利用libmp3lame實(shí)現(xiàn)在Android上錄音MP3文件示例-創(chuàng)新互聯(lián)

之前項(xiàng)目需要實(shí)現(xiàn)MP3的錄音，于是使用上了Lame這個(gè)庫(kù)。這次做一個(gè)demo，使用AndroidStudio+Cmake+NDK進(jìn)行開發(fā)。利用Android SDK提供的AndroidRecorder進(jìn)行錄音，得到PCM數(shù)據(jù)，并使用jni調(diào)用Lame這個(gè)C庫(kù)將PCM數(shù)據(jù)轉(zhuǎn)換為MP3文件。并使用MediaPlayer對(duì)錄音的MP3文件進(jìn)行播放。另外此次的按鍵是仿微信的語(yǔ)音按鍵，按下錄音，松開結(jié)束，若中途上滑松開即取消

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效果如下：

利用libmp3lame實(shí)現(xiàn)在Android上錄音MP3文件示例

項(xiàng)目地址: LameMp3ForAndroid_jb51.rar

一、主要類的介紹

Mp3Recorder—— 是負(fù)責(zé)調(diào)用AudioRecorder進(jìn)行錄音的類
SimpleLame——是負(fù)責(zé)將MP3Recorder錄制出的PCM數(shù)據(jù)轉(zhuǎn)換成MP3文件
DataEncodeThread——是負(fù)責(zé)執(zhí)行PCM轉(zhuǎn)MP3的線程
LameMp3Manager——是對(duì)Mp3Recorder的多一次封裝，增加了取消后刪除之前錄制的數(shù)據(jù)的邏輯
MediaPlayerUtil——是對(duì)系統(tǒng)的MediaPlayer進(jìn)行簡(jiǎn)單的封裝，使其只需要三步就可以播放音頻文件
MediaRecorderButton ——是一個(gè)仿微信錄音按鍵的控件，按下錄制，松開結(jié)束，錄制時(shí)上滑則取消錄制

二、錄制的流程

Mp3Recorder調(diào)用startRecording()開始錄制并初始化DataEncoderThread線程，并定期將錄制的PCM數(shù)據(jù)，傳入DataEncoderThread中。
在DataEncoderThread里，SimpleLame將Mp3Recorder傳入的PCM數(shù)據(jù)轉(zhuǎn)換成MP3格式并寫入文件，其中SimpleLame通過jni對(duì)Lame庫(kù)進(jìn)行調(diào)用
Mp3Recorder調(diào)用stopRecording()停止錄制，并通知DataEncoderThread線程錄制結(jié)束，DataEncoderThread將剩余的數(shù)據(jù)轉(zhuǎn)換完畢。

三、主要的實(shí)現(xiàn)代碼

Mp3Recorder

public class Mp3Recorder {
  static {
    System.loadLibrary("lamemp3");
  }
  //默認(rèn)采樣率
  private static final int DEFAULT_SAMPLING_RATE = 44100;
  //轉(zhuǎn)換周期，錄音每滿160幀，進(jìn)行一次轉(zhuǎn)換
  private static final int FRAME_COUNT = 160;
  //輸出MP3的碼率
  private static final int BIT_RATE = 32;
  //根據(jù)資料假定的大值。 實(shí)測(cè)時(shí)有時(shí)超過此值。
  private static final int MAX_VOLUME = 2000;
  private AudioRecord audioRecord = null;
  private int bufferSize;
  private File mp3File;
  private int mVolume;
  private short[] mPCMBuffer;
  private FileOutputStream os = null;
  private DataEncodeThread encodeThread;
  private int samplingRate;
  private int channelConfig;
  private PCMFormat audioFormat;
  private boolean isRecording = false;
  private ExecutorService executor = Executors.newFixedThreadPool(1);
  private OnFinishListener finishListener;

  public interface OnFinishListener {
    void onFinish(String mp3SavePath);
  }

  public Mp3Recorder(int samplingRate, int channelConfig, PCMFormat audioFormat) {
    this.samplingRate = samplingRate;
    this.channelConfig = channelConfig;
    this.audioFormat = audioFormat;
  }

