如何从Wowza transcoder获得实时流的视频截图?

这篇文章介绍了两种方法用于从Wowza Transcoder 插件获得视频截图。要让这功能正常工作，Wowza Transcoder 必须处于正常运行状态并正在对一个视频流进行转码。 

注意: 这个功能要求Wowza Media Server® 3.0.0及更高版本。

 

 

一、HTTP Provider

你可以用一个已经内建的，位于管理端口8086上的HTTP接口来从正在运行中的Wowza transcoder获得一个位图。Http URL格式如下: 

http://[wowza-ip-address]:8086/transcoderthumbnail?application=[application-name]&streamname=[stream-name]&format=[jpegor png]&size=[widthxheight]

其中: 

• [wowza-ip-address]: 运行Wowza Server的服