我能够编写一个程序来捕获音频信号,消除背景噪音,应用窗口功能和信号可视化。我的程序正在努力到这一点,没有错误。现在我正在尝试为我的代码实现高通滤波器。我已经找到了这部分的API。但我根据我的代码无法应用它。这是我的代码:
private class RecordAudio extends AsyncTask<Void, double[], Void> {
@Override
protected Void doInBackground(Void... params) {
started = true;
try {
DataOutputStream dos = new DataOutputStream(
new BufferedOutputStream(new FileOutputStream(
recordingFile)));
int bufferSize = AudioRecord.getMinBufferSize(frequency,
channelConfiguration, audioEncoding);
audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC,
frequency, channelConfiguration, audioEncoding,
bufferSize);
NoiseSuppressor.create(audioRecord.getAudioSessionId());
short[] buffer = new short[blockSize];
double[] toTransform = new double[blockSize];
long t = System.currentTimeMillis();
long end = t + 15000;
audioRecord.startRecording();
while (started && System.currentTimeMillis() < end) {
int bufferReadResult = audioRecord.read(buffer, 0,
blockSize);
for (int i = 0; i < blockSize && i < bufferReadResult; i++) {
toTransform[i] = (double) buffer[i] / 32768.0;
dos.writeShort(buffer[i]);
}
toTransform = hann(toTransform);
transformer.ft(toTransform);
publishProgress(toTransform);
}
audioRecord.stop();
dos.close();
} catch (Throwable t) {
Log.e("AudioRecord", "Recording Failed");
}
return null;
}
This是API链接。
任何人都可以帮我做这个功能吗?我真的很感激! :)
提前致谢!
答案 0 :(得分:6)
这是我从c#中找到的库转换为java的类。我用它,效果很好。您也可以将此类用于低通滤波器
public class Filter {
/// <summary>
/// rez amount, from sqrt(2) to ~ 0.1
/// </summary>
private float resonance;
private float frequency;
private int sampleRate;
private PassType passType;
public float value;
private float c, a1, a2, a3, b1, b2;
/// <summary>
/// Array of input values, latest are in front
/// </summary>
private float[] inputHistory = new float[2];
/// <summary>
/// Array of output values, latest are in front
/// </summary>
private float[] outputHistory = new float[3];
public Filter(float frequency, int sampleRate, PassType passType, float resonance)
{
this.resonance = resonance;
this.frequency = frequency;
this.sampleRate = sampleRate;
this.passType = passType;
switch (passType)
{
case Lowpass:
c = 1.0f / (float)Math.tan(Math.PI * frequency / sampleRate);
a1 = 1.0f / (1.0f + resonance * c + c * c);
a2 = 2f * a1;
a3 = a1;
b1 = 2.0f * (1.0f - c * c) * a1;
b2 = (1.0f - resonance * c + c * c) * a1;
break;
case Highpass:
c = (float)Math.tan(Math.PI * frequency / sampleRate);
a1 = 1.0f / (1.0f + resonance * c + c * c);
a2 = -2f * a1;
a3 = a1;
b1 = 2.0f * (c * c - 1.0f) * a1;
b2 = (1.0f - resonance * c + c * c) * a1;
break;
}
}
public enum PassType
{
Highpass,
Lowpass,
}
public void Update(float newInput)
{
float newOutput = a1 * newInput + a2 * this.inputHistory[0] + a3 * this.inputHistory[1] - b1 * this.outputHistory[0] - b2 * this.outputHistory[1];
this.inputHistory[1] = this.inputHistory[0];
this.inputHistory[0] = newInput;
this.outputHistory[2] = this.outputHistory[1];
this.outputHistory[1] = this.outputHistory[0];
this.outputHistory[0] = newOutput;
}
public float getValue()
{
return this.outputHistory[0];
}
}
这就是我使用这个
的方式 Filter filter = new Filter(15000,44100, Filter.PassType.Highpass,1);
for (int i = 0; i < numSamples; i++)
{
filter.Update(floatArray[i]);
floatArray[i] = filter.getValue();
}
获得floatArray的fft后,您会看到它被过滤掉了。 希望它有所帮助