Develop Reference

Issue with Android AudioRecord

In my app, I use an AudioRecorder to detect when an audio signal is received. I have the app working on a single Android device but am getting errors testing on other devices. Namely, I get the error
start() status -38
Here is my code:
protected AudioTrack mAudioTrack;
protected AudioRecord mRecorder;
protected Runnable mRecordFeed = new Runnable() {
#Override
public void run() {
while (mRecorder.getRecordingState() == AudioRecord.RECORDSTATE_RECORDING) {
short[] data = new short[mBufferSize/2]; //the buffer size is in bytes
// gets the audio output from microphone to short array samples
mRecorder.read(data, 0, mBufferSize/2);
mDecoder.appendSignal(data);
}
}
};
protected void setupAudioRecorder(){
Log.d(TAG, "set up audio recorder");
//make sure that the settings of the recorder match the settings of the decoder
//most devices cant record anything but 44100 samples in 16bit PCM format...
mBufferSize = AudioRecord.getMinBufferSize(FSKConfig.SAMPLE_RATE_44100, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);
//scale up the buffer... reading larger amounts of data
//minimizes the chance of missing data because of thread priority
mBufferSize *= 10;
//again, make sure the recorder settings match the decoder settings
mRecorder = new AudioRecord(MediaRecorder.AudioSource.MIC, FSKConfig.SAMPLE_RATE_44100, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, mBufferSize);
if (mRecorder.getState() == AudioRecord.STATE_INITIALIZED) {
mRecorder.startRecording();
//start a thread to read the audio data
Thread thread = new Thread(mRecordFeed);
thread.setPriority(Thread.MAX_PRIORITY);
thread.start();
}
else {
Log.i(TAG, "Please check the recorder settings, something is wrong!");
}
}
What does this status -38 mean, and how can I resolve it? I can't seem to find any documentation anywhere.

Record MIC sound into byte array in android

I'm trying to record from the MIC direcly to a short array.
The goal is not to write a file with the audio track, just save it within a short array.
If've tried several methods and the best I've found is recording with AudioRecord and to play it with AudioTrack. I've found a good class here:
Android: Need to record mic input
This class makes all I need, I just have to modify it to achieve my desired result, but...I don't get it well, I'm missing something...
Here's is my modification (not working at all):
private class Audio extends Thread {
private boolean stopped = false;
/**
* Give the thread high priority so that it's not canceled unexpectedly, and start it
*/
private Audio()
{
android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_URGENT_AUDIO);
start();
}
#Override
public void run()
{
Log.i("Audio", "Running Audio Thread");
AudioRecord recorder = null;
AudioTrack track = null;
//short[][] buffers = new short[256][160];
int ix = 0;
/*
* Initialize buffer to hold continuously recorded audio data, start recording, and start
* playback.
*/
try
{
int N = AudioRecord.getMinBufferSize(8000,AudioFormat.CHANNEL_IN_MONO,AudioFormat.ENCODING_PCM_16BIT);
recorder = new AudioRecord(AudioSource.MIC, 8000, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, N*10);
short[] buff = new short[N];
recorder.startRecording();
/*
* Loops until something outside of this thread stops it.
* Reads the data from the recorder and writes it to the audio track for playback.
*/
while(!stopped) {
//Log.i("Map", "Writing new data to buffer");
//short[] buffer = buffer[ix++ % buffer.length];
N = recorder.read(buff, 0, buff.length);
}
recorder.stop();
recorder.release();
track = new AudioTrack(AudioManager.STREAM_MUSIC, 8000,
AudioFormat.CHANNEL_OUT_MONO, AudioFormat.ENCODING_PCM_16BIT, N*10, AudioTrack.MODE_STREAM);
track.play();
for (int i =0; i< buff.length;i++) {
track.write(buff, i, buff.length);
}
} catch(Exception x) {
//Log.e("Audio", x.getMessage());
x.printStackTrace();
} finally {
track.stop();
track.release();
}
}
/**
* Called from outside of the thread in order to stop the recording/playback loop
*/
private void close()
{
stopped = true;
}
}
What I need is to record the sound in the short array buffer and when the user push a button, play it...But right now, I'm trying to record the sound and, when user push a button, recording stop and the sound start playing...
Anyone can help me?
Thanks.

