Tocando um tom arbitrário com Android

Existe alguma maneira de fazer o Android emitir um som de frequência arbitrária (ou seja, não quero ter arquivos de som pré-gravados)?

Eu olhei em volta e ToneGenerator foi a única coisa que consegui encontrar que estava ainda perto, mas parece ser capaz de emitir apenas os tons DTMF padrão.

Alguma ideia?

Eu originalmente encontrei este código de exemplo em um blog, mas ele tinha alguns bugs que geravam alguns sons horríveis. Corrigi os bugs e postei o código resultante aqui. Parece funcionar bem para mim!

public class PlaySound extends Activity {
    // originally from http://marblemice.blogspot.com/2010/04/generate-and-play-tone-in-android.html
    // and modified by Steve Pomeroy <[email protected]>
    private final int duration = 3; // 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();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.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() {
                genTone();
                handler.post(new Runnable() {

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

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

        // convert to 16 bit pcm sound array
        // assumes the sample buffer is normalised.
        int idx = 0;
        for (final double dVal : sample) {
            // 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);

        }
    }

    void playSound(){
        final AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
                sampleRate, AudioFormat.CHANNEL_OUT_MONO,
                AudioFormat.ENCODING_PCM_16BIT, generatedSnd.length,
                AudioTrack.MODE_STATIC);
        audioTrack.write(generatedSnd, 0, generatedSnd.length);
        audioTrack.play();
    }
}

Melhorando o código acima:

Adicione amplitude de aumento e redução para evitar os cliques.

Adicione o código para determinar quando a tacada terminou de tocar.

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{                                                              // Monitor 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.

Eu envolvi as soluções maravilhosas acima em um pequeno pacote que é mais utilizável fora da caixa como uma campainha configurável simples. Ele o executa em um thread de segundo plano e tem métodos de parar e reproduzir e um punhado de opções que você pode definir.

Ele está no JCenter para que você possa adicioná-lo à sua lista de dependências assim

compile 'net.mabboud:android-tone-player:0.2'

e você o usa assim para uma campainha contínua

ContinuousBuzzer tonePlayer = new ContinuousBuzzer();
tonePlayer.play();

// just an example don't actually use Thread.sleep in your app
Thread.sleep(1000); 
tonePlayer.stop();

ou uma campainha tocada apenas uma vez e você pode definir a frequência e o volume como este

OneTimeBuzzer buzzer = new OneTimeBuzzer();
buzzer.setDuration(5);

// volume values are from 0-100
buzzer.setVolume(50);
buzzer.setToneFreqInHz(110);

Postagem estendida do blog aqui sobre isso aqui GitHub aqui

Como há um bug em algumas versões mais antigas do Android que causa um vazamento de memória ao usar MODE_STATIC, modifiquei a resposta do Xarph acima para usar MODE_STREAM. Espero que ajude alguns.

public void playTone(double freqOfTone, double duration) {
 //double duration = 1000;                // 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 {
         int bufferSize = AudioTrack.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, bufferSize,
                AudioTrack.MODE_STREAM);
        audioTrack.play();                                          // Play the track
        audioTrack.write(generatedSnd, 0, generatedSnd.length);     // Load the track
    }
    catch (Exception e){
    }
    if (audioTrack != null) audioTrack.release();           // Track play done. Release track.
}

Aqui está outro blog demonstrando um sintetizador simples mais alguma interface do usuário

http://audioprograming.wordpress.com/2012/10/18/a-simple-synth-in-android-step-by-step-guide-using-the-java-sdk/

Você também pode estar interessado em csound ou pdlib (pure data lib) para Android.

Código modificado com base na resposta de 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();
    }
}

    float synth_frequency = 440;
    int minSize = AudioTrack.getMinBufferSize(SAMPLE_RATE,
AudioFormat.CHANNEL_OUT_MONO,
AudioFormat.ENCODING_PCM_16BIT);
AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
SAMPLE_RATE,
AudioFormat.CHANNEL_OUT_MONO,
AudioFormat.ENCODING_PCM_16BIT,
minSize,
AudioTrack.MODE_STREAM);
audioTrack.play();
short[] buffer = new short[minSize];
float angle = 0;
while (true) 
{
    if (play)
    {
        for (int i = 0; i < buffer.length; i++)
        {
            float angular_frequency =
            (float)(2*Math.PI) * synth_frequency / SAMPLE_RATE;
            buffer[i] = (short)(Short.MAX_VALUE * ((float) Math.sin(angle)));
            angle += angular_frequency;
    }
        audioTrack.write(buffer, 0, buffer.length);
    } 

// Você pode adicionar um valor arbitrário em synth_frequency para mudar o som, por exemplo, você pode adicionar uma variável aleatória para obter o som

Faça maior (16 notas)

 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();
  }

}

veja esta biblioteca útil

https://github.com/karlotoy/perfectTune

é fácil de usar

adicione isso às suas dependências

 compile 'com.github.karlotoy:perfectTune:1.0.2'

E você o usa assim:

PerfectTune perfectTune = new PerfectTune();
perfectTune.setTuneFreq(desire_freq);
perfectTune.playTune();

para parar a melodia:

perfectTune.stopTune();

Existem vários programas para isso, mas eles são uma merda. Eu medi alguns:

http://www.endolith.com/wordpress/2009/11/24/android-audio-applications/

Portanto, não faça o que eles fazem. : D