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현재 Android 값은 AudioRecord로 수집 된 AudioData에 대해 FFT를 수행하려고 시도한 후에 모두 0입니다. 내 문제는 모든 값은 FFT 후 0입니다. 나는 이유를 모른다.FFT
다음 코드를 FFT (FFT library in android Sdk)로 사용하고 있습니다. 샘플 수는 균일합니다.
private void writeToScreen()
{
while(isRecording)
{
double[] y = new double[bufferSize];
for (int i = 0; i < y.length; i++) {
y[i]=0;
}
double[] x = new double[bufferSize];
//short[] to double[]
for (int i = 0; i < x.length; i++)
{
x[i]= audioBuffer[i]/32768;
}
//perform fft
fft meinfft = new fft(bufferSize);
meinfft.FFT(x, y);
System.out.println("Alle Werte x und y nach FFT:");
for (int i = 0; i < x.length; i++) { //Every Value is 0.0
if(x[i] != 0 || y[i] != 0)
System.out.println("x["+i+"]: "+ x[i] +" y["+i+"]: "+y[i]);
}
System.out.println("Ende Aller Werte");
// calculate index of max Value
int maxIndex =0;
for (int i = 1; i < x.length; i++) {
if(Math.sqrt(x[i]*x[i]+y[i]*y[i]) > Math.sqrt(x[maxIndex]*x[maxIndex]+y[maxIndex]*y[maxIndex]))
{
maxIndex = i;
}
}
System.out.println("Index des Maximums: "+maxIndex);
double freq = ((1.0 * sampleRate)/(1.0 * bufferSize)) * maxIndex; //Frequency is always 0
System.out.println("wahrscheinliche Frequenz: "+freq);
try
{
Thread.sleep(1000);
}
catch (InterruptedException e)
{}
}
System.out.println("Writethread beendet");
}
불행하게도 내가 FFT에 대해 매우 많이 알고 dosn't : (8192)
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;
}
}
}
}
}
는이 주파수를 계산하는 코드입니다. 나는 짧은 []에서 이중 []으로의 변환이 잘못되었거나 완전한 FFT 자체를 상상할 수 있습니다. 누군가가 나를 도울 수 있기를 바랍니다.
당신은 당신이 찾을 시도 할 경우 아래의 전체 코드 :
import java.io.IOException;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.LinearLayout;
import android.widget.TextView;
//import android.os.Bundle;
import android.os.Environment;
import android.view.ViewGroup;
import android.widget.Button;
import android.view.View;
import android.view.View.OnClickListener;
import android.content.Context;
import android.util.Log;
import android.media.MediaRecorder;
import android.media.MediaPlayer;
import de.benediktbock.fft.fft;
import android.media.AudioFormat;
import android.media.AudioRecord;
import android.media.MediaRecorder.AudioSource;
import java.io.IOException;
public class MainActivity extends Activity {
private static final String LOG_TAG = "FFTTEST";
private PlayButton mPlayButton = null;
private TextView realTeil = null;
private TextView imgTeil = null;
private fft mFFT = null;
private int channel_config = AudioFormat.CHANNEL_IN_MONO;
private int format = AudioFormat.ENCODING_PCM_16BIT;
private int sampleRate = 8000;
private int bufferSize = AudioRecord.getMinBufferSize(sampleRate, channel_config, format);
private AudioRecord audioInput = null; //new AudioRecord(AudioSource.MIC, sampleSize, channel_config, format, bufferSize);
private short[] audioBuffer = new short[bufferSize];
private Thread readingThread = null,writingThread=null;
private boolean isRecording = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LinearLayout ll = new LinearLayout(this);
mPlayButton = new PlayButton(this);
ll.addView(mPlayButton,new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT,
0));
realTeil = new TextView(this);
ll.addView(realTeil,new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT,
0));
imgTeil = new TextView(this);
ll.addView(imgTeil,new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT,
0));
setContentView(ll);
realTeil.setText("Realteil");
imgTeil.setText("Imaginärteil");
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
class PlayButton extends Button {
boolean mStartPlaying = true;
OnClickListener clicker = new OnClickListener() {
public void onClick(View v) {
onPlay(mStartPlaying);
if (mStartPlaying) {
setText("Stop");
} else {
setText("Start");
}
mStartPlaying = !mStartPlaying;
}
};
public PlayButton(Context ctx) {
super(ctx);
setText("Start");
setOnClickListener(clicker);
}
}
private void onPlay(boolean start) {
if (start) {
startRecording();
} else {
stopRecording();
}
}
private void startRecording()
{
audioInput = new AudioRecord(AudioSource.MIC, sampleRate, channel_config, format, bufferSize);
audioInput.startRecording();
isRecording = true;
readingThread = new Thread(new Runnable()
{
@Override
public void run()
{
readAudioToBuffer();
}
},"readAudio Thread");
readingThread.start();
writingThread = new Thread(new Runnable()
{
@Override
public void run()
{
writeToScreen();
}
},"write Thread");
writingThread.start();
}
private void writeToScreen()
{
while(isRecording)
{
double[] y = new double[bufferSize];
for (int i = 0; i < y.length; i++) {
y[i]=0;
}
double[] x = new double[bufferSize];
//short[] to double[]
for (int i = 0; i < x.length; i++)
{
x[i]= audioBuffer[i]/32768;
}
//perform fft
fft meinfft = new fft(bufferSize);
meinfft.FFT(x, y);
System.out.println("Alle Werte x und y nach FFT:");
for (int i = 0; i < x.length; i++) { //Every Value is 0.0
if(x[i] != 0 || y[i] != 0)
System.out.println("x["+i+"]: "+ x[i] +" y["+i+"]: "+y[i]);
}
System.out.println("Ende Aller Werte");
// calculate index of max Value
int maxIndex =0;
for (int i = 1; i < x.length; i++) {
if(Math.sqrt(x[i]*x[i]+y[i]*y[i]) > Math.sqrt(x[maxIndex]*x[maxIndex]+y[maxIndex]*y[maxIndex]))
{
maxIndex = i;
}
}
System.out.println("Index des Maximums: "+maxIndex);
double freq = ((1.0 * sampleRate)/(1.0 * bufferSize)) * maxIndex; //Frequency is always 0
System.out.println("wahrscheinliche Frequenz: "+freq);
try
{
Thread.sleep(1000);
}
catch (InterruptedException e)
{}
}
System.out.println("Writethread beendet");
}
private void readAudioToBuffer()
{
while(isRecording)
{
audioInput.read(audioBuffer, 0,bufferSize);
}
System.out.println("Thread wurde beendet");
}
private void stopRecording()
{
isRecording = false;
audioInput.stop();
audioInput.release();
audioInput= null;
readingThread = null;
}
}
그리고 아마도 트위 요인이 있습니다 또한 정의에서 정수 나누기 i/n 때문에 잘못되었습니다. pi/n * i로 더 잘 재정렬하십시오. – LutzL
질문에 대해서는 직접적인 내용이 아니지만 ((1.0 * sampleRate)/(1.0 * bufferSize)) * maxIndex가 맞습니까? 순간에 나는 +/- 5Hz에 대해 tollerance 있습니다. 아니면 마이크입니까? –