Android音视频学习(二)

引用

感谢灰色飘零大佬的这篇指南

概念

Android提供了两种音频录制方式, 这里讲比较底层一些的AudioRecord.

引用一下google的定义:

AudioRecord类管理Java程序的音频资源, 以记录来自音频输入硬件的音频. 这是经过向AudioRecord对象读取数据来实现的. 应用经过如下三种方法之一及时的查询AudioRecord对象:

1. read(byte[], int, int)
2. read(short[], int, int)
3. read(ByteBuffer, int)

具体使用哪一个, 是根据音频数据存储格式自由选择的. 建立后, AudioRecord对象初始化其关联的音频缓冲区, 它将填充新的音频数据. 在构造期间指定的缓冲区大小决定了AudioRecord在"过分运行"时, 还没有读取的数据能够保存多长时间. 所以从音频硬件读取的数据块大小应该小于缓冲区大小.

下面是具体实现

权限申请

private void checkPermission() {
    //6.0之后须要动态申请权限
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
      //检查是否已经获取权限, 没有获取的权限放到list里
      for (String permission : permissions) {
        if (ContextCompat.checkSelfPermission(this, permission)
            != PackageManager.PERMISSION_GRANTED) {
          mPermissionList.add(permission);
        }
      }

      //list不为空, 就去申请所须要的权限
      if (!mPermissionList.isEmpty()) {
        String[] permissions = mPermissionList.toArray(new String[0]);
        ActivityCompat.requestPermissions(this, permissions, MY_PERMISSIONS_REQUEST);
      }
    }
  }
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建立AudioRecord

这里写了个方法来建立AudioRecord:

private void createAudioRecord() {
    //这里经过AudioRecord类获取最小的缓存大小
    recordBufSize =
        AudioRecord.getMinBufferSize(GlobalConfig.SAMPLE_RATE_INHZ, GlobalConfig.CHANNEL_CONFIG,
            GlobalConfig.AUDIO_FORMAT);
    mAudioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, GlobalConfig.SAMPLE_RATE_INHZ,
        GlobalConfig.CHANNEL_CONFIG, GlobalConfig.AUDIO_FORMAT, recordBufSize);
  }
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用到的配置类:

public class GlobalConfig {

  //采样率
  public static final int SAMPLE_RATE_INHZ = 44100;

  //声道
  public static final int CHANNEL_CONFIG = AudioFormat.CHANNEL_IN_MONO;

  //返回的音频数据格式
  public static final int AUDIO_FORMAT = AudioFormat.ENCODING_PCM_16BIT;
}
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开始录制音频

private void startRecord() {
    createAudioRecord();

    //buffer, 用来从AudioRecord中获取录制的音频
    final byte[] data = new byte[recordBufSize];
    //pcm文件存储位置
    final File file = new File(getExternalFilesDir(Environment.DIRECTORY_MUSIC), "test.pcm");
    if (!file.mkdirs()) {
      Log.d(TAG, "startRecord: " + "Directory not created");
    }
    if (file.exists()) {
      file.delete();
    }

    //开始录制
    mAudioRecord.startRecording();
    //录制标记
    isRecording = true;

    //不阻塞主线程
    new Thread(new Runnable() {
      @Override public void run() {
        //新建文件输出流, 把录制音频存储
        FileOutputStream fileOutputStream = null;
        try {
          fileOutputStream = new FileOutputStream(file);
        } catch (FileNotFoundException e) {
          e.printStackTrace();
        }

        if (fileOutputStream != null) {
          while (isRecording) {
            //将录制音频传到buffer里
            int read = mAudioRecord.read(data, 0, recordBufSize);
            if (read != AudioRecord.ERROR_INVALID_OPERATION) {
              try {
                //buffer数据没问题写入到文件中
                fileOutputStream.write(data);
              } catch (IOException e) {
                e.printStackTrace();
              }
            }
          }

          try {
            //不要忘记关文件输出流
            fileOutputStream.close();
          } catch (IOException e) {
            e.printStackTrace();
          }
        }
      }
    }).start();
  }
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中止录制

private void stopRecord() {
  //中止录音
  isRecording = false;
  //不要泄露
  if (mAudioRecord != null) {
    mAudioRecord.stop();
    mAudioRecord.release();
    mAudioRecord = null;
  }
}
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原始音频文件转化

