Merge pull request #76 from Nantonos/chorusflange

Chorus and flange gui docs

effect_chorus.h

@@ -43,7 +43,6 @@ public:
 
   boolean begin(short *delayline,int delay_length,int n_chorus);
   virtual void update(void);
-  void stop(void);
   void voices(int n_chorus);
   
 private:

effect_flange.h

@@ -43,7 +43,6 @@ public:
   boolean begin(short *delayline,int d_length,int delay_offset,int d_depth,float delay_rate);
   boolean voices(int delay_offset,int d_depth,float delay_rate);
   virtual void update(void);
-  void stop(void);
   
 private:
   audio_block_t *inputQueueArray[1];

gui/list.html

@@ -1113,25 +1113,43 @@ The actual packets are taken
 	});
 </script>
 <script type="text/x-red" data-help-name="AudioEffectChorus">
-	<h3>Summary</h3>
-	<p>description</p>
+<h3>Summary</h3>
+	<p>The chorus effect simulates the richness of several nearly-identical
+	sound sources (like the way a choir sounds different to a single singer).
+	It does this by sampling from a delay line, so each voice is actually
+	the same but at a slightly different point in time. This is a type of
+	comb filtering.</p>
+	<p>Chorus combines one or more samples ranging from the most recent 
+	sample back to about 50ms ago. The additional samples are evenly spread 
+	through the supplied delay line, and there is no modulation.</p>
+	<p>If the number of voices is specified as 2, then the 
+	effect combines the current sample and the oldest sample (the last one 
+	in the delay line). If the number of voices is 3 then the effect combines 
+	the most recent sample, the oldest sample and the sample in the middle of 
+	the delay line.</p>
+	<p>For two voices the effect can be represented as:<br/>
+	result = (sample(0) + sample(dt))/2<br/>
+	where sample(0) represents the current sample and sample(dt) 
+	is the sample in the delay line from dt milliseconds ago.</p>
 	<h3>Audio Connections</h3>
 	<table class=doc align=center cellpadding=3>
-		<tr class=top><th>Port</th><th>Purpose</th></tr>
-		<tr class=odd><td align=center></td><td></td></tr>
+		<tr class="top"><th>Port</th><th>Purpose</th></tr>
+		<tr class="odd"><td align="center">In 0</td><td>Signal Input</td></tr>
+		<tr class="odd"><td align="center">Out 0</td><td>Chorused Output</td></tr>
 	</table>
 	<h3>Functions</h3>
 	<p class=func><span class=keyword>begin</span>(delayBuffer, length, n_chorus);</p>
-	<p class=desc>blah blah blah blah
-	</p>
-	<p class=func><span class=keyword>stop</span>();</p>
-	<p class=desc>blah blah blah blah
+	<p class=desc>Create a chorus by specifying the address of the delayline, the
+	total number of samples in the delay line (often done as an integer multiple of 
+	AUDIO_BLOCK_SAMPLES) and the number of voices in the chorus <em>including</em>
+	the original voice (so, 2 and up to get a chorus effect, although you can 
+	specify 1 if you want).
 	</p>
 	<p class=func><span class=keyword>modify</span>(n_chorus);</p>
-	<p class=desc>blah blah blah blah
+	<p class=desc>Alters the number of voices in a running chorus (previously started with begin).
 	</p>
 	<h3>Notes</h3>
-	<p></p>
+	<p>The longer the length of the chorus, the more memory blocks are used.</p>
 </script>
 <script type="text/x-red" data-template-name="AudioEffectChorus">
 	<div class="form-row">
@@ -1152,25 +1170,54 @@ The actual packets are taken
 	});
 </script>
 <script type="text/x-red" data-help-name="AudioEffectFlange">
-	<h3>Summary</h3>
-	<p>description</p>
+<h3>Summary</h3>
+	<p>Originally, flanging was produced by playing the same signal on two synchronized 
+	reel-to-reel tape recorders and making one of the reels slow down and speed up by
+	pressing on the flange of the reel (hence the name). This is a type of
+	comb filtering, and produces a harmonically-related series of peaks and notches 
+	in the audio spectrum.</p>
+	<p>This flanger uses a delay line, combining the original voice with only one sample from the delay 
+	line, but the position of that sample varies sinusoidally.</p>
+	<p>The effect can be represented as:<br>
+	result = sample(0) + sample(dt + depth*sin(2*PI*Fe))</p>
+	<p>The value of the sine function is always a number from -1 to +1 and 
+	so the result of depth*(sin(Fe)) is always a number from -depth to +depth. 
+	Thus, the delayed sample will be selected from the range (dt-depth) to 
+	(dt+depth). This selection will vary at whatever rate is specified as the 
+	frequency of the effect, Fe. Typically a low frequency (a few Hertz) is used.
 	<h3>Audio Connections</h3>
 	<table class=doc align=center cellpadding=3>
-		<tr class=top><th>Port</th><th>Purpose</th></tr>
-		<tr class=odd><td align=center></td><td></td></tr>
+		<tr class="top"><th>Port</th><th>Purpose</th></tr>
+		<tr class="odd"><td align="center">In 0</td><td>Signal Input</td></tr>
+		<tr class="odd"><td align="center">Out 0</td><td>Flanged Output</td></tr>
 	</table>
 	<h3>Functions</h3>
 	<p class=func><span class=keyword>begin</span>(delayBuffer, length, offset, depth, delayRate);</p>
-	<p class=desc>blah blah blah blah
+	<p class=desc>Create a flanger by specifying the address of the delayline, the
+	total number of samples in the delay line (often done as an integer multiple of 
+	AUDIO_BLOCK_SAMPLES), the offset (how far back the flanged sample is from the original voice),
+	the modulation depth (larger values give a greater variation) and the modulation
+	frequency, in Hertz.
 	</p>
 	<p class=func><span class=keyword>modify</span>(offset, depth, delayRate);</p>
-	<p class=desc>blah blah blah blah
-	</p>
-	<p class=func><span class=keyword>stop</span>();</p>
-	<p class=desc>blah blah blah blah
+	<p class=desc>Alters the parameters in a running flanger (previously started with begin).
 	</p>
+
 	<h3>Notes</h3>
-	<p></p>
+	<p>The longer the length of the delay buffer, the more memory blocks are used.</p>
+	<p>Try these settings:<br>
+#define FLANGE_DELAY_LENGTH (2*AUDIO_BLOCK_SAMPLES)<br>
+and<br>
+int s_idx = 2*FLANGE_DELAY_LENGTH/4;<br>
+int s_depth = FLANGE_DELAY_LENGTH/4;<br>
+double s_freq = 3;</p>
+<p>The flange effect can also produce a chorus-like effect if a longer
+delay line is used with a slower modulation rate, for example try:<br>
+#define FLANGE_DELAY_LENGTH (12*AUDIO_BLOCK_SAMPLES)<br>
+and<br>
+int s_idx = 3*FLANGE_DELAY_LENGTH/4;<br>
+int s_depth = FLANGE_DELAY_LENGTH/8;<br>
+double s_freq = .0625;</p>
 </script>
 <script type="text/x-red" data-template-name="AudioEffectFlange">
 	<div class="form-row">