获取音频文件的频率，每1/4秒的android [英] Get the frequency of an audio file in every 1/4 seconds in android
问题描述
我有一个声音文件（名为.3gp）及其有关〜1分钟。我想获得这个声音文件的频率，每1/4秒。我的想法是从音频文件接收样品中每1/4秒和用FFT我可能得到的频率值。有没有办法做到这一点？
I have a sound file (.3gp) and its about ~1 min. I would like to get the frequency of this sound file in every 1/4 seconds. My idea is to receive samples in every 1/4 seconds from the audio file and using FFT I might get the frequency values. Is there any way to do this?
其实我会分裂的声音文件转换成1/4秒的样本声音文件（alwyas覆盖preveious一个），然后使用FFT算法和检测频率，其中magintude是bigggest。但也有可能是更容易的解决方案，但是我没有一个线索如何可以做到这一点。
Actually I would split the sound file into 1/4sec samples sound files (alwyas overwriting the preveious one), then using FFT algorithm and detect the frequency where the magintude is the bigggest. But there might be easier solutions however I dont have a clue how to do this either.
***更新2 - 新的code
***UPDATE 2 - new code
我用这个code到目前为止：
I use this code so far:
公共类RecordAudio扩展的AsyncTask {
public class RecordAudio extends AsyncTask {
@Override
protected Void doInBackground(Void... arg0) {
try {
int bufferSize = AudioRecord.getMinBufferSize(frequency,
AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);
//int bufferSize = AudioRecord.getMinBufferSize(frequency,
// channelConfiguration, audioEncoding);
AudioRecord audioRecord = new AudioRecord(
MediaRecorder.AudioSource.MIC, frequency,
channelConfiguration, audioEncoding, bufferSize);
short[] buffer = new short[blockSize];
//double[] toTransform = new double[blockSize];
audioRecord.startRecording();
// started = true; hopes this should true before calling
// following while loop
while (started) {
sampling++;
double[] re = new double[blockSize];
double[] im = new double[blockSize];
double[] newArray = new double[blockSize*2];
double[] magns = new double[blockSize];
double MaxMagn=0;
double pitch = 0;
int bufferReadResult = audioRecord.read(buffer, 0,
blockSize);
for (int i = 0; i < blockSize && i < bufferReadResult; i++) {
re[i] = (double) buffer[i] / 32768.0; // signed 16bit
im[i] = 0;
}
newArray = FFTbase.fft(re, im,true);
for (int i = 0; i < newArray.length; i+=2) {
re[i/2]=newArray[i];
im[i/2]=newArray[i+1];
magns[i/2] = Math.sqrt(re[i/2]*re[i/2]+im[i/2]*im[i/2]);
}
//我只需要上半年
// I only need the first half
for (int i = 0; i < (magns.length)/2; i++) {
if (magns[i]>MaxMagn)
{
MaxMagn = magns[i];
pitch=i;
}
}
if (sampling > 50) {
Log.i("pitch and magnitude", "" + MaxMagn + " " + pitch*15.625f);
sampling=0;
MaxMagn=0;pitch=0;
}
}
audioRecord.stop();
} catch (Throwable t) {
t.printStackTrace();
Log.e("AudioRecord", "Recording Failed");
}
return null;
}
我用这个： http://www.wikijava.org/wiki/The_Fast_Fourier_Transform_in_Java_% 28part_1％29
吉他弦似乎正确的，但我自己的声音，因为这样并不好：
Guitar strings seem correct, but my own sound is not good because of this:
两峰的幅度改变大部分时间，我总能找到最大的，以获得基本频率。
The magnitude of the two peaks change most of the time and I always find the biggest to get the fundamental frequency.
推荐答案
间距跟踪与FFT人们常常要求对堆栈溢出，我写了的blog进入样品code 。在code是C，但与解释和链接，您应该可以做你想做的。
Pitch tracking with the FFT is asked so often on Stack Overflow I wrote a blog entry with sample code. The code is in C, but with the explanation and links you should be able to do what you want.
至于它划分成1/4秒为单位，你可以简单地利用，而不是默认的（我认为这是大约1秒）的1/4第二部分的FFT如你所说。如果这不会给你想要的频率分辨率，您可能需要使用不同的音高的识别方法。你可以做的另一件事是使用重叠的部分，比1/4秒的时间越长，但启动时间间隔是1/4秒分开。此方法提到的博客条目，但它可能无法满足您的设计规格。
As to dividing it up into 1/4 second increments, you could simply take FFTs of 1/4 second segments as you suggested, instead of the default (which I think is about 1 second). If this doesn't give you the frequency resolution you want, you may have to use a different pitch recognition method. Another thing you could do is use overlapping segments that are longer than 1/4 second, but start at intervals that are 1/4 second apart. This method is alluded to the blog entry, but it may not meet your design spec.
这篇关于获取音频文件的频率，每1/4秒的android的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
