我使用this FFTBasedSpectrumAnalyzer來分析麥克風收集的聲音。但是,FFTBasedSpectrumAnalyzer創建了一個圖形,而我想要一個單獨的頻率,我可以將其放置在一個標籤中,所以我試圖通過以下公式獲得峯值的頻率:mFreq = (((1.0 * frequency)/(1.0 * blockSize)) * mPeakPos)/2
。我也通過這個公式得到幅度(以及因此的峯值和峯值頻率):Android:通過fft獲取更精確的頻率
int mPeakPos = 0;
double mMaxFFTSample = 150.0;
for (int i = 0; i < progress[0].length; i++) {
int x = i;
int downy = (int) (150 - (progress[0][i] * 10));
int upy = 150;
//Log.i("SETTT", "X: " + i + " downy: " + downy + " upy: " + upy);
if(downy < mMaxFFTSample)
{
mMaxFFTSample = downy;
//mMag = mMaxFFTSample;
mPeakPos = i;
}
}
但是,我有兩個問題。首先,最大頻率偏離10-40赫茲,即使我演奏的是穩定的音調也會變化。其次,我只能分析高達4000赫茲的音頻。有沒有辦法讓這個更準確和/或分析高達22 kHz的音頻?也許通過編輯塊大小爲非256或8000以外的頻率(即使當我嘗試這樣做時,mFreq會降至0,並且mMaxFFTSample通常會變爲-2)。 謝謝。
下面是完整的代碼:
public class FrequencyListener extends AppCompatActivity {
private double mFreq;
private double mMag;
private boolean mDidHitTargetFreq;
private View mBackgroundView;
int frequency = 8000;
int channelConfiguration = AudioFormat.CHANNEL_IN_MONO;
int audioEncoding = AudioFormat.ENCODING_PCM_16BIT;
AudioRecord audioRecord;
private RealDoubleFFT transformer;
int blockSize;
boolean started = false;
boolean CANCELLED_FLAG = false;
RecordAudio recordTask;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
blockSize = 256;
transformer = new RealDoubleFFT(blockSize);
started = true;
CANCELLED_FLAG = false;
recordTask = new RecordAudio();
recordTask.execute();
}
private class RecordAudio extends AsyncTask<Void, double[], Boolean> {
@Override
protected Boolean doInBackground(Void... params) {
int bufferSize = AudioRecord.getMinBufferSize(frequency,
channelConfiguration, audioEncoding);
audioRecord = new AudioRecord(
MediaRecorder.AudioSource.DEFAULT, frequency,
channelConfiguration, audioEncoding, bufferSize);
int bufferReadResult;
short[] buffer = new short[blockSize];
double[] toTransform = new double[blockSize];
try {
audioRecord.startRecording();
} catch (IllegalStateException e) {
Log.e("Recording failed", e.toString());
}
while (started) {
if (isCancelled() || (CANCELLED_FLAG == true)) {
started = false;
//publishProgress(cancelledResult);
Log.d("doInBackground", "Cancelling the RecordTask");
break;
} else {
bufferReadResult = audioRecord.read(buffer, 0, blockSize);
for (int i = 0; i < blockSize && i < bufferReadResult; i++) {
toTransform[i] = (double) buffer[i]/32768.0; // signed 16 bit
}
transformer.ft(toTransform);
publishProgress(toTransform);
}
}
return true;
}
@Override
protected void onProgressUpdate(double[]...progress) {
int mPeakPos = 0;
double mMaxFFTSample = 150.0;
for (int i = 0; i < progress[0].length; i++) {
int x = i;
int downy = (int) (150 - (progress[0][i] * 10));
int upy = 150;
//Log.i("SETTT", "X: " + i + " downy: " + downy + " upy: " + upy);
if(downy < mMaxFFTSample)
{
mMaxFFTSample = downy;
//mMag = mMaxFFTSample;
mPeakPos = i;
}
}
mFreq = (((1.0 * frequency)/(1.0 * blockSize)) * mPeakPos)/2;
Log.i("SETTT", "FREQ: " + mFreq + " MAG: " + mMaxFFTSample);
}
@Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
try{
audioRecord.stop();
}
catch(IllegalStateException e){
Log.e("Stop failed", e.toString());
}
}
}
@Override
protected void onPause() {
super.onPause();
started = false;
}
@Override
protected void onResume() {
super.onResume();
started = true;
}
}
因此,如果我要將頻率從8,000增加到,40,000我將能夠檢測到更高的頻率,但他們會更不準確 我試圖改變頻率從8,000到4,000,但有一個錯誤:'無效au dio buffer size'在這部分代碼中: 'int bufferSize = AudioRecord.getMinBufferSize(frequency, channelConfiguration,audioEncoding); audioRecord =新的AudioRecord( MediaRecorder.AudioSource。默認,頻率, channelConfiguration,audioEncoding,bufferSize);' – Jameson
是的,這是正確的。但你總是可以增加FFT大小來補償。關於這個錯誤,我猜想40000是不支持的速率,而'getMinBufferSize'返回一個你沒有檢查的錯誤。嘗試44100或48000. – jaket
在iOS上我是如何設計相同的東西的,但它能夠檢測高達21kHz的頻率,同時保持高水平的準確度?通過增加垃圾箱數量和採樣率?出於某種原因無法運作 - 頻率我得到的都是0或接近0。 如果我不得不滿足於出大的採樣率和很高的精確度,是有辦法,我可以只具有高精確度低於2 kHz?這只是減少採樣率,並以某種方式避免我剛剛收到的錯誤? – Jameson