">start</span> ( <span class="type"><a href="qiodevice.html">QIODevice</a></span> * <i>device</i> )</h3>
<p>Uses the <i>device</i> as the <a href="qiodevice.html">QIODevice</a> to transfer data. Passing a <a href="qiodevice.html">QIODevice</a> allows the data to be transferred without any extra code. All that is required is to open the <a href="qiodevice.html">QIODevice</a>.</p>
<p>If able to successfully output audio data to the systems audio device the <a href="qaudiooutput.html#state">state</a>() is set to <a href="qaudio.html#State-enum">QAudio::ActiveState</a>, <a href="qaudiooutput.html#error">error</a>() is set to <a href="qaudio.html#Error-enum">QAudio::NoError</a> and the <a href="qaudiooutput.html#stateChanged">stateChanged</a>() signal is emitted.</p>
<p>If a problem occurs during this process the <a href="qaudiooutput.html#error">error</a>() is set to <a href="qaudio.html#Error-enum">QAudio::OpenError</a>, <a href="qaudiooutput.html#state">state</a>() is set to <a href="qaudio.html#State-enum">QAudio::StoppedState</a> and <a href="qaudiooutput.html#stateChanged">stateChanged</a>() signal is emitted.</p>
<p>In either case, the <a href="qaudiooutput.html#stateChanged">stateChanged</a>() signal may be emitted either synchronously during execution of the start() function or asynchronously after start() has returned to the caller.</p>
<p><b>See also </b><a href="qiodevice.html">QIODevice</a>.</p>
<!-- @@@start -->
<!-- $$$start$$$start -->
<h3 class="fn"><a name="start-2"></a><span class="type"><a href="qiodevice.html">QIODevice</a></span> * QAudioOutput::<span class="name">start</span> ()</h3>
<p>Returns a pointer to the <a href="qiodevice.html">QIODevice</a> being used to handle the data transfer. This <a href="qiodevice.html">QIODevice</a> can be used to write() audio data directly.</p>
<p>If able to access the systems audio device the <a href="qaudiooutput.html#state">state</a>() is set to <a href="qaudio.html#State-enum">QAudio::IdleState</a>, <a href="qaudiooutput.html#error">error</a>() is set to <a href="qaudio.html#Error-enum">QAudio::NoError</a> and the <a href="qaudiooutput.html#stateChanged">stateChanged</a>() signal is emitted.</p>
<p>If a problem occurs during this process the <a href="qaudiooutput.html#error">error</a>() is set to <a href="qaudio.html#Error-enum">QAudio::OpenError</a>, <a href="qaudiooutput.html#state">state</a>() is set to <a href="qaudio.html#State-enum">QAudio::StoppedState</a> and <a href="qaudiooutput.html#stateChanged">stateChanged</a>() signal is emitted.</p>
<p>In either case, the <a href="qaudiooutput.html#stateChanged">stateChanged</a>() signal may be emitted either synchronously during execution of the <a href="qaudiooutput.html#start">start</a>() function or asynchronously after <a href="qaudiooutput.html#start">start</a>() has returned to the caller.</p>
<p><b>See also </b><a href="qiodevice.html">QIODevice</a>.</p>
<!-- @@@start -->
<!-- $$$state[overload1]$$$state -->
<h3 class="fn"><a name="state"></a><span class="type"><a href="qaudio.html#State-enum">QAudio::State</a></span> QAudioOutput::<span class="name">state</span> () const</h3>
<p>Returns the state of audio processing.</p>
<!-- @@@state -->
<!-- $$$stateChanged[overload1]$$$stateChangedQAudio::State -->
<h3 class="fn"><a name="stateChanged"></a><span class="type">void</span> QAudioOutput::<span class="name">stateChanged</span> ( <span class="type"><a href="qaudio.html#State-enum">QAudio::State</a></span> <i>state</i> )<tt> [signal]</tt></h3>
<p>This signal is emitted when the device <i>state</i> has changed. This is the current state of the audio output.</p>
<!-- @@@stateChanged -->
<!-- $$$stop[overload1]$$$stop -->
<h3 class="fn"><a name="stop"></a><span class="type">void</span> QAudioOutput::<span class="name">stop</span> ()</h3>
<p>Stops the audio output, detaching from the system resource.</p>
<p>Sets <a href="qaudiooutput.html#error">error</a>() to <a href="qaudio.html#Error-enum">QAudio::NoError</a>, <a href="qaudiooutput.html#state">state</a>() to <a href="qaudio.html#State-enum">QAudio::StoppedState</a> and emit <a href="qaudiooutput.html#stateChanged">stateChanged</a>() signal.</p>
<!-- @@@stop -->
<!-- $$$suspend[overload1]$$$suspend -->
<h3 class="fn"><a name="suspend"></a><span class="type">void</span> QAudioOutput::<span class="name">suspend</span> ()</h3>
<p>Stops processing audio data, preserving buffered audio data.</p>
<p>Sets <a href="qaudiooutput.html#error">error</a>() to <a href="qaudio.html#Error-enum">QAudio::NoError</a>, <a href="qaudiooutput.html#state">state</a>() to <a href="qaudio.html#State-enum">QAudio::SuspendedState</a> and emit <a href="qaudiooutput.html#stateChanged">stateChanged</a>() signal.</p>
<!-- @@@suspend -->
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