Android - AudioRecord class does not read data, audioData and fftArray return zero

Question

I am new to android and I have been working on a Pitch Analyzer application (minimum SDK: 8). I read many articles on how to implement Audiorecord class but I wonder why it does not read any data when I record. I tried to display the values of the audioData and fftArray but zero is returned, so I assumed the problem is with the read method. Please try to check these. Here are the codes I used:

FFT.java
Complex.java

record.java

final Intent intent = new Intent("pitch.analyzer.PitZer.ASSESSMENT");
MediaRecorder recorder;
AudioRecord tuner;
int audioSource = MediaRecorder.AudioSource.MIC;
int sampleRateInHz = AudioTrack.getNativeOutputSampleRate(AudioManager.STREAM_SYSTEM);
int channelConfig = AudioFormat.CHANNEL_CONFIGURATION_MONO;
int audioFormat = AudioFormat.ENCODING_PCM_16BIT;
int bufferSizeInBytes = 4096;

int samples;
short[] audioBuffer;
short[] audioData;
double[] temp;
TextView fft;
TextView results;
//TextView bufferSize;
Complex[] fftTempArray;
Complex[] fftArray;
Complex[] fftInverse;

@Override
protected void onCreate(Bundle savedInstanceState) {


    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.record);

    Button start=(Button)findViewById(R.id.record);
    Button stop=(Button)findViewById(R.id.stop);
    fft = (TextView)findViewById(R.id.fft);
    results = (TextView)findViewById(R.id.results);
    //bufferSize = (TextView)findViewById(R.id.bufferSize);     
    audioData = new short[bufferSizeInBytes];
    tuner = new AudioRecord(audioSource, sampleRateInHz, channelConfig, audioFormat, bufferSizeInBytes);
    //final AudioRecorder recorder = new AudioRecorder("/audiometer/temp");

    start.setOnClickListener(new OnClickListener() {

        public void onClick(View v) {
            acquire();
            computeFFT();
            display();
        }
    });       

    //â€¦.wait a while

        stop.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                startActivity(intent);

            }
        });
}
public void acquire(){
    try {
        tuner.startRecording();
        samples = tuner.read(audioData, 0, bufferSizeInBytes);
    }
    catch (Throwable t){

    }   
}

public void computeFFT(){
    //Conversion from short to double
    double[] micBufferData = new double[bufferSizeInBytes];//size may need to change
    final int bytesPerSample = 2; // As it is 16bit PCM
    final double amplification = 100.0; // choose a number as you like
    for (int index = 0, floatIndex = 0; index < bufferSizeInBytes - bytesPerSample + 1; index += bytesPerSample, floatIndex++) {
        double sample = 0;
        for (int b = 0; b < bytesPerSample; b++) {
            int v = audioData[index + b];
            if (b < bytesPerSample - 1 || bytesPerSample == 1) {
                v &= 0xFF;
            }
            sample += v << (b * 8);
        }
        double sample32 = amplification * (sample / 32768.0);
        micBufferData[floatIndex] = sample32;
    }

    //Create Complex array for use in FFT
    fftTempArray = new Complex[bufferSizeInBytes];
    for (int i=0; i<bufferSizeInBytes; i++)
    {
        fftTempArray[i] = new Complex(micBufferData[i], 0);
    }

    //Obtain array of FFT data
    fftArray = FFT.fft(fftTempArray);
    fftInverse = FFT.ifft(fftTempArray);
    double[] freq2 = new double[fftArray.length];
    //Create an array of magnitude of fftArray
    double[] magnitude = new double[fftArray.length];
    for (int i=0; i<fftArray.length; i++){
        magnitude[i]= fftArray[i].abs();
        freq2[i] = ComputeFrequency(magnitude[i]);
    }

    fft.setTextColor(Color.BLUE);
    //fft.setText("fftArray is "+ fftArray[500] +" and fftTempArray is "+fftTempArray[500] + " and fftInverse is "+fftInverse[500]+" and audioData is "+audioData[500]+ " and magnitude is "+ magnitude[1] + ", "+magnitude[500]+", "+magnitude[1000]+ " and freq2 is "+ freq2[1]+" You rock dude!");
    /*for(int i = 2; i < samples; i++){
        fft.append(" " + magnitude[i] + " Hz");
    }
    for(int i = 2; i < samples; i++){
        fft.append(" " + freq2[i] + " Hz");
    }
    */
}

private double ComputeFrequency(double arrayIndex) {
    return ((1.0 * sampleRateInHz) / (1.0 * 100)) * arrayIndex;
    }

public void display(){
    results.setTextColor(Color.BLUE);
    results.setText("results: "+audioData[1]+"");
    for(int i = 2; i < samples; i++){
        results.append(" " + audioData[i]);
    }
    results.invalidate();
    //fft.setTextColor(Color.GREEN);
    fft.setText("sampleRateInHz: "+sampleRateInHz);
    fft.append("\nfftArray: "+fftArray[0]+" Hz");
    for(int i = 1; i < samples; i++){
        fft.append(" " + fftArray[i] + " Hz");
        }
    fft.append("\naudioData: "+audioData[1]);
    fft.append("\nsamples: "+samples);
    //fft.invalidate();
}
public void stop() throws IOException {
    tuner.stop();
    //audioInput.reset();
    tuner.release();

    //recorder.stop();
    //recorder.reset();
    //recorder.release();
  }

talel talel · Accepted Answer · 2012-06-16T09:44:23

Before reading from the device you should start a recording(and stop it once you finish).
Here is the code i use for a simple read:

 short[] audioData = new short[bufferSize];

 int offset =0;
 int shortRead = 0;

 //start tapping into the microphone
 audioRecored.startRecording();

 //start reading from the microphone to an internal buffer - chuck by chunk
 while (offset < bufferSize)
 {
    shortRead = audioRecored.read(audioData, offset ,bufferSize - offset);
        offset += shortRead;
 }

 //stop tapping into the microphone
 audioRecored.stop();

Android - AudioRecord class does not read data, audioData and fftArray return zero

2 Answers