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58 lines
2.6 KiB
58 lines
2.6 KiB
8 years ago
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<script type="text/x-red" data-help-name="AudioAnalyzeNoteFrequency">
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<h3>Summary</h3>
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<div class=tooltipinfo>
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<p>Detect with fairly good accuracy the fundamental frequency f<sub>o</sub>
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of musical notes, such as electric guitar and bass.</p>
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</div>
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<p>Written By Collin Duffy</p>
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<h3>Audio Connections</h3>
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<table class=doc align=center cellpadding=3>
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<tr class=top><th>Port</th><th>Purpose</th></tr>
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<tr class=odd><td align=center>In 0</td><td>Signal to analyze</td></tr>
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</table>
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<h3>Functions</h3>
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<p class=func><span class=keyword>begin</span>(threshold);</p>
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<p class=desc>Initialize and start detecting frequencies,
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with an initial threshold (the amount of allowed uncertainty).
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</p>
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<p class=func><span class=keyword>available</span>();</p>
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<p class=desc>Returns true (non-zero) when a valid
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frequency is detected.
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</p>
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<p class=func><span class=keyword>read</span>();</p>
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<p class=desc>Read the detected frequency.
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</p>
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<p class=func><span class=keyword>probability</span>();</p>
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<p class=desc>Return the level of certainty, betweeo 0 to 1.0.
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</p>
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<p class=func><span class=keyword>threshold</span>(level);</p>
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<p class=desc>Set the detection threshold, the amount of allowed uncertainty.
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</p>
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<h3>Examples</h3>
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<p class=exam>File > Examples > Audio > Analysis > NoteFrequency
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</p>
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<h3>Notes</h3>
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<p>The <a href="http://recherche.ircam.fr/equipes/pcm/cheveign/pss/2002_JASA_YIN.pdf">YIN algorithm</a> (PDF)
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is used to detect frequencies, with many optimizations for
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frequencies between 29-400Hz. This algorithm can be somewhat
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memory and processor hungry but will allow you to detect with
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fairly good accuracy the fundamental frequencies from
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electric guitars and basses.</p>
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<p>Within the code, AUDIO_GUITARTUNER_BLOCKS
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may be edited to control low frequency range. The default
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(24) allows measurement down to 29.14 Hz, or B(flat)0.</p>
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<p>TODO: The usable upper range of this object is not well known.
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Duff says "it should be good up to 1000Hz", but may have trouble
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at 4 kHz. Please <a href="https://forum.pjrc.com/threads/32252-Different-Range-FFT-Algorithm/page2">post feedback here</a>, ideally with audio clips for the NoteFrequency example.</p>
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<p>This object was contributed by Collin Duffy from his
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<a href="https://github.com/duff2013/AudioTuner">AudioTuner project</a>.
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Additional details and documentation may be found there.</p>
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</script>
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<script type="text/x-red" data-template-name="AudioAnalyzeNoteFrequency">
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<div class="form-row">
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<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
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<input type="text" id="node-input-name" placeholder="Name">
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</div>
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</script>
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