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<li class="navelem"><a class="el" href="dir_7672bb780010713f2d2504f90f5cfe22.html">spectral</a></li> </ul>
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<a href="#typedef-members">Typedefs</a> |
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<div class="title">specdesc.h File Reference</div> </div>
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<p>Spectral description functions.
<a href="#details">More...</a></p>
<p><a href="specdesc_8h_source.html">Go to the source code of this file.</a></p>
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<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="typedef-members"></a>
Typedefs</h2></td></tr>
<tr class="memitem:ab4cc8c77914bb009143a4e8c5ea2358d"><td class="memItemLeft" align="right" valign="top"><a id="ab4cc8c77914bb009143a4e8c5ea2358d"></a>
typedef struct _aubio_specdesc_t </td><td class="memItemRight" valign="bottom"><a class="el" href="specdesc_8h.html#ab4cc8c77914bb009143a4e8c5ea2358d">aubio_specdesc_t</a></td></tr>
<tr class="memdesc:ab4cc8c77914bb009143a4e8c5ea2358d"><td class="mdescLeft"> </td><td class="mdescRight">spectral description structure <br /></td></tr>
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<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="func-members"></a>
Functions</h2></td></tr>
<tr class="memitem:a3180622c8c37adf8fdad2ef9c17b0956"><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="specdesc_8h.html#a3180622c8c37adf8fdad2ef9c17b0956">aubio_specdesc_do</a> (<a class="el" href="specdesc_8h.html#ab4cc8c77914bb009143a4e8c5ea2358d">aubio_specdesc_t</a> *o, <a class="el" href="structcvec__t.html">cvec_t</a> *fftgrain, <a class="el" href="structfvec__t.html">fvec_t</a> *desc)</td></tr>
<tr class="memdesc:a3180622c8c37adf8fdad2ef9c17b0956"><td class="mdescLeft"> </td><td class="mdescRight">execute spectral description function on a spectral frame <a href="#a3180622c8c37adf8fdad2ef9c17b0956">More...</a><br /></td></tr>
<tr class="separator:a3180622c8c37adf8fdad2ef9c17b0956"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a80b65fbf7eb01116bfff20943ca689fe"><td class="memItemLeft" align="right" valign="top"><a class="el" href="specdesc_8h.html#ab4cc8c77914bb009143a4e8c5ea2358d">aubio_specdesc_t</a> * </td><td class="memItemRight" valign="bottom"><a class="el" href="specdesc_8h.html#a80b65fbf7eb01116bfff20943ca689fe">new_aubio_specdesc</a> (<a class="el" href="types_8h.html#a40bb5262bf908c328fbcfbe5d29d0201">char_t</a> *method, <a class="el" href="types_8h.html#a12a1e9b3ce141648783a82445d02b58d">uint_t</a> buf_size)</td></tr>
<tr class="memdesc:a80b65fbf7eb01116bfff20943ca689fe"><td class="mdescLeft"> </td><td class="mdescRight">creation of a spectral description object <a href="#a80b65fbf7eb01116bfff20943ca689fe">More...</a><br /></td></tr>
<tr class="separator:a80b65fbf7eb01116bfff20943ca689fe"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a17a1acf7ce970e2ae34fb4cf654da2af"><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="specdesc_8h.html#a17a1acf7ce970e2ae34fb4cf654da2af">del_aubio_specdesc</a> (<a class="el" href="specdesc_8h.html#ab4cc8c77914bb009143a4e8c5ea2358d">aubio_specdesc_t</a> *o)</td></tr>
<tr class="memdesc:a17a1acf7ce970e2ae34fb4cf654da2af"><td class="mdescLeft"> </td><td class="mdescRight">deletion of a spectral descriptor <a href="#a17a1acf7ce970e2ae34fb4cf654da2af">More...</a><br /></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p>Spectral description functions. </p>
<p>All of the following spectral description functions take as arguments the FFT of a windowed signal (as created with aubio_pvoc). They output one smpl_t per buffer (stored in a vector of size [1]).</p>
<h1><a class="anchor" id="specdesc"></a>
Spectral description functions</h1>
<p>A list of the spectral description methods currently available follows.</p>
<h2><a class="anchor" id="onsetdesc"></a>
Onset detection functions</h2>
<p>These functions are designed to raise at notes attacks in music signals.</p>
<p><b><code>energy</code> </b>: Energy based onset detection function</p>
<p>This function calculates the local energy of the input spectral frame.</p>
<p><b><code>hfc</code> </b>: High Frequency Content onset detection function</p>