这里直接给一个大佬提供的转化工具类:

/** * 将pcm音频文件转换为wav音频文件 */
public class PcmToWavUtil {

    /** * 缓存的音频大小 */
    private int mBufferSize;
    /** * 采样率 */
    private int mSampleRate;
    /** * 声道数 */
    private int mChannel;


    /** * @param sampleRate sample rate、采样率 * @param channel channel、声道 * @param encoding Audio data format、音频格式 */
    PcmToWavUtil(int sampleRate, int channel, int encoding) {
        this.mSampleRate = sampleRate;
        this.mChannel = channel;
        this.mBufferSize = AudioRecord.getMinBufferSize(mSampleRate, mChannel, encoding);
    }


    /** * pcm文件转wav文件 * * @param inFilename 源文件路径 * @param outFilename 目标文件路径 */
    public void pcmToWav(String inFilename, String outFilename) {
        FileInputStream in;
        FileOutputStream out;
        long totalAudioLen;
        long totalDataLen;
        long longSampleRate = mSampleRate;
        int channels = mChannel == AudioFormat.CHANNEL_IN_MONO ? 1 : 2;
        long byteRate = 16 * mSampleRate * channels / 8;
        byte[] data = new byte[mBufferSize];
        try {
            in = new FileInputStream(inFilename);
            out = new FileOutputStream(outFilename);
            totalAudioLen = in.getChannel().size();
            totalDataLen = totalAudioLen + 36;

            writeWaveFileHeader(out, totalAudioLen, totalDataLen,
                longSampleRate, channels, byteRate);
            while (in.read(data) != -1) {
                out.write(data);
            }
            in.close();
            out.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    /** * 加入wav文件头 */
    private void writeWaveFileHeader(FileOutputStream out, long totalAudioLen, long totalDataLen, long longSampleRate, int channels, long byteRate) throws IOException {
        byte[] header = new byte[44];
        // RIFF/WAVE header
        header[0] = 'R';
        header[1] = 'I';
        header[2] = 'F';
        header[3] = 'F';
        header[4] = (byte) (totalDataLen & 0xff);
        header[5] = (byte) ((totalDataLen >> 8) & 0xff);
        header[6] = (byte) ((totalDataLen >> 16) & 0xff);
        header[7] = (byte) ((totalDataLen >> 24) & 0xff);
        //WAVE
        header[8] = 'W';
        header[9] = 'A';
        header[10] = 'V';
        header[11] = 'E';
        // 'fmt ' chunk
        header[12] = 'f';
        header[13] = 'm';
        header[14] = 't';
        header[15] = ' ';
        // 4 bytes: size of 'fmt ' chunk
        header[16] = 16;
        header[17] = 0;
        header[18] = 0;
        header[19] = 0;
        // format = 1
        header[20] = 1;
        header[21] = 0;
        header[22] = (byte) channels;
        header[23] = 0;
        header[24] = (byte) (longSampleRate & 0xff);
        header[25] = (byte) ((longSampleRate >> 8) & 0xff);
        header[26] = (byte) ((longSampleRate >> 16) & 0xff);
        header[27] = (byte) ((longSampleRate >> 24) & 0xff);
        header[28] = (byte) (byteRate & 0xff);
        header[29] = (byte) ((byteRate >> 8) & 0xff);
        header[30] = (byte) ((byteRate >> 16) & 0xff);
        header[31] = (byte) ((byteRate >> 24) & 0xff);
        // block align
        header[32] = (byte) (2 * 16 / 8);
        header[33] = 0;
        // bits per sample
        header[34] = 16;
        header[35] = 0;
        //data
        header[36] = 'd';
        header[37] = 'a';
        header[38] = 't';
        header[39] = 'a';
        header[40] = (byte) (totalAudioLen & 0xff);
        header[41] = (byte) ((totalAudioLen >> 8) & 0xff);
        header[42] = (byte) ((totalAudioLen >> 16) & 0xff);
        header[43] = (byte) ((totalAudioLen >> 24) & 0xff);
        out.write(header, 0, 44);
    }
}
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总结

到这里, 就能够进行音频录制啦