Android：-将录制的音频文件转换为浮动数组

Question

我正在做一个简单的Android应用程序，我从智能手机麦克风录制一些东西，保存在一个文件中，然后播放该文件。

现在我想对音频文件应用高通滤波器，但要做到这一点，我需要首先将音频文件转换为浮点数组。谁能帮我一下吗。

谢谢

package abc.com.please;

import android.content.pm.PackageManager;
import android.media.MediaPlayer;
import android.media.MediaRecorder;
import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;


public class MainActivity extends AppCompatActivity {

private static MediaRecorder mediaRecorder = new MediaRecorder();
private static MediaPlayer mediaPlayer;

private static String audioFilePath;
private static Button stopButton;
private static Button playButton;
private static Button recordButton;

private boolean isRecording = false;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    recordButton = (Button) findViewById(R.id.recordButton);
    playButton = (Button) findViewById(R.id.playButton);
    stopButton = (Button) findViewById(R.id.stopButton);

    if (!hasMicrophone())
    {
        stopButton.setEnabled(false);
        playButton.setEnabled(false);
        recordButton.setEnabled(false);
    } else {
        playButton.setEnabled(false);
        stopButton.setEnabled(false);
    }

    audioFilePath =
            Environment.getExternalStorageDirectory().getAbsolutePath()
                    + "/myaudio.3gp";


    recordButton.setOnClickListener(new View.OnClickListener(){

        public void onClick (View v)
        {

            isRecording = true;
            stopButton.setEnabled(true);
            playButton.setEnabled(false);
            recordButton.setEnabled(false);

            try {
                mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
                                   mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
                mediaRecorder.setOutputFile(audioFilePath);
                  mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
                mediaRecorder.prepare();
                mediaRecorder.start();
            }catch (Exception e) {
                e.printStackTrace();

            }



        }
    });

    stopButton.setOnClickListener(new View.OnClickListener() {
        public void onClick (View view)
        {

            stopButton.setEnabled(false);
            playButton.setEnabled(true);
            if (isRecording)
            {
                recordButton.setEnabled(false);
                isRecording = false;
                mediaRecorder.stop();
                mediaRecorder.release();
                recordButton.setEnabled(true);
            }
            else
            {
                Toast.makeText(getApplicationContext(),"No recording going      on",Toast.LENGTH_SHORT).show();
            }
        }});

    playButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view)

        {

            playButton.setEnabled(false);
            recordButton.setEnabled(false);
            stopButton.setEnabled(true);
            try {
                mediaPlayer = new MediaPlayer();
                mediaPlayer.setDataSource(audioFilePath);
                mediaPlayer.prepare();
                mediaPlayer.start();
            } catch (Exception e) {
                e.printStackTrace();
            }

        }
    });
}

protected boolean hasMicrophone() {
    PackageManager pmanager = this.getPackageManager();
    return pmanager.hasSystemFeature(
            PackageManager.FEATURE_MICROPHONE);
}








}

Answer 1

字节到浮点数转换的细节将取决于您用于音频文件的文件格式。我无法从您的代码中分辨出该格式。如果您的文件是WAV、44100 fps、16位、小端、立体声（这是标准的Java、“光盘质量”格式），您可以尝试使用我写的以下代码。关键的转换点是当两个字节串联并转换为单个数字时（其中“缓冲区”包含从音频文件读取的html" target="_blank">数据：

float audioVal = ( buffer[bufferIdx++] & 0xff )
                        | ( buffer[bufferIdx++] << 8 );

如果是big endian，则颠倒移位顺序。如果是24位或32位，那么您将

我一直在Java上下文中使用以下内容一段时间没有问题，但我不知道Android是否支持javax.sound.sampled.AudioInputStream等。也许在文件读取的上下文中查看转换仍然有用？代码假设我们有“CD质量”音频格式，并且音频文件不长于整数。最大帧数。

public float[] loadSoundFileURL(URL url) throws UnsupportedAudioFileException,
        IOException
{
    AudioInputStream ais = AudioSystem.getAudioInputStream(url);

    int framesCount = (int)ais.getFrameLength();

    // assuming stereo format, so two entries per frame
    float[] temp = new float[framesCount * 2];
    long tempCountdown = temp.length;

    int bytesRead = 0;
    int bufferIdx;
    int clipIdx = 0;
    byte[] buffer = new byte[1024];
    while((bytesRead = ais.read(buffer, 0, 1024)) != -1)
    {
        bufferIdx = 0;
        for (int i = 0, n = (bytesRead >> 1); i < n; i ++)
        {
            if ( tempCountdown-- >= 0)
            {
                temp[clipIdx++] = 
                        ( buffer[bufferIdx++] & 0xff )
                        | ( buffer[bufferIdx++] << 8 ) ;
            }
        }
    }

    // QUESTION: better to do following in above loop?
    for (int i = 0; i < temp.length; i++)
    {
        temp[i] = temp[i] / 32767f;
    }

    return temp;
}