Add AudioEffectEnvelope releaseNoteOn

https://forum.pjrc.com/threads/27806-Clicking-envelope-with-Audio-Library

effect_envelope.cpp

 #define STATE_DECAY	4
 #define STATE_SUSTAIN	5
 #define STATE_RELEASE	6
+#define STATE_FORCED	7
 
 void AudioEffectEnvelope::noteOn(void)
 {
 	__disable_irq();
-	mult_hires = 0;
-	count = delay_count;
-	if (count > 0) {
-		state = STATE_DELAY;
-		inc_hires = 0;
-	} else {
-		state = STATE_ATTACK;
-		count = attack_count;
-		inc_hires = 0x40000000 / (int32_t)count;
+	if (state == STATE_IDLE || state == STATE_DELAY || release_forced_count == 0) {
+		mult_hires = 0;
+		count = delay_count;
+		if (count > 0) {
+			state = STATE_DELAY;
+			inc_hires = 0;
+		} else {
+			state = STATE_ATTACK;
+			count = attack_count;
+			inc_hires = 0x40000000 / (int32_t)count;
+		}
+	} else if (state != STATE_FORCED) {
+		state = STATE_FORCED;
+		count = release_forced_count;
+		inc_hires = (-mult_hires) / (int32_t)count;
 	}
 	__enable_irq();
 }
 void AudioEffectEnvelope::noteOff(void)
 {
 	__disable_irq();
-	if (state != STATE_IDLE) {
+	if (state != STATE_IDLE && state != STATE_FORCED) {
 		state = STATE_RELEASE;
 		count = release_count;
 		inc_hires = (-mult_hires) / (int32_t)count;
 					*p++ = 0;
 				}
 				break;
+			} else if (state == STATE_FORCED) {
+				mult_hires = 0;
+				count = delay_count;
+				if (count > 0) {
+					state = STATE_DELAY;
+					inc_hires = 0;
+				} else {
+					state = STATE_ATTACK;
+					count = attack_count;
+					inc_hires = 0x40000000 / (int32_t)count;
+				}
 			} else if (state == STATE_DELAY) {
 				state = STATE_ATTACK;
 				count = attack_count;

effect_envelope.h

 public:
 	AudioEffectEnvelope() : AudioStream(1, inputQueueArray) {
 		state = 0;
-		delay(0.0);  // default values...
-		attack(1.5);
-		hold(0.5);
-		decay(15.0);
-		sustain(0.667);
-		release(30.0);
+		delay(0.0f);  // default values...
+		attack(10.5f);
+		hold(2.5f);
+		decay(35.0f);
+		sustain(0.5f);
+		release(300.0f);
+		releaseNoteOn(5.0f);
 	}
 	void noteOn();
 	void noteOff();
 		release_count = milliseconds2count(milliseconds);
 		if (release_count == 0) release_count = 1;
 	}
+	void releaseNoteOn(float milliseconds) {
+		release_forced_count = milliseconds2count(milliseconds);
+		if (release_count == 0) release_count = 1;
+	}
 	using AudioStream::release;
 	virtual void update(void);
 private:
 	}
 	audio_block_t *inputQueueArray[1];
 	// state
-	uint8_t  state;      // idle, delay, attack, hold, decay, sustain, release
+	uint8_t  state;      // idle, delay, attack, hold, decay, sustain, release, forced
 	uint16_t count;      // how much time remains in this state, in 8 sample units
 	int32_t  mult_hires; // attenuation, 0=off, 0x40000000=unity gain
 	int32_t  inc_hires;  // amount to change mult_hires every 8 samples
 	uint16_t decay_count;
 	int32_t  sustain_mult;
 	uint16_t release_count;
+	uint16_t release_forced_count;
 
 };
 

gui/index.html

 		default is zero, for no delay.
 	</p>
 	<p class=func><span class=keyword>attack</span>(milliseconds);</p>
-	<p class=desc>Set the attack time.  The default is 1.5 milliseconds.
+	<p class=desc>Set the attack time.  The default is 10.5 milliseconds.
 	</p>
 	<p class=func><span class=keyword>hold</span>(milliseconds);</p>
-	<p class=desc>Set the hold time.  The default is 0.5 milliseconds.
+	<p class=desc>Set the hold time.  The default is 2.5 milliseconds.
 	</p>
 	<p class=func><span class=keyword>decay</span>(milliseconds);</p>
-	<p class=desc>Set the decay time.  The default is 15 milliseconds.
+	<p class=desc>Set the decay time.  The default is 35 milliseconds.
 	</p>
 	<p class=func><span class=keyword>sustain</span>(level);</p>
 	<p class=desc>Set the sustain level.  The range is 0 to 1.0.  The
 		until noteOff() is called.
 	</p>
 	<p class=func><span class=keyword>release</span>(milliseconds);</p>
-	<p class=desc>Set the release time.  The default is 30 millisecond.
+	<p class=desc>Set the release time.  The default is 300 millisecond.
+	</p>
+	<p class=func><span class=keyword>releaseNoteOn</span>(milliseconds);</p>
+	<p class=desc>Set a quick release time to be used when a new note is
+		started while the envelop is in any state passing the signal.
+		This will add latency before your new attack phase begins, so
+		short times are recommended.  Zero may be used to completely
+		disable this feature (never extra latency).  Longer times help
+		reduce clicks or pops.  The default is 5 millisecond.
 	</p>
 	<h3>Examples</h3>
 	<p class=exam>File &gt; Examples &gt; Audio &gt; Synthesis &gt; PlaySynthMusic

keywords.txt

 decay	KEYWORD2
 sustain	KEYWORD2
 release	KEYWORD2
+releaseNoteOn	KEYWORD2
 inputLevel	KEYWORD2
 inputSelect	KEYWORD2
 muteHeadphone	KEYWORD2