Android 音频编码(AAC编码)

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Android 音频编码(AAC编码)

需求

Android设备上录制音频并通过MediaCodeC 硬编码为AAC文件.

技术点

1.AudioRecord 的使用.
2.MediaCodeC 的使用.
3.文件输入输出流.

关键代码

首先需要对编码器MediaCodeC ,和AudioRecord进行初始化配置.

private final String MINE_TYPE = MediaFormat.MIMETYPE_AUDIO_AAC;
    private int rate = 256000;
    //录音设置
    private int sampleRate = 44100;   //采样率44.1k
    private int channelCount = 2;     //音频采样通道，2通道
    private int channelConfig = AudioFormat.CHANNEL_IN_STEREO;        //通道设置，立体声
    private int audioFormat = AudioFormat.ENCODING_PCM_16BIT;     //设置采样数据格式，16比特PCM
    private int bufferSize;
    private volatile boolean isRecording;

if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            fileStore = Environment.getExternalStorageDirectory() + "/encode_aac_file.aac";
        }else {
            fileStore = getCacheDir().getAbsolutePath() + "/encode_aac_file.aac";
        }
        try {
            fos = new FileOutputStream(fileStore);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        //编码器设置
        MediaFormat format = MediaFormat.createAudioFormat(MINE_TYPE, sampleRate, channelCount);
        format.setInteger(MediaFormat.KEY_AAC_PROFILE, MediaCodecInfo.CodecProfileLevel.AACObjectLC);
        format.setInteger(MediaFormat.KEY_BIT_RATE, rate);

        try {
            // TODO: 18-10-26  需判断设备支不支持 MINE_TYPE 编码
            mEncode = MediaCodec.createEncoderByType(MINE_TYPE);
            mEncode.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
        } catch (IOException e) {
            e.printStackTrace();
        }

        //audio recorder init
        bufferSize = AudioRecord.getMinBufferSize(sampleRate, channelConfig, audioFormat) * 2;
        mRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, sampleRate, channelConfig,
                audioFormat, bufferSize);

其次,在子线程中进行录音编码工作.

private View.OnClickListener mStartListener = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (mRecord==null) return;
            mEncode.start();
            mRecord.startRecording();
            isRecording = true;
            if (mThread == null) {
                mThread = new MyThread("Thread-Audio-Encode");
                mThread.start();
            }
        }
    };

    private View.OnClickListener mStopListener = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            stop();
        }
    };


    /**
     * 给编码出的aac裸流添加adts头字段
     *
     * @param packet    要空出前7个字节，否则会搞乱数据
     * @param packetLen
     */
    private void addADTStoPacket(byte[] packet, int packetLen) {
        int profile = 2;  //AAC LC
        int freqIdx = 4;  //44.1KHz
        int chanCfg = 2;  //CPE
        packet[0] = (byte) 0xFF;
        packet[1] = (byte) 0xF9;
        packet[2] = (byte) (((profile - 1) << 6) + (freqIdx << 2) + (chanCfg >> 2));
        packet[3] = (byte) (((chanCfg & 3) << 6) + (packetLen >> 11));
        packet[4] = (byte) ((packetLen & 0x7FF) >> 3);
        packet[5] = (byte) (((packetLen & 7) << 5) + 0x1F);
        packet[6] = (byte) 0xFC;
    }


    class MyThread extends Thread {
        MyThread(@NonNull String name) {
            super(name);
        }

        @Override
        public void run() {
            super.run();
            while (isRecording) {
                try {
                    readOutputData();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }


    //TODO Add End Flag
    private void readOutputData() throws IOException {
        int index = mEncode.dequeueInputBuffer(-1);
        Log.e(TAG, "readOutputData: index=" + index);
        if (index >= 0) {
            final ByteBuffer buffer = getInputBuffer(index);
            buffer.clear();
            int length = mRecord.read(buffer, bufferSize);
            Log.e(TAG, "length-->" + length);
            if (length > 0) {
                mEncode.queueInputBuffer(index, 0, length, System.nanoTime() / 1000, 0);
            }
        }
        MediaCodec.BufferInfo mInfo = new MediaCodec.BufferInfo();
        int outIndex;
        do {
            outIndex = mEncode.dequeueOutputBuffer(mInfo, 0);
            Log.e(TAG, "outIndex=" + outIndex);
            if (outIndex >= 0) {
                ByteBuffer buffer = getOutputBuffer(outIndex);
                buffer.position(mInfo.offset);
                byte[] temp = new byte[mInfo.size + 7];
                buffer.get(temp, 7, mInfo.size);
                addADTStoPacket(temp, temp.length);
                fos.write(temp);
                mEncode.releaseOutputBuffer(outIndex, false);
            }
        } while (outIndex >= 0);
    }

    private ByteBuffer getInputBuffer(int index) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            return mEncode.getInputBuffer(index);
        } else {
            return mEncode.getInputBuffers()[index];
        }
    }

    private ByteBuffer getOutputBuffer(int index) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            return mEncode.getOutputBuffer(index);
        } else {
            return mEncode.getOutputBuffers()[index];
        }
    }

最后,不要忘了释放资源.

/**
     * 停止录制
     * 释放资源
     */
    public void stop() {
        try {
            isRecording = false;
            mThread.join();
            mThread = null;
            mRecord.stop();
            mRecord.release();
            mRecord = null;
            mEncode.stop();
            mEncode.release();
            mEncode=null;
            fos.flush();
            fos.close();
            Toast.makeText(SecondActivity.this,"音频文件位置:"+fileStore,Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }