Android Open Source - Modulo Oscillator

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License

The source code is released under:

GNU General Public License

Java Source Code

package com.modulo;
//from w  w w .j ava  2 s .co m
import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;

public class Oscillator {

  public Oscillator() {
    // 440hz = "concert A", standard pitch
    frequency = 440;
    volume = 50;
    isPlaying = false;
    bufferSize = AudioTrack.getMinBufferSize(sampleRate, AudioFormat.CHANNEL_OUT_MONO,
        AudioFormat.ENCODING_PCM_16BIT);

    buffer = new short[bufferSize];
    sample = new short[sampleRate];

    audioTrack = initializeAudioTrack();

    // Waveform arrays
    sqr = new short[sampleRate];
    sin = new short[sampleRate];
    tri = new short[sampleRate];
    saw = new short[sampleRate];

    // Pre-generates the lookup tables for each waveform, allows instant
    // waveform switching
    sqr = generateSqr();
    sin = generateSin();
    tri = generateTri();
    saw = generateSaw();

    // Sine wave is default
    sample = sin;
  }

  public void pause() {
    // Checks if audioTrack is initialized and if so, immediately pauses and
    // flushes the audio data
    if (audioTrack.getState() == AudioTrack.STATE_INITIALIZED) {
      setIsPlaying(false);
      audioTrack.pause();
      audioTrack.flush();
    }
  }

  // Sets up an AudioTrack
  public AudioTrack initializeAudioTrack() {
    AudioTrack returnTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
        sampleRate, AudioFormat.CHANNEL_OUT_MONO,
        AudioFormat.ENCODING_PCM_16BIT, buffer.length,
        AudioTrack.MODE_STREAM);
    Float scaled = (float)(volume/100.0f);
    returnTrack.setStereoVolume(AudioTrack.getMaxVolume() * scaled, AudioTrack.getMaxVolume() * scaled);

    return returnTrack;
  }

  public void play() {
    if (audioTrack.getState() != AudioTrack.STATE_INITIALIZED) {
      audioTrack = initializeAudioTrack();
    }

    setIsPlaying(true);
    fillBuffer();
    audioTrack.play();
  }

  public void stop() {
    if (audioTrack.getState() == AudioTrack.STATE_INITIALIZED) {
      setIsPlaying(false);
      audioTrack.pause();
      audioTrack.flush();
      audioTrack.release();
    }
  }

  public void setFreq(int freq) {
    frequency = freq;
  }

  public int getFreq() {
    return frequency;
  }

  public void setIsPlaying(boolean boo) {
    isPlaying = boo;
  }

  public boolean getIsPlaying() {
    return isPlaying;
  }

  public void setVolume(int vol) {
    volume = vol;
    Float scaled = (float) (volume / 100.0f);
    audioTrack.setStereoVolume(AudioTrack.getMaxVolume() * scaled, AudioTrack.getMaxVolume() * scaled);
  }

  public int getVolume() {
    return volume;
  }

  // Generates the sine wave lookup table
  private short[] generateSin() {
    short[] returnArray = new short[sampleRate];
    for (int i = 0; i < sampleRate; i++) {
      returnArray[i] = (short) ((float) Short.MIN_VALUE * (Math.sin((2.0f * (float) Math.PI * ((float) i))
          / ((float) sampleRate))));
    }
    return returnArray;
  }

  // Generates the sawtooth wave lookup table
  private short[] generateSaw() {
    short[] returnArray = new short[sampleRate];
    for (int i = 0; i < sampleRate; i++) {
      returnArray[i] = (short) ((float) Short.MIN_VALUE + (((float) i * (2.0f * (float) Short.MAX_VALUE)) / (float) sampleRate));
    }
    return returnArray;
  }

  // Generates the triangle wave lookup table
  private short[] generateTri() {
    short[] returnArray = new short[sampleRate];
    for (int i = 0; i < sampleRate; i++) {
      // First quarter of the waveform lookup table
      if (i < (sampleRate / 4)) {
        returnArray[i] = (short) (((float) i * (4.0f * (float) Short.MAX_VALUE)) / (float) sampleRate);
      }
      // Last quarter of the waveform lookup table
      else if (i > (3 * (sampleRate / 4))) {
        returnArray[i] = (short) ((((float) i * (4.0f * (float) Short.MAX_VALUE)) / (float) sampleRate) - 2.0f * Short.MAX_VALUE);
      }
      // Middle two sections of the waveform lookup table
      else {
        returnArray[i] = (short) ((float) 2.0f * Short.MAX_VALUE - (((float) i * (4.0f * (float) Short.MAX_VALUE)) / (float) sampleRate));
      }
    }
    return returnArray;
  }

  // Generates the square wave lookup table
  private short[] generateSqr() {
    short[] returnArray = new short[sampleRate];
    // The square wave is represented by two values (Short.MAX_VALUE and
    // Short.MIN_VALUE)
    // with the max value for the first half of the waveform, and the min
    // for the second
    for (int i = 0; i < sampleRate; i++) {
      if (i < (sampleRate / 2)) {
        returnArray[i] = Short.MAX_VALUE;
      }
      else {
        returnArray[i] = Short.MIN_VALUE;
      }
    }
    return returnArray;
  }

  public void fillBuffer() {
    for (int i = 0; i < buffer.length; i++) {
      // Causes phase to wrap around to the front of the lookup table
      // when it exceeds its length
      phase %= sample.length;

      // Sets the short at buffer[i] to the value found in the lookup
      // table
      // of the current waveform sample
      buffer[i] = sample[phase];

      // Increments the phase by the current frequency, allowing it to
      // step
      // through the table at the correct speed and resulting in a change
      // of pitch
      phase += frequency;
    }

    // Writes the buffer to the audioTrack
    audioTrack.write(buffer, 0, buffer.length);
  }

  // Changes the waveform
  public void setWave(int pos) {
    switch (pos) {
    case 0:
      sample = sin;
      break;
    case 1:
      sample = saw;
      break;
    case 2:
      sample = sqr;
      break;
    case 3:
      sample = tri;
      break;
    default:
      sample = sin;
      break;
    }
  }

  private int frequency;
  public static final int MAX_FREQUENCY = 20000;
  public static final int MIN_FREQUENCY = 20;
  private boolean isPlaying;
  private AudioTrack audioTrack;
  private int volume;
  private final int sampleRate = 44100;
  private int bufferSize;
  private short[] sample, buffer, sin, sqr, tri, saw;
  private int phase;
}

Java Source Code List

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