Issue 4907: Midi_walker::do_start_note: skip ignored notes in stop_note_queue

For each semitone pitch value, stop_note_queue is likely supposed to
contain at most one Midi_note event with its "ignore_" flag set to
false, and the comparisons between notes of equal semitone pitch to be
always done between the input note and this unique queued note that is
not (yet) being ignored.

If notes which are already being ignored are not skipped in the loop,
the task of raising the "ignore_" flags for note events of equal
semitone pitch (overlapping in time) which stop before the maximum
stopping time of these notes may, due to breaking out of the loop,
fail to work if the queue grows to contain three or more notes of equal
semitone pitch, leading to the emission of premature "note off" events
for this pitch, as demonstrated, for example, in
<http://lists.gnu.org/archive/html/bug-lilypond/2016-06/msg00042.html>.

diff --git a/input/regression/midi/midi-overlapping-notes.ly b/input/regression/midi/midi-overlapping-notes.ly
new file mode 100644 (file)
index 0000000..e808bb9
--- /dev/null
+++ b/input/regression/midi/midi-overlapping-notes.ly
@@ -0,0 +1,22 @@
+\header {
+
+  texidoc = "Notes with equal pitch overlapping in time on the same
+MIDI channel should produce multiple MIDI note-on events, but no
+isolated note-off events before the last of these notes ends."
+
+}
+
+\version "2.19.45"
+
+\score {
+  \new Staff \with { midiInstrument = "church organ" }
+  \new Voice \relative c' <<
+    % This combination of music expressions should not produce audible
+    % pauses between notes in the MIDI output, in particular, before the
+    % 'g1' note in the first expression.
+    { c1 s1 g1 }
+    { s4 c4 }
+    { s2 c2~ c1 s1 }
+  >>
+  \midi { }
+}

diff --git a/lily/midi-walker.cc b/lily/midi-walker.cc
index bc6c93dc56344f0a5a8b3b96078dfcdf0ac6d7c0..d9765c681450931fe85acca5c81213a90a153001 100644 (file)
--- a/lily/midi-walker.cc
+++ b/lily/midi-walker.cc
@@ -89,8 +89,9 @@ Midi_walker::do_start_note (Midi_note *note)
                         Real (384 * 4)) + now_ticks;
   for (vsize i = 0; i < stop_note_queue.size (); i++)
     {
-      /* if this pitch already in queue */
-      if (stop_note_queue[i].val->get_semitone_pitch ()
+      /* if this pitch already in queue, and is not already ignored */
+      if (!stop_note_queue[i].ignore_ &&
+          stop_note_queue[i].val->get_semitone_pitch ()
           == note->get_semitone_pitch ())
         {
           int queued_ticks