Android平台实现无纸化同屏并推送RTMP或轻量级RTSP服务(毫秒级延迟)

技术背景

在写这篇文章之前，实际上几年之前，我们就有非常稳定的无纸化同屏的模块，本文借demo更新，算是做个新的总结，废话不多说，先看图，本文以Android平台屏幕实时采集推送，Windows播放为例，和大家做个技术分享。

技术考量指标

本文以大牛直播SDK前些年实现的Android同屏采集推送为例，大概介绍下一些技术考量指标。

1. 轻量级RTSP服务还是RTMP？

我们在做无纸化同屏的时候，问的最多的是，能不能不要自建服务，直接主讲人或教师端，直接启动轻量级RTSP服务，其他终端拉流，如果是小并发，比如5人内的小范围的同屏，Windows平台走轻量级RTSP无可厚非，如果是30-60甚至100人的会议室，建议走RTMP。

2. 推送分辨率和码率选择

我们接触到好多设备，性能一般，但是屏幕是高分屏，甚至可以采集到4K的，考虑到实时编码和并发环境下，AP的承载能力，一般建议选择适合自己的分辨率码率即可，不要只追求高分辨率高码率，导致组网困难，单个或双通道AP压力大，一般建议控制在1920*1080分辨率内，码率控制在1-5M。

3. 软编码还是硬编码

Windows平台，一般优先考虑软编，因为大多Windows性能瓶颈不太大，超过1080P可以考虑硬编，Android平台建议直接硬编码。

4. 高分屏采集编码效率低怎么办

高分屏，不管是Windows还是Android，采集后的数据，建议先压缩，再编码，Windows平台我们可以设置压缩比例（scale rate），Android平台亦可，比如采集原始屏幕，或者缩放后的屏幕，具体见下图：

  /* BackgroudService.java* Author: daniusdk.com*/ private void createScreenEnvironment() {sreenWindowWidth = mWindowManager.getDefaultDisplay().getWidth();screenWindowHeight = mWindowManager.getDefaultDisplay().getHeight();Log.i(TAG, "screenWindowWidth: " + sreenWindowWidth + ",screenWindowHeight: "+ screenWindowHeight);if (sreenWindowWidth > 800){if (screen_resolution_type_ == SCREEN_RESOLUTION_STANDARD){scale_rate = SCALE_RATE_HALF;sreenWindowWidth = align(sreenWindowWidth / 2, 16);screenWindowHeight = align(screenWindowHeight / 2, 16);}else if(screen_resolution_type_ == SCREEN_RESOLUTION_LOW){scale_rate = SCALE_RATE_TWO_FIFTHS;sreenWindowWidth = align(sreenWindowWidth * 2 / 5, 16);screenWindowHeight = align(screenWindowHeight * 2 / 5, 16);}}Log.i(TAG, "After adjust mWindowWidth: " + sreenWindowWidth + ", mWindowHeight: " + screenWindowHeight);int pf = mWindowManager.getDefaultDisplay().getPixelFormat();Log.i(TAG, "display format:" + pf);DisplayMetrics displayMetrics = new DisplayMetrics();mWindowManager.getDefaultDisplay().getMetrics(displayMetrics);mScreenDensity = displayMetrics.densityDpi;mImageReader = ImageReader.newInstance(sreenWindowWidth,screenWindowHeight, 0x1, 6);mMediaProjectionManager = (MediaProjectionManager) getSystemService(Context.MEDIA_PROJECTION_SERVICE);}

5. Android横竖屏自动适配

Android平台，如果是pad采集，基本就是横屏采集，如果手机端，需要确保横竖屏模式下都可以正常采集。

4. 为什么要考虑补帧

Android的时候，一定的采集模式下，屏幕如果没有变化，不会一直有实时屏幕数据回调下来，这时候，为了保持帧率或数据采集的完整性，建议补帧。

5. 异常网络处理、事件回调机制

网络状态，不管是推送端，还是播放端，都是需要有实时的状态回调，确保客户端可以实时感知网络状态。

backgroudService.SetEventListener(new EventListener() {@Overridepublic void onPublisherEventCallback(long handle, int id, long param1, long param2, String param3, String param4, Object param5) {String publisher_event = "";switch (id) {case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_STARTED:publisher_event = "开始..";break;case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_CONNECTING:publisher_event = "连接中..";break;case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_CONNECTION_FAILED:publisher_event = "连接失败..";break;case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_CONNECTED:publisher_event = "连接成功..";break;case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_DISCONNECTED:publisher_event = "连接断开..";break;case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_STOP:publisher_event = "关闭..";break;case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_RECORDER_START_NEW_FILE:publisher_event = "开始一个新的录像文件 : " + param3;break;case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_ONE_RECORDER_FILE_FINISHED:publisher_event = "已生成一个录像文件 : " + param3;break;case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_SEND_DELAY:publisher_event = "发送时延: " + param1 + " 帧数:" + param2;break;case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_CAPTURE_IMAGE:publisher_event = "快照: " + param1 + " 路径：" + param3;if (param1 == 0) {publisher_event = publisher_event + "截取快照成功..";} else {publisher_event = publisher_event + "截取快照失败..";}break;case NTSmartEventID.EVENT_DANIULIVE_ERC_PUBLISHER_RTSP_URL:publisher_event = "RTSP服务URL: " + param3;break;case NTSmartEventID.EVENT_DANIULIVE_ERC_PUSH_RTSP_SERVER_RESPONSE_STATUS_CODE:publisher_event = "RTSP status code received, codeID: " + param1 + ", RTSP URL: " + param3;break;case NTSmartEventID.EVENT_DANIULIVE_ERC_PUSH_RTSP_SERVER_NOT_SUPPORT:publisher_event = "服务器不支持RTSP推送, 推送的RTSP URL: " + param3;break;}String str = "当前状态：" + publisher_event;Log.i(TAG, str);if (handler_ != null) {Message message = new Message();message.what = PUBLISHER_EVENT_MSG;message.obj = publisher_event;handler_.sendMessage(message);}}});