You need to restructure the code to do what you want it to do. If I understand correctly you want to read sound until the 'stopped' is set true, then play the data.
Just so you understand that is potentially a lot of buffered data depending on how long that recording time is. You could write it to a file or store a series of buffers into some abstract data type.
Just to get something to work create a Vector of short [] and allocate a new short [] buffer in your 'while(!stopped)' loop and then stuff it into the vector.
After the while loop stops you can iterate through the vector and write the buffers to the AudioTrack.
As you now understand, the blip you were hearing is just the last 20ms or so of audio since your buffer only kept that last little bit.

Playing music with AudioTrack buffer by buffer on Eclipse - no sound

i'm programming for Android 2.1.Could you help me with the following problem?
I have three files, and the general purpose is to play a sound with audiotrack buffer by buffer. I'm getting pretty desperate here because I tried about everything, and there still is no sound coming out of my speakers (while android's integrated mediaplayer has no problem playing sounds via the emulator).
Source code:
An audioplayer class, which implements the audio track. It will receive a buffer, in which the sound is contained.
public AudioPlayer(int sampleRate, int channelConfiguration, int audioFormat) throws ProjectException {
minBufferSize = AudioTrack.getMinBufferSize(sampleRate, channelConfiguration, audioFormat);
audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, sampleRate, channelConfiguration,
audioFormat, minBufferSize, AudioTrack.MODE_STREAM);
if(audioTrack == null)
throw new ProjectException("Erreur lors de l'instantiation de AudioTrack");
audioTrack.setStereoVolume((float)1.0, (float)1.0);
}
#Override
public void addToQueue(short[] buffer) {
audioTrack.write(buffer, 0, buffer.length*Short.SIZE);
if(!isPlaying ) {
audioTrack.play();
isPlaying = true;
}
}
A model class, which I use to fill the buffer. Normally, it would load sound from a file, but here it just uses a simulator (440Hz), for debugging.
Buffer sizes are chosen very loosely; normally first buffer size should be 6615 and then 4410. That's, again, only for debug.
public void onTimeChange() {
if(begin) {
//First fill about 300ms
begin = false;
short[][] buffer = new short[channels][numFramesBegin];
//numFramesBegin is for example 10000
//For debugging only buffer[0] is useful
fillSimulatedBuffer(buffer, framesRead);
framesRead += numFramesBegin;
audioPlayer.addToQueue(buffer[0]);
}
else {
try {
short[][] buffer = new short[channels][numFrames];
//Afterwards fill like 200ms
fillSimulatedBuffer(buffer, framesRead);
framesRead += numFrames;
audioPlayer.addToQueue(buffer[0]);
} catch (Exception e) {
e.printStackTrace();
}
}
}
private short simulator(int time, short amplitude) {
//a pure A (frequency=440)
//this is probably wrong due to sampling rate, but 44 and 4400 won't work either
return (short)(amplitude*((short)(Math.sin((double)(simulatorFrequency*time)))));
}
private void fillSimulatedBuffer(short[][] buffer, int offset) {
for(int i = 0; i < buffer[0].length; i++)
buffer[0][i] = simulator(offset + i, amplitude);
}
A timeTask class that calls model.ontimechange() every 200 ms.
public class ReadMusic extends TimerTask {
private final Model model;
public ReadMusic(Model model) {
this.model = model;
}
#Override
public void run() {
System.out.println("Task run");
model.onTimeChange();
}
}
What debugging showed me:
timeTask works fine, it does its job;
Buffer values seem coherent, and buffer size is bigger than minBufSize;
Audiotrack's playing state is "playing"
no exceptions are caught in model functions.
Any ideas would be greatly appreciated!

OK I found the problem.
There is an error in the current AudioTrack documentation regarding AudioTrack and short buffer input: the specified buffer size should be the size of the buffer itself (buffer.length) and not the size in bytes.

Android: Need to record mic input

Is there a way to record mic input in android while it is being process for playback/preview in real time? I tried to use AudioRecord and AudioTrack to do this but the problem is that my device cannot play the recorded audio file. Actually, any android player application cannot play the recorded audio file.
On the other hand, Using Media.Recorder to record generates a good recorded audio file that can be played by any player application. But the thing is that I cannot make a preview/palyback while recording the mic input in real time.

