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<h1>BlitSaw.h</h1><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="preprocessor">#ifndef STK_BLITSAW_H</span>
<a name="l00002"></a>00002 <span class="preprocessor"></span><span class="preprocessor">#define STK_BLITSAW_H</span>
<a name="l00003"></a>00003 <span class="preprocessor"></span>
<a name="l00004"></a>00004 <span class="preprocessor">#include "Generator.h"</span>
<a name="l00005"></a>00005 <span class="preprocessor">#include &lt;cmath&gt;</span>
<a name="l00006"></a>00006 <span class="preprocessor">#include &lt;limits&gt;</span>
<a name="l00007"></a>00007
<a name="l00008"></a>00008 <span class="keyword">namespace </span>stk {
<a name="l00009"></a>00009
<a name="l00010"></a>00010 <span class="comment">/***************************************************/</span>
<a name="l00029"></a>00029 <span class="comment">/***************************************************/</span>
<a name="l00030"></a>00030
<a name="l00031"></a><a class="code" href="classstk_1_1BlitSaw.html">00031</a> <span class="keyword">class </span><a class="code" href="classstk_1_1BlitSaw.html" title="STK band-limited sawtooth wave class.">BlitSaw</a>: <span class="keyword">public</span> <a class="code" href="classstk_1_1Generator.html" title="STK abstract unit generator parent class.">Generator</a>
<a name="l00032"></a>00032 {
<a name="l00033"></a>00033 <span class="keyword">public</span>:
<a name="l00035"></a>00035 <a class="code" href="classstk_1_1BlitSaw.html#8a245ef05cc58c521edaded5c6cdd5ee" title="Class constructor.">BlitSaw</a>( StkFloat frequency = 220.0 );
<a name="l00036"></a>00036
<a name="l00038"></a>00038 <a class="code" href="classstk_1_1BlitSaw.html#24cd2cc9852ce73252a99f7eff63879b" title="Class destructor.">~BlitSaw</a>();
<a name="l00039"></a>00039
<a name="l00041"></a>00041 <span class="keywordtype">void</span> <a class="code" href="classstk_1_1BlitSaw.html#3010cf9a0905368b857df2d332968036" title="Resets the oscillator state and phase to 0.">reset</a>();
<a name="l00042"></a>00042
<a name="l00044"></a>00044 <span class="keywordtype">void</span> <a class="code" href="classstk_1_1BlitSaw.html#fa6f1103a61221eebf5f49f3a7df4145" title="Set the sawtooth oscillator rate in terms of a frequency in Hz.">setFrequency</a>( StkFloat frequency );
<a name="l00045"></a>00045
<a name="l00047"></a>00047
<a name="l00059"></a>00059 <span class="keywordtype">void</span> <a class="code" href="classstk_1_1BlitSaw.html#8abd2b9a5b8d26926a383c1e56605545" title="Set the number of harmonics generated in the signal.">setHarmonics</a>( <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> nHarmonics = 0 );
<a name="l00060"></a>00060
<a name="l00062"></a><a class="code" href="classstk_1_1BlitSaw.html#254758ecd4166cc4e7d6fced5650a198">00062</a> StkFloat <a class="code" href="classstk_1_1BlitSaw.html#254758ecd4166cc4e7d6fced5650a198" title="Return the last computed output value.">lastOut</a>( <span class="keywordtype">void</span> )<span class="keyword"> const </span>{ <span class="keywordflow">return</span> lastFrame_[0]; };
<a name="l00063"></a>00063
<a name="l00065"></a>00065 StkFloat <a class="code" href="classstk_1_1BlitSaw.html#03536a1f1823ea41649b4a62ba98007c" title="Compute and return one output sample.">tick</a>( <span class="keywordtype">void</span> );
<a name="l00066"></a>00066
<a name="l00068"></a>00068
<a name="l00075"></a>00075 <a class="code" href="classstk_1_1StkFrames.html" title="An STK class to handle vectorized audio data.">StkFrames</a>&amp; <a class="code" href="classstk_1_1BlitSaw.html#03536a1f1823ea41649b4a62ba98007c" title="Compute and return one output sample.">tick</a>( <a class="code" href="classstk_1_1StkFrames.html" title="An STK class to handle vectorized audio data.">StkFrames</a>&amp; frames, <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> channel = 0 );
<a name="l00076"></a>00076
<a name="l00077"></a>00077 <span class="keyword">protected</span>:
<a name="l00078"></a>00078
<a name="l00079"></a>00079 <span class="keywordtype">void</span> updateHarmonics( <span class="keywordtype">void</span> );
<a name="l00080"></a>00080
<a name="l00081"></a>00081 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> nHarmonics_;
<a name="l00082"></a>00082 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> m_;
<a name="l00083"></a>00083 StkFloat rate_;
<a name="l00084"></a>00084 StkFloat phase_;
<a name="l00085"></a>00085 StkFloat p_;
<a name="l00086"></a>00086 StkFloat C2_;
<a name="l00087"></a>00087 StkFloat a_;
<a name="l00088"></a>00088 StkFloat state_;
<a name="l00089"></a>00089
<a name="l00090"></a>00090 };
<a name="l00091"></a>00091
<a name="l00092"></a><a class="code" href="classstk_1_1BlitSaw.html#03536a1f1823ea41649b4a62ba98007c">00092</a> <span class="keyword">inline</span> StkFloat <a class="code" href="classstk_1_1BlitSaw.html#03536a1f1823ea41649b4a62ba98007c" title="Compute and return one output sample.">BlitSaw :: tick</a>( <span class="keywordtype">void</span> )
<a name="l00093"></a>00093 {
