1. AAC音频编码流程

AAC编码简单流程.png

2. AAC音频编码代码

/**
 * AAC音频编码
 * AudioRecord + MediaCodec AAC编码
 */
public class MediaAudioEncoder implements Runnable {

    // 麦克风
    private AudioRecord audioRecord;
    // 开启状态
    private AtomicBoolean isStar = new AtomicBoolean(false);
    // 数据架设监听
    private OnAudioRecordListener onAudioRecordListener;
    // 双声道，立体声
    private int sampleRate = 44100;
    private int audioFormat = AudioFormat.ENCODING_PCM_16BIT;
    private int channels = 2;
    // 编解码
    private MediaCodec mediaCodec;
    private int timeOutUs = 30;

    public MediaAudioEncoder() {
        // 找到系统的麦克风
        audioRecord = chooseAudioRecord();
        if (audioRecord == null) {
            throw new RuntimeException("audioRecord is null");
        }
        Log.e("TAG", "AudioRecord channels " + channels);
        initMediaCodec();
    }

    private void initMediaCodec() {
        try {
            MediaFormat format = MediaFormat.createAudioFormat(MediaFormat.MIMETYPE_AUDIO_AAC, sampleRate, channels);
            format.setString(MediaFormat.KEY_MIME, MediaFormat.MIMETYPE_AUDIO_AAC);
            format.setInteger(MediaFormat.KEY_AAC_PROFILE, MediaCodecInfo.CodecProfileLevel.AACObjectLC);
            format.setInteger(MediaFormat.KEY_BIT_RATE, getPcmBufferSize());
            format.setInteger(MediaFormat.KEY_MAX_INPUT_SIZE, getPcmBufferSize() * channels * 2);
            mediaCodec = MediaCodec.createEncoderByType(MediaFormat.MIMETYPE_AUDIO_AAC);
            mediaCodec.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public AudioRecord chooseAudioRecord() {
        // AudioFormat.CHANNEL_IN_MONO;// 单声道
        // AudioFormat.CHANNEL_IN_STEREO; // 双声道
        int audioSource = MediaRecorder.AudioSource.DEFAULT;
        // 1. 优先找立体声的
        AudioRecord mic = new AudioRecord(audioSource, sampleRate,
                AudioFormat.CHANNEL_IN_STEREO,
                audioFormat, getPcmBufferSize() * 2);
        // 2. 双通道不行，找单通道
        if (mic.getState() != AudioRecord.STATE_INITIALIZED) {
            mic = new AudioRecord(audioSource, sampleRate, AudioFormat.CHANNEL_IN_MONO,
                    audioFormat, getPcmBufferSize() * 2);
            if (mic.getState() != AudioRecord.STATE_INITIALIZED) {
                mic = null;
            } else {
                channels = 1;
            }
        } else {
            channels = 2;
        }
        return mic;
    }

    private int getPcmBufferSize() {
        // AudioFormat.CHANNEL_IN_MONO;// 单声道
        // AudioFormat.CHANNEL_IN_STEREO; // 双声道
        int pcmBufSize = AudioRecord.getMinBufferSize(44100,
                AudioFormat.CHANNEL_IN_STEREO,
                AudioFormat.ENCODING_PCM_16BIT) + 8191;
        return pcmBufSize - (pcmBufSize % 8192);
    }

    // 开始录音和AAC编码
    public void start() {
        if (isStar.compareAndSet(false, true)) {
            // 拿到编码后AAC的数据
            Executors.newSingleThreadExecutor().execute(readAacTask);
            // 用麦克风录音 + MediaCodec编码音频数据
            Executors.newSingleThreadExecutor().execute(this);
        }
    }

    // 停止AAC录音和编码
    public void stop() {
        isStar.set(false);
    }

    // 读取编码后AAC的数据
    private Runnable readAacTask = new Runnable() {
        @Override
        public void run() {
            if (mediaCodec == null) {
                return;
            }
            Log.e("TAG", "start read aac ....");
            MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();
            long pts = 0;
            while (isStar.get()) {
                try {
                    // 读取编码结果
                    int outIndex = mediaCodec.dequeueOutputBuffer(info, timeOutUs);
                    while (isStar.get() && outIndex >= 0) {
                        ByteBuffer buffer = mediaCodec.getOutputBuffer(outIndex);
                        buffer.position(info.offset);
                        buffer.limit(info.size);
                        byte[] data = new byte[info.size];
                        buffer.get(data);
                        if (pts == 0) {
                            pts = info.presentationTimeUs;
                        }
                        info.presentationTimeUs -= pts;
                        // 就是少了这句话
                        mediaCodec.releaseOutputBuffer(outIndex, false);
                        // AAC编码回调
                        if (onAudioRecordListener != null) {
                            onAudioRecordListener.onAudioRecord(data, info.size, channels, info.presentationTimeUs);
                        }
                        outIndex = mediaCodec.dequeueOutputBuffer(info, timeOutUs);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }

            }

            Log.e("TAG", "stop read aac....");
        }
    };

    @Override
    public void run() {
        if (audioRecord == null || mediaCodec == null) {
            return;
        }
        Log.e("TAG", "start aac encode ...");
        mediaCodec.start();
        // 开始录音（调用Android的API录制手机麦克风的声音）
        audioRecord.startRecording();
        int length = getPcmBufferSize();
        ByteBuffer buffer = ByteBuffer.allocateDirect(length);
        int readSize;
        while (isStar.get()) {
            try {
                // 每次读多少数据要根据编码器来定！
                readSize = audioRecord.read(buffer, length);
                if (readSize > 0) {
                    // 这里是设置数据读到的位置
                    buffer.position(readSize);
                    buffer.flip();
                    // AAC编码
                    int index = mediaCodec.dequeueInputBuffer(timeOutUs);
                    if (index >= 0) {
                        ByteBuffer inputBuffer = mediaCodec.getInputBuffer(index);
                        // 将容量重置
                        inputBuffer.clear();
                        inputBuffer.put(buffer);
                        // 给MediaCodec塞数据
                        mediaCodec.queueInputBuffer(index, 0, readSize,
                                System.nanoTime() / 1000, 0);
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        // 清空信息
        release();
        Log.e("TAG", "stop aac encode ....");
    }

    // 回收信息
    private void release() {
        onAudioRecordListener = null;
        if (audioRecord != null) {
            audioRecord.stop();
            audioRecord.release();
            audioRecord = null;
        }
        if (mediaCodec != null) {
            mediaCodec.stop();
            mediaCodec.release();
            mediaCodec = null;
        }
    }


    public interface OnAudioRecordListener {
        void onAudioRecord(byte[] data, int len, int channels, long time);
    }

    public void setOnAudioRecordListener(OnAudioRecordListener onAudioRecordListener) {
        this.onAudioRecordListener = onAudioRecordListener;
    }
}