Riproduzione di un tono arbitrario con Android



Answers

Migliorando il codice sopra:

Aggiungi ampiezza di accelerazione e decelerazione per evitare i clic.

Aggiungi il codice per determinare quando la puntina ha finito di giocare.

        double duration = 1;                // seconds
        double freqOfTone = 1000;           // hz
        int sampleRate = 8000;              // a number

        double dnumSamples = duration * sampleRate;
        dnumSamples = Math.ceil(dnumSamples);
        int numSamples = (int) dnumSamples;
        double sample[] = new double[numSamples];
        byte generatedSnd[] = new byte[2 * numSamples];


        for (int i = 0; i < numSamples; ++i) {      // Fill the sample array
            sample[i] = Math.sin(freqOfTone * 2 * Math.PI * i / (sampleRate));
        }

        // convert to 16 bit pcm sound array
        // assumes the sample buffer is normalized.
        // convert to 16 bit pcm sound array
        // assumes the sample buffer is normalised.
        int idx = 0;
        int i = 0 ;

        int ramp = numSamples / 20 ;                                    // Amplitude ramp as a percent of sample count


        for (i = 0; i< ramp; ++i) {                                     // Ramp amplitude up (to avoid clicks)
            double dVal = sample[i];
                                                                        // Ramp up to maximum
            final short val = (short) ((dVal * 32767 * i/ramp));
                                                                        // in 16 bit wav PCM, first byte is the low order byte
            generatedSnd[idx++] = (byte) (val & 0x00ff);
            generatedSnd[idx++] = (byte) ((val & 0xff00) >>> 8);
        }


        for (i = i; i< numSamples - ramp; ++i) {                        // Max amplitude for most of the samples
            double dVal = sample[i];
                                                                        // scale to maximum amplitude
            final short val = (short) ((dVal * 32767));
                                                                        // in 16 bit wav PCM, first byte is the low order byte
            generatedSnd[idx++] = (byte) (val & 0x00ff);
            generatedSnd[idx++] = (byte) ((val & 0xff00) >>> 8);
        }

        for (i = i; i< numSamples; ++i) {                               // Ramp amplitude down
            double dVal = sample[i];
                                                                        // Ramp down to zero
            final short val = (short) ((dVal * 32767 * (numSamples-i)/ramp ));
                                                                        // in 16 bit wav PCM, first byte is the low order byte
            generatedSnd[idx++] = (byte) (val & 0x00ff);
            generatedSnd[idx++] = (byte) ((val & 0xff00) >>> 8);
        }

        AudioTrack audioTrack = null;                                   // Get audio track
        try {
            audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
                    sampleRate, AudioFormat.CHANNEL_CONFIGURATION_MONO,
                    AudioFormat.ENCODING_PCM_16BIT, (int)numSamples*2,
                    AudioTrack.MODE_STATIC);
            audioTrack.write(generatedSnd, 0, generatedSnd.length);     // Load the track
            audioTrack.play();                                          // Play the track
        }
        catch (Exception e){
            RunTimeError("Error: " + e);
            return false;
        }

        int x =0;
        do{                                                     // Montior playback to find when done
             if (audioTrack != null) 
                 x = audioTrack.getPlaybackHeadPosition(); 
             else 
                 x = numSamples;            
        }while (x<numSamples);

        if (audioTrack != null) audioTrack.release();           // Track play done. Release track.
Question

C'è un modo per far sì che Android emetta un suono di frequenza arbitraria (cioè, non voglio avere file audio preregistrati)?

Mi sono guardato intorno e ToneGenerator era l'unica cosa che riuscivo a trovare che fosse anche vicino, ma sembra essere in grado di emettere solo i toni DTMF standard.

Qualche idea?




Codice modificato basato sulla risposta di Singhaks

public class MainActivity extends Activity {
    private final int duration = 30; // seconds
    private final int sampleRate = 8000;
    private final int numSamples = duration * sampleRate;
    private final double sample[] = new double[numSamples];
    private final double freqOfTone = 440; // hz
    private final byte generatedSnd[] = new byte[2 * numSamples];
    Handler handler = new Handler();
    private AudioTrack audioTrack;
    private boolean play = false;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
                8000, AudioFormat.CHANNEL_OUT_MONO,
                AudioFormat.ENCODING_PCM_16BIT, numSamples,
                AudioTrack.MODE_STREAM);
    }

    @Override
    protected void onResume() {
        super.onResume();

        // Use a new tread as this can take a while
        Thread thread = new Thread(new Runnable() {
            public void run() {

                handler.post(new Runnable() {

                    public void run() {
                        playSound();
                        genTone();
                    }
                });
            }   
        });
        thread.start();
    }

    void genTone(){
        // fill out the array
        while(play){
                for (int i = 0; i < numSamples; ++i) {
                //  float angular_frequency = 
                    sample[i] = Math.sin(2 * Math.PI * i / (sampleRate/freqOfTone));
                }
                int idx = 0;

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


    void playSound(){
        play = true;
        audioTrack.play();
    }
}









Do major (16 note)

 public class MainActivity extends AppCompatActivity {

  private double mInterval = 0.125;
  private int mSampleRate = 8000;
  private byte[] generatedSnd;

  private final double mStandardFreq = 440;

  Handler handler = new Handler();
  private AudioTrack audioTrack;


  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
  }

  @Override
  protected void onResume() {
    super.onResume();

    // Use a new tread as this can take a while
    final Thread thread = new Thread(new Runnable() {
        public void run() {

            byte[] tempByte = new byte[0];
            for (int i = 0; i < 16 ; i++ ){
                double note = getNoteFrequencies(i);
                byte[] tonByteNote = getTone(mInterval, mSampleRate, note);
                tempByte = concat(tonByteNote, tempByte);
            }
            generatedSnd = tempByte;

            handler.post(new Runnable() {
                public void run() {
                    playTrack(generatedSnd);
                }
            });
        }
    });
    thread.start();
  }

  public byte[] concat(byte[] a, byte[] b) {
    int aLen = a.length;
    int bLen = b.length;
    byte[] c= new byte[aLen+bLen];
    System.arraycopy(a, 0, c, 0, aLen);
    System.arraycopy(b, 0, c, aLen, bLen);
    return c;
  }

  private double getNoteFrequencies(int index){
    return mStandardFreq * Math.pow(2, (double) index/12.0d);
  }

  private byte[] getTone(double duration, int rate, double frequencies){

    int maxLength = (int)(duration * rate);
    byte generatedTone[] = new byte[2 * maxLength];

    double[] sample = new double[maxLength];
    int idx = 0;

    for (int x = 0; x < maxLength; x++){
        sample[x] = sine(x, frequencies / rate);
    }


    for (final double dVal : sample) {

        final short val = (short) ((dVal * 32767));

        // in 16 bit wav PCM, first byte is the low order byte
        generatedTone[idx++] = (byte) (val & 0x00ff);
        generatedTone[idx++] = (byte) ((val & 0xff00) >>> 8);

    }

    return generatedTone;
}

  private AudioTrack getAudioTrack(int length){

    if (audioTrack == null)
        audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
                mSampleRate, AudioFormat.CHANNEL_OUT_MONO,
                AudioFormat.ENCODING_PCM_16BIT, length,
                AudioTrack.MODE_STATIC);

    return audioTrack;
  }

  private double sine(int x, double frequencies){
    return Math.sin(  2*Math.PI * x * frequencies);
  }

  void playTrack(byte[] generatedSnd){
    getAudioTrack(generatedSnd.length)
            .write(generatedSnd, 0, generatedSnd.length);
    audioTrack.play();
  }

}



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