TempoEvent Parsing Issue

Yorgg commented 5 years ago

Hello,

I am using Logic Pro X 10.0.0 to create piano midi files.

Each of these files has a single tempo, and it is found in the last midi event (as a tempo-change event).

I used these midi files in another program, and the playback was fine. However, Drywetmidi does not seem to correctly parse them and always uses the default (120bpm) tempo.

For a quick fix (untested) I modified the CollectTempoChanges() method in TempoMapManager.cs

 private void CollectTempoChanges()
        {
            int count = 0;
            var lastEvent = _timedEventsManagers.SelectMany(m => m.Events).Last();

            foreach (var tempoEvent in GetTimedEvents(IsTempoEvent))
            {
                count += 1;

                var setTempoEvent = tempoEvent.Event as SetTempoEvent;

                if (setTempoEvent == null)
                    continue;

                // if:
                //   - the last event in the midi file is the tempo event, and
                //   - there is only one tempo event, 
                // then make the time of the tempo event = 0

                // this is so if the last event is the tempo event 
                // we capture that tempo for the entire file 
                // (a fix for Logic Pro X) 

                bool oneTempoChangeAndIsLastEvent = count == 1 && lastEvent == tempoEvent;
                long time = oneTempoChangeAndIsLastEvent ? 0 : tempoEvent.Time;

                TempoMap.Tempo.SetValue(time, new Tempo(setTempoEvent.MicrosecondsPerQuarterNote));
            }
        }

I also attached an example midi file, which was exported from Logic Pro X 10.0.0: prelude_124bpm.mid.zip