Equalizer setEnabled returns invalid operation error

Question

I'm trying to create a simple equalizer for my music player application, following the AudioFxDemo I've created a simple activity in witch I've 4 different seekbars that should change the volumes of some bands. For now I have my MediaPlayer and Equalizer instantiated in the MainActivity that calls my EqualizerActivity, I've set the equalizer variable as a public static so that I can get it into my EqualizerActivity.

//MediaPlayer
        mp = new MediaPlayer();
        equalizer = new Equalizer(0, mp.getAudioSessionId());
        int val = equalizer.setEnabled(true);
        if(val != Equalizer.SUCCESS)
            Log.v("A", "EQUALIZER NON ATTIVO");
        setVolumeControlStream(AudioManager.STREAM_MUSIC);

My problem is that the equalizer.setEnabled(true) returns ERROE_INVALID_OPERATION (-5) instead of SUCCESS, at this point I've got the code working but I can't use the equalizer. I really don't know what's the problem, but I think it could be that I'm setting the equalizer as static, is the another way to pass the equalizer to the EqualizerActivity?

public class EqualizerActivity extends Activity {

private Equalizer equalizer;

@Override
public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    equalizer = MainActivity.equalizer; //preso dall'activity -> sempre attivo
    int val = equalizer.setEnabled(true);
    if(val != Equalizer.SUCCESS)
        Log.v("A", "EQUALIZER NON ATTIVO " + val);
    setupEqualizerFXandUI();

}


//generato dinamicamente a seconda delle bande percepite
private void setupEqualizerFXandUI()
{
    TextView eqTextView = new TextView(this);
    eqTextView.setText("Equalizer:");
    LinearLayout ll = new LinearLayout(this);
    ll.setOrientation(LinearLayout.VERTICAL);
    ll.addView(eqTextView);

    setContentView(ll);

     short bands = equalizer.getNumberOfBands();
     final short minEQLevel = equalizer.getBandLevelRange()[0];
     final short maxEQLevel = equalizer.getBandLevelRange()[1];

     for(short i = 0; i< bands; i++)
     {
         final short band = i;
         //Log.v("A", "B "+ band);
         TextView freqTv = new TextView(this);
         freqTv.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
         freqTv.setGravity(Gravity.CENTER_HORIZONTAL);
         freqTv.setText((equalizer.getCenterFreq(band) /1000) + " Hz");
         ll.addView(freqTv);

         LinearLayout row = new LinearLayout(this);
         row.setOrientation(LinearLayout.HORIZONTAL);

         TextView minDbTv = new TextView(this);
         minDbTv.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
         minDbTv.setText((minEQLevel / 100) + " dB");

         TextView maxDbTv = new TextView(this);
         maxDbTv.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
         maxDbTv.setText((maxEQLevel / 100) + " dB");

         LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
         layoutParams.weight = 1;

         SeekBar bar = new SeekBar(this);
         bar.setLayoutParams(layoutParams);
         bar.setMax(maxEQLevel - minEQLevel);
         bar.setProgress(equalizer.getBandLevel(band)); // Volume della banda

         bar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onProgressChanged(SeekBar seekBar, int progress,
                    boolean fromUser) {
                equalizer.setBandLevel(band, (short)(progress + minEQLevel));
                Log.v("A", "LEVEL: " + (progress + minEQLevel));
            }
        });

         row.addView(minDbTv);
         row.addView(bar);
         row.addView(maxDbTv);

         ll.addView(row);

     }

}

}

In the MainActivity I release the equalizer:

public void onDestroy()
{
        super.onDestroy();

        if(mNotify != null)
            mNotify.cancel(001);
        if(mHandler != null)
            mHandler.removeCallbacks(mUpdateTimeTask); //rimuovo il thread che aggiorna la seekbar
        if(mp != null){
            mp.release(); //rilascio il media player
        }
        if(equalizer != null)
            equalizer.release();
        if(bassboost != null)
            bassboost.release();
}

Answer 1

Ok, seems like that n7player (a music application I'm using) had a process that took the equalizer with the highest priority (I think). Closing the n7player process I'm able to use the equalizer and the bass booster.

Answer 2

the priority – an equalizer engine can be shared by a number of apps. Each app provides a priority when they create their equalizer object. The app with the highest priority controls the engine.

But i am unable to find a way to set my Equalizer with highest priority.Let me know if someone find a solution.

Edit

I think i find a solution.but i haven't tested it yet.

@Override
protected void onResume() {
    super.onResume();
    if (mEqualizer.hasControl() == false) {
        prepareEqualizer();//force re-gaining control
    }
}