  public Mp3Recorder() {
    this(DEFAULT_SAMPLING_RATE, AudioFormat.CHANNEL_IN_MONO, PCMFormat.PCM_16BIT);
  }


  public void startRecording(File mp3Save) throws IOException {
    if (isRecording) return;
    this.mp3File = mp3Save;
    if (audioRecord == null) {
      initAudioRecorder();
    }
    audioRecord.startRecording();
    Runnable runnable = new Runnable() {
      @Override
      public void run() {
        isRecording = true;
        //循環(huán)的從AudioRecord獲取錄音的PCM數(shù)據(jù)
        while (isRecording) {
          int readSize = audioRecord.read(mPCMBuffer, 0, bufferSize);
          if (readSize > 0) {
            //待轉(zhuǎn)換的PCM數(shù)據(jù)放到轉(zhuǎn)換線程中
            encodeThread.addChangeBuffer(mPCMBuffer,readSize);
            calculateRealVolume(mPCMBuffer, readSize);
          }
        }
        // 錄音完畢，釋放AudioRecord的資源
        try {
          audioRecord.stop();
          audioRecord.release();
          audioRecord = null;
          // 錄音完畢，通知轉(zhuǎn)換線程停止，并等待直到其轉(zhuǎn)換完畢
          Message msg = Message.obtain(encodeThread.getHandler(), DataEncodeThread.PROCESS_STOP);
          msg.sendToTarget();
          encodeThread.join();
          //轉(zhuǎn)換完畢后回調(diào)監(jiān)聽
          if(finishListener != null) finishListener.onFinish(mp3File.getPath());
        } catch (InterruptedException e) {
          e.printStackTrace();
        } finally {
          if (os != null) {
            try {
              os.close();
            } catch (IOException e) {
              e.printStackTrace();
            }
          }
        }
      }
    };
    executor.execute(runnable);
  }

  public void stopRecording() throws IOException {
    isRecording = false;
  }

  //計(jì)算音量大小
  private void calculateRealVolume(short[] buffer, int readSize) {
    double sum = 0;
    for (int i = 0; i < readSize; i++) {
      sum += buffer[i] * buffer[i];
    }
    if (readSize > 0) {
      double amplitude = sum / readSize;
      mVolume = (int) Math.sqrt(amplitude);
    }
  }

  public int getVolume(){
    if (mVolume >= MAX_VOLUME) {
      return MAX_VOLUME;
    }
    return mVolume;
  }

  public int getMaxVolume(){
    return MAX_VOLUME;
  }

  public void setFinishListener(OnFinishListener listener){
    this.finishListener = listener;
  }

  private void initAudioRecorder() throws IOException {
    int bytesPerFrame = audioFormat.getBytesPerFrame();
    //計(jì)算緩沖區(qū)的大小，使其是設(shè)置周期幀數(shù)的整數(shù)倍，方便循環(huán)
    int frameSize = AudioRecord.getMinBufferSize(samplingRate, channelConfig, audioFormat.getAudioFormat()) / bytesPerFrame;
    if (frameSize % FRAME_COUNT != 0) {
      frameSize = frameSize + (FRAME_COUNT - frameSize % FRAME_COUNT);
    }
    bufferSize = frameSize * bytesPerFrame;

    audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, samplingRate, channelConfig, audioFormat.getAudioFormat(), bufferSize);
    mPCMBuffer = new short[bufferSize];
    SimpleLame.init(samplingRate, 1, samplingRate, BIT_RATE);
    os = new FileOutputStream(mp3File);
    // 創(chuàng)建轉(zhuǎn)碼的線程
    encodeThread = new DataEncodeThread(os, bufferSize);
    encodeThread.start();
    //給AudioRecord設(shè)置刷新監(jiān)聽，待錄音幀數(shù)每次達(dá)到FRAME_COUNT，就通知轉(zhuǎn)換線程轉(zhuǎn)換一次數(shù)據(jù)
    audioRecord.setRecordPositionUpdateListener(encodeThread, encodeThread.getHandler());
    audioRecord.setPositionNotificationPeriod(FRAME_COUNT);
  }
}

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