To record and play back audio in (almost) real time you can start a separate thread and use an AudioRecord and an AudioTrack.
Just be careful with feedback. If the speakers are turned up loud enough on your device, the feedback can get pretty nasty pretty fast.
/*
* Thread to manage live recording/playback of voice input from the device's microphone.
*/
private class Audio extends Thread
{
private boolean stopped = false;
/**
* Give the thread high priority so that it's not canceled unexpectedly, and start it
*/
private Audio()
{
android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_URGENT_AUDIO);
start();
}
#Override
public void run()
{
Log.i("Audio", "Running Audio Thread");
AudioRecord recorder = null;
AudioTrack track = null;
short[][] buffers = new short[256][160];
int ix = 0;
/*
* Initialize buffer to hold continuously recorded audio data, start recording, and start
* playback.
*/
try
{
int N = AudioRecord.getMinBufferSize(8000,AudioFormat.CHANNEL_IN_MONO,AudioFormat.ENCODING_PCM_16BIT);
recorder = new AudioRecord(AudioSource.MIC, 8000, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, N*10);
track = new AudioTrack(AudioManager.STREAM_MUSIC, 8000,
AudioFormat.CHANNEL_OUT_MONO, AudioFormat.ENCODING_PCM_16BIT, N*10, AudioTrack.MODE_STREAM);
recorder.startRecording();
track.play();
/*
* Loops until something outside of this thread stops it.
* Reads the data from the recorder and writes it to the audio track for playback.
*/
while(!stopped)
{
Log.i("Map", "Writing new data to buffer");
short[] buffer = buffers[ix++ % buffers.length];
N = recorder.read(buffer,0,buffer.length);
track.write(buffer, 0, buffer.length);
}
}
catch(Throwable x)
{
Log.w("Audio", "Error reading voice audio", x);
}
/*
* Frees the thread's resources after the loop completes so that it can be run again
*/
finally
{
recorder.stop();
recorder.release();
track.stop();
track.release();
}
}
/**
* Called from outside of the thread in order to stop the recording/playback loop
*/
private void close()
{
stopped = true;
}
}
EDIT
The audio is not really recording to a file. The AudioRecord object encodes the audio as 16 bit PCM data and places it in a buffer. Then the AudioTrack object reads the data from that buffer and plays it through the speakers. There is no file on the SD card that you will be able to access later.
You can't read and write a file from the SD card at the same time to get playback/preview in real time, so you have to use buffers.

Following permission in manifest is required to work properly:
<uses-permission android:name="android.permission.RECORD_AUDIO" ></uses-permission>
Also, 2d buffer array is not necessary. The logic of the code is valid even with just one buffer, like this:
short[] buffer = new short[160];
while (!stopped) {
//Log.i("Map", "Writing new data to buffer");
int n = recorder.read(buffer, 0, buffer.length);
track.write(buffer, 0, n);
}

