ExtAudioRecorder:"write failed: EBADF (Bad file descriptor) " 正在将音频录制到 WAV 文件中 - Android Studio

ExtAudioRecorder: "write failed: EBADF (Bad file descriptor) " in recording Audio to WAV files - Android Studio

我正在尝试创建一个从麦克风录音并将文件保存为 WAV 格式的应用程序。 我发现这个 java class 帮助我以 WAV 格式录制和保存我的录音。

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;

import android.media.AudioFormat;
import android.media.AudioRecord;
import android.media.MediaRecorder;
import android.media.MediaRecorder.AudioSource;
import android.util.Log;

public class ExtAudioRecorder
{
    private final static int[] sampleRates = {44100, 22050, 11025, 8000};

    public static ExtAudioRecorder getInstanse(Boolean recordingCompressed)
    {
        ExtAudioRecorder result = null;

        if(recordingCompressed)
        {
            result = new ExtAudioRecorder(  false,
                    AudioSource.MIC,
                    sampleRates[3],
                    AudioFormat.CHANNEL_CONFIGURATION_MONO,
                    AudioFormat.ENCODING_PCM_16BIT);
        }
        else
        {
            int i=0;
            do
            {
                result = new ExtAudioRecorder(  true,
                        AudioSource.MIC,
                        sampleRates[i],
                        AudioFormat.CHANNEL_CONFIGURATION_MONO,
                        AudioFormat.ENCODING_PCM_16BIT);

            } while((++i<sampleRates.length) & !(result.getState() == ExtAudioRecorder.State.INITIALIZING));
        }
        return result;
    }

    /**
     * INITIALIZING : recorder is initializing;
     * READY : recorder has been initialized, recorder not yet started
     * RECORDING : recording
     * ERROR : reconstruction needed
     * STOPPED: reset needed
     */
    public enum State {INITIALIZING, READY, RECORDING, ERROR, STOPPED};

    public static final boolean RECORDING_UNCOMPRESSED = true;
    public static final boolean RECORDING_COMPRESSED = false;

    // The interval in which the recorded samples are output to the file
    // Used only in uncompressed mode
    private static final int TIMER_INTERVAL = 120;

    // Toggles uncompressed recording on/off; RECORDING_UNCOMPRESSED / RECORDING_COMPRESSED
    private boolean         rUncompressed;

    // Recorder used for uncompressed recording
    private AudioRecord     audioRecorder = null;

    // Recorder used for compressed recording
    private MediaRecorder   mediaRecorder = null;

    // Stores current amplitude (only in uncompressed mode)
    private int             cAmplitude= 0;

    // Output file path
    private String          filePath = null;

    // Recorder state; see State
    private State           state;

    // File writer (only in uncompressed mode)
    private RandomAccessFile randomAccessWriter;

    // Number of channels, sample rate, sample size(size in bits), buffer size, audio source, sample size(see AudioFormat)
    private short                    nChannels;
    private int                      sRate;
    private short                    bSamples;
    private int                      bufferSize;
    private int                      aSource;
    private int                      aFormat;

    // Number of frames written to file on each output(only in uncompressed mode)
    private int                      framePeriod;

    // Buffer for output(only in uncompressed mode)
    private byte[]                   buffer;

    // Number of bytes written to file after header(only in uncompressed mode)
    // after stop() is called, this size is written to the header/data chunk in the wave file
    private int                      payloadSize;

    /**
     *
     * Returns the state of the recorder in a RehearsalAudioRecord.State typed object.
     * Useful, as no exceptions are thrown.
     *
     * @return recorder state
     */
    public State getState()
    {
        return state;
    }

    /*
     *
     * Method used for recording.
     *
     */
    private AudioRecord.OnRecordPositionUpdateListener updateListener = new AudioRecord.OnRecordPositionUpdateListener()
    {
        public void onPeriodicNotification(AudioRecord recorder)
        {
            audioRecorder.read(buffer, 0, buffer.length); // Fill buffer
            try
            {
                randomAccessWriter.write(buffer); // Write buffer to file
                payloadSize += buffer.length;
                if (bSamples == 16)
                {
                    for (int i=0; i<buffer.length/2; i++)
                    { // 16bit sample size
                        short curSample = getShort(buffer[i*2], buffer[i*2+1]);
                        if (curSample > cAmplitude)
                        { // Check amplitude
                            cAmplitude = curSample;
                        }
                    }
                }
                else
                { // 8bit sample size
                    for (int i=0; i<buffer.length; i++)
                    {
                        if (buffer[i] > cAmplitude)
                        { // Check amplitude
                            cAmplitude = buffer[i];
                        }
                    }
                }
            }
            catch (IOException e)
            {
                Log.e(ExtAudioRecorder.class.getName(), "Error occured in updateListener, recording is aborted");
                //stop();
            }
        }

