Convenient classes for loading and analyzing midi files in Processing / java, using the Sequence Object

MIDI_Loader.pde

class MidiLoader {
/**
*loads a midi file from disk and stores all notes in a nested Array List, using the Helper class "Note"
* needs some cleanup though
*/
  ArrayList<ArrayList<Note>> tracks;
  long maxTicks = 0;
  final boolean DO_PRINT = false;

  MidiLoader(String fileName) {

    //Notes are stored in this nested array list to mirror the track-note structure (depending on type of midi file)
    tracks = new ArrayList<ArrayList<Note>>();
    Track[] trx;

    try {
      
      File myMidiFile = new File(dataPath(fileName));
      Sequence mySeq = MidiSystem.getSequence(myMidiFile);
      trx = mySeq.getTracks();

      for (int i = 0; i < trx.length; i++) {
        ArrayList<Note> trackAsList = new ArrayList<Note>();
        tracks.add(trackAsList);
        Track t = trx[i];
        if (DO_PRINT) {
          println("track ");
          println("length:"+ t.ticks());
          println("num events:" + t.size());
        }
        int counter = 0;
        //iterate over the vector, and remove each handled event.
        while (t.size () > 0 && counter < t.size()) {
          counter ++;
          if (t.get(0).getMessage() instanceof ShortMessage) {

            ShortMessage s = (ShortMessage)(t.get(0).getMessage());
            //find note on events
            if (s.getCommand() == ShortMessage.NOTE_ON) {
              if (DO_PRINT)println(s.getCommand() + " " + s.getChannel() +" " + s.getData1() + " " + s.getData2());              
              //store all the values temporarily in order to find the associated note off event
              long startTime = t.get(0).getTick();
              long endTime = 0;
              int ch = s.getChannel();
              int pitch = s.getData1();
              int vel = s.getData2();
              
              //if the first note has zero velocity (== noteOff), remove it
              if (vel == 0) {
                t.remove(t.get(0));
              } 
              
              else {
                //start to look for the associated note off
                for (int j = 0; j < t.size(); j++) {
                  if (t.get(j).getMessage() instanceof ShortMessage) {
                    ShortMessage s2 = (ShortMessage)(t.get(j).getMessage());
                    //two types to send a note off... either as a clean command or as note on with 0 velocity
                    if ((s2.getCommand() == ShortMessage.NOTE_OFF) || s2.getCommand() == ShortMessage.NOTE_ON) {
                      //compare to stored values, sending a note off with same channel and pitch means to stop the note
                      if (s2.getChannel() == ch && s2.getData1() == pitch && s2.getData2() == 0) {
                        //calculate note duration
                        endTime = t.get(j).getTick();
                        //extend maxticks, so we know when the last midi event happened (sometimes tracks are much longer than the last note
                        if (endTime > maxTicks)maxTicks = endTime;
                        //create a new "Note" instance, store it
                        Note n = new Note(startTime, endTime-startTime, ch, vel, pitch);
                        trackAsList.add(n);
                        t.remove(t.get(0));
                        break;
                      }
                    }
                  }
                }
              }
              //remove event when done
              t.remove(t.get(0));
            }
            else {
              //remove events which are shortmessages but not note on (e.g. control change)
              t.remove(t.get(0));
            }
          } 
          else {
            //remove events which are not of type short message
            t.remove(t.get(0));
          }
        }
      }
    }
    catch (Exception e) {
      e.printStackTrace();
    }
  }
  ArrayList<Note> trackAsArrayList(int i) {
    return tracks.get(i);
    // return null;
  }
  int numTracks() {
    return tracks.size();
  }
}

/**
*Helper Class Note, stores start time, end time, channel, pitch and duration
*/
class Note {
  long start;
  long duration;

  int channel;
  int velocity;
  int pitch;

  Note(long theStart, long theDuration, int theChannel, int theVelocity, int thePitch) {
    start = theStart;
    channel = theChannel;
    pitch = thePitch;
    velocity = theVelocity;
    duration = theDuration;
  }
}