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<!-- Generated by Doxygen 1.6.2 -->
<div class="navpath"><a class="el" href="namespacestk.html">stk</a>::<a class="el" href="classstk_1_1TwoPole.html">TwoPole</a>
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<div class="contents">
<h1>stk::TwoPole Class Reference</h1><!-- doxytag: class="stk::TwoPole" --><!-- doxytag: inherits="stk::Filter" -->
<p>STK two-pole filter class.
<a href="#_details">More...</a></p>
<p><code>#include &lt;<a class="el" href="TwoPole_8h_source.html">TwoPole.h</a>&gt;</code></p>
<div class="dynheader">
Inheritance diagram for stk::TwoPole:</div>
<div class="dynsection">
<div class="center">
<img src="classstk_1_1TwoPole.png" usemap="#stk::TwoPole_map" alt=""/>
<map id="stk::TwoPole_map" name="stk::TwoPole_map">
<area href="classstk_1_1Filter.html" alt="stk::Filter" shape="rect" coords="0,56,81,80"/>
<area href="classstk_1_1Stk.html" alt="stk::Stk" shape="rect" coords="0,0,81,24"/>
</map>
</div>
</div>
<p><a href="classstk_1_1TwoPole-members.html">List of all members.</a></p>
<table border="0" cellpadding="0" cellspacing="0">
<tr><td colspan="2"><h2>Public Member Functions</h2></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="a01a2b3b3d286e00a097918ec5f8a287b"></a><!-- doxytag: member="stk::TwoPole::TwoPole" ref="a01a2b3b3d286e00a097918ec5f8a287b" args="(void)" -->
&nbsp;</td><td class="memItemRight" valign="bottom"><a class="el" href="classstk_1_1TwoPole.html#a01a2b3b3d286e00a097918ec5f8a287b">TwoPole</a> (void)</td></tr>
<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">Default constructor creates a second-order pass-through filter. <br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="aabc2e1046f8f908fc78a53b50b00ed9f"></a><!-- doxytag: member="stk::TwoPole::~TwoPole" ref="aabc2e1046f8f908fc78a53b50b00ed9f" args="()" -->
&nbsp;</td><td class="memItemRight" valign="bottom"><a class="el" href="classstk_1_1TwoPole.html#aabc2e1046f8f908fc78a53b50b00ed9f">~TwoPole</a> ()</td></tr>
<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">Class destructor. <br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="ad0a3ac1b5d4e651a7ff1efb1d5362c0b"></a><!-- doxytag: member="stk::TwoPole::ignoreSampleRateChange" ref="ad0a3ac1b5d4e651a7ff1efb1d5362c0b" args="(bool ignore=true)" -->
void&nbsp;</td><td class="memItemRight" valign="bottom"><a class="el" href="classstk_1_1TwoPole.html#ad0a3ac1b5d4e651a7ff1efb1d5362c0b">ignoreSampleRateChange</a> (bool ignore=true)</td></tr>
<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">A function to enable/disable the automatic updating of class data when the STK sample rate changes. <br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="a0a5bfc68061c1dbaa40bfbb9ddb67b7d"></a><!-- doxytag: member="stk::TwoPole::setB0" ref="a0a5bfc68061c1dbaa40bfbb9ddb67b7d" args="(StkFloat b0)" -->
void&nbsp;</td><td class="memItemRight" valign="bottom"><a class="el" href="classstk_1_1TwoPole.html#a0a5bfc68061c1dbaa40bfbb9ddb67b7d">setB0</a> (StkFloat b0)</td></tr>
<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">Set the b[0] coefficient value. <br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="ad0c2f8ddc09ca1eb864515d816ebacdd"></a><!-- doxytag: member="stk::TwoPole::setA1" ref="ad0c2f8ddc09ca1eb864515d816ebacdd" args="(StkFloat a1)" -->
void&nbsp;</td><td class="memItemRight" valign="bottom"><a class="el" href="classstk_1_1TwoPole.html#ad0c2f8ddc09ca1eb864515d816ebacdd">setA1</a> (StkFloat a1)</td></tr>
<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">Set the a[1] coefficient value. <br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="a309960a8b2cf6858f43f43dc739146ea"></a><!-- doxytag: member="stk::TwoPole::setA2" ref="a309960a8b2cf6858f43f43dc739146ea" args="(StkFloat a2)" -->
void&nbsp;</td><td class="memItemRight" valign="bottom"><a class="el" href="classstk_1_1TwoPole.html#a309960a8b2cf6858f43f43dc739146ea">setA2</a> (StkFloat a2)</td></tr>
<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">Set the a[2] coefficient value. <br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="af9b68df9cc424a09e3ecb7f078bcacd3"></a><!-- doxytag: member="stk::TwoPole::setCoefficients" ref="af9b68df9cc424a09e3ecb7f078bcacd3" args="(StkFloat b0, StkFloat a1, StkFloat a2, bool clearState=false)" -->