        public void onMarkerReached(AudioRecord recorder)
        {
            // NOT USED
        }
    };
    /**
     *
     *
     * Default constructor
     *
     * Instantiates a new recorder, in case of compressed recording the parameters can be left as 0.
     * In case of errors, no exception is thrown, but the state is set to ERROR
     *
     */
    public ExtAudioRecorder(boolean uncompressed, int audioSource, int sampleRate, int channelConfig, int audioFormat)
    {
        try
        {
            rUncompressed = uncompressed;
            if (rUncompressed)
            { // RECORDING_UNCOMPRESSED
                Log.e(ExtAudioRecorder.class.getName(), "uncompressed recording");

                if (audioFormat == AudioFormat.ENCODING_PCM_16BIT)
                {
                    bSamples = 16;
                }
                else
                {
                    bSamples = 8;
                }

                if (channelConfig == AudioFormat.CHANNEL_CONFIGURATION_MONO)
                {
                    nChannels = 1;
                }
                else
                {
                    nChannels = 2;
                }

                aSource = audioSource;
                sRate   = sampleRate;
                aFormat = audioFormat;

                framePeriod = sampleRate * TIMER_INTERVAL / 1000;
                bufferSize = framePeriod * 2 * bSamples * nChannels / 8;
                if (bufferSize < AudioRecord.getMinBufferSize(sampleRate, channelConfig, audioFormat))
                { // Check to make sure buffer size is not smaller than the smallest allowed one
                    bufferSize = AudioRecord.getMinBufferSize(sampleRate, channelConfig, audioFormat);
                    // Set frame period and timer interval accordingly
                    framePeriod = bufferSize / ( 2 * bSamples * nChannels / 8 );
                    Log.w(ExtAudioRecorder.class.getName(), "Increasing buffer size to " + Integer.toString(bufferSize));
                }

                audioRecorder = new AudioRecord(audioSource, sampleRate, channelConfig, audioFormat, bufferSize);

                if (audioRecorder.getState() != AudioRecord.STATE_INITIALIZED)
                    throw new Exception("AudioRecord initialization failed");
                audioRecorder.setRecordPositionUpdateListener(updateListener);
                audioRecorder.setPositionNotificationPeriod(framePeriod);
            } else
            { // RECORDING_COMPRESSED
                Log.e(ExtAudioRecorder.class.getName(), "compressed recording");
                mediaRecorder = new MediaRecorder();
                mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
                mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
                mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
            }
            cAmplitude = 0;
            filePath = null;
            state = State.INITIALIZING;
        } catch (Exception e)
        {
            if (e.getMessage() != null)
            {
                Log.e(ExtAudioRecorder.class.getName(), e.getMessage());
            }
            else
            {
                Log.e(ExtAudioRecorder.class.getName(), e.getMessage());
            }
            state = State.ERROR;
        }
    }

    /**
     * Sets output file path, call directly after construction/reset.
     *
     * # @param output file path
     *
     */
    public void setOutputFile(String argPath)
    {
        try
        {
            if (state == State.INITIALIZING)
            {
                filePath = argPath;
                if (!rUncompressed)
                {
                    mediaRecorder.setOutputFile(filePath);
                }
            }
        }
        catch (Exception e)
        {
            if (e.getMessage() != null)
            {
                Log.e(ExtAudioRecorder.class.getName(), e.getMessage());
            }
            else
            {
                Log.e(ExtAudioRecorder.class.getName(), "Unknown error occured while setting output path");
            }
            state = State.ERROR;
        }
    }

    /**
     *
     * Returns the largest amplitude sampled since the last call to this method.
     *
     * @return returns the largest amplitude since the last call, or 0 when not in recording state.
     *
     */
    public int getMaxAmplitude()
    {
        if (state == State.RECORDING)
        {
            if (rUncompressed)
            {
                int result = cAmplitude;
                cAmplitude = 0;
                return result;
            }
            else
            {
                try
                {
                    return mediaRecorder.getMaxAmplitude();
                }
                catch (IllegalStateException e)
                {
                    return 0;
                }
            }
        }
        else
        {
            return 0;
        }
    }


