Android 视频通信，低延时解决方案

背景：

　　由于，项目需要，需要进行视频通信，把a的画面，转给b。

运维部署：

　　APP1：编码摄像头采集的数据，并且发送数据到服务端

　　APP2：从服务端，拉取数据，并且进行解码显示

　　服务端：接收APP1提交的数据，发送APP1提交数据到APP2

应用说明：

　　APP1：camera = Camera.open(Camera.CameraInfo.CAMERA_FACING_FRONT);

        Camera.Parameters parameters = camera.getParameters();
        parameters.setPreviewFormat(ImageFormat.NV21);
        parameters.setPreviewSize(width, height);

        // 设置屏幕亮度
        parameters.setExposureCompensation(parameters.getMaxExposureCompensation() / 2);
        camera.setParameters(parameters);
        camera.setDisplayOrientation(90);
        camera.setPreviewCallback(new Camera.PreviewCallback() {
            @Override
            public void onPreviewFrame(byte[] data, Camera camera) {
                // 采集视频数据，同时记录采集视频的时间点，解码需要（保证视频连续，流畅，且不花屏需要）
                stamptime = System.nanoTime();
                yuv_data = data;
            }
        });

public class AvcKeyFrameEncoder {
    private final static String TAG = "MeidaCodec";
    private int TIMEOUT_USEC = 12000;

    private MediaCodec mediaCodec;
    int m_width;
    int m_height;
    int m_framerate;

    public byte[] configbyte;

    //待解码视频缓冲队列，静态成员！
    public byte[] yuv_data = null;
    public long stamptime = 0;

    public AvcKeyFrameEncoder(int width, int height, int framerate) {
        m_width = width;
        m_height = height;
        m_framerate = framerate;

        //正常的编码出来是横屏的。因为手机本身采集的数据默认就是横屏的
        // MediaFormat mediaFormat = MediaFormat.createVideoFormat(mime, width, height);
        //如果你需要旋转90度或者270度，那么需要把宽和高对调。否则会花屏。因为比如你320 X 240，图像旋转90°之后宽高变成了240 X 320。
        MediaFormat mediaFormat = MediaFormat.createVideoFormat("video/avc", width, height);
        mediaFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT, MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420SemiPlanar);
        mediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, 125000);
        mediaFormat.setInteger(MediaFormat.KEY_FRAME_RATE, framerate); // 30
        mediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, 1);
        try {
            mediaCodec = MediaCodec.createEncoderByType("video/avc");
        } catch (IOException e) {
            e.printStackTrace();
        }

        //配置编码器参数
        mediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);

        //启动编码器
        mediaCodec.start();
    }

    public void StopEncoder() {
        try {
            mediaCodec.stop();
            mediaCodec.release();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public boolean isRuning = false;

    public void StartEncoderThread(final ISaveVideo saveVideo, final ICall callback) {
        isRuning = true;
        new Thread(new Runnable() {
            @Override
            public void run() {
                byte[] input = null;
                long pts = 0;
                while (isRuning) {
                    // 访问MainActivity用来缓冲待解码数据的队列
                    if(yuv_data == null){
                        continue;
                    }

                    if (yuv_data != null) {
                        //从缓冲队列中取出一帧
                        input = yuv_data;
                        pts = stamptime;
                        yuv_data = null;
                        byte[] yuv420sp = new byte[m_width * m_height * 3 / 2];

                        NV21ToNV12(input, yuv420sp, m_width, m_height);
                        input = yuv420sp;
                    }

                    if (input != null) {
                        try {
                            //编码器输入缓冲区
                            ByteBuffer[] inputBuffers = mediaCodec.getInputBuffers();

                            //编码器输出缓冲区
                            ByteBuffer[] outputBuffers = mediaCodec.getOutputBuffers();
                            int inputBufferIndex = mediaCodec.dequeueInputBuffer(-1);
                            if (inputBufferIndex >= 0) {
                                ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
                                inputBuffer.clear();
                                //把转换后的YUV420格式的视频帧放到编码器输入缓冲区中
                                inputBuffer.put(input);
                                mediaCodec.queueInputBuffer(inputBufferIndex, 0, input.length, pts, 0);
                            }

                            MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
                            int outputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo, TIMEOUT_USEC);
                            while (outputBufferIndex >= 0) {
                                //Log.i("AvcEncoder", "Get H264 Buffer Success! flag = "+bufferInfo.flags+",pts = "+bufferInfo.presentationTimeUs+"");
                                ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
                                byte[] outData = new byte[bufferInfo.size];
                                outputBuffer.get(outData);
                                if (bufferInfo.flags == BUFFER_FLAG_CODEC_CONFIG) {
                                    configbyte = new byte[bufferInfo.size];
                                    configbyte = outData;
                                } else if (bufferInfo.flags == BUFFER_FLAG_KEY_FRAME) {
                                    byte[] keyframe = new byte[bufferInfo.size + configbyte.length];
                                    System.arraycopy(configbyte, 0, keyframe, 0, configbyte.length);
                                    //把编码后的视频帧从编码器输出缓冲区中拷贝出来
                                    System.arraycopy(outData, 0, keyframe, configbyte.length, outData.length);

