音视频学习系列第（三）篇---wav文件的存储和解析

音视频系列

什么是wav

wav是一种无损的音频文件格式，wav文件有两部分，第一部分是文件头，记录一些重要的参数信息，如音频的采样率，通道数，数据位宽，第二部分是数据部分，数据部分可以是PCM，也可以是其它的编码格式的数据

为什么要将音频存储wav格式

存储为该格式，音乐播放器可以通过读取wav头，识别出它是音频文件，从而进行播放。
因为后缀名是可以任意修改的，不能简单的通过后缀名来判断该文件是否是音频文件

wav与pcm的区别

pcm是一种未经压缩的编码方式
wav是一种无损的音频文件格式

wav文件结构说明

wav文件结构图.png

little
小端法，低位字节放在内存的低地址端
big
大端法，低位字节放在内存的高地址端

public final void writeInt(int v) throws IOException {
    out.write((v >>> 24) & 0xFF);
    out.write((v >>> 16) & 0xFF);
    out.write((v >>>  8) & 0xFF);
    out.write((v >>>  0) & 0xFF);
    incCount(4);
}

write(int)和writeInt(int)区别
write只写入最低的8位
writeInt会按大端法写

字段详细说明

WaveHeader代码

public class WavFileHeader {

  public static final int WAV_FILE_HEADER_SIZE = 44;
  public static final int WAV_CHUNKSIZE_EXCLUDE_DATA = 36;

  public static final int WAV_CHUNKSIZE_OFFSET = 4;
  public static final int WAV_SUB_CHUNKSIZE1_OFFSET = 16;
  public static final int WAV_SUB_CHUNKSIZE2_OFFSET = 40;

  public String mChunkID="RIFF";
  public int mChunkSize=0;
  public String mFormat="WAVE";

  public String mSubChunk1ID="fmt ";
  public int mSubChunk1Size = 16;
  public short mAudioFormat = 1;
  public short mNumChannel = 1;
  public int mSampleRate = 8000;
  public int mByteRate = 0;
  public short mBlockAlign = 0;
  public short mBitsPerSample = 8;

  public String mSubChunk2ID = "data";
  public int mSubChunk2Size = 0;

  public WavFileHeader(){

  }

  public WavFileHeader(int sampleRateInHz, int channels, int bitsPerSample){
    mSampleRate = sampleRateInHz;
    mNumChannel = (short) channels;
    mBitsPerSample = (short) bitsPerSample;
    mByteRate = mSampleRate * mNumChannel * mBitsPerSample / 8;
    mBlockAlign = (short) (mNumChannel * mBitsPerSample / 8);
  }
}

将录音存储为wav文件

public class WavFileWriter {

private static final String TAG = "WavFileWriter";

private String mFilePath;
private int mDataSize = 0;
private DataOutputStream dos;

/**
 *
 * @param filePath
 * @param sampleRateInHz  采样率 44100
 * @param channels        声道数  1单声道  2双声道
 * @param bitsPerSample   每个样点对应的位数  16
 * @return
 */
public boolean openFile(String filePath, int sampleRateInHz, int channels, int bitsPerSample) {
    if (dos != null) {
        closeFile();
    }

    mFilePath = filePath;
    try {
        dos = new DataOutputStream(new FileOutputStream(mFilePath));
        return writeHeader(sampleRateInHz, channels, bitsPerSample);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
        return false;
    }
}

public boolean closeFile() {
    boolean result=false;
    if (dos != null) {
        try {
            result=writeDataSize();
            dos.close();
            dos=null;
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return result;
}

public boolean writeData(byte[] buffer, int offset, int count) {
    if (dos == null) {
        return false;
    }
    try {
        dos.write(buffer, offset, count);
        mDataSize += count;
    } catch (IOException e) {
        e.printStackTrace();
        return false;
    }
    return true;
}

/**
 * 将一些需要计算出来的字段重新赋值
 * mChunkSize  位置4-8，值=36+原始音频数据大小
 * mSubChunk1Size  固定值16
 * mSubChunk2Size  位置40-44  值=原始音频数据大小
 */
private boolean writeDataSize() {
    if (dos == null) {
        return false;
    }
    try {
        RandomAccessFile waveAccessFile = new RandomAccessFile(mFilePath, "rw");
        waveAccessFile.seek(WavFileHeader.WAV_CHUNKSIZE_OFFSET);
        waveAccessFile.write(intToByteArray(WavFileHeader.WAV_CHUNKSIZE_EXCLUDE_DATA + mDataSize), 0, 4);
        waveAccessFile.seek(WavFileHeader.WAV_SUB_CHUNKSIZE2_OFFSET);
        waveAccessFile.write(intToByteArray(mDataSize), 0, 4);
        waveAccessFile.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
        return false;
    } catch (IOException e) {
        e.printStackTrace();
        return false;
    }
    return true;
}

private boolean writeHeader(int sampleRateInHz, int channels, int bitsPerSample) {
    if (dos == null) {
        return false;
    }