    /**
     *
     * Prepares the recorder for recording, in case the recorder is not in the INITIALIZING state and the file path was not set
     * the recorder is set to the ERROR state, which makes a reconstruction necessary.
     * In case uncompressed recording is toggled, the header of the wave file is written.
     * In case of an exception, the state is changed to ERROR
     *
     */
    public void prepare()
    {
        try
        {
            if (state == State.INITIALIZING)
            {
                if (rUncompressed)
                {
                    if ((audioRecorder.getState() == AudioRecord.STATE_INITIALIZED) & (filePath != null))
                    {
                        // write file header

                        randomAccessWriter = new RandomAccessFile(filePath, "rw");

                        randomAccessWriter.setLength(0); // Set file length to 0, to prevent unexpected behavior in case the file already existed
                        randomAccessWriter.writeBytes("RIFF");
                        randomAccessWriter.writeInt(0); // Final file size not known yet, write 0
                        randomAccessWriter.writeBytes("WAVE");
                        randomAccessWriter.writeBytes("fmt ");
                        randomAccessWriter.writeInt(Integer.reverseBytes(16)); // Sub-chunk size, 16 for PCM
                        randomAccessWriter.writeShort(Short.reverseBytes((short) 1)); // AudioFormat, 1 for PCM
                        randomAccessWriter.writeShort(Short.reverseBytes(nChannels));// Number of channels, 1 for mono, 2 for stereo
                        randomAccessWriter.writeInt(Integer.reverseBytes(sRate)); // Sample rate
                        randomAccessWriter.writeInt(Integer.reverseBytes(sRate*bSamples*nChannels/8)); // Byte rate, SampleRate*NumberOfChannels*BitsPerSample/8
                        randomAccessWriter.writeShort(Short.reverseBytes((short)(nChannels*bSamples/8))); // Block align, NumberOfChannels*BitsPerSample/8
                        randomAccessWriter.writeShort(Short.reverseBytes(bSamples)); // Bits per sample
                        randomAccessWriter.writeBytes("data");
                        randomAccessWriter.writeInt(0); // Data chunk size not known yet, write 0

                        buffer = new byte[framePeriod*bSamples/8*nChannels];
                        state = State.READY;
                    }
                    else
                    {
                        Log.e(ExtAudioRecorder.class.getName(), "prepare() method called on uninitialized recorder");
                        state = State.ERROR;
                    }
                }
                else
                {
                    mediaRecorder.prepare();
                    state = State.READY;
                }
            }
            else
            {
                Log.e(ExtAudioRecorder.class.getName(), "prepare() method called on illegal state");
                release();
                state = State.ERROR;
            }
        }
        catch(Exception e)
        {
            if (e.getMessage() != null)
            {
                Log.e(ExtAudioRecorder.class.getName(), e.getMessage());
            }
            else
            {
                Log.e(ExtAudioRecorder.class.getName(), "Unknown error occured in prepare()");
            }
            state = State.ERROR;
        }
    }

    /**
     *
     *
     *  Releases the resources associated with this class, and removes the unnecessary files, when necessary
     *
     */
    public void release()
    {
        if (state == State.RECORDING)
        {
            stop();
        }
        else
        {
            if ((state == State.READY) & (rUncompressed))
            {
                try
                {
                    randomAccessWriter.close(); // Remove prepared file
                }
                catch (IOException e)
                {
                    Log.e(ExtAudioRecorder.class.getName(), "I/O exception occured while closing output file");
                }
                (new File(filePath)).delete();
            }
        }

        if (rUncompressed)
        {
            if (audioRecorder != null)
            {
                audioRecorder.release();
            }
        }
        else
        {
            if (mediaRecorder != null)
            {
                mediaRecorder.release();
            }
        }
    }

    /**
     *
     *
     * Resets the recorder to the INITIALIZING state, as if it was just created.
     * In case the class was in RECORDING state, the recording is stopped.
     * In case of exceptions the class is set to the ERROR state.
     *
     */
    public void reset()
    {
        try
        {
            if (state != State.ERROR)
            {
                release();
                filePath = null; // Reset file path
                cAmplitude = 0; // Reset amplitude
                if (rUncompressed)
                {
                    audioRecorder = new AudioRecord(aSource, sRate, nChannels+1, aFormat, bufferSize);
                }
                else
                {
                    mediaRecorder = new MediaRecorder();
                    mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
                    mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
                    mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
                }
                state = State.INITIALIZING;
            }
        }
        catch (Exception e)
        {
            Log.e(ExtAudioRecorder.class.getName(), e.getMessage());
            state = State.ERROR;
        }
    }

