android getting sound frequencies real time?

Question

I have been trying to get the sound frequency(number) in real time using fft and i am having run time errors. can any one help? ``` package com.example.recordsound; import edu.emory.mathcs.jtransforms.fft.DoubleFFT_1D; import ca.uol.aig.fftpack.RealDoubleFFT; public class MainActivity extends Activity implements OnClickListener{ int audioSource = MediaRecorder.AudioSource.MIC; // Audio source is the device MIC int channelConfig = AudioFormat.CHANNEL_IN_MONO; // Recording in mono int audioEncoding = AudioFormat.ENCODING_PCM_16BIT; // Records in 16bit private DoubleFFT_1D fft; // The fft double array private RealDoubleFFT transformer; int blockSize = 256; // deal with this many samples at a time int sampleRate = 8000; // Sample rate in Hz public double frequency = 0.0; // the frequency given RecordAudio recordTask; // Creates a Record Audio command TextView tv; // Creates a text view for the frequency boolean started = false; Button startStopButton; @Override protected void onCreate(Bun…

Accepted Answer

Try this FFT:

```
public class FFT {

int n, m;

// Lookup tables. Only need to recompute when size of FFT changes.
  double[] cos;
  double[] sin;

public FFT(int n) {
      this.n = n;
      this.m = (int) (Math.log(n) / Math.log(2));

// Make sure n is a power of 2
      if (n != (1 << m))
          throw new RuntimeException("FFT length must be power of 2");

// precompute tables
      cos = new double[n / 2];
      sin = new double[n / 2];

for (int i = 0; i < n / 2; i++) {
          cos[i] = Math.cos(-2 * Math.PI * i / n);
          sin[i] = Math.sin(-2 * Math.PI * i / n);
      }

}

public void fft(double[] x, double[] y) {
      int i, j, k, n1, n2, a;
      double c, s, t1, t2;

// Bit-reverse
      j = 0;
      n2 = n / 2;
      for (i = 1; i < n - 1; i++) {
          n1 = n2;
          while (j >= n1) {
              j = j - n1;
              n1 = n1 / 2;
          }
          j = j + n1;

if (i < j) {
              t1 = x[i];
              x[i] = x[j];
              x[j] = t1;
              t1 = y[i];
              y[i] = y[j];
              y[j] = t1;
          }
      }

// FFT
      n1 = 0;
      n2 = 1;

for (i = 0; i < m; i++) {
          n1 = n2;
          n2 = n2 + n2;
          a = 0;

for (j = 0; j < n1; j++) {
              c = cos[a];
              s = sin[a];
              a += 1 << (m - i - 1);

for (k = j; k < n; k = k + n2) {
                  t1 = c * x[k + n1] - s * y[k + n1];
                  t2 = s * x[k + n1] + c * y[k + n1];
                  x[k + n1] = x[k] - t1;
                  y[k + n1] = y[k] - t2;
                  x[k] = x[k] + t1;
                  y[k] = y[k] + t2;
              }
          }
      }
  }
}
```

It should address what you have in mind. If you decided to re-use it, give the proper credit to the author.

Source/Author: EricLarch

android getting sound frequencies real time?

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