- Evoral::Sequence<double>::const_iterator& i = _model_iter;
-
- // If the cached iterator is invalid, search for the first event past start
- if (_last_read_end == 0 || start != _last_read_end || !_model_iter_valid) {
- DEBUG_TRACE (DEBUG::MidiSourceIO, string_compose ("*** %1 search for relevant iterator for %1 / %2\n", _name, source_start, start));
- for (i = _model->begin(0, false, filtered); i != _model->end(); ++i) {
- if (converter.to(i->time()) >= start) {
- DEBUG_TRACE (DEBUG::MidiSourceIO, string_compose ("***\tstop iterator search @ %1\n", i->time()));
+ // Find appropriate model iterator
+ Evoral::Sequence<Evoral::Beats>::const_iterator& i = _model_iter;
+ const bool linear_read = _last_read_end != 0 && start == _last_read_end;
+ if (!linear_read || !_model_iter_valid) {
+#if 0
+ // Cached iterator is invalid, search for the first event past start
+ i = _model->begin(converter.from(start), false, filtered,
+ linear_read ? &_model->active_notes() : NULL);
+ _model_iter_valid = true;
+ if (!linear_read) {
+ _model->active_notes().clear();
+ }
+#else
+ /* hot-fix http://tracker.ardour.org/view.php?id=6541
+ * "parallel playback of linked midi regions -> no note-offs"
+ *
+ * A midi source can be used by multiple tracks simultaneously,
+ * in which case midi_read() may be called from different tracks for
+ * overlapping time-ranges.
+ *
+ * However there is only a single iterator for a given midi-source.
+ * This results in every midi_read() performing a seek.
+ *
+ * If seeking is performed with
+ * _model->begin(converter.from(start),...)
+ * the model is used for seeking. That method seeks to the first
+ * *note-on* event after 'start'.
+ *
+ * _model->begin(converter.from( ) ,..) eventually calls
+ * Sequence<Time>::const_iterator() in libs/evoral/src/Sequence.cpp
+ * which looks up the note-event via seq.note_lower_bound(t);
+ * but the sequence 'seq' only contains note-on events(!).
+ * note-off events are implicit in Sequence<Time>::operator++()
+ * via _active_notes.pop(); and not part of seq.
+ *
+ * see also http://tracker.ardour.org/view.php?id=6287#c16671
+ *
+ * The linear search below assures that reading starts at the first
+ * event for the given time, regardless of its event-type.
+ *
+ * The performance of this approach is O(N), while the previous
+ * implementation is O(log(N)). This needs to be optimized:
+ * The model-iterator or event-sequence needs to be re-designed in
+ * some way (maybe keep an iterator per playlist).
+ */
+ for (i = _model->begin(); i != _model->end(); ++i) {
+ if (i->time().to_double() + (beat - start_beat) >= beat) {