    /**
     *
     *
     * Starts the recording, and sets the state to RECORDING.
     * Call after prepare().
     *
     */
    public void start()
    {
        if (state == State.READY)
        {
            if (rUncompressed)
            {
                payloadSize = 0;
                audioRecorder.startRecording();
                audioRecorder.read(buffer, 0, buffer.length);
            }
            else
            {
                mediaRecorder.start();
            }
            state = State.RECORDING;
        }
        else
        {
            Log.e(ExtAudioRecorder.class.getName(), "start() called on illegal state");
            state = State.ERROR;
        }
    }

    /**
     *
     *
     *  Stops the recording, and sets the state to STOPPED.
     * In case of further usage, a reset is needed.
     * Also finalizes the wave file in case of uncompressed recording.
     *
     */
    public void stop()
    {
        if (state == State.RECORDING)
        {
            if (rUncompressed)
            {
                audioRecorder.stop();

                try
                {
                    randomAccessWriter.seek(4); // Write size to RIFF header
                    randomAccessWriter.writeInt(Integer.reverseBytes(36+payloadSize));

                    randomAccessWriter.seek(40); // Write size to Subchunk2Size field
                    randomAccessWriter.writeInt(Integer.reverseBytes(payloadSize));

                    randomAccessWriter.close();
                }
                catch(IOException e)
                {
                    Log.e(ExtAudioRecorder.class.getName(), "I/O exception occured while closing output file");
                    state = State.ERROR;
                }
            }
            else
            {
                mediaRecorder.stop();
            }
            state = State.STOPPED;
        }
        else
        {
            Log.e(ExtAudioRecorder.class.getName(), "stop() called on illegal state");
            state = State.ERROR;
        }
    }

    /*
     *
     * Converts a byte[2] to a short, in LITTLE_ENDIAN format
     *
     */
    private short getShort(byte argB1, byte argB2)
    {
        return (short)(argB1 | (argB2 << 8));
    }

}

我的主要activity是这样的:

import static android.Manifest.permission.RECORD_AUDIO;
import static android.Manifest.permission.WRITE_EXTERNAL_STORAGE;
public class MainActivity extends AppCompatActivity {

    Button buttonStart, buttonStop, buttonPlayLastRecordAudio,
            buttonStopPlayingRecording, buttonGet;
    String AudioSavePathInDevice = null;
    MediaRecorder mediaRecorder ;
    Random random ;
    View loader;
    AudioRecordView audioRecordView;
    String RandomAudioFileName = "ABCDEFGHIJKLMNOPQ";
    public static final int RequestPermissionCode = 1;
    MediaPlayer mediaPlayer ;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        buttonStart = (Button) findViewById(R.id.button_record);
        buttonStop = (Button) findViewById(R.id.button_stop_record);
        buttonPlayLastRecordAudio = (Button) findViewById(R.id.button_play);
        buttonStopPlayingRecording = (Button)findViewById(R.id.button_stop_play);
        loader = findViewById(R.id.loader);
        ExtAudioRecorder extAudioRecorder = ExtAudioRecorder.getInstanse(false);
        random = new Random();




        buttonStart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                if(checkPermission()) {

                    AudioSavePathInDevice =
                            Environment.getExternalStorageDirectory().getAbsolutePath() + "/" +
                                    CreateRandomAudioFileName(5) + "AudioRecording.WAV";

                    extAudioRecorder.setOutputFile(AudioSavePathInDevice);
                    try {
                        extAudioRecorder.prepare();
                        extAudioRecorder.start();
                    } catch (IllegalStateException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                } else {
                    requestPermission();
                }

            }
        });

        buttonStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                extAudioRecorder.stop();
                extAudioRecorder.release();
                Toast.makeText(MainActivity.this, "Recording Completed",
                        Toast.LENGTH_LONG).show();
            }
        });

        buttonPlayLastRecordAudio.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) throws IllegalArgumentException,
                    SecurityException, IllegalStateException {
                mediaPlayer = new MediaPlayer();
                try {
                    mediaPlayer.setDataSource(AudioSavePathInDevice);
                    mediaPlayer.prepare();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                mediaPlayer.start();
                Toast.makeText(MainActivity.this, "Recording Playing",
                        Toast.LENGTH_LONG).show();
            }
        });

        buttonStopPlayingRecording.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(mediaPlayer != null){
                    mediaPlayer.stop();
                    mediaPlayer.release();
                    MediaRecorderReady();
                }

