Android Open Source - Music-Theory Midi Track

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From Project

Back to project page Music-Theory.

License

The source code is released under:

GNU General Public License

Java Source Code

package com.mt.audio;
/*from w w  w.  j  a  v a  2  s . c  o m*/
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Vector;

public class MidiTrack {

  private static final int[] FOOTER = new int[] {
    0x01, 0xFF, 0x2F, 0x00 };

  private static final int[] HEADER = new int[] {
    0x4d, 0x54, 0x68, 0x64, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x01, 0x00, 0x10, 0x4d, 0x54, 0x72, 0x6B };

  private static final int[] KEY_SIGNATURE = new int[] {
    0x00, 0xFF, 0x59, 0x02, 0x00, 0x00 };
  private static final int MICROSECONDS_PER_MINUTE = 60000000;

  private static final int[] TIME_SIGNATURE = new int[] {
    0x00, 0xFF, 0x58, 0x04, 0x04, 0x02, 0x30, 0x08 };

  protected static byte[] intArrayToBytes(int[] data) {
    byte[] out = new byte[data.length];
    for (int i = 0; i < data.length; i++) {
      out[i] = (byte) data[i];
    }
    return out;
  }

  protected Vector<int[]> playEvents;

  public MidiTrack() {
    playEvents = new Vector<int[]>();
  }

  public void noteOff(int delta, int pitch) {
    playEvents.add(new int[] {delta, 0x80, pitch, 0x0});
  }

  public void noteOn(int delta, int pitch, int velocity) {
    playEvents.add(new int[] {delta, 0x90, pitch, velocity});
  }

  public void addNote(int duration, int pitch, int velocity) {
    noteOn(0x0, pitch, velocity);
    noteOff(duration, pitch);
  }

  public void progChange(int program) {
    playEvents.add(new int[] {0x0, 0xC0, program});
  }

  public void setBPM(int bpm) {
    int mpqn = MICROSECONDS_PER_MINUTE / bpm;
    if (mpqn > 8355711) {
      mpqn = 8355711;
    } else if (mpqn < 100000) {
      mpqn = 100000;
    }

    int tempoEvent[] = new int[7];
    tempoEvent[0] = 0x00;
    tempoEvent[1] = 0xFF;
    tempoEvent[2] = 0x51;
    tempoEvent[3] = 0x03;
    for (int i = 0; i < 3; i++) {
      int offset = (2 - i) * 8;
      tempoEvent[i + 4] = (byte) ((mpqn >>> offset) & 0xFF);
    }

    playEvents.add(tempoEvent);
  }

  public void writeToFile(String filename, File directory) throws IOException {
    File file = new File(directory, filename);

    FileOutputStream out = new FileOutputStream(file, false);

    out.write(intArrayToBytes(HEADER));

    int size = KEY_SIGNATURE.length + TIME_SIGNATURE.length + FOOTER.length;

    for (int i = 0; i < playEvents.size(); i++)
      size += playEvents.elementAt(i).length;

    int high = size / 256;
    int low = size - (high * 256);
    out.write((byte) 0);
    out.write((byte) 0);
    out.write((byte) high);
    out.write((byte) low);

    out.write(intArrayToBytes(KEY_SIGNATURE));
    out.write(intArrayToBytes(TIME_SIGNATURE));

    for (int i = 0; i < playEvents.size(); i++) {
      out.write(intArrayToBytes(playEvents.elementAt(i)));
    }

    out.write(intArrayToBytes(FOOTER));
    out.close();
  }
}

Java Source Code List

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