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:
ini
/* 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。
ini
backgroudService.SetEventListener(new EventListener() {
@Override
public 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。
scss
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。
ini
//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() {
@Override
public 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);
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
8. 可以同时启动轻量级RTSP服务吗
ini
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;
}
- 同屏延迟,能不能做到毫秒级
废话不多说,见上图,延迟毫秒级。
10. 能不能采集到扬声器的audio?
Windows不在话下,Android平台需要高版本支持,高版本是可以采集到扬声器数据的,我们也实现了相关的demo,可以同时采集麦克风和扬声器的audio,单独推送或者同时混音输出。
11. 同屏过程中,重点画面可以快照吗?
当然可以,我们同屏采集端,支持采集编码png或jpg格式输出。
总结
其实一个好的无纸化同屏系统,需要考虑的有整体组网、分辨率、码率、实时延迟、音视频同步和连续性等各个指标,做容易,做好难,上述抛砖引玉,未能面面俱到,感兴趣的开发者,可以跟我单独Q我89030985交流。