Can I get TrackChunks from NotesPlaybackStarted event?

[garcon33]

Hi, I'm a compete beginner of drywetmidi!
I'd like to get the note information at real time when it's played, but don't know how to check on which trackchunk the note is.

I can access to TrackChunk from MidiFile object, but cannot do it from NotesEventArgs.

For example, what I'd like to do is as follows:

void StartMidi()
{
     MidiFile midifile = MidiFile.Read(filepath);
     OutputDevice outputdevice = OutputDevice.GetByIndex(0);
     Playback playback = midifile.GetPlayback(outputdevice);
     playback.NotesPlaybackStarted += OnNotesStarted;
     playback.Start();
}

void OnNotesStarted(object sender, NotesEventArgs e)
{
     // Print note information here
     foreach (var n in e.Notes.ToList())
     {
        Debug.Log("****************");
        Debug.Log("Time: " + n.Time);
        Debug.Log("NoteNumber: " + n.NoteNumber);
        Debug.Log("Velocity: " + n.Velocity);
        Debug.Log("OffVelocity: " + n.OffVelocity);
        Debug.Log("Channel: " + n.Channel);
        Debug.Log("Octave: " + n.Octave.ToString());
        Debug.Log("Length: " + n.Length);
        Debug.Log("NoteName: " + n.NoteName.ToString());
        Debug.Log("****************");
        
        ////////////////////////////////////////////////////////
        // **** Want to display the track ID here too! ****
       ////////////////////////////////////////////////////////
     }
}

I'd be so glad if someone could help me!

Many thanks!!
Yj

[melanchall]

Hi,

First of all, you have a big problem in your code:

     Playback playback = midifile.GetPlayback(outputdevice);
     playback.NotesPlaybackStarted += OnNotesStarted;
     playback.Start();
}

What do you think will happen when the program leaves the method? Yes, all local variables will be cleaned up by the garbage collector. And thus playback won't work (or will work some small time). You need to define playback field and use Playback via class field and not via local variable. The same problem with outputDevice.

Well, as for knowing of track chunk – there is no simple way. But there is a workaround. First, create this class:

private sealed class TimedEventWithTrackChunkIndex : TimedEvent, IMetadata
{
    public TimedEventWithTrackChunkIndex(MidiEvent midiEvent, long time, int trackChunkIndex)
        : base(midiEvent, time)
    {
        Metadata = trackChunkIndex;
    }

    public object Metadata { get; set; }

    public override TimedEvent Clone()
    {
        return new TimedEventWithTrackChunkIndex(Event, Time, Convert.ToInt32(Metadata));
    }
}

And create playback with this code:

var timedEvents = midiFile
    .GetTrackChunks()
    .SelectMany((c, i) => c.GetTimedEvents().Select(e => new TimedEventWithTrackChunkIndex(e.Event, e.Time, i)))
    .OrderBy(e => e.Time);

var tempoMap = midiFile.GetTempoMap();

playback = new Playback(timedEvents, tempoMap);

And now you can get track chunk index in the OnNotesStarted:

////////////////////////////////////////////////////////
// **** Want to display the track ID here too! ****
////////////////////////////////////////////////////////
var metadata = (IMetadata)note.GetTimedNoteOnEvent();
var trackChunkIndex = Convert.ToInt32(metadata.Metadata);

[garcon33]

Hi melanchall,

Thank you so much for your advice and nice solution!
It works like a charm!:)

I just added outputdevice here to play sound:
playback = new Playback(timedEvents, tempoMap, outputdevice);

I declared playback and outputdevice as global variables under the class.

Thanks again!!