From bbe605c0faf134040859a27bb6f6c6de40d7063a Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Mon, 9 Sep 2019 04:10:59 +0200
Subject: [PATCH] Send NoteOff on when muting MIDI, drop note events when
 silent

---
 libs/ardour/amp.cc | 84 ++++++++++++++++++++++++++--------------------
 1 file changed, 48 insertions(+), 36 deletions(-)

diff --git a/libs/ardour/amp.cc b/libs/ardour/amp.cc
index 26c7e95c21..75a18cbf98 100644
--- a/libs/ardour/amp.cc
+++ b/libs/ardour/amp.cc
@@ -192,36 +192,9 @@ Amp::apply_gain (BufferSet& bufs, samplecnt_t sample_rate, samplecnt_t nframes,
 		return target;
 	}
 
-	/* MIDI Gain */
-	if (midi_amp) {
-		/* don't Trim midi velocity -- only relevant for Midi on Audio tracks */
-		for (BufferSet::midi_iterator i = bufs.midi_begin(); i != bufs.midi_end(); ++i) {
-
-			gain_t  delta;
-			if (target < initial) {
-				/* fade out: remove more and more of delta from initial */
-				delta = -(initial - target);
-			} else {
-				/* fade in: add more and more of delta from initial */
-				delta = target - initial;
-			}
-
-			MidiBuffer& mb (*i);
-
-			for (MidiBuffer::iterator m = mb.begin(); m != mb.end(); ++m) {
-				Evoral::Event<MidiBuffer::TimeType> ev = *m;
-
-				if (ev.is_note_on()) {
-					const gain_t scale = delta * (ev.time()/(double) nframes);
-					scale_midi_velocity (ev, fabsf (initial + scale));
-				}
-			}
-		}
-	}
-
-	/* Audio Gain */
-
-	/* Low pass filter coefficient: 1.0 - e^(-2.0 * π * f / 48000) f in Hz.
+	/* Apply Audio Gain first, calculate target LFP'ed gain coefficient
+	 *
+	 * Low pass filter coefficient: 1.0 - e^(-2.0 * π * f / 48000) f in Hz.
 	 * for f << SR,  approx a ~= 6.2 * f / SR;
 	 */
 	const gain_t a = 156.825f / (gain_t)sample_rate; // 25 Hz LPF
@@ -238,7 +211,46 @@ Amp::apply_gain (BufferSet& bufs, samplecnt_t sample_rate, samplecnt_t nframes,
 			rv = lpf;
 		}
 	}
-	if (fabsf (rv - target) < GAIN_COEFF_DELTA) return target;
+
+	if (fabsf (rv - target) < GAIN_COEFF_DELTA) {
+		rv = target;
+	}
+
+	/* MIDI Velocity scale from initial to LPF target */
+	if (midi_amp) {
+		/* don't Trim midi velocity -- only relevant for Midi on Audio tracks */
+		for (BufferSet::midi_iterator i = bufs.midi_begin(); i != bufs.midi_end(); ++i) {
+
+			gain_t  delta;
+			if (rv < initial) {
+				/* fade out: remove more and more of delta from initial */
+				delta = -(initial - rv);
+			} else {
+				/* fade in: add more and more of delta from initial */
+				delta = rv - initial;
+			}
+
+			MidiBuffer& mb (*i);
+
+			for (MidiBuffer::iterator m = mb.begin(); m != mb.end(); ++m) {
+				Evoral::Event<MidiBuffer::TimeType> ev = *m;
+
+				if (ev.is_note_on()) {
+					const gain_t scale = delta * (ev.time() / (double) nframes);
+					scale_midi_velocity (ev, fabsf (initial + scale));
+				}
+			}
+
+			/* queue MIDI all-note-off when going silent */
+			if (initial > GAIN_COEFF_SMALL && rv <= GAIN_COEFF_SMALL) {
+				for (uint8_t channel = 0; channel <= 0xF; channel++) {
+					uint8_t ev[3] = { ((uint8_t) (MIDI_CMD_CONTROL | channel)), ((uint8_t) MIDI_CTL_ALL_NOTES_OFF), 0 };
+					mb.push_back (nframes - 1, 3, ev);
+				}
+			}
+		}
+	}
+
 	return rv;
 }
 
@@ -278,14 +290,15 @@ Amp::apply_simple_gain (BufferSet& bufs, samplecnt_t nframes, gain_t target, boo
 	if (fabsf (target) < GAIN_COEFF_SMALL) {
 
 		if (midi_amp) {
-			/* don't Trim midi velocity -- only relevant for Midi on Audio tracks */
 			for (BufferSet::midi_iterator i = bufs.midi_begin(); i != bufs.midi_end(); ++i) {
 				MidiBuffer& mb (*i);
 
-				for (MidiBuffer::iterator m = mb.begin(); m != mb.end(); ++m) {
+				for (MidiBuffer::iterator m = mb.begin(); m != mb.end();) {
 					Evoral::Event<MidiBuffer::TimeType> ev = *m;
-					if (ev.is_note_on()) {
-						ev.set_velocity (0);
+					if (ev.is_note_on() || ev.is_note_off()) {
+						m = mb.erase (m);
+					} else {
+						++m;
 					}
 				}
 			}
@@ -298,7 +311,6 @@ Amp::apply_simple_gain (BufferSet& bufs, samplecnt_t nframes, gain_t target, boo
 	} else if (target != GAIN_COEFF_UNITY) {
 
 		if (midi_amp) {
-			/* don't Trim midi velocity -- only relevant for Midi on Audio tracks */
 			for (BufferSet::midi_iterator i = bufs.midi_begin(); i != bufs.midi_end(); ++i) {
 				MidiBuffer& mb (*i);