void&nbsp;</td><td class="memItemRight" valign="bottom"><a class="el" href="classstk_1_1TwoPole.html#af9b68df9cc424a09e3ecb7f078bcacd3">setCoefficients</a> (StkFloat b0, StkFloat a1, StkFloat a2, bool clearState=false)</td></tr>
<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">Set all filter coefficients. <br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void&nbsp;</td><td class="memItemRight" valign="bottom"><a class="el" href="classstk_1_1TwoPole.html#a00997b12a1cf0a04888124eaf85c565d">setResonance</a> (StkFloat frequency, StkFloat radius, bool normalize=false)</td></tr>
<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">Sets the filter coefficients for a resonance at <em>frequency</em> (in Hz). <a href="#a00997b12a1cf0a04888124eaf85c565d"></a><br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="a8a4fb4afe3e06c689827ecaec478aad1"></a><!-- doxytag: member="stk::TwoPole::lastOut" ref="a8a4fb4afe3e06c689827ecaec478aad1" args="(void) const " -->
StkFloat&nbsp;</td><td class="memItemRight" valign="bottom"><a class="el" href="classstk_1_1TwoPole.html#a8a4fb4afe3e06c689827ecaec478aad1">lastOut</a> (void) const </td></tr>
<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">Return the last computed output value. <br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="ad4612f9b6f971a4dd76b23bb2b9fefbc"></a><!-- doxytag: member="stk::TwoPole::tick" ref="ad4612f9b6f971a4dd76b23bb2b9fefbc" args="(StkFloat input)" -->
StkFloat&nbsp;</td><td class="memItemRight" valign="bottom"><a class="el" href="classstk_1_1TwoPole.html#ad4612f9b6f971a4dd76b23bb2b9fefbc">tick</a> (StkFloat input)</td></tr>
<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">Input one sample to the filter and return one output. <br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="el" href="classstk_1_1StkFrames.html">StkFrames</a> &amp;&nbsp;</td><td class="memItemRight" valign="bottom"><a class="el" href="classstk_1_1TwoPole.html#a9e8bd9ed925a1c4966fbc0b0799ce46b">tick</a> (<a class="el" href="classstk_1_1StkFrames.html">StkFrames</a> &amp;frames, unsigned int channel=0)</td></tr>
<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">Take a channel of the <a class="el" href="classstk_1_1StkFrames.html" title="An STK class to handle vectorized audio data.">StkFrames</a> object as inputs to the filter and replace with corresponding outputs. <a href="#a9e8bd9ed925a1c4966fbc0b0799ce46b"></a><br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"><a class="el" href="classstk_1_1StkFrames.html">StkFrames</a> &amp;&nbsp;</td><td class="memItemRight" valign="bottom"><a class="el" href="classstk_1_1TwoPole.html#a5c9b52082c0d2845a5ca01ca276fe8f8">tick</a> (<a class="el" href="classstk_1_1StkFrames.html">StkFrames</a> &amp;iFrames, <a class="el" href="classstk_1_1StkFrames.html">StkFrames</a> &amp;oFrames, unsigned int iChannel=0, unsigned int oChannel=0)</td></tr>
<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">Take a channel of the <code>iFrames</code> object as inputs to the filter and write outputs to the <code>oFrames</code> object. <a href="#a5c9b52082c0d2845a5ca01ca276fe8f8"></a><br/></td></tr>
</table>
<hr/><a name="_details"></a><h2>Detailed Description</h2>
<p>STK two-pole filter class. </p>
<p>This class implements a two-pole digital filter. A method is provided for creating a resonance in the frequency response while maintaining a nearly constant filter gain.</p>
<p>by Perry R. Cook and Gary P. Scavone, 1995-2011. </p>
<hr/><h2>Member Function Documentation</h2>
<a class="anchor" id="a00997b12a1cf0a04888124eaf85c565d"></a><!-- doxytag: member="stk::TwoPole::setResonance" ref="a00997b12a1cf0a04888124eaf85c565d" args="(StkFloat frequency, StkFloat radius, bool normalize=false)" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
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<td class="memname">void stk::TwoPole::setResonance </td>
<td>(</td>
<td class="paramtype">StkFloat&nbsp;</td>
<td class="paramname"> <em>frequency</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">StkFloat&nbsp;</td>
<td class="paramname"> <em>radius</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">bool&nbsp;</td>
<td class="paramname"> <em>normalize</em> = <code>false</code></td><td>&nbsp;</td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td><td></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>Sets the filter coefficients for a resonance at <em>frequency</em> (in Hz). </p>