                                    Logs.i("上传I帧 " + keyframe.length);
                                    byte[] send_data = new byte[13 + keyframe.length];
                                    System.arraycopy(new byte[]{0x01}, 0, send_data, 0, 1);
                                    System.arraycopy(IntBytes.longToBytes(pts), 0, send_data, 1, 8);
                                    System.arraycopy(IntBytes.intToByteArray(keyframe.length), 0, send_data, 9, 4);
                                    System.arraycopy(keyframe, 0, send_data, 13, keyframe.length);
                                    if(saveVideo != null){
                                        saveVideo.SaveVideoData(send_data);
                                    }

                                    if(callback != null){
                                        callback.callback(keyframe, pts);
                                    }
                                } else {
                                    byte[] send_data = new byte[13 + outData.length];
                                    System.arraycopy(new byte[]{0x02}, 0, send_data, 0, 1);
                                    System.arraycopy(IntBytes.longToBytes(pts), 0, send_data, 1, 8);
                                    System.arraycopy(IntBytes.intToByteArray(outData.length), 0, send_data, 9, 4);
                                    System.arraycopy(outData, 0, send_data, 13, outData.length);
                                    if(saveVideo != null){
                                        saveVideo.SaveVideoData(send_data);
                                    }

                                    if(callback != null){
                                        callback.callback(outData, pts);
                                    }
                                }

                                mediaCodec.releaseOutputBuffer(outputBufferIndex, false);
                                outputBufferIndex = mediaCodec.dequeueOutputBuffer(bufferInfo, TIMEOUT_USEC);
                            }

                        } catch (Throwable t) {
                            t.printStackTrace();
                            break;
                        }
                    }
                }
            }
        }).start();
    }

    private void NV21ToNV12(byte[] nv21, byte[] nv12, int width, int height) {
        if (nv21 == null || nv12 == null) return;
        int framesize = width * height;
        int i = 0, j = 0;
        System.arraycopy(nv21, 0, nv12, 0, framesize);
        for (i = 0; i < framesize; i++) {
            nv12[i] = nv21[i];
        }

        for (j = 0; j < framesize / 2; j += 2) {
            nv12[framesize + j - 1] = nv21[j + framesize];
        }

        for (j = 0; j < framesize / 2; j += 2) {
            nv12[framesize + j] = nv21[j + framesize - 1];
        }
    }
}

其中使用到了，接口用于，把采集和编码后的数据，往外部传递，通过线程提交到服务端。或者通过本地解码显示，查看，编码解码时间差。

通过使用 ArrayBlockingQueue<byte[]> H264Queue = new ArrayBlockingQueue<byte[]>(10); 队列，对接口提交数据，进行暂时保存，在后台对数据，进行解码或提交到服务端。

　　APP2：接入服务端，然后从I帧数据开始拿数据，（且数据是最新的I帧开始保存的数据）。同时需要把，之前采集得到的时间点传给：

MediaCodec 对象的 queueInputBuffer 方法的时间戳参数（第四个）。

 服务端：一帧一帧接收APP1传入数据，对I帧开始的数据进行记录，同时对非I帧开始的数据，进行丢弃。一次只保存一帧内容。读取数据，并且移除已经添加数据，循环发送给APP2

public class VideoDecoder {
    private Thread mDecodeThread;
    private MediaCodec mCodec;
    private boolean mStopFlag = false;
    private int Video_Width = 640;
    private int Video_Height = 480;
    private int FrameRate = 25;
    private Boolean isUsePpsAndSps = false;
    private ReceiveVideoThread runThread = null;

    public VideoDecoder(String ip, int port, byte type, int roomId){
        runThread = new ReceiveVideoThread(ip, port, type, roomId);
        new Thread(runThread).start();
    }

    public void InitReadData(Surface surface){
        try {
            //通过多媒体格式名创建一个可用的解码器
            mCodec = MediaCodec.createDecoderByType("video/avc");
        } catch (IOException e) {
            e.printStackTrace();
        }

        //初始化编码器
        final MediaFormat mediaformat = MediaFormat.createVideoFormat("video/avc", Video_Width, Video_Height);

        //设置帧率
        mediaformat.setInteger(MediaFormat.KEY_FRAME_RATE, FrameRate);