Android: AudioRecord Class Problem: Callback is never called

My Android Java Application needs to record audio data into the RAM and process it.
This is why I use the class "AudioRecord" and not the "MediaRecorder" (records only to file).
Till now, I used a busy loop polling with "read()" for the audio data. this has been working so far, but it peggs the CPU too much.
Between two polls, I put the thread to sleep to avoid 100% CPU usage.
However, this is not really a clean solution, since the time of the sleep is
not guaranteed and you must subtract a security time in order not to loose audio
snippets. This is not CPU optimal. I need as many free CPU cycles as possible for
a parallel running thread.
Now I implemented the recording using the "OnRecordPositionUpdateListener".
This looks very promising and the right way to do it according the SDK Docs.
Everything seems to work (opening the audio device, read()ing the data etc.)
but the Listner is never called.
Does anybody know why?
Info:
I am working with a real Device, not under the Emulator. The Recording using a Busy Loop basically works (however not satifiying). Only the Callback Listener is never called.
Here is a snippet from my Sourcecode:
public class myApplication extends Activity {
/* audio recording */
private static final int AUDIO_SAMPLE_FREQ = 16000;
private static final int AUDIO_BUFFER_BYTESIZE = AUDIO_SAMPLE_FREQ * 2 * 3; // = 3000ms
private static final int AUDIO_BUFFER_SAMPLEREAD_SIZE = AUDIO_SAMPLE_FREQ / 10 * 2; // = 200ms
private short[] mAudioBuffer = null; // audio buffer
private int mSamplesRead; // how many samples are recently read
private AudioRecord mAudioRecorder; // Audio Recorder
...
private OnRecordPositionUpdateListener mRecordListener = new OnRecordPositionUpdateListener() {
public void onPeriodicNotification(AudioRecord recorder) {
mSamplesRead = recorder.read(mAudioBuffer, 0, AUDIO_BUFFER_SAMPLEREAD_SIZE);
if (mSamplesRead > 0) {
// do something here...
}
}
public void onMarkerReached(AudioRecord recorder) {
Error("What? Hu!? Where am I?");
}
};
...
public void onCreate(Bundle savedInstanceState) {
try {
mAudioRecorder = new AudioRecord(
android.media.MediaRecorder.AudioSource.MIC,
AUDIO_SAMPLE_FREQ,
AudioFormat.CHANNEL_CONFIGURATION_MONO,
AudioFormat.ENCODING_PCM_16BIT,
AUDIO_BUFFER_BYTESIZE);
} catch (Exception e) {
Error("Unable to init audio recording!");
}
mAudioBuffer = new short[AUDIO_BUFFER_SAMPLEREAD_SIZE];
mAudioRecorder.setPositionNotificationPeriod(AUDIO_BUFFER_SAMPLEREAD_SIZE);
mAudioRecorder.setRecordPositionUpdateListener(mRecordListener);
mAudioRecorder.startRecording();
/* test if I can read anything at all... (and yes, this here works!) */
mSamplesRead = mAudioRecorder.read(mAudioBuffer, 0, AUDIO_BUFFER_SAMPLEREAD_SIZE);
}
}

I believe the problem is that you still need to do the read loop. If you setup callbacks, they will fire when you've read the number of frames that you specify for the callbacks. But you still need to do the reads. I've tried this and the callbacks get called just fine. Setting up a marker causes a callback when that number of frames has been read since the start of recording. In other words, you could set the marker far into the future, after many of your reads, and it will fire then. You can set the period to some bigger number of frames and that callback will fire every time that number of frames has been read. I think they do this so you can do low-level processing of the raw data in a tight loop, then every so often your callback can do summary-level processing. You could use the marker to make it easier to decide when to stop recording (instead of counting in the read loop).

Here is my code used to find average noise. Notice that it is based on listener notifications so it will save device battery. It is definitely based on examples above. Those example saved much time for me, thanks.
private AudioRecord recorder;
private boolean recorderStarted;
private Thread recordingThread;
private int bufferSize = 800;
private short[][] buffers = new short[256][bufferSize];
private int[] averages = new int[256];
private int lastBuffer = 0;
protected void startListenToMicrophone() {
if (!recorderStarted) {
recordingThread = new Thread() {
#Override
public void run() {
int minBufferSize = AudioRecord.getMinBufferSize(8000, AudioFormat.CHANNEL_CONFIGURATION_MONO,
AudioFormat.ENCODING_PCM_16BIT);
recorder = new AudioRecord(AudioSource.MIC, 8000, AudioFormat.CHANNEL_CONFIGURATION_MONO,
AudioFormat.ENCODING_PCM_16BIT, minBufferSize * 10);
recorder.setPositionNotificationPeriod(bufferSize);
recorder.setRecordPositionUpdateListener(new OnRecordPositionUpdateListener() {
#Override
public void onPeriodicNotification(AudioRecord recorder) {
short[] buffer = buffers[++lastBuffer % buffers.length];
recorder.read(buffer, 0, bufferSize);
long sum = 0;
for (int i = 0; i < bufferSize; ++i) {
sum += Math.abs(buffer[i]);
}
averages[lastBuffer % buffers.length] = (int) (sum / bufferSize);
lastBuffer = lastBuffer % buffers.length;
}
#Override
public void onMarkerReached(AudioRecord recorder) {
}
});
recorder.startRecording();
short[] buffer = buffers[lastBuffer % buffers.length];
recorder.read(buffer, 0, bufferSize);
while (true) {
if (isInterrupted()) {
recorder.stop();
recorder.release();
break;
}
}
}
};
recordingThread.start();
recorderStarted = true;
}
}
private void stopListenToMicrophone() {
if (recorderStarted) {
if (recordingThread != null && recordingThread.isAlive() && !recordingThread.isInterrupted()) {
recordingThread.interrupt();
}
recorderStarted = false;
}
}