    WavFileHeader header = new WavFileHeader(sampleRateInHz, channels, bitsPerSample);

    //按照wav文件结构依次写入
    try {
        dos.writeBytes(header.mChunkID);
        //这里不直接用writeInt的原因是它采用的大端法存储
        dos.write(intToByteArray(header.mChunkSize), 0, 4);
        dos.writeBytes(header.mFormat);
        dos.writeBytes(header.mSubChunk1ID);
        dos.write(intToByteArray(header.mSubChunk1Size), 0, 4);
        dos.write(shortToByteArray(header.mAudioFormat), 0, 2);
        dos.write(shortToByteArray(header.mNumChannel), 0, 2);
        dos.write(intToByteArray(header.mSampleRate), 0, 4);
        dos.write(intToByteArray(header.mByteRate), 0, 4);
        dos.write(shortToByteArray(header.mBlockAlign), 0, 2);
        dos.write(shortToByteArray(header.mBitsPerSample), 0, 2);
        dos.writeBytes(header.mSubChunk2ID);
        dos.write(intToByteArray(header.mSubChunk2Size), 0, 4);
    } catch (IOException e) {
        e.printStackTrace();
        return false;
    }
    return true;
}

private static byte[] intToByteArray(int data) {
    return ByteBuffer.allocate(4).order(ByteOrder.LITTLE_ENDIAN).putInt(data).array();
}

private static byte[] shortToByteArray(short data) {
    return ByteBuffer.allocate(2).order(ByteOrder.LITTLE_ENDIAN).putShort(data).array();
}
}

解析wav文件并播放

public class WavFileReader {
private static final String TAG="WavFileReader";

private DataInputStream dis;
private WavFileHeader mWavFileHeader;

public WavFileHeader getWavFileHeader(){
    return mWavFileHeader;
}

public boolean openFile(String filePath){
    if(dis!=null){
        closeFile();
    }
    try {
        dis=new DataInputStream(new FileInputStream(filePath));
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }

    return readHeader();
}

public void closeFile(){
    if(dis!=null){
        try {
            dis.close();
            dis=null;
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

public int readData(byte[] buffer, int offset, int count) {
    if (dis == null || mWavFileHeader == null) {
        return -1;
    }

    try {
        int nbytes = dis.read(buffer, offset, count);
        if (nbytes == -1) {
            return 0;
        }
        return nbytes;
    } catch (IOException e) {
        e.printStackTrace();
    }

    return -1;
}

/**
 *read和read(byte b[])
 * read每次读取一个字节，返回0-255的int字节值
 * read(byte b[])读取一定数量的字节，返回实际读取的字节的数量
 */
private boolean readHeader(){
    if(dis==null){
        return false;
    }

    WavFileHeader header=new WavFileHeader();
    byte[] intValue = new byte[4];
    byte[] shortValue = new byte[2];

    try {
        header.mChunkID = "" + (char) dis.readByte() + (char) dis.readByte() + (char) dis.readByte() + (char) dis.readByte();
        Log.d(TAG, "Read file chunkID:" + header.mChunkID);

        dis.read(intValue);
        header.mChunkSize=byteArrayToInt(intValue);
        Log.d(TAG, "Read file chunkSize:" + header.mChunkSize);

        header.mFormat = "" + (char) dis.readByte() + (char) dis.readByte() + (char) dis.readByte() + (char) dis.readByte();
        Log.d(TAG, "Read file format:" + header.mFormat);

        header.mSubChunk1ID = "" + (char) dis.readByte() + (char) dis.readByte() + (char) dis.readByte() + (char) dis.readByte();
        Log.d(TAG, "Read fmt chunkID:" + header.mSubChunk1ID);

        dis.read(intValue);
        header.mSubChunk1Size = byteArrayToInt(intValue);
        Log.d(TAG, "Read fmt chunkSize:" + header.mSubChunk1Size);

        dis.read(shortValue);
        header.mAudioFormat = byteArrayToShort(shortValue);
        Log.d(TAG, "Read audioFormat:" + header.mAudioFormat);

