Question

I’m trying to create an app that generates a tone depending on where you touch on the screen (currently the frequency is determined by the y value of the touch point) however I’m not able to generate a tone of less than a second without crashing my app! I took the code from the answer here and tweaked it to play when i touch the screen, but when I change the duration variable to a value of less than 1 the app crashes! Is it possible to generate a tone of less than 1 second?

The only reason I want to create a tone of less than a second is that the audio player does not seem to cut off straight away when i pause or stop the audiotrack. these are my methods for playing and generating the tone:

RelativeLayout background;
SoundPool soundPool;
TextView textView;


private final float duration = 1f; // seconds
private final int sampleRate = 8000;//was 8000
private final int numSamples = (int) duration * sampleRate;
private final double sample[] = new double[numSamples];
private final double freqOfTone = 250; // hz

AudioTrack audioTrack ;

int dispWidth = 0, dispHeight = 0;

Handler handler = new Handler();

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_audio);
    background = (RelativeLayout) findViewById(R.id.background);
    textView = (TextView) findViewById(R.id.textView2);
    soundPool = new SoundPool(1, AudioManager.STREAM_MUSIC, 0);
    dispWidth = AppHelper.getDisplayWidth(getApplicationContext());
    dispHeight = AppHelper.getDisplayHeight(getApplicationContext());
    audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
            sampleRate, AudioFormat.CHANNEL_OUT_MONO,
            AudioFormat.ENCODING_PCM_16BIT, numSamples,
            AudioTrack.MODE_STREAM);
    final byte genTone[]= genTone(freqOfTone);

    background.setClickable(true);



         background.setOnTouchListener(new OnTouchListener() {

          @Override
         public boolean onTouch(View v, MotionEvent event) {
        if(event.getAction()==MotionEvent.ACTION_UP)
            {
                Log.d(LOG_TAG, "Touch up! Stopping tone...");
                audioTrack.pause();
                audioTrack.flush();

            }
            else
            {
                //these apparently cause immediate stop
                audioTrack.pause();
                audioTrack.flush();

                int R = (int) (event.getY()%255);
                int G =  (int)(event.getX()%255);
                int B = (int) ((event.getY()+event.getX())%255);
                Log.i(LOG_TAG, "Changine colour to "+R+","+G+","+B);
                background.setBackgroundColor(Color.rgb(R, G, B));
                int colorFromPressure = (int) (event.getPressure()*255);
                textView.setTextColor(Color.rgb(colorFromPressure,colorFromPressure,colorFromPressure));
                playSoundAtFrequency(250+event.getY(), event.getX()/dispWidth);
            }
            return false;
    }
     });
}

byte[] genTone(double toneFrequency){
    final byte generatedSnd[] = new byte[2 * numSamples];
    // fill out the array
    for (int i = 0; i < numSamples; ++i) {
        sample[i] = Math.sin(2 * Math.PI * i / (sampleRate/toneFrequency));
    }

    // convert to 16 bit pcm sound array
    // assumes the sample buffer is normalised.
    int idx = 0;
    for (double dVal : sample) {
        short val = (short) (dVal * 32767);
        generatedSnd[idx++] = (byte) (val & 0x00ff);
        generatedSnd[idx++] = (byte) ((val & 0xff00) >>> 8);
    }
    return generatedSnd;
}


void playSound(final byte[] generatedSnd, float volume){        

    //these apparently cause immediate stop
    audioTrack.pause();
    audioTrack.flush();

    audioTrack.write(generatedSnd, 0, numSamples);
    audioTrack.setStereoVolume(volume, volume);


    audioTrack.play();
    Log.d(LOG_TAG, "Playing tone...");
}

public void playSoundAtFrequency(final double toneFrequency,float volume)
{

    final byte genTone[]= genTone(toneFrequency);
    playSound(genTone, volume);

}

Answer 1

I think your crash is coming from using a buffer size that is too small for the AudioTrack you are trying to create.

int audioBufferSize = AudioTract.getMinBufferSize(sampleRate,
                                                  AudioFormat.CHANNEL_OUT_MONO,
                                                  AudioFormat.ENCODING_PCM-16BIT);
audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
        sampleRate, AudioFormat.CHANNEL_OUT_MONO,
        AudioFormat.ENCODING_PCM_16BIT, audioBufferSize,
        AudioTrack.MODE_STREAM);

Then numSamples still applies to your generating buffer and the AudioTrack will have the buffer size it wants.