6. 采集到的数据可以按需录像吗

可以，而且很有必要，同屏的时候，如果需要把开会或教授内容实时保存下来，可以随时启动录像。

    public boolean startRecorder(){Log.i(TAG, "onClick startRecorder..");if(!stream_publisher_.is_publishing()){startCaptureScreen();}if (layer_post_thread_ != null)layer_post_thread_.update_layers();if (stream_publisher_.is_recording()) {stopRecorder();return false;}InitAndSetConfig();ConfigRecorderParam();boolean start_ret = stream_publisher_.StartRecorder();if (!start_ret) {stream_publisher_.try_release();Log.e(TAG, "Failed to start recorder.");return false;}startAudioRecorder();startLayerPostThread();return true;}//停止录像public void stopRecorder() {stream_publisher_.StopRecorder();stream_publisher_.try_release();if (!stream_publisher_.is_publishing())stopAudioRecorder();}

7. 文字、图片水印

需要而且建议支持，比如实时时间、学校或公司logo等。

        //水印效果选择++++++++++watermarkSelctor = (Spinner) findViewById(R.id.watermarkSelctor);watermarkSelctor.setEnabled(false);final String[] watermarks = new String[]{"图片水印", "全部水印", "文字水印", "不加水印"};ArrayAdapter<String> adapterWatermark = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item, watermarks);adapterWatermark.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);watermarkSelctor.setAdapter(adapterWatermark);watermarkSelctor.setSelection(3,true);watemarkType = 3;   //默认不加水印watermarkSelctor.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {@Overridepublic void onItemSelected(AdapterView<?> parent, View view,int position, long id) {watemarkType = position;Log.i(TAG, "[水印类型]Currently choosing: " + watermarks[position] + ", watemarkType: " + watemarkType);if(backgroudService !=null) {backgroudService.updateWatermarker(watemarkType);}}@Overridepublic void onNothingSelected(AdapterView<?> parent) {}});

8. 可以同时启动轻量级RTSP服务吗

    public boolean startRtspService(int port){Log.i(TAG, "startRtspService++");rtsp_handle_ = lib_publisher_.OpenRtspServer(0);if (rtsp_handle_ == 0) {Log.e(TAG, "创建rtsp server实例失败! 请检查SDK有效性");} else {if (lib_publisher_.SetRtspServerPort(rtsp_handle_, port) != 0) {lib_publisher_.CloseRtspServer(rtsp_handle_);rtsp_handle_ = 0;Log.e(TAG, "创建rtsp server端口失败! 请检查端口是否重复或者端口不在范围内!");}if (lib_publisher_.StartRtspServer(rtsp_handle_, 0) == 0) {Log.i(TAG, "启动rtsp server 成功!");} else {lib_publisher_.CloseRtspServer(rtsp_handle_);rtsp_handle_ = 0;Log.e(TAG, "启动rtsp server失败! 请检查设置的端口是否被占用!");}isRTSPServiceRunning = true;}return true;}//停止RTSP服务public void stopRtspService() {Log.i(TAG, "stopRtspService++");if(!isRTSPServiceRunning){return;}if (lib_publisher_ != null && rtsp_handle_ != 0) {lib_publisher_.StopRtspServer(rtsp_handle_);lib_publisher_.CloseRtspServer(rtsp_handle_);rtsp_handle_ = 0;}isRTSPServiceRunning = false;}public boolean startRtspPublisher(){Log.i(TAG, "startRtspPublisher++");if(!stream_publisher_.is_publishing()){startCaptureScreen();}InitAndSetConfig();String rtsp_stream_name = "stream1";stream_publisher_.SetRtspStreamName(rtsp_stream_name);stream_publisher_.ClearRtspStreamServer();stream_publisher_.AddRtspStreamServer(rtsp_handle_);if (!stream_publisher_.StartRtspStream()) {stream_publisher_.try_release();Log.e(TAG, "调用发布rtsp流接口失败!");return false;}startAudioRecorder();startLayerPostThread();return true;}//停止发布RTSP流public void stopRtspPublisher() {Log.i(TAG, "stopRtspPublisher++");stream_publisher_.StopRtspStream();stream_publisher_.try_release();if (!stream_publisher_.is_publishing())stopAudioRecorder();}public int getRtspSessionNumbers(){int session_numbers = 0;if (lib_publisher_ != null && rtsp_handle_ != 0) {session_numbers = lib_publisher_.GetRtspServerClientSessionNumbers(rtsp_handle_);Log.i(TAG, "GetRtspSessionNumbers: " + session_numbers);}return session_numbers;}

9. 同屏延迟，能不能做到毫秒级

废话不多说，上视频，延迟毫秒级。

安卓采集屏幕至轻量级RTSP服务|推送RTMP整体毫秒级延迟