Android应用程序来记录声音实时并确定频率 [英] Android app to record sound in real time and identify frequency
问题描述
我需要使用手机的麦克风来开发一个应用程序来记录的频率实时，然后显示它们（文本）。我在这里发布我的code。该FFT和复杂的类已经从 HTTP使用：//introcs.cs。 princeton.edu/java/97data/FFT.java.html 并的 http://introcs.cs.princeton.edu/java/97data/Complex.java.html 。问题是，当我在模拟器上运行这个频率从一些随机值开始并不断增加，直到7996它然后重复整个过程。有人可以plz帮助我吗？
I need to develop an app to record frequencies in real time using the phone's mic and then display them (in text). I am posting my code here. The FFT and complex classes have been used from http://introcs.cs.princeton.edu/java/97data/FFT.java.html and http://introcs.cs.princeton.edu/java/97data/Complex.java.html .The problem is when i run this on the emulator the frequency starts from some random value and keeps on increasing till 7996. It then repeats the whole process. Can someone plz help me out?
public class Main extends Activity {
TextView disp;
private static int[] sampleRate = new int[] { 44100, 22050, 11025, 8000 };
short audioData[];
double finalData[];
int bufferSize,srate;
String TAG;
public boolean recording;
AudioRecord recorder;
Complex[] fftArray;
float freq;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
disp = (TextView) findViewById(R.id.display);
Thread t1 = new Thread(new Runnable(){
public void run() {
Log.i(TAG,"Setting up recording");
for (int rate : sampleRate) {
try{
Log.d(TAG, "Attempting rate " + rate);
bufferSize=AudioRecord.getMinBufferSize(rate,AudioFormat.CHANNEL_CONFIGURATION_MONO,
AudioFormat.ENCODING_PCM_16BIT)*3; //get the buffer size to use with this audio record
if (bufferSize != AudioRecord.ERROR_BAD_VALUE) {
recorder = new AudioRecord (MediaRecorder.AudioSource.MIC,rate,AudioFormat.CHANNEL_CONFIGURATION_MONO,
AudioFormat.ENCODING_PCM_16BIT,2048); //instantiate the AudioRecorder
Log.d(TAG, "BufferSize " +bufferSize);
srate = rate;
}
} catch (Exception e) {
Log.e(TAG, rate + "Exception, keep trying.",e);
}
}
bufferSize=2048;
recording=true; //variable to use start or stop recording
audioData = new short [bufferSize]; //short array that pcm data is put into.
Log.i(TAG,"Got buffer size =" + bufferSize);
while (recording) { //loop while recording is needed
Log.i(TAG,"in while 1");
if (recorder.getState()==android.media.AudioRecord.STATE_INITIALIZED) // check to see if the recorder has initialized yet.
if (recorder.getRecordingState()==android.media.AudioRecord.RECORDSTATE_STOPPED)
recorder.startRecording(); //check to see if the Recorder has stopped or is not recording, and make it record.
else {
Log.i(TAG,"in else");
// audiorecord();
finalData=convert_to_double(audioData);
Findfft();
for(int k=0;k<fftArray.length;k++)
{
freq = ((float)srate/(float) fftArray.length) *(float)k;
runOnUiThread(new Runnable(){
public void run()
{
disp.setText("The frequency is " + freq);
if(freq>=15000)
recording = false;
}
});
}
}//else recorder started
} //while recording
if (recorder.getState()==android.media.AudioRecord.RECORDSTATE_RECORDING)
recorder.stop(); //stop the recorder before ending the thread
recorder.release(); //release the recorders resources
recorder=null; //set the recorder to be garbage collected.
} //运行
});
t1.start();
}
private void Findfft() {
// TODO Auto-generated method stub
Complex[] fftTempArray = new Complex[bufferSize];
for (int i=0; i<bufferSize; i++)
{
fftTempArray[i] = new Complex(finalData[i], 0);
}
fftArray = FFT.fft(fftTempArray);
}
private double[] convert_to_double(short data[]) {
// TODO Auto-generated method stub
double[] transformed = new double[data.length];
for (int j=0;j<data.length;j++) {
transformed[j] = (double)data[j];
}
return transformed;
}
@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;
}
}
推荐答案
您的问题就在这里：
Findfft();
for(int k=0;k<fftArray.length;k++) {
freq = ((float)srate/(float) fftArray.length) *(float)k;
runOnUiThread(new Runnable() {
public void run() {
disp.setText("The frequency is " + freq);
if(freq>=15000) recording = false;
}
});
}
这一切为循环所做的是通过你的FFT值的数组，数组索引转换为赫兹的频率，并打印。
All this for loop does is go through your array of FFT values, convert the array index to a frequency in Hz, and print it.
如果要输出什么频率你录音，你至少应该看看你的阵列中的数据 - 最原始的方法是计算方实际大小和找到的最大频率仓
If you want to output what frequency you're recording, you should at least look at the data in your array - the crudest method would be to calculate the square real magnitude and find the frequency bin with the biggest.
除此之外，我不认为你正在使用的FFT算法做任何precalculations - 有其他人做的，看到，因为你的移动设备开发，你可能要采取CPU占用率和功耗使用考虑。
In addition to that, I don't think the FFT algorithm you're using does any precalculations - there are others that do, and seeing as you're developing for a mobile device, you might want to take CPU usage and power use into account.
JTransforms 是一个库，做使用precalculation来降低CPU加载，它的文档非常齐全。
JTransforms is one library that does use precalculation to lower CPU load, and its documentation is very complete.
您还可以找到如何跨preT将数据从FFT在维基百科返回有用的信息 - 没有进攻，但看起来你不太清楚你在做什么，所以我给指针
You may also find useful information on how to interpret the data returned from the FFT at Wikipedia - no offense, but it looks like you're not quite sure what you're doing, so I'm giving pointers.
最后，如果你打算使用这个应用程序的音符，我好像记得很多人说的FFT是不是做的最好的方法，但我不记得是什么。也许别人可以添加几分？
Lastly, if you're looking to use this app for musical notes, I seem to remember lots of people saying that an FFT isn't the best way to do that, but I can't remember what is. Maybe someone else can add that bit?
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