Immediate Audio Input & Output Android

Question

In my Android App, I would like to take in some audio from the mic of the smartphone and play it immediately, live, like a microphone, with no lag. I am currently thinking of using AudioRecord and AudioTrack classes (from what I have read), but I'm not quite sure how to proceed.

I checked out some other questions on Stack Overflow but they don't exactly answer what I would like to do. And most are from 2012.

So how can I use these classes to input and output audio simultaneously?

ALSO: I had a look at the MediaRecorder API, but from what I read, that requires you to save the audio to a file, which I don't want to do. Can it be tweeked to meet my requirements? Or am I better off just using AudioRecord?

Thanks

EDIT:

Here is my updated code below as @Pradip Pramanick suggested:

final Thread record = new Thread(new Runnable() {
        @Override
        public void run() {
            while (!Thread.interrupted()) {
                MediaRecorder microphone = new MediaRecorder();
                microphone.setAudioSource(MediaRecorder.AudioSource.MIC);
                    microphone.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
                microphone.setOutputFile(filename);
                microphone.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
                try {
                    microphone.prepare();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                microphone.start();
            }
        }
    });

    final Thread play = new Thread(new Runnable() {
        @Override
        public void run() {
            while (!Thread.interrupted()) {
                player = new MediaPlayer();
                try {
                    player.setDataSource(filename);
                    player.prepare();
                    player.start();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    });

I am getting an Illegal State Exception | Start failed: -38. But I am calling microphone.start after microphone.prepare... What seems to be the problem? I searched other threads which said there might be other background apps using the microphone. I searched my device: Moto X Play (3rd Gen) and found none. (I even turned off "Ok Google" voice recognition, but the error kept coming).

ERROR LOG:

Here is the log-cat showing the most recent errors:

01-31 09:37:21.064 344-3339/? E/MediaPlayerService: offset error
01-31 09:37:21.065 1835-1922/com.synerflow.testapp E/MediaPlayer: Unable to create media player

01-31 09:37:21.065 1835-1922/com.synerflow.testapp I/Player: player.prepare() has failed
01-31 09:37:21.065 1835-1922/com.synerflow.testapp W/System.err: java.io.IOException: setDataSourceFD failed.: status=0x80000000

The IO Exception seems to be at player.setDataSource(filename), the filename variable is a string: Environment.getExternalStorageDirectory().getAbsolutePath() + "\voice.3gp"

Answer 1

As far as I can think it can be done in a very simple way. I haven't tried it,but you try it. I think it'll work:

Create two threads one for recording another for playing. Say the threads are TRecord and TPlay.

In TRecord's run method do this :

public void run(){
        MediaRecorder mRecorder = null;
        mRecorder = new MediaRecorder();
        mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        mRecorder.setOutputFile(mFileName);
        mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);

        try {
            mRecorder.prepare();
        } catch (IOException e) {
            //todo
        }

        mRecorder.start();
}

And it TPlay's run method do this :

public void run() {
MediaPlayer   mPlayer = null;
mPlayer = new MediaPlayer();
        try {
            mPlayer.setDataSource(mFileName);
            mPlayer.prepare();
            mPlayer.start();
        } catch (IOException e) {
            //todo
        }
}

Now on mainactivity simply create two threads. First start the TRecord thread then Tplay . Try it.

here is the code for file extension:

mFileName = Environment.getExternalStorageDirectory().getAbsolutePath();
 mFileName += "/audiorecordtest.3gp";

Answer 2

This is actually really tricky on Android. Google themselves have a very good (but slightly long) video explaining the issues.

They also have a page explaining their latency testing methods and benchmarks for various devices.

Essentially, stock Android can't do zero-latency audio, however there's nothing stopping hardware partners from adding the required hardware and platform extensions to do so.

Answer 3

try this. I have not run this.

      recorder = new AudioRecord(MediaRecorder.AudioSource.MIC,
      RECORDER_SAMPLERATE, RECORDER_CHANNELS,
      RECORDER_AUDIO_ENCODING, bufferSize * BytesPerElement);

    recorder.startRecording();

    isRecording = true;

    recordingThread = new Thread(new Runnable() {

     public void run() {

      try {
          int intSize = android.media.AudioTrack.getMinBufferSize(RECORDER_SAMPLERATE,AudioFormat.CHANNEL_OUT_MONO , RECORDER_AUDIO_ENCODING);
          byte[] sData = new byte[bufferSize];
          AudioTrack at = new AudioTrack(AudioManager.STREAM_MUSIC, RECORDER_SAMPLERATE, AudioFormat.CHANNEL_OUT_MONO, RECORDER_AUDIO_ENCODING, intSize, AudioTrack.MODE_STREAM);
          while(isRecording){
          recorder.read(sData, 0, bufferSize);  //isRecording = false; onStop button

          if (at!=null) { 
              at.play();
              // Write the byte array to the track
              at.write(sData, 0, sData.length); 
              at.stop();
              at.release();
          }
          }
    } catch (IOException e) {
        e.printStackTrace();
    }
 }
  }, "AudioRecorder Thread");
    recordingThread.start();