Q:

android, AudioRecord.read() --> bufferoverflow, how to handle the buffer?

for a university project my prof. wants me to write an android application, would be my first one. I have some Java experience but I am new to Android programming, so please be gentle with me.
First I create an Activity where I have only two buttons, one for starting an AsyncTask and one for stopping it, I mean I just set the boolean "isRecording" to false, everything else is handled in the AsyncTask, which is attached as source code.
The thing is running quite okay, but after a while I can find some bufferoverflow messages in the LogCat and after that it crashes with an uncaught exception. I figured out why it's crashing, and the uncaught exception shouldn't be the purpose of that question.
03-07 11:34:02.474: INFO/buffer 247:(558): 40
03-07 11:34:02.484: WARN/AudioFlinger(33): RecordThread: buffer overflow
03-07 11:34:02.484: INFO/MutantAudioRecorder:doInBackground()(558): isRecoding
03-07 11:34:02.484: INFO/MutantAudioRecorder:doInBackground()(558): isRecoding
03-07 11:34:02.494: WARN/AudioFlinger(33): RecordThread: buffer overflow
03-07 11:34:02.494: INFO/buffer 248:(558): -50

I write out the buffer as you can see, but somehow I think I made a mistake in configuring the AudioRecord correctly, can anybody tell why I get the bufferoverflow?
And the next question would be, how can I handle the buffer? I mean, I have the values inside it and want them to show in graphical spectrogram on the screen. Does anyone have experience with it and can me give a hint? How can I go on ...

Thanks in advance for your help.
Source code of the AsyncTask:
package nomihodai.audio;

import android.media.AudioFormat;
import android.media.AudioRecord;
import android.os.AsyncTask;
import android.util.Log;

public class MutantAudioRecorder extends AsyncTask<Void, Void, Void> {

private boolean isRecording = false;
public AudioRecord audioRecord = null;
public int mSamplesRead;
public int buffersizebytes;
public int buflen;
public int channelConfiguration = AudioFormat.CHANNEL_CONFIGURATION_MONO;
public int audioEncoding = AudioFormat.ENCODING_PCM_16BIT;
public static short[] buffer;
public static final int SAMPLESPERSEC = 8000;

@Override
protected Void doInBackground(Void... params) {

    while(isRecording) {

        audioRecord.startRecording();
        mSamplesRead = audioRecord.read(buffer, 0, buffersizebytes);

        if(!readerT.isAlive())
            readerT.start();

        Log.i("MutantAudioRecorder:doInBackground()", "isRecoding");
    }

    readerT.stop();

    return null;
}

Thread readerT = new Thread() {
    public void run() {
        for(int i = 0; i < 256; i++){ 
            Log.i("buffer " + i + ": ", Short.toString(buffer[i]));
        }
    }
};

@Override
public void onPostExecute(Void unused) {
    Log.i("MutantAudioRecorder:onPostExecute()", "try to release the audio hardware");

    audioRecord.release();

    Log.i("MutantAudioRecorder:onPostExecute()", "released...");
}

public void setRecording(boolean rec) {
    this.isRecording = rec;

    Log.i("MutantAudioRecorder:setRecording()", "isRecoding set to " + rec);
}

@Override
protected void onPreExecute() {

    buffersizebytes = AudioRecord.getMinBufferSize(SAMPLESPERSEC, channelConfiguration, audioEncoding);
    buffer = new short[buffersizebytes];
    buflen = buffersizebytes/2;

    Log.i("MutantAudioRecorder:onPreExecute()", "buffersizebytes: " + buffersizebytes
                                                + ", buffer: " + buffer.length
                                                + ", buflen: " + buflen);

    audioRecord = new AudioRecord(android.media.MediaRecorder.AudioSource.MIC,
            SAMPLESPERSEC,
            channelConfiguration,
            audioEncoding,
            buffersizebytes);

    if(audioRecord != null)
        Log.i("MutantAudioRecorder:onPreExecute()", "audiorecord object created");
    else
        Log.i("MutantAudioRecorder:onPreExecute()", "audiorecord NOT created");
}

}

A:

It's probably some live analyzing process working on the recorded audio bytes?
Since the buffer size for recording is limited, once your "analyzing process" is slower than the rate of recording, the data in the buffer will be stuck, but the recording bytes are always coming thus buffer overflows.
Try use threads on recording and the other process on the recorded bytes, there's a open source sample code for this approach: http://musicg.googlecode.com/files/musicg_android_demo.zip

