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63 lines
2.9 KiB
63 lines
2.9 KiB
8 years ago
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<script type="text/x-red" data-help-name="AudioEffectFlange">
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<h3>Summary</h3>
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<div class=tooltipinfo>
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<p>Originally, flanging was produced by playing the same signal on two synchronized
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reel-to-reel tape recorders and making one of the reels slow down and speed up by
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pressing on the flange of the reel (hence the name). This is a type of
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comb filtering, and produces a harmonically-related series of peaks and notches
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in the audio spectrum.</p>
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</div>
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<p>This flanger uses a delay line, combining the original voice with only one sample from the delay
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line, but the position of that sample varies sinusoidally.</p>
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<p>The effect can be represented as:<br>
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result = sample(0) + sample(dt + depth*sin(2*PI*Fe))</p>
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<p>The value of the sine function is always a number from -1 to +1 and
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so the result of depth*(sin(Fe)) is always a number from -depth to +depth.
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Thus, the delayed sample will be selected from the range (dt-depth) to
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(dt+depth). This selection will vary at whatever rate is specified as the
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frequency of the effect, Fe. Typically a low frequency (a few Hertz) is used.
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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 Input</td></tr>
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<tr class="odd"><td align="center">Out 0</td><td>Flanged Output</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>(delayBuffer, length, offset, depth, delayRate);</p>
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<p class=desc>Create a flanger by specifying the address of the delayline, the
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total number of samples in the delay line (often done as an integer multiple of
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AUDIO_BLOCK_SAMPLES), the offset (how far back the flanged sample is from the original voice),
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the modulation depth (larger values give a greater variation) and the modulation
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frequency, in Hertz.
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</p>
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<p class=func><span class=keyword>voices</span>(offset, depth, delayRate);</p>
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<p class=desc>Alters the parameters in a running flanger (previously started with begin).
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</p>
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<h3>Examples</h3>
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<p class=exam>File > Examples > Audio > Effects > Flange
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</p>
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<h3>Notes</h3>
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<p>The longer the length of the delay buffer, the more memory blocks are used.</p>
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<p>Try these settings:<br>
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#define FLANGE_DELAY_LENGTH (2*AUDIO_BLOCK_SAMPLES)<br>
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and<br>
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int s_idx = 2*FLANGE_DELAY_LENGTH/4;<br>
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int s_depth = FLANGE_DELAY_LENGTH/4;<br>
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double s_freq = 3;</p>
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<p>The flange effect can also produce a chorus-like effect if a longer
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delay line is used with a slower modulation rate, for example try:<br>
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#define FLANGE_DELAY_LENGTH (12*AUDIO_BLOCK_SAMPLES)<br>
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and<br>
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int s_idx = 3*FLANGE_DELAY_LENGTH/4;<br>
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int s_depth = FLANGE_DELAY_LENGTH/8;<br>
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double s_freq = .0625;</p>
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</script>
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<script type="text/x-red" data-template-name="AudioEffectFlange">
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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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