            }
        });
    }


    public void MediaRecorderReady(){
        mediaRecorder = new MediaRecorder();
        mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        mediaRecorder.setAudioEncoder(MediaRecorder.OutputFormat.AMR_NB);
        mediaRecorder.setOutputFile(AudioSavePathInDevice);
    }

    public String CreateRandomAudioFileName(int string){
        StringBuilder stringBuilder = new StringBuilder( string );
        int i = 0 ;
        while(i < string ) {
            stringBuilder.append(RandomAudioFileName.
                    charAt(random.nextInt(RandomAudioFileName.length())));

            i++ ;
        }
        return stringBuilder.toString();
    }

    private void requestPermission() {
        ActivityCompat.requestPermissions(MainActivity.this, new
                String[]{WRITE_EXTERNAL_STORAGE, RECORD_AUDIO}, RequestPermissionCode);
    }
    @Override
    public void onRequestPermissionsResult(int requestCode,
                                           String permissions[], int[] grantResults) {
        switch (requestCode) {
            case RequestPermissionCode:
                if (grantResults.length> 0) {
                    boolean StoragePermission = grantResults[0] ==
                            PackageManager.PERMISSION_GRANTED;
                    boolean RecordPermission = grantResults[1] ==
                            PackageManager.PERMISSION_GRANTED;

                    if (StoragePermission && RecordPermission) {
                        Toast.makeText(MainActivity.this, "Permission Granted",
                                Toast.LENGTH_LONG).show();
                    } else {
                        Toast.makeText(MainActivity.this,"Permission Denied",Toast.LENGTH_LONG).show();
                    }
                }
                break;
        }
    }
    public boolean checkPermission() {
        int result = ContextCompat.checkSelfPermission(getApplicationContext(),
                WRITE_EXTERNAL_STORAGE);
        int result1 = ContextCompat.checkSelfPermission(getApplicationContext(),
                RECORD_AUDIO);
        return result == PackageManager.PERMISSION_GRANTED &&
                result1 == PackageManager.PERMISSION_GRANTED;
    }
    public static String getMimeType(String url) {
        String type = null;
        String extension = MimeTypeMap.getFileExtensionFromUrl(url);
        if (extension != null) {
            type = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
        }
        return type;
    }
}

我可以录制我的第一个录音并用媒体录音机播放它,但是我似乎无法录制第二个录音也无法播放它。

停止第一次录制后出现此错误:

E/com.example.app.ExtAudioRecorder: write failed: EBADF (Bad file descriptor)

我已经添加了所有必需的权限,但我真的卡在了这一点上。

有什么想法吗?

事实证明,我找到了解决我的问题的方法,如果其他人遇到过同样的问题的话。我实际上修改了 ExtAudioRecorder class,现在一切似乎都正常工作。

尤其是在更改此行之后:

audioRecorder = new AudioRecord(aSource, sRate, nChannels + 1, aFormat, bufferSize);

进入这个:

audioRecorder = new AudioRecord(aSource, sRate, nChannels, aFormat, bufferSize);

我认为问题出在某处。

这是 ExtAudioRecorder.java 文件的修改代码:


public class ExtAudioRecorder
{
    private final static int[] sampleRates = {44100, 22050, 11025, 8000};

    public static ExtAudioRecorder getInstanse(Boolean recordingCompressed)
    {
        ExtAudioRecorder result = null;

        if(recordingCompressed)
        {
            result = new ExtAudioRecorder(  false,
                    AudioSource.MIC,
                    sampleRates[3],
                    AudioFormat.CHANNEL_CONFIGURATION_MONO,
                    AudioFormat.ENCODING_PCM_16BIT);
        }
        else
        {
            int i=0;
            do
            {
                result = new ExtAudioRecorder(  true,
                        AudioSource.MIC,
                        sampleRates[i],
                        AudioFormat.CHANNEL_CONFIGURATION_MONO,
                        AudioFormat.ENCODING_PCM_16BIT);

            } while((++i<sampleRates.length) & !(result.getState() == ExtAudioRecorder.State.INITIALIZING));
        }
        return result;
    }

    /**
     * INITIALIZING : recorder is initializing;
     * READY : recorder has been initialized, recorder not yet started
     * RECORDING : recording
     * ERROR : reconstruction needed
     * STOPPED: reset needed
     */
    public enum State {INITIALIZING, READY, RECORDING, ERROR, STOPPED};

    public static final boolean RECORDING_UNCOMPRESSED = true;
    public static final boolean RECORDING_COMPRESSED = false;

    // The interval in which the recorded samples are output to the file
    // Used only in uncompressed mode
    private static final int TIMER_INTERVAL = 120;