<a name="l00094"></a>00094 <span class="comment">// The code below implements the BLIT algorithm of Stilson and</span>
<a name="l00095"></a>00095 <span class="comment">// Smith, followed by a summation and filtering operation to produce</span>
<a name="l00096"></a>00096 <span class="comment">// a sawtooth waveform. After experimenting with various approaches</span>
<a name="l00097"></a>00097 <span class="comment">// to calculate the average value of the BLIT over one period, I</span>
<a name="l00098"></a>00098 <span class="comment">// found that an estimate of C2_ = 1.0 / period (in samples) worked</span>
<a name="l00099"></a>00099 <span class="comment">// most consistently. A "leaky integrator" is then applied to the</span>
<a name="l00100"></a>00100 <span class="comment">// difference of the BLIT output and C2_. (GPS - 1 October 2005)</span>
<a name="l00101"></a>00101
<a name="l00102"></a>00102 <span class="comment">// A fully optimized version of this code would replace the two sin </span>
<a name="l00103"></a>00103 <span class="comment">// calls with a pair of fast sin oscillators, for which stable fast </span>
<a name="l00104"></a>00104 <span class="comment">// two-multiply algorithms are well known. In the spirit of STK,</span>
<a name="l00105"></a>00105 <span class="comment">// which favors clarity over performance, the optimization has </span>
<a name="l00106"></a>00106 <span class="comment">// not been made here.</span>
<a name="l00107"></a>00107
<a name="l00108"></a>00108 <span class="comment">// Avoid a divide by zero, or use of a denormalized divisor </span>
<a name="l00109"></a>00109 <span class="comment">// at the sinc peak, which has a limiting value of m_ / p_.</span>
<a name="l00110"></a>00110 StkFloat tmp, denominator = sin( phase_ );
<a name="l00111"></a>00111 <span class="keywordflow">if</span> ( fabs(denominator) &lt;= std::numeric_limits&lt;StkFloat&gt;::epsilon() )
<a name="l00112"></a>00112 tmp = a_;
<a name="l00113"></a>00113 <span class="keywordflow">else</span> {
<a name="l00114"></a>00114 tmp = sin( m_ * phase_ );
<a name="l00115"></a>00115 tmp /= p_ * denominator;
<a name="l00116"></a>00116 }
<a name="l00117"></a>00117
<a name="l00118"></a>00118 tmp += state_ - C2_;
<a name="l00119"></a>00119 state_ = tmp * 0.995;
<a name="l00120"></a>00120
<a name="l00121"></a>00121 phase_ += rate_;
<a name="l00122"></a>00122 <span class="keywordflow">if</span> ( phase_ &gt;= PI ) phase_ -= PI;
<a name="l00123"></a>00123
<a name="l00124"></a>00124 lastFrame_[0] = tmp;
<a name="l00125"></a>00125 <span class="keywordflow">return</span> lastFrame_[0];
<a name="l00126"></a>00126 }
<a name="l00127"></a>00127
<a name="l00128"></a><a class="code" href="classstk_1_1BlitSaw.html#b53f6ba99ef5c4f8982f6c0f07bf2e1d">00128</a> <span class="keyword">inline</span> <a class="code" href="classstk_1_1StkFrames.html" title="An STK class to handle vectorized audio data.">StkFrames</a>&amp; <a class="code" href="classstk_1_1BlitSaw.html#03536a1f1823ea41649b4a62ba98007c" title="Compute and return one output sample.">BlitSaw :: tick</a>( <a class="code" href="classstk_1_1StkFrames.html" title="An STK class to handle vectorized audio data.">StkFrames</a>&amp; frames, <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> channel )
<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> ( channel &gt;= frames.<a class="code" href="classstk_1_1StkFrames.html#ec7ef9c46675a24111aa6e2fda3ba870" title="Return the number of channels represented by the data.">channels</a>() ) {
<a name="l00132"></a>00132 errorString_ &lt;&lt; <span class="stringliteral">"BlitSaw::tick(): channel and StkFrames arguments are incompatible!"</span>;
<a name="l00133"></a>00133 <a class="code" href="classstk_1_1Stk.html#48ac73a0d8ca28445ba1a054e1f061ff" 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
<a name="l00138"></a>00138 StkFloat *samples = &amp;frames[channel];
<a name="l00139"></a>00139 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> hop = frames.<a class="code" href="classstk_1_1StkFrames.html#ec7ef9c46675a24111aa6e2fda3ba870" title="Return the number of channels represented by the data.">channels</a>();
<a name="l00140"></a>00140 <span class="keywordflow">for</span> ( <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> i=0; i&lt;frames.<a class="code" href="classstk_1_1StkFrames.html#05b1ab6fa750a8221a7d65c30e0cdab9" title="Return the number of sample frames represented by the data.">frames</a>(); i++, samples += hop )
<a name="l00141"></a>00141 *samples = <a class="code" href="classstk_1_1BlitSaw.html#03536a1f1823ea41649b4a62ba98007c" title="Compute and return one output sample.">BlitSaw::tick</a>();
<a name="l00142"></a>00142
<a name="l00143"></a>00143 <span class="keywordflow">return</span> frames;
<a name="l00144"></a>00144 }
<a name="l00145"></a>00145
<a name="l00146"></a>00146 } <span class="comment">// stk namespace</span>
<a name="l00147"></a>00147
<a name="l00148"></a>00148 <span class="preprocessor">#endif</span>
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