Now I implemented the recording using the
"OnRecordPositionUpdateListener". This looks very promising and the
right way to do it according the SDK Docs. Everything seems to work
(opening the audio device, read()ing the data etc.) but the Listner is
never called.
Does anybody know why?
I found that the OnRecordPositionUpdateListener is ignored until you do your first .read().
In other words, I found that if I set up everything per the docs, my the Listener never got called. However, if I first called a .read() just after doing my initial .start() then the Listener would get called -- provided I did a .read() every time the Listener was called.
In other words, it almost seems like the Listener event is only good for once per .read() or some such.
I also found that if I requested any less than buffSize/2 samples to be read, that the Listener would not be called. So it seems that the listener is only called AFTER a .read() of at least half of the buffer size. To keep using the Listener callback, one must call read each time the listener is run. (In other words, put the call to read in the Listener code.)
However, the listener seems to be called at a time when the data isn't ready yet, causing blocking.
Also, if your notification period or time are greater than half of your bufferSize they will never get called, it seems.
UPDATE:
As I continue to dig deeper, I have found that the callback seems to ONLY be called when a .read() finishes......!
I don't know if that's a bug or a feature. My initial thought would be that I want a callback when it's time to read. But maybe the android developers had the idea the other way around, where you'd just put a while(1){xxxx.read(...)} in a thread by itself, and to save you from having to keep track of each time read() finished, the callback can essentially tell you when a read has finished.
Oh. Maybe it just dawned on me. And I think others have pointed this out before me here but it didn't sink in: The position or period callback must operate on bytes that have been read already...
I guess maybe I'm stuck with using threads.
In this style, one would have a thread continuously calling read() as soon as it returned, since read is blocking and patiently waits for enough data to return.
Then, independently, the callback would call your specified function every x number of samples.

For the ones who are recording Audio over an Intent Service, they might also experience this callback problem. I have been working on this issue lately and I came up with a simple solution where you call your recording method in a seperate thread. This should call onPeriodicNotification method while recording without any problems.
Something like this:
public class TalkService extends IntentService {
...
#Override
protected void onHandleIntent(Intent intent) {
Context context = getApplicationContext();
tRecord = new Thread(new recordAudio());
tRecord.start();
...
while (tRecord.isAlive()) {
if (getIsDone()) {
if (aRecorder.getRecordingState() == AudioRecord.RECORDSTATE_STOPPED) {
socketConnection(context, host, port);
}
}
} }
...
class recordAudio implements Runnable {
public void run() {
try {
OutputStream osFile = new FileOutputStream(file);
BufferedOutputStream bosFile = new BufferedOutputStream(osFile);
DataOutputStream dosFile = new DataOutputStream(bosFile);
aRecorder = new AudioRecord(MediaRecorder.AudioSource.MIC,
sampleRate, channelInMode, encodingMode, bufferSize);
data = new short[bufferSize];
aRecorder.setPositionNotificationPeriod(sampleRate);
aRecorder
.setRecordPositionUpdateListener(new AudioRecord.OnRecordPositionUpdateListener() {
int count = 1;
#Override
public void onPeriodicNotification(
AudioRecord recorder) {
Log.e(WiFiDirect.TAG, "Period notf: " + count++);
if (getRecording() == false) {
aRecorder.stop();
aRecorder.release();
setIsDone(true);
Log.d(WiFiDirect.TAG,
"Recorder stopped and released prematurely");
}
}
#Override
public void onMarkerReached(AudioRecord recorder) {
// TODO Auto-generated method stub
}
});
aRecorder.startRecording();
Log.d(WiFiDirect.TAG, "start Recording");
aRecorder.read(data, 0, bufferSize);
for (int i = 0; i < data.length; i++) {
dosFile.writeShort(data[i]);
}
if (aRecorder.getRecordingState() == AudioRecord.RECORDSTATE_RECORDING) {
aRecorder.stop();
aRecorder.release();
setIsDone(true);
Log.d(WiFiDirect.TAG, "Recorder stopped and released");
}
} catch (Exception e) {
// TODO: handle exception
}
}
}