    // Toggles uncompressed recording on/off; RECORDING_UNCOMPRESSED / RECORDING_COMPRESSED
    private boolean         rUncompressed;

    // Recorder used for uncompressed recording
    private AudioRecord     audioRecorder = null;

    // Recorder used for compressed recording
    private MediaRecorder   mediaRecorder = null;

    // Stores current amplitude (only in uncompressed mode)
    private int             cAmplitude= 0;

    // Output file path
    private String          filePath = null;

    // Recorder state; see State
    private State           state;

    // File writer (only in uncompressed mode)
    private RandomAccessFile randomAccessWriter;

    // Number of channels, sample rate, sample size(size in bits), buffer size, audio source, sample size(see AudioFormat)
    private short                    nChannels;
    private int                      sRate;
    private short                    bSamples;
    private int                      bufferSize;
    private int                      aSource;
    private int                      aFormat;

    // Number of frames written to file on each output(only in uncompressed mode)
    private int                      framePeriod;

    // Buffer for output(only in uncompressed mode)
    private byte[]                   buffer;

    // Number of bytes written to file after header(only in uncompressed mode)
    // after stop() is called, this size is written to the header/data chunk in the wave file
    private int                      payloadSize;

    /**
     *
     * Returns the state of the recorder in a RehearsalAudioRecord.State typed object.
     * Useful, as no exceptions are thrown.
     *
     * @return recorder state
     */
    public State getState()
    {
        return state;
    }

    /*
     *
     * Method used for recording.
     *
     */
    private AudioRecord.OnRecordPositionUpdateListener updateListener = new AudioRecord.OnRecordPositionUpdateListener()
    {
        public void onPeriodicNotification(AudioRecord recorder)
        {   
            if (State.STOPPED == state) {
                Log.d(ExtAudioRecorder.this.getClass().getName(), "recorder stopped");
                return;
            }
            audioRecorder.read(buffer, 0, buffer.length); // Fill buffer
            try
            {   randomAccessWriter.write(buffer); // Write buffer to file
                payloadSize += buffer.length;
                if (bSamples == 16)
                {
                    for (int i=0; i<buffer.length/2; i++)
                    { // 16bit sample size
                        short curSample = getShort(buffer[i*2], buffer[i*2+1]);
                        if (curSample > cAmplitude)
                        { // Check amplitude
                            cAmplitude = curSample;
                        }
                    }
                }
                else
                { // 8bit sample size

                    for (int i=0; i<buffer.length; i++)
                    {
                        if (buffer[i] > cAmplitude)
                        { // Check amplitude
                            cAmplitude = buffer[i];
                        }
                    }
                }
            }
            catch (IOException e)
            {
                Log.e(ExtAudioRecorder.class.getName(), e.getMessage());
            }
        }

        public void onMarkerReached(AudioRecord recorder)
        {
        }
    };
    /**
     *
     *
     * Default constructor
     *
     * Instantiates a new recorder, in case of compressed recording the parameters can be left as 0.
     * In case of errors, no exception is thrown, but the state is set to ERROR
     *
     */
    public ExtAudioRecorder(boolean uncompressed, int audioSource, int sampleRate, int channelConfig, int audioFormat)
    {
        try
        {
            rUncompressed = uncompressed;
            if (rUncompressed)
            { // RECORDING_UNCOMPRESSED
                Log.d(ExtAudioRecorder.class.getName(), "uncompressed recording");

                if (audioFormat == AudioFormat.ENCODING_PCM_16BIT)
                {
                    bSamples = 16;
                }
                else
                {
                    bSamples = 8;
                }

                if (channelConfig == AudioFormat.CHANNEL_CONFIGURATION_MONO)
                {
                    nChannels = 1;
                }
                else
                {
                    nChannels = 2;
                }

                aSource = audioSource;
                sRate   = sampleRate;
                aFormat = audioFormat;

                framePeriod = sampleRate * TIMER_INTERVAL / 1000;
                bufferSize = framePeriod * 2 * bSamples * nChannels / 8;
                if (bufferSize < AudioRecord.getMinBufferSize(sampleRate, channelConfig, audioFormat))
                { // Check to make sure buffer size is not smaller than the smallest allowed one
                    bufferSize = AudioRecord.getMinBufferSize(sampleRate, channelConfig, audioFormat);
                    // Set frame period and timer interval accordingly
                    framePeriod = bufferSize / ( 2 * bSamples * nChannels / 8 );
                    Log.w(ExtAudioRecorder.class.getName(), "Increasing buffer size to " + Integer.toString(bufferSize));
                }

                audioRecorder = new AudioRecord(audioSource, sampleRate, channelConfig, audioFormat, bufferSize);

                if (audioRecorder.getState() != AudioRecord.STATE_INITIALIZED)
                    throw new Exception("AudioRecord initialization failed");
                audioRecorder.setRecordPositionUpdateListener(updateListener);
                audioRecorder.setPositionNotificationPeriod(framePeriod);