        //https://developer.android.com/reference/android/media/MediaFormat.html#KEY_MAX_INPUT_SIZE
        //设置配置参数，参数介绍 ：
        // format   如果为解码器，此处表示输入数据的格式；如果为编码器，此处表示输出数据的格式。
        //surface   指定一个surface，可用作decode的输出渲染。
        //crypto    如果需要给媒体数据加密，此处指定一个crypto类.
        //   flags  如果正在配置的对象是用作编码器，此处加上CONFIGURE_FLAG_ENCODE 标签。
        mCodec.configure(mediaformat, surface, null, 0);
        startDecodingThread();
    }

    private void startDecodingThread() {
        mCodec.start();

        mDecodeThread = new Thread(new decodeH264Thread());
        mDecodeThread.start();
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    private class decodeH264Thread implements Runnable {
        @Override
        public void run() {
            try {
                // saveDataLoop();
                decodeLoop_New();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        private void decodeLoop_New() {
            // 存放目标文件的数据
            ByteBuffer[] inputBuffers = mCodec.getInputBuffers();
            // 解码后的数据，包含每一个buffer的元数据信息，例如偏差，在相关解码器中有效的数据大小
            MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();
            long timeoutUs = 1000;
            byte[] marker0 = new byte[]{0, 0, 0, 1};
            byte[] dummyFrame = new byte[]{0x00, 0x00, 0x01, 0x20};
            byte[] streamBuffer = null;
            while (true) {
                if(runThread.H264Queue.size() > 0){
                    streamBuffer = runThread.H264Queue.poll();
                }else{
                    try {
                        Thread.sleep(20);
                    }catch (Exception ex){
                    }

                    continue;
                }

                byte[] time_data = new byte[8];
                System.arraycopy(streamBuffer, 0, time_data, 0, 8);
                long pts = IntBytes.bytesToLong(time_data);
                byte[] video_data = new byte[streamBuffer.length - 8];
                System.arraycopy(streamBuffer, 8, video_data, 0, video_data.length);
                streamBuffer = video_data;

                Logs.i("得到 streamBuffer " + streamBuffer.length + " pts " + pts);
                int bytes_cnt = 0;
                mStopFlag = false;
                while (mStopFlag == false) {
                    bytes_cnt = streamBuffer.length;
                    if (bytes_cnt == 0) {
                        streamBuffer = dummyFrame;
                    }

                    int startIndex = 0;
                    int remaining = bytes_cnt;
                    while (true) {
                        if (remaining == 0 || startIndex >= remaining) {
                            break;
                        }
                        int nextFrameStart = KMPMatch(marker0, streamBuffer, startIndex + 2, remaining);
                        if (nextFrameStart == -1) {
                            nextFrameStart = remaining;
                        } else {
                        }

                        int inIndex = mCodec.dequeueInputBuffer(timeoutUs);
                        if (inIndex >= 0) {
                            ByteBuffer byteBuffer = inputBuffers[inIndex];
                            byteBuffer.clear();
                            byteBuffer.put(streamBuffer, startIndex, nextFrameStart - startIndex);
                            //在给指定Index的inputbuffer[]填充数据后，调用这个函数把数据传给解码器
                            mCodec.queueInputBuffer(inIndex, 0, nextFrameStart - startIndex, pts, 0);
                            startIndex = nextFrameStart;
                        } else {
                            continue;
                        }

                        int outIndex = mCodec.dequeueOutputBuffer(info, timeoutUs);
                        if (outIndex >= 0) {
                            //帧控制是不在这种情况下工作，因为没有PTS H264是可用的
                            /*
                            while (info.presentationTimeUs / 1000 > System.currentTimeMillis() - startMs) {
                                try {
                                    Thread.sleep(100);
                                } catch (InterruptedException e) {
                                    e.printStackTrace();
                                }
                            }
                            */
                            boolean doRender = (info.size != 0);
                            //对outputbuffer的处理完后，调用这个函数把buffer重新返回给codec类。

                            // TODO:添加处理，保存原始帧数据
                            if (doRender) {
                                Image image = mCodec.getOutputImage(outIndex);
                                if (image != null) {
                                    // 通过反射
                                    // 发送数据到指定接口
                                    byte[] data = getDataFromImage(image, COLOR_FormatNV21);
                                }
                            }

                            mCodec.releaseOutputBuffer(outIndex, doRender);
                        } else {
                            // Log.e(TAG, "bbbb");
                        }
                    }
                    mStopFlag = true;
                }

