From ae0aa50b6f4df9df525dd3b65e3e70f5346b8a18 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Sun, 15 May 2022 18:55:17 +0200
Subject: [PATCH] Fix MIDI delay-line (amend 25098ed)

Events in the delay-buffer must be shifted back every cycle.
Also in case of fixed-delay-lines events may not be in sequence
since events are only sorted at backend port-level.
---
 libs/ardour/delayline.cc   | 26 ++++++++++++--------------
 libs/ardour/fixed_delay.cc | 11 +++++++++--
 2 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/libs/ardour/delayline.cc b/libs/ardour/delayline.cc
index d3f4982f79..19ac357db3 100644
--- a/libs/ardour/delayline.cc
+++ b/libs/ardour/delayline.cc
@@ -231,20 +231,18 @@ DelayLine::run (BufferSet& bufs, samplepos_t /* start_sample */, samplepos_t /*
 				dly->silence (n_samples);
 			}
 
-			if (delay_diff != 0) {
-				/* If the delay time changes, iterate over all events in the dly-buffer
-				 * and adjust the time in-place. <= 0 becomes 0.
-				 *
-				 * iterate over all events in dly-buffer and subtract one cycle
-				 * (n_samples) from the timestamp, bringing them closer to de-queue.
-				 */
-				for (MidiBuffer::iterator m = dly->begin (); m != dly->end (); ++m) {
-					MidiBuffer::TimeType *t = m.timeptr ();
-					if (*t > n_samples + delay_diff) {
-						*t -= n_samples + delay_diff;
-					} else {
-						*t = 0;
-					}
+			/* If the delay time changes, iterate over all events in the dly-buffer
+			 * and adjust the time in-place. <= 0 becomes 0.
+			 *
+			 * iterate over all events in dly-buffer and subtract one cycle
+			 * (n_samples) from the timestamp, bringing them closer to de-queue.
+			 */
+			for (MidiBuffer::iterator m = dly->begin (); m != dly->end (); ++m) {
+				MidiBuffer::TimeType *t = m.timeptr ();
+				if (*t > n_samples + delay_diff) {
+					*t -= n_samples + delay_diff;
+				} else {
+					*t = 0;
 				}
 			}
 
diff --git a/libs/ardour/fixed_delay.cc b/libs/ardour/fixed_delay.cc
index 6606197047..75586ef13b 100644
--- a/libs/ardour/fixed_delay.cc
+++ b/libs/ardour/fixed_delay.cc
@@ -148,7 +148,7 @@ FixedDelay::delay (
 			if (ev.time () < n_samples) {
 				mout->push_back (ev);
 			} else {
-				mdly->push_back (ev);
+				mdly->insert_event (ev);
 			}
 		}
 
@@ -158,9 +158,16 @@ FixedDelay::delay (
 			if (ev.time () >= n_samples) {
 				break;
 			}
-			mout->push_back (ev);
+			mout->insert_event (ev);
 			m = mdly->erase (m);
 		}
+
+		/* prepare for next cycle */
+		for (MidiBuffer::iterator m = mdly->begin (); m != mdly->end (); ++m) {
+			MidiBuffer::TimeType *t = m.timeptr ();
+			assert (*t >= n_samples);
+			*t -= n_samples;
+		}
 		return;
 	}