            } else
            { // RECORDING_COMPRESSED
                Log.e(ExtAudioRecorder.class.getName(), "compressed recording");
                mediaRecorder = new MediaRecorder();
                mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
                mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
                mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
            }
            cAmplitude = 0;
            filePath = null;
            state = State.INITIALIZING;
        } catch (Exception e)
        {
            if (e.getMessage() != null)
            {
                Log.e(ExtAudioRecorder.class.getName(), e.getMessage());
            }
            else
            {
                Log.e(ExtAudioRecorder.class.getName(), "Unknown error occured while initializing recording");
            }
            state = State.ERROR;
        }
    }

    /**
     * Sets output file path, call directly after construction/reset.
     *
     * # @param output file path
     *
     */
    public void setOutputFile(String argPath)
    {
        try
        {
            if (state == State.INITIALIZING)
            {
                filePath = argPath;
                if (!rUncompressed)
                {
                    mediaRecorder.setOutputFile(filePath);
                }
            }
        }
        catch (Exception e)
        {
            if (e.getMessage() != null)
            {
                Log.e(ExtAudioRecorder.class.getName(), e.getMessage());
            }
            else
            {
                Log.e(ExtAudioRecorder.class.getName(), "Unknown error occured while setting output path");
            }
            state = State.ERROR;
        }
    }

    /**
     *
     * Returns the largest amplitude sampled since the last call to this method.
     *
     * @return returns the largest amplitude since the last call, or 0 when not in recording state.
     *
     */
    public int getMaxAmplitude()
    {
        if (state == State.RECORDING)
        {
            if (rUncompressed)
            {
                int result = cAmplitude;
                cAmplitude = 0;
                return result;
            }
            else
            {
                try
                {
                    return mediaRecorder.getMaxAmplitude();
                }
                catch (IllegalStateException e)
                {
                    return 0;
                }
            }
        }
        else
        {
            return 0;
        }
    }


    /**
     *
     * Prepares the recorder for recording, in case the recorder is not in the INITIALIZING state and the file path was not set
     * the recorder is set to the ERROR state, which makes a reconstruction necessary.
     * In case uncompressed recording is toggled, the header of the wave file is written.
     * In case of an exception, the state is changed to ERROR
     *
     */
    public void prepare()
    {
        try
        {
            if (state == State.INITIALIZING)
            {
                if (rUncompressed)
                {
                    if ((audioRecorder.getState() == AudioRecord.STATE_INITIALIZED) & (filePath != null))
                    {
                        // write file header

                        randomAccessWriter = new RandomAccessFile(filePath, "rw");

                        randomAccessWriter.setLength(0); // Set file length to 0, to prevent unexpected behavior in case the file already existed
                        randomAccessWriter.writeBytes("RIFF");
                        randomAccessWriter.writeInt(0); // Final file size not known yet, write 0
                        randomAccessWriter.writeBytes("WAVE");
                        randomAccessWriter.writeBytes("fmt ");
                        randomAccessWriter.writeInt(Integer.reverseBytes(16)); // Sub-chunk size, 16 for PCM
                        randomAccessWriter.writeShort(Short.reverseBytes((short) 1)); // AudioFormat, 1 for PCM
                        randomAccessWriter.writeShort(Short.reverseBytes(nChannels));// Number of channels, 1 for mono, 2 for stereo
                        randomAccessWriter.writeInt(Integer.reverseBytes(sRate)); // Sample rate
                        randomAccessWriter.writeInt(Integer.reverseBytes(sRate*bSamples*nChannels/8)); // Byte rate, SampleRate*NumberOfChannels*BitsPerSample/8
                        randomAccessWriter.writeShort(Short.reverseBytes((short)(nChannels*bSamples/8))); // Block align, NumberOfChannels*BitsPerSample/8
                        randomAccessWriter.writeShort(Short.reverseBytes(bSamples)); // Bits per sample
                        randomAccessWriter.writeBytes("data");
                        randomAccessWriter.writeInt(0); // Data chunk size not known yet, write 0

