Real-time microphone audio playback

Question

I have a function that records audio and saves it to a file. Here is what it looks like:

private void startRecord(){ File file = new File(Environment.getExternalStorageDirectory(), "test.pcm"); int sampleFreq = (Integer)spFrequency.getSelectedItem(); try { file.createNewFile(); OutputStream outputStream = new FileOutputStream(file); BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream); DataOutputStream dataOutputStream = new DataOutputStream(bufferedOutputStream); int minBufferSize = AudioRecord.getMinBufferSize(sampleFreq, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT); short[] audioData = new short[minBufferSize]; AudioRecord audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, sampleFreq, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT, minBufferSize); audioRecord.startRecording(); while(recording){ int numberOfShort = audioRecord.read(audioData, 0, minBufferSize); for(int i = 0; i < numberOfShort; i++){ dataOutputStream.writeShort(audioData[i]); } } audioRecord.stop(); dataOutputStream.close(); } catch (IOException e) { e.printStackTrace(); } } 

I have another function called playrecord that plays the recorded sound:

 void playRecord(){ File file = new File(Environment.getExternalStorageDirectory(), "test.pcm"); int shortSizeInBytes = Short.SIZE/Byte.SIZE; int bufferSizeInBytes = (int)(file.length()/shortSizeInBytes); short[] audioData = new short[bufferSizeInBytes]; try { InputStream inputStream = new FileInputStream(file); BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream); DataInputStream dataInputStream = new DataInputStream(bufferedInputStream); int i = 0; while(dataInputStream.available() > 0){ audioData[i] = dataInputStream.readShort(); i++; } dataInputStream.close(); int sampleFreq = (Integer)spFrequency.getSelectedItem(); AudioTrack audioTrack = new AudioTrack( AudioManager.STREAM_MUSIC, sampleFreq, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT, bufferSizeInBytes, AudioTrack.MODE_STREAM); audioTrack.play(); audioTrack.write(audioData, 0, bufferSizeInBytes); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } 

These two functions work fine. If I call startRecord () and then call playRecord, I can hear the sound. But I want to reproduce the sound in REAL time, i.e. as soon as I start recording, I want the sound to play. What should I do for this?

Answer 1

This works for me:

 boolean isRecording = false; AudioManager am = null; AudioRecord record = null; AudioTrack track = null; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); setVolumeControlStream(AudioManager.MODE_IN_COMMUNICATION); initRecordAndTrack(); am = (AudioManager) this.getSystemService(Context.AUDIO_SERVICE); am.setSpeakerphoneOn(true); (new Thread() { @Override public void run() { recordAndPlay(); } }).start(); Button startButton = (Button) findViewById(R.id.start_button); startButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { if (!isRecording) { startRecordAndPlay(); } } }); Button stopButton = (Button) findViewById(R.id.stop_button); stopButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { if (isRecording) { stopRecordAndPlay(); } } }); } private void initRecordAndTrack() { int min = AudioRecord.getMinBufferSize(8000, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT); record = new AudioRecord(MediaRecorder.AudioSource.VOICE_COMMUNICATION, 8000, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, min); if (AcousticEchoCanceler.isAvailable()) { AcousticEchoCanceler echoCancler = AcousticEchoCanceler.create(record.getAudioSessionId()); echoCancler.setEnabled(true); } int maxJitter = AudioTrack.getMinBufferSize(8000, AudioFormat.CHANNEL_OUT_MONO, AudioFormat.ENCODING_PCM_16BIT); track = new AudioTrack(AudioManager.MODE_IN_COMMUNICATION, 8000, AudioFormat.CHANNEL_OUT_MONO, AudioFormat.ENCODING_PCM_16BIT, maxJitter, AudioTrack.MODE_STREAM); } private void recordAndPlay() { short[] lin = new short[1024]; int num = 0; am.setMode(AudioManager.MODE_IN_COMMUNICATION); while (true) { if (isRecording) { num = record.read(lin, 0, 1024); track.write(lin, 0, num); } } } private void startRecordAndPlay() { record.startRecording(); track.play(); isRecording = true; } private void stopRecordAndPlay() { record.stop(); track.pause(); isRecording = false; } 

You also need two buttons in the activity_main layout with the identifiers start_button and stop_button .

This sample also contains an EchoCanceler!

Good luck