Android AudioRecord class - process live mic audio quickly, set up callback function

Question

I want to record audio from the mic and access it for possible playback in near real-time. I am unsure of how to use the Android AudioRecord class to record some mic audio a

Answer 1

private int freq =8000;
private AudioRecord audioRecord = null;
private Thread Rthread = null;

private AudioManager audioManager=null;
private AudioTrack audioTrack=null;
byte[] buffer = new byte[freq];

//call this method at start button

protected void Start()

{

loopback();

}

protected void loopback() { 

    android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_URGENT_AUDIO);
    final int bufferSize = AudioRecord.getMinBufferSize(freq,
            AudioFormat.CHANNEL_CONFIGURATION_MONO,
            AudioFormat.ENCODING_PCM_16BIT);


    audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, freq,
            AudioFormat.CHANNEL_CONFIGURATION_MONO,
            MediaRecorder.AudioEncoder.AMR_NB, bufferSize);

    audioTrack = new AudioTrack(AudioManager.ROUTE_HEADSET, freq,
            AudioFormat.CHANNEL_CONFIGURATION_MONO,
            MediaRecorder.AudioEncoder.AMR_NB, bufferSize,
            AudioTrack.MODE_STREAM);



    audioTrack.setPlaybackRate(freq);
     final byte[] buffer = new byte[bufferSize];
    audioRecord.startRecording();
    Log.i(LOG_TAG, "Audio Recording started");
    audioTrack.play();
    Log.i(LOG_TAG, "Audio Playing started");
    Rthread = new Thread(new Runnable() {
        public void run() {
            while (true) {
                try {
                    audioRecord.read(buffer, 0, bufferSize);                                    
                    audioTrack.write(buffer, 0, buffer.length);

                } catch (Throwable t) {
                    Log.e("Error", "Read write failed");
                    t.printStackTrace();
                }
            }
        }
    });
    Rthread.start();

}

It plays the recorded audio less than 100 ms delay.