                        buffer = new byte[framePeriod*bSamples/8*nChannels];
                        state = State.READY;
                    }
                    else
                    {
                        Log.e(ExtAudioRecorder.class.getName(), "prepare() method called on uninitialized recorder");
                        state = State.ERROR;
                    }
                }
                else
                {
                    mediaRecorder.prepare();
                    state = State.READY;
                }
            }
            else
            {
                Log.e(ExtAudioRecorder.class.getName(), "prepare() method called on illegal state");
                release();
                state = State.ERROR;
            }
        }
        catch(Exception e)
        {
            if (e.getMessage() != null)
            {
                Log.e(ExtAudioRecorder.class.getName(), e.getMessage());
            }
            else
            {
                Log.e(ExtAudioRecorder.class.getName(), "Unknown error occured in prepare()");
            }
            state = State.ERROR;
        }
    }

    /**
     *
     *
     *  Releases the resources associated with this class, and removes the unnecessary files, when necessary
     *
     */
    public void release()
    {
        if (state == State.RECORDING)
        {
            stop();
        }
        else
        {
            if ((state == State.READY) & (rUncompressed))
            {
                try
                {
                    randomAccessWriter.close(); // Remove prepared file
                }
                catch (IOException e)
                {
                    Log.e(ExtAudioRecorder.class.getName(), "I/O exception occured while closing output file");
                }
                (new File(filePath)).delete();
            }
        }

        if (rUncompressed)
        {
            if (audioRecorder != null)
            {
                audioRecorder.release();
            }
        }
        else
        {
            if (mediaRecorder != null)
            {
                mediaRecorder.release();
            }
        }

    }

    /**
     *
     *
     * Resets the recorder to the INITIALIZING state, as if it was just created.
     * In case the class was in RECORDING state, the recording is stopped.
     * In case of exceptions the class is set to the ERROR state.
     *
     */
    public void reset()
    {
        try
        {
            if (state != State.ERROR)
            {
                release();
                filePath = null; // Reset file path
                cAmplitude = 0; // Reset amplitude
                if (rUncompressed)
                { 
                    audioRecorder = new AudioRecord(aSource, sRate, nChannels, aFormat, bufferSize);
                    audioRecorder.setRecordPositionUpdateListener(updateListener);
                    audioRecorder.setPositionNotificationPeriod(framePeriod);
                }
                else
                {
                    mediaRecorder = new MediaRecorder();
                    mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
                    mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
                    mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
                }
                state = State.INITIALIZING;
            }
        }
        catch (Exception e)
        {
            Log.e(ExtAudioRecorder.class.getName(), e.getMessage());
            state = State.ERROR;
        }
    }

    /**
     *
     *
     * Starts the recording, and sets the state to RECORDING.
     * Call after prepare().
     *
     */
    public void start()
    {
        if (state == State.READY)
        {
            if (rUncompressed)
            {
                payloadSize = 0;
                audioRecorder.startRecording();
                audioRecorder.read(buffer, 0, buffer.length);
            }
            else
            {
                mediaRecorder.start();
            }
            state = State.RECORDING;
        }
        else
        {
            Log.e(ExtAudioRecorder.class.getName(), "start() called on illegal state");
            state = State.ERROR;
        }
    }

    /**
     *
     *
     *  Stops the recording, and sets the state to STOPPED.
     * In case of further usage, a reset is needed.
     * Also finalizes the wave file in case of uncompressed recording.
     *
     */
    public void stop()
    {
        if (state == State.RECORDING)
        {
            if (rUncompressed)
            {
                audioRecorder.stop();

                try
                {
                    randomAccessWriter.seek(4); // Write size to RIFF header
                    randomAccessWriter.writeInt(Integer.reverseBytes(36+payloadSize));

                    randomAccessWriter.seek(40); // Write size to Subchunk2Size field
                    randomAccessWriter.writeInt(Integer.reverseBytes(payloadSize));

                    randomAccessWriter.close();
                }
                catch(IOException e)
                {
                    Log.e(ExtAudioRecorder.class.getName(), "I/O exception occured while closing output file");
                    state = State.ERROR;
                }
            }
            else
            {
                mediaRecorder.stop();
            }
            state = State.STOPPED;
        }
        else
        {
            Log.e(ExtAudioRecorder.class.getName(), "stop() called on illegal state");
            state = State.ERROR;
        }
    }

    /*
     *
     * Converts a byte[2] to a short, in LITTLE_ENDIAN format
     *
     */
    private short getShort(byte argB1, byte argB2)
    {
        return (short)(argB1 | (argB2 << 8));
    }

}