<p>This method determines the filter coefficients corresponding to two complex-conjugate poles with the given <em>frequency</em> (in Hz) and <em>radius</em> from the z-plane origin. If <em>normalize</em> is true, the coefficients are then normalized to produce unity gain at <em>frequency</em> (the actual maximum filter gain tends to be slightly greater than unity when <em>radius</em> is not close to one). The resulting filter frequency response has a resonance at the given <em>frequency</em>. The closer the poles are to the unit-circle (<em>radius</em> close to one), the narrower the resulting resonance width. An unstable filter will result for <em>radius</em> &gt;= 1.0. The <em>frequency</em> value should be between zero and half the sample rate. For a better resonance filter, use a <a class="el" href="classstk_1_1BiQuad.html" title="STK biquad (two-pole, two-zero) filter class.">BiQuad</a> filter. </p>
<dl class="see"><dt><b>See also:</b></dt><dd><a class="el" href="classstk_1_1BiQuad.html" title="STK biquad (two-pole, two-zero) filter class.">BiQuad</a> filter class </dd></dl>
</div>
</div>
<a class="anchor" id="a9e8bd9ed925a1c4966fbc0b0799ce46b"></a><!-- doxytag: member="stk::TwoPole::tick" ref="a9e8bd9ed925a1c4966fbc0b0799ce46b" args="(StkFrames &amp;frames, unsigned int channel=0)" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname"><a class="el" href="classstk_1_1StkFrames.html">StkFrames</a> &amp; stk::TwoPole::tick </td>
<td>(</td>
<td class="paramtype"><a class="el" href="classstk_1_1StkFrames.html">StkFrames</a> &amp;&nbsp;</td>
<td class="paramname"> <em>frames</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">unsigned int&nbsp;</td>
<td class="paramname"> <em>channel</em> = <code>0</code></td><td>&nbsp;</td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td><td><code> [inline, virtual]</code></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>Take a channel of the <a class="el" href="classstk_1_1StkFrames.html" title="An STK class to handle vectorized audio data.">StkFrames</a> object as inputs to the filter and replace with corresponding outputs. </p>
<p>The <a class="el" href="classstk_1_1StkFrames.html" title="An STK class to handle vectorized audio data.">StkFrames</a> argument reference is returned. The <code>channel</code> argument must be less than the number of channels in the <a class="el" href="classstk_1_1StkFrames.html" title="An STK class to handle vectorized audio data.">StkFrames</a> argument (the first channel is specified by 0). However, range checking is only performed if _STK_DEBUG_ is defined during compilation, in which case an out-of-range value will trigger an <a class="el" href="classstk_1_1StkError.html" title="STK error handling class.">StkError</a> exception. </p>
<p>Implements <a class="el" href="classstk_1_1Filter.html#a3260a238824c4a748ac057b84b7d3f21">stk::Filter</a>.</p>
<p><div class="fragment"><pre class="fragment"><a name="l00107"></a>00107 {
<a name="l00108"></a>00108 <span class="preprocessor">#if defined(_STK_DEBUG_)</span>
<a name="l00109"></a>00109 <span class="preprocessor"></span> <span class="keywordflow">if</span> ( channel &gt;= frames.channels() ) {
<a name="l00110"></a>00110 oStream_ &lt;&lt; <span class="stringliteral">&quot;TwoPole::tick(): channel and StkFrames arguments are incompatible!&quot;</span>;
<a name="l00111"></a>00111 <a class="code" href="classstk_1_1Stk.html#a48ac73a0d8ca28445ba1a054e1f061ff" title="Static function for error reporting and handling using c-strings.">handleError</a>( StkError::FUNCTION_ARGUMENT );
<a name="l00112"></a>00112 }
<a name="l00113"></a>00113 <span class="preprocessor">#endif</span>
<a name="l00114"></a>00114 <span class="preprocessor"></span>
<a name="l00115"></a>00115 StkFloat *samples = &amp;frames[channel];
<a name="l00116"></a>00116 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> hop = frames.channels();
<a name="l00117"></a>00117 <span class="keywordflow">for</span> ( <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> i=0; i&lt;frames.frames(); i++, samples += hop ) {
<a name="l00118"></a>00118 inputs_[0] = gain_ * *samples;
<a name="l00119"></a>00119 *samples = b_[0] * inputs_[0] - a_[1] * outputs_[1] - a_[2] * outputs_[2];
<a name="l00120"></a>00120 outputs_[2] = outputs_[1];
<a name="l00121"></a>00121 outputs_[1] = *samples;
<a name="l00122"></a>00122 }
