Android wav文件的存储

ゝ一世哀愁。 2022-11-12 04:15 156阅读 0赞

#### 一、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

#### 二、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

#### 三、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

#### 四、wav文件结构说明 ####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjYwMDM5OA_size_16_color_FFFFFF_t_70]

#### 五、存储wav格式文件 ####

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);
      }
    }

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();
    }
    }

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