                // Logs.i("处理单帧视频耗时：" + (System.currentTimeMillis() - c_start));
            }
        }
    }

    private static final boolean VERBOSE = false;
    private static final long DEFAULT_TIMEOUT_US = 10000;

    private static final int COLOR_FormatI420 = 1;
    private static final int COLOR_FormatNV21 = 2;

    private static boolean isImageFormatSupported(Image image) {
        int format = image.getFormat();
        switch (format) {
            case ImageFormat.YUV_420_888:
            case ImageFormat.NV21:
            case ImageFormat.YV12:
                return true;
        }
        return false;
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    private static byte[] getDataFromImage(Image image, int colorFormat) {
        if (colorFormat != COLOR_FormatI420 && colorFormat != COLOR_FormatNV21) {
            throw new IllegalArgumentException("only support COLOR_FormatI420 " + "and COLOR_FormatNV21");
        }
        if (!isImageFormatSupported(image)) {
            throw new RuntimeException("can't convert Image to byte array, format " + image.getFormat());
        }

        Rect crop = image.getCropRect();
        int format = image.getFormat();
        int width = crop.width();
        int height = crop.height();
        Image.Plane[] planes = image.getPlanes();
        byte[] data = new byte[width * height * ImageFormat.getBitsPerPixel(format) / 8];
        byte[] rowData = new byte[planes[0].getRowStride()];
        if (VERBOSE) Logs.i("get data from " + planes.length + " planes");
        int channelOffset = 0;
        int outputStride = 1;
        for (int i = 0; i < planes.length; i++) {
            switch (i) {
                case 0:
                    channelOffset = 0;
                    outputStride = 1;
                    break;
                case 1:
                    if (colorFormat == COLOR_FormatI420) {
                        channelOffset = width * height;
                        outputStride = 1;
                    } else if (colorFormat == COLOR_FormatNV21) {
                        channelOffset = width * height + 1;
                        outputStride = 2;
                    }
                    break;
                case 2:
                    if (colorFormat == COLOR_FormatI420) {
                        channelOffset = (int) (width * height * 1.25);
                        outputStride = 1;
                    } else if (colorFormat == COLOR_FormatNV21) {
                        channelOffset = width * height;
                        outputStride = 2;
                    }
                    break;
            }
            ByteBuffer buffer = planes[i].getBuffer();
            int rowStride = planes[i].getRowStride();
            int pixelStride = planes[i].getPixelStride();
            if (VERBOSE) {
                Logs.i("pixelStride " + pixelStride);
                Logs.i("rowStride " + rowStride);
                Logs.i("width " + width);
                Logs.i("height " + height);
                Logs.i("buffer size " + buffer.remaining());
            }
            int shift = (i == 0) ? 0 : 1;
            int w = width >> shift;
            int h = height >> shift;
            buffer.position(rowStride * (crop.top >> shift) + pixelStride * (crop.left >> shift));
            for (int row = 0; row < h; row++) {
                int length;
                if (pixelStride == 1 && outputStride == 1) {
                    length = w;
                    buffer.get(data, channelOffset, length);
                    channelOffset += length;
                } else {
                    length = (w - 1) * pixelStride + 1;
                    buffer.get(rowData, 0, length);
                    for (int col = 0; col < w; col++) {
                        data[channelOffset] = rowData[col * pixelStride];
                        channelOffset += outputStride;
                    }
                }
                if (row < h - 1) {
                    buffer.position(buffer.position() + rowStride - length);
                }
            }
            if (VERBOSE) Logs.i("Finished reading data from plane " + i);
        }
        return data;
    }

    private int KMPMatch(byte[] pattern, byte[] bytes, int start, int remain) {
        try {
            Thread.sleep(30);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        int[] lsp = computeLspTable(pattern);

        int j = 0;  // Number of chars matched in pattern
        for (int i = start; i < remain; i++) {
            while (j > 0 && bytes[i] != pattern[j]) {
                // Fall back in the pattern
                j = lsp[j - 1];  // Strictly decreasing
            }
            if (bytes[i] == pattern[j]) {
                // Next char matched, increment position
                j++;
                if (j == pattern.length)
                    return i - (j - 1);
            }
        }
        return -1;  // Not found
    }

    private int[] computeLspTable(byte[] pattern) {
        int[] lsp = new int[pattern.length];
        lsp[0] = 0;  // Base case
        for (int i = 1; i < pattern.length; i++) {
            // Start by assuming we're extending the previous LSP
            int j = lsp[i - 1];
            while (j > 0 && pattern[i] != pattern[j])
                j = lsp[j - 1];
            if (pattern[i] == pattern[j])
                j++;
            lsp[i] = j;
        }
        return lsp;
    }

    public void StopDecode() {
        if(runThread != null){
            runThread.StopReceive();
        }
    }
}

总结：

　　通过对视频的处理，学习到了，一些处理视频的细节点。同时加深了，依赖导致在实际项目中的使用。to android.