<a name="l00123"></a>00123
<a name="l00124"></a>00124 lastFrame_[0] = outputs_[1];
<a name="l00125"></a>00125 <span class="keywordflow">return</span> frames;
<a name="l00126"></a>00126 }
</pre></div></p>
</div>
</div>
<a class="anchor" id="a5c9b52082c0d2845a5ca01ca276fe8f8"></a><!-- doxytag: member="stk::TwoPole::tick" ref="a5c9b52082c0d2845a5ca01ca276fe8f8" args="(StkFrames &amp;iFrames, StkFrames &amp;oFrames, unsigned int iChannel=0, unsigned int oChannel=0)" -->
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname"><a class="el" href="classstk_1_1StkFrames.html">StkFrames</a> &amp; stk::TwoPole::tick </td>
<td>(</td>
<td class="paramtype"><a class="el" href="classstk_1_1StkFrames.html">StkFrames</a> &amp;&nbsp;</td>
<td class="paramname"> <em>iFrames</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="classstk_1_1StkFrames.html">StkFrames</a> &amp;&nbsp;</td>
<td class="paramname"> <em>oFrames</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">unsigned int&nbsp;</td>
<td class="paramname"> <em>iChannel</em> = <code>0</code>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">unsigned int&nbsp;</td>
<td class="paramname"> <em>oChannel</em> = <code>0</code></td><td>&nbsp;</td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td><td><code> [inline]</code></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>Take a channel of the <code>iFrames</code> object as inputs to the filter and write outputs to the <code>oFrames</code> object. </p>
<p>The <code>iFrames</code> object reference is returned. Each channel argument must be less than the number of channels in the corresponding <a class="el" href="classstk_1_1StkFrames.html" title="An STK class to handle vectorized audio data.">StkFrames</a> argument (the first channel is specified by 0). However, range checking is only performed if _STK_DEBUG_ is defined during compilation, in which case an out-of-range value will trigger an <a class="el" href="classstk_1_1StkError.html" title="STK error handling class.">StkError</a> exception. </p>
<p><div class="fragment"><pre class="fragment"><a name="l00129"></a>00129 {
<a name="l00130"></a>00130 <span class="preprocessor">#if defined(_STK_DEBUG_)</span>
<a name="l00131"></a>00131 <span class="preprocessor"></span> <span class="keywordflow">if</span> ( iChannel &gt;= iFrames.channels() || oChannel &gt;= oFrames.channels() ) {
<a name="l00132"></a>00132 oStream_ &lt;&lt; <span class="stringliteral">&quot;TwoPole::tick(): channel and StkFrames arguments are incompatible!&quot;</span>;
<a name="l00133"></a>00133 <a class="code" href="classstk_1_1Stk.html#a48ac73a0d8ca28445ba1a054e1f061ff" title="Static function for error reporting and handling using c-strings.">handleError</a>( StkError::FUNCTION_ARGUMENT );
<a name="l00134"></a>00134 }
<a name="l00135"></a>00135 <span class="preprocessor">#endif</span>
<a name="l00136"></a>00136 <span class="preprocessor"></span>
<a name="l00137"></a>00137 StkFloat *iSamples = &amp;iFrames[iChannel];
<a name="l00138"></a>00138 StkFloat *oSamples = &amp;oFrames[oChannel];
<a name="l00139"></a>00139 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> iHop = iFrames.channels(), oHop = oFrames.channels();
<a name="l00140"></a>00140 <span class="keywordflow">for</span> ( <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> i=0; i&lt;iFrames.frames(); i++, iSamples += iHop, oSamples += oHop ) {
<a name="l00141"></a>00141 inputs_[0] = gain_ * *iSamples;
<a name="l00142"></a>00142 *oSamples = b_[0] * inputs_[0] - a_[1] * outputs_[1] - a_[2] * outputs_[2];
<a name="l00143"></a>00143 outputs_[2] = outputs_[1];
<a name="l00144"></a>00144 outputs_[1] = *oSamples;
<a name="l00145"></a>00145 }
<a name="l00146"></a>00146
<a name="l00147"></a>00147 lastFrame_[0] = outputs_[1];
<a name="l00148"></a>00148 <span class="keywordflow">return</span> iFrames;
<a name="l00149"></a>00149 }
</pre></div></p>
</div>
</div>
<hr/>The documentation for this class was generated from the following file:<ul>
<li><a class="el" href="TwoPole_8h_source.html">TwoPole.h</a></li>
</ul>
</div>
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<tr><td><A HREF="http://ccrma.stanford.edu/software/stk/"><I>The Synthesis ToolKit in C++ (STK)</I></A></td></tr>
<tr><td>&copy;1995-2011 Perry R. Cook and Gary P. Scavone. All Rights Reserved.</td></tr>
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