Android音频开发之尝试音频混合

音频混合：实时录制audio时录制麦克风数据 和 写入背景音乐

测试代码：https://github.com/CL-window/audio_mix

本次案例实现了

＊MediaPlayer 播放音频
＊AudioTrack 播放音频 mp3 --> pcm data ( libs/jl1.0.1.jar )
＊AudioRecord 录制音频 pcm file
＊AudioTrack 播放音频 pcm data
＊AudioRecord 录制音频 use MediaCodec & MediaMuxer write data

＊MediaExtractor 和 MediaCodec 手动解码出 pcm 数据
＊混合音频

音频混合核心算法来自前辈，表示感谢

/**
     * 采用简单的平均算法 average audio mixing algorithm
     * code from :    http://www.codexiu.cn/android/blog/3618/
     * 测试发现这种算法会降低 录制的音量
     */
    private byte[] averageMix(byte[][] bMulRoadAudioes) {

        if (bMulRoadAudioes == null || bMulRoadAudioes.length == 0)
            return null;
        byte[] realMixAudio = bMulRoadAudioes[0];

        if (bMulRoadAudioes.length == 1)
            return realMixAudio;

        for (int rw = 0; rw < bMulRoadAudioes.length; ++rw) {
            if (bMulRoadAudioes[rw].length != realMixAudio.length) {
                Log.e("app", "column of the road of audio + " + rw + " is diffrent.");
                return null;
            }
        }

        int row = bMulRoadAudioes.length;
        int coloum = realMixAudio.length / 2;
        short[][] sMulRoadAudioes = new short[row][coloum];
        for (int r = 0; r < row; ++r) {
            for (int c = 0; c < coloum; ++c) {
                sMulRoadAudioes[r][c] = (short) ((bMulRoadAudioes[r][c * 2] & 0xff) | (bMulRoadAudioes[r][c * 2 + 1] & 0xff) << 8);
            }
        }
        short[] sMixAudio = new short[coloum];
        int mixVal;
        int sr = 0;
        for (int sc = 0; sc < coloum; ++sc) {
            mixVal = 0;
            sr = 0;
            for (; sr < row; ++sr) {
                mixVal += sMulRoadAudioes[sr][sc];
            }
            sMixAudio[sc] = (short) (mixVal / row);
        }
        for (sr = 0; sr < coloum; ++sr) {
            realMixAudio[sr * 2] = (byte) (sMixAudio[sr] & 0x00FF);
            realMixAudio[sr * 2 + 1] = (byte) ((sMixAudio[sr] & 0xFF00) >> 8);
        }
        return realMixAudio;
    }

1.MediaPlayer 播放音乐，这个简单

private void initMediaPlayer(String filePath) {
        releaseMediaPlayer();
        mMediaPlayer = new MediaPlayer();
        mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        mMediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
            @Override
            public void onPrepared(MediaPlayer mp) {
                Log.i("slack", "onPrepared...");
                mMediaPlayer.start();
            }
        });
        try {
            mMediaPlayer.setDataSource(filePath);
            mMediaPlayer.prepareAsync();
        } catch (IOException e) {
            e.printStackTrace();
            Log.i("slack", e.getMessage());
        }
    }

2.AudioTrack 播放音频 mp3 --> pcm data 使用了( libs/jl1.0.1.jar )

class PlayTask extends AsyncTask<Void, Void, Void> {
        @Override
        protected Void doInBackground(Void... arg0) {
            mIsPlaying = true;
            Decoder mDecoder = new Decoder();
            try {
                int bufferSize = AudioTrack.getMinBufferSize(mFrequence,
                        mPlayChannelConfig, mAudioEncoding);
                short[] buffer = new short[bufferSize];
                // 定义输入流，将音频写入到AudioTrack类中，实现播放
                FileInputStream fin = new FileInputStream(mp3FilePath);
                Bitstream bitstream = new Bitstream(fin);
                // 实例AudioTrack
                AudioTrack track = new AudioTrack(AudioManager.STREAM_MUSIC,
                        mFrequence,
                        mPlayChannelConfig, mAudioEncoding, bufferSize,
                        AudioTrack.MODE_STREAM);
                // 开始播放
                track.play();
                // 由于AudioTrack播放的是流，所以，我们需要一边播放一边读取
                Header header;
                while (mIsPlaying && (header = bitstream.readFrame()) != null) {
                    SampleBuffer sampleBuffer = (SampleBuffer) mDecoder.decodeFrame(header, bitstream);
                    buffer = sampleBuffer.getBuffer();
                    track.write(buffer, 0, buffer.length);
                    bitstream.closeFrame();
                }

                // 播放结束
                track.stop();
                track.release();
                fin.close();
            } catch (Exception e) {
                // TODO: handle exception
                Log.e("slack", "error:" + e.getMessage());
            }
            return null;
        }


        protected void onPostExecute(Void result) {

        }


        protected void onPreExecute() {

        }
    }

3.AudioRecord 录制音频 pcm file

class RecordTask extends AsyncTask<Void, Integer, Void> {
        @Override
        protected Void doInBackground(Void... arg0) {
            mIsRecording = true;
            try {
                // 开通输出流到指定的文件
                DataOutputStream dos = new DataOutputStream(
                        new BufferedOutputStream(
                                new FileOutputStream(mAudioFile)));
                // 根据定义好的几个配置，来获取合适的缓冲大小
                int bufferSize = AudioRecord.getMinBufferSize(mFrequence,
                        mChannelStereo, mAudioEncoding);
                // 实例化AudioRecord
//                AudioRecord record = findAudioRecord();
                AudioRecord record = new AudioRecord(
                        MediaRecorder.AudioSource.MIC, mFrequence,
                        mChannelConfig, mAudioEncoding, bufferSize);
                // 定义缓冲
                short[] buffer = new short[bufferSize];


                // 开始录制
                record.startRecording();


                int r = 0; // 存储录制进度
                // 定义循环，根据isRecording的值来判断是否继续录制
                while (mIsRecording) {
                    // 从bufferSize中读取字节，返回读取的short个数
                    int bufferReadResult = record
                            .read(buffer, 0, buffer.length);
                    // 循环将buffer中的音频数据写入到OutputStream中
                    for (int i = 0; i < bufferReadResult; i++) {
                        dos.writeShort(buffer[i]);
                    }
                    publishProgress(new Integer(r)); // 向UI线程报告当前进度
                    r++; // 自增进度值
                }
                // 录制结束
                record.stop();
                Log.i("slack", "::" + mAudioFile.length());
                dos.close();
            } catch (Exception e) {
                // TODO: handle exception
                Log.e("slack", "::" + e.getMessage());
            }
            return null;
        }


        // 当在上面方法中调用publishProgress时，该方法触发,该方法在UI线程中被执行
        protected void onProgressUpdate(Integer... progress) {
            //
        }


        protected void onPostExecute(Void result) {

        }

    }

4.AudioTrack 播放音频 pcm data

class PlayPCMTask extends AsyncTask<Void, Void, Void> {
        @Override
        protected Void doInBackground(Void... arg0) {
            mIsPlaying = true;
            int bufferSize = AudioTrack.getMinBufferSize(mFrequence,
                    mPlayChannelConfig, mAudioEncoding);
            short[] buffer = new short[bufferSize];
            try {
                // 定义输入流，将音频写入到AudioTrack类中，实现播放
                DataInputStream dis = new DataInputStream(
                        new BufferedInputStream(new FileInputStream(mAudioFile)));
                // 实例AudioTrack
                // AudioTrack AudioFormat.CHANNEL_IN_STEREO here may some problem