        dis.read(shortValue);
        header.mNumChannel = byteArrayToShort(shortValue);
        Log.d(TAG, "Read channel number:" + header.mNumChannel);

        dis.read(intValue);
        header.mSampleRate = byteArrayToInt(intValue);
        Log.d(TAG, "Read samplerate:" + header.mSampleRate);

        dis.read(intValue);
        header.mByteRate = byteArrayToInt(intValue);
        Log.d(TAG, "Read byterate:" + header.mByteRate);

        dis.read(shortValue);
        header.mBlockAlign = byteArrayToShort(shortValue);
        Log.d(TAG, "Read blockalign:" + header.mBlockAlign);

        dis.read(shortValue);
        header.mBitsPerSample = byteArrayToShort(shortValue);
        Log.d(TAG, "Read bitspersample:" + header.mBitsPerSample);

        header.mSubChunk2ID = "" + (char) dis.readByte() + (char) dis.readByte() + (char) dis.readByte() + (char) dis.readByte();
        Log.d(TAG, "Read data chunkID:" + header.mSubChunk2ID);

        dis.read(intValue);
        header.mSubChunk2Size = byteArrayToInt(intValue);
        Log.d(TAG, "Read data chunkSize:" + header.mSubChunk2Size);

        Log.d(TAG, "Read wav file success !");
    } catch (IOException e) {
        e.printStackTrace();
        return false;
    }

    mWavFileHeader=header;
    return true;
}

private int byteArrayToInt(byte[] b){
    return ByteBuffer.wrap(b).order(ByteOrder.LITTLE_ENDIAN).getInt();
}

private short byteArrayToShort(byte[] b){
    return ByteBuffer.wrap(b).order(ByteOrder.LITTLE_ENDIAN).getShort();
}
}

测试

public class AudioWavActivity extends UIRootActivity {

private Button btn_audio_record;
private Button btn_audio_record_play;

private AudioCapture audioCapture;
private AudioPlayer audioPlayer;

private WavFileWriter wavFileWriter;
private WavFileReader wavFileReader;
private boolean isReading;

private String path="";

@Override
protected int getLayoutId() {
    return R.layout.activity_media_audio;
}

@Override
protected void initTitle() {
    head_title.setText("wav音频文件的存储和解析");
}

@Override
public void initView() {
    btn_audio_record=findViewById(R.id.btn_audio_record);
    btn_audio_record_play=findViewById(R.id.btn_audio_record_play);
}

@Override
public void initData() {
    path=FileUtil.getAudioDir(this)+"/audioTest.wav";
    audioCapture=new AudioCapture();
    audioPlayer=new AudioPlayer();
    wavFileReader=new WavFileReader();
    wavFileWriter=new WavFileWriter();

    String des = "录音权限被禁止，我们需要打开录音权限";
    String[] permissions = new String[]{Manifest.permission.RECORD_AUDIO};
    baseAt.requestPermissions(des, permissions, 100, new PermissionsResultListener() {
        @Override
        public void onPermissionGranted() {

        }
        @Override
        public void onPermissionDenied() {
            finish();

        }
    });

}

@Override
public void initEvent() {
    btn_audio_record.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            if(event.getAction()==MotionEvent.ACTION_DOWN){
                Log.d("TAG","按住");
                start();
            }else if(event.getAction()==MotionEvent.ACTION_UP){
                Log.d("TAG","松开");
                stop();
            }
            return false;
        }
    });

    btn_audio_record_play.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            play();

        }
    });

}

//播放录音
private void play(){
    isReading=true;
    wavFileReader.openFile(path);
    audioPlayer.startPlay();
    new AudioTrackThread().start();
}

private class AudioTrackThread extends Thread{
    @Override
    public void run() {
        byte[] buffer = new byte[1024];
        while (isReading && wavFileReader.readData(buffer,0,buffer.length)>0){
            audioPlayer.play(buffer,0,buffer.length);
        }
        audioPlayer.stopPlay();
        wavFileReader.closeFile();
    }
}

//开始录音
private void start(){
    wavFileWriter.openFile(path,44100,2,16);
    btn_audio_record.setText("松开 结束");
    audioCapture.startRecord();
    audioCapture.setOnAudioFrameCaptureListener(new AudioCapture.onAudioFrameCaptureListener() {
        @Override
        public void onAudioFrameCapture(byte[] audioData) {
            wavFileWriter.writeData(audioData,0,audioData.length);
        }
    });
}

//结束录音
private void stop(){
    btn_audio_record.setText("按住 录音");
    audioCapture.stopRecord();
    wavFileWriter.closeFile();
}
}