Play music synchronous using 3 MediaPlayer Objects on Android/Eclipse

Question

What i have: I have implemented three MediaPlayer.Objects in my App. All Three are created using a thread:

protected void onResume() {
    // Threads
    mTT1 = new TrackThread(this, R.raw.audiofile1, 1, mHandler);
    mTT2 = new TrackThread(this, R.raw.audiofile2, 2, mHandler);
    mTT3 = new TrackThread(this, R.raw.audiofile3, 3, mHandler);
    // start thread
    mTT1.start();
    mTT2.start();
    mTT3.start();
    super.onResume();
}

"simplified" Code in the Thread for creating:

public class TrackThread extends Thread implements OnPreparedListener {
...
...
...
 public void run() {
    super.run();
            try {
                mMp.setDataSource(afd.getFileDescriptor(),
                        afd.getStartOffset(), afd.getDeclaredLength());
                mMp.prepare();
            } catch (IllegalArgumentException | IllegalStateException
                    | IOException e) {
                Log.e(TAG, "Unable to play audio queue do to exception: "
                        + e.getMessage(), e);
            }
      }

As I read in several Tutorials the "prepare()" methode takes a little bit of time to finish. Therefore i implemented a "Waiting loop" which waits until all MPs are prepared and created.

When "prepare and create" are done i enable the Start button and i want to start all 3 Mediaplayers SIMULTANEOUSLY.

I again use a Thread for dooing so:

public void onClick(View v) {
    // Button 1
    if (mBtn.getId() == v.getId()) {
                mTT1.startMusic();
                mTT2.startMusic();
                mTT3.startMusic();
    }

Code in the thread:

public class TrackThread extends Thread implements OnPreparedListener {
...
...
...

// start
public void startMusic() {
    if (mMp == null)
        return;
    mMp.start();
}

Please note that the code above is not the full code, but it should be enough to define my problem.

What i want, My problem:

All MPs should play their Music in Sync, unfortunately sometimes when i start the music, there is a time delay between them.

The MPs must start at the exact same time as the 3Audio-files must be played simultaneously (and exactly in sync)

What i have already tried:

+) using SoundPool: My Audio-files are to big(5Megabyte and larger) for SoundPool

+) seekTo(msec): i wanted to seek every MP to a Specific time: eg.: 0, but this did not solve the problem.

+) to reach more Programmers i also asked this question on: coderanch.com

I hope somebody can help me!

Thanks in advance

Answer 1

As nobody could help me I found a solution on my own. MediaPlayer did not fulfill my requirements but Android JETPlayer in combination with JETCreator did.

CAUTION: Installing Python for using JETCreator is very tricky, therfore follow this tutorial. And be careful with the versions of python and wxpython, not all versions support the JETCreator.

I used:

• Python Version 2.5.4 (python-2.5.4.msi)
• wxPython 2.8 (wxPython2.8-win32-unicode-2.8.7.1-py25.exe)

For those who do not know how to implement the Jetplayer watch this video (at min.5 he starts with programming the Jetplayer). Unfortunately I do not speak French so I just followed the code which worked for me.

Using Android JETCreator you can create your own JET Files and use them as your resource.

Useful links:

• Demo data

• Manual

• Code/class

Answer 2

The bottleneck here will certainly be preparing the mediaplayers to play. The Android framework provides an asynchronous method to perform this loading, and so with a bit of synchronization code you should be able to get these audio sources to play at roughly the same time. To keep from sound artifacting, you'll want less than 10ms of latency.

Initialize an atomic counter, C, to the number of things to load.

Use the prepareAsync() functions within MediaPlayer to prepare all three. Immediately after calling prepareAsync, supply a listener using setOnPreparedListener(listener).

Inside this listener, decrement C and check the value. If the value is greater than 0, wait on an object using the java object .wait() function. If the value is equal to 0, call notifyAll() on the object to wake up all of the other mediaplayer prepared-listener callback threads.

public void startMediaPlayers(List<MediaPlayer> mediaPlayers) {
     private AtomicInteger counter = new AtomicInteger(mediaPlayers.size());
     Object barrier = new Object();
     /* start off all media players */
     for (MediaPlayer player : mediaPlayers) {
          player.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
                                @Override
                                public void onPrepared(final MediaPlayer mediaPlayer) {
                                    int value = counter.decrementAndGet();
                                    if (value == 0) {
                                        // all media players are done loading.
                                        // wake up all the ones that are asleep
                                        barrier.notifyAll();
                                    } else {
                                       while (value > 0) {
                                            try {
                                              // wait for everyone else to load
                                              barrier.wait();
                                            } catch (InterruptedException e) {
                                              // ignore
                                            } 
                                       }
                                    }
                                    mediaPlayer.start();
                                    callback.success(true);
                                }
          player.prepareAsync();
     }
}