<p>This method computes the High Frequency Content (HFC) of the input spectral frame. The resulting function is efficient at detecting percussive onsets.</p>
<p>Paul Masri. Computer modeling of Sound for Transformation and Synthesis of Musical Signal. PhD dissertation, University of Bristol, UK, 1996.</p>
<p><b><code>complex</code> </b>: Complex Domain Method onset detection function</p>
<p>Christopher Duxbury, Mike E. Davies, and Mark B. Sandler. Complex domain onset detection for musical signals. In Proceedings of the Digital Audio Effects Conference, DAFx-03, pages 90-93, London, UK, 2003.</p>
<p><b><code>phase</code> </b>: Phase Based Method onset detection function</p>
<p>Juan-Pablo Bello, Mike P. Davies, and Mark B. Sandler. Phase-based note onset detection for music signals. In Proceedings of the IEEE International Conference on Acoustics Speech and Signal Processing, pages 441444, Hong-Kong, 2003.</p>
<p><b><code>specdiff</code> </b>: Spectral difference method onset detection function</p>
<p>Jonhatan Foote and Shingo Uchihashi. The beat spectrum: a new approach to rhythm analysis. In IEEE International Conference on Multimedia and Expo (ICME 2001), pages 881884, Tokyo, Japan, August 2001.</p>
<p><b><code>kl</code> </b>: Kullback-Liebler onset detection function</p>
<p>Stephen Hainsworth and Malcom Macleod. Onset detection in music audio signals. In Proceedings of the International Computer Music Conference (ICMC), Singapore, 2003.</p>
<p><b><code>mkl</code> </b>: Modified Kullback-Liebler onset detection function</p>
<p>Paul Brossier, ``Automatic annotation of musical audio for interactive systems'', Chapter 2, Temporal segmentation, PhD thesis, Centre for Digital music, Queen Mary University of London, London, UK, 2006.</p>
<p><b><code>specflux</code> </b>: Spectral Flux</p>
<p>Simon Dixon, Onset Detection Revisited, in ``Proceedings of the 9th International Conference on Digital Audio Effects'' (DAFx-06), Montreal, Canada, 2006.</p>
<h2><a class="anchor" id="shapedesc"></a>
Spectral shape descriptors</h2>
<p>The following descriptors are described in:</p>
<p>Geoffroy Peeters, <em>A large set of audio features for sound description (similarity and classification) in the CUIDADO project</em>, CUIDADO I.S.T. Project Report 2004 (<a href="http://www.ircam.fr/anasyn/peeters/ARTICLES/Peeters_2003_cuidadoaudiofeatures.pdf">pdf</a>)</p>
<p><b><code>centroid</code> </b>: Spectral centroid</p>
<p>The spectral centroid represents the barycenter of the spectrum.</p>
<p><em>Note:</em> This function returns the result in bin. To get the spectral centroid in Hz, <a class="el" href="musicutils_8h.html#a08cbeb1881cd3d9adba9e8606bb3f089" title="convert frequency bin to frequency (Hz) ">aubio_bintofreq()</a> should be used.</p>
<p><b><code>spread</code> </b>: Spectral spread</p>
<p>The spectral spread is the variance of the spectral distribution around its centroid.</p>
<p>See also <a href="http://en.wikipedia.org/wiki/Standard_deviation">Standard deviation</a> on Wikipedia.</p>
<p><b><code>skewness</code> </b>: Spectral skewness</p>
<p>Similarly, the skewness is computed from the third order moment of the spectrum. A negative skewness indicates more energy on the lower part of the spectrum. A positive skewness indicates more energy on the high frequency of the spectrum.</p>
<p>See also <a href="http://en.wikipedia.org/wiki/Skewness">Skewness</a> on Wikipedia.</p>
<p><b><code>kurtosis</code> </b>: Spectral kurtosis</p>
<p>The kurtosis is a measure of the flatness of the spectrum, computed from the fourth order moment.</p>
<p>See also <a href="http://en.wikipedia.org/wiki/Kurtosis">Kurtosis</a> on Wikipedia.</p>
<p><b><code>slope</code> </b>: Spectral slope</p>
<p>The spectral slope represents decreasing rate of the spectral amplitude, computed using a linear regression.</p>
<p><b><code>decrease</code> </b>: Spectral decrease</p>
<p>The spectral decrease is another representation of the decreasing rate, based on perceptual criteria.</p>
<p><b><code>rolloff</code> </b>: Spectral roll-off</p>
<p>This function returns the bin number below which 95% of the spectrum energy is found. </p>
<p class="definition">Definition in file <a class="el" href="specdesc_8h_source.html">specdesc.h</a>.</p>
</div><h2 class="groupheader">Function Documentation</h2>
<a id="a3180622c8c37adf8fdad2ef9c17b0956"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a3180622c8c37adf8fdad2ef9c17b0956">◆ </a></span>aubio_specdesc_do()</h2>
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<td class="memname">void aubio_specdesc_do </td>
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<td class="paramtype"><a class="el" href="specdesc_8h.html#ab4cc8c77914bb009143a4e8c5ea2358d">aubio_specdesc_t</a> * </td>
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<td class="paramtype"><a class="el" href="structcvec__t.html">cvec_t</a> * </td>
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<td class="paramtype"><a class="el" href="structfvec__t.html">fvec_t</a> * </td>
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<p>execute spectral description function on a spectral frame </p>
<p>Generic function to compute spectral detescription.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">o</td><td>spectral description object as returned by <a class="el" href="specdesc_8h.html#a80b65fbf7eb01116bfff20943ca689fe" title="creation of a spectral description object ">new_aubio_specdesc()</a> </td></tr>
<tr><td class="paramname">fftgrain</td><td>input signal spectrum as computed by aubio_pvoc_do </td></tr>
<tr><td class="paramname">desc</td><td>output vector (one sample long, to send to the peak picking) </td></tr>
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<dl><dt><b>Examples: </b></dt><dd><a class="el" href="spectral_2test-specdesc_8c-example.html#a5">spectral/test-specdesc.c</a>.</dd>
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<h2 class="memtitle"><span class="permalink"><a href="#a17a1acf7ce970e2ae34fb4cf654da2af">◆ </a></span>del_aubio_specdesc()</h2>
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<td class="memname">void del_aubio_specdesc </td>
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<td class="paramtype"><a class="el" href="specdesc_8h.html#ab4cc8c77914bb009143a4e8c5ea2358d">aubio_specdesc_t</a> * </td>
<td class="paramname"><em>o</em></td><td>)</td>
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<p>deletion of a spectral descriptor </p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">o</td><td>spectral descriptor object as returned by <a class="el" href="specdesc_8h.html#a80b65fbf7eb01116bfff20943ca689fe" title="creation of a spectral description object ">new_aubio_specdesc()</a> </td></tr>
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<dl><dt><b>Examples: </b></dt><dd><a class="el" href="spectral_2test-specdesc_8c-example.html#a6">spectral/test-specdesc.c</a>.</dd>
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<h2 class="memtitle"><span class="permalink"><a href="#a80b65fbf7eb01116bfff20943ca689fe">◆ </a></span>new_aubio_specdesc()</h2>
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<td class="memname"><a class="el" href="specdesc_8h.html#ab4cc8c77914bb009143a4e8c5ea2358d">aubio_specdesc_t</a>* new_aubio_specdesc </td>
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<td class="paramtype"><a class="el" href="types_8h.html#a40bb5262bf908c328fbcfbe5d29d0201">char_t</a> * </td>
<td class="paramname"><em>method</em>, </td>
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<td class="paramtype"><a class="el" href="types_8h.html#a12a1e9b3ce141648783a82445d02b58d">uint_t</a> </td>
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<p>creation of a spectral description object </p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">method</td><td>spectral description method </td></tr>
<tr><td class="paramname">buf_size</td><td>length of the input spectrum frame</td></tr>
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<p>The parameter <code>method</code> is a string that can be any of:</p>
<ul>
<li><code>energy</code>, <code>hfc</code>, <code>complex</code>, <code>phase</code>, <code>specdiff</code>, <code>kl</code>, <code>mkl</code>, <code>specflux</code></li>
<li><code>centroid</code>, <code>spread</code>, <code>skewness</code>, <code>kurtosis</code>, <code>slope</code>, <code>decrease</code>, <code>rolloff</code> </li>
</ul>
<dl><dt><b>Examples: </b></dt><dd><a class="el" href="spectral_2test-specdesc_8c-example.html#a4">spectral/test-specdesc.c</a>.</dd>
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