Skip to content

Instantly share code, notes, and snippets.

@qwasd1224k
Last active September 12, 2023 08:03
Show Gist options
  • Save qwasd1224k/ccf4e793677348e05984 to your computer and use it in GitHub Desktop.
Save qwasd1224k/ccf4e793677348e05984 to your computer and use it in GitHub Desktop.
Androidで周波数解析
public class MainActivity extends Activity {
// サンプリングレート
int SAMPLING_RATE = 44100;
// FFTのポイント数
int FFT_SIZE = 4096;
// デシベルベースラインの設定
double dB_baseline = Math.pow(2, 15) * FFT_SIZE * Math.sqrt(2);
// 分解能の計算
double resol = ((SAMPLING_RATE / (double) FFT_SIZE));
AudioRecord audioRec = null;
boolean bIsRecording = false;
int bufSize;
Thread fft;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bufSize = AudioRecord.getMinBufferSize(SAMPLING_RATE,
AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);
}
@Override
protected void onResume() {
super.onResume();
// AudioRecordの作成
audioRec = new AudioRecord(MediaRecorder.AudioSource.MIC,
SAMPLING_RATE, AudioFormat.CHANNEL_IN_MONO,
AudioFormat.ENCODING_PCM_16BIT, bufSize * 2);
audioRec.startRecording();
bIsRecording = true;
//フーリエ解析スレッド
fft = new Thread(new Runnable() {
@Override
public void run() {
byte buf[] = new byte[bufSize * 2];
while (bIsRecording) {
audioRec.read(buf, 0, buf.length);
//エンディアン変換
ByteBuffer bf = ByteBuffer.wrap(buf);
bf.order(ByteOrder.LITTLE_ENDIAN);
short[] s = new short[(int) bufSize];
for (int i = bf.position(); i < bf.capacity() / 2; i++) {
s[i] = bf.getShort();
}
//FFTクラスの作成と値の引き渡し
FFT4g fft = new FFT4g(FFT_SIZE);
double[] FFTdata = new double[FFT_SIZE];
for (int i = 0; i < FFT_SIZE; i++) {
FFTdata[i] = (double) s[i];
}
fft.rdft(1, FFTdata);
// デシベルの計算
double[] dbfs = new double[FFT_SIZE / 2];
double max_db = -120d;
int max_i = 0;
for (int i = 0; i < FFT_SIZE; i += 2) {
dbfs[i / 2] = (int) (20 * Math.log10(Math.sqrt(Math
.pow(FFTdata[i], 2)
+ Math.pow(FFTdata[i + 1], 2)) / dB_baseline));
if (max_db < dbfs[i / 2]) {
max_db = dbfs[i / 2];
max_i = i / 2;
}
}
//音量が最大の周波数と,その音量を表示
Log.d("fft","周波数:"+ resol * max_i+" [Hz] 音量:" + max_db+" [dB]");
}
// 録音停止
audioRec.stop();
audioRec.release();
}
});
//スレッドのスタート
fft.start();
}
@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;
}
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment