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clarify midi-iterator comment

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Robin Gareus 2015-08-27 14:43:28 +02:00
parent b3e9231a4e
commit e2902a0b76
1 changed files with 9 additions and 5 deletions
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14
libs/ardour/midi_source.cc
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@ -218,18 +218,18 @@ MidiSource::midi_read (const Lock& lm,
* "parallel playback of linked midi regions -> no note-offs"
*
* A midi source can be used by multiple tracks simultaneously,
* in which case midi_read() can called from different tracks for
* 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.
* This results in every midi_read() performing a seek.
*
* if seeking is performed with
* 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(conveter.from( ) ,..) eventually calls
* _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(!).
@ -237,10 +237,14 @@ MidiSource::midi_read (const Lock& lm,
* via _active_notes.pop(); and not part of seq.
*
* see also http://tracker.ardour.org/view.php?id=6287#c16671
* and call 1-900-ardour-midi ($4.99/min)
*
* 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) {
const framecnt_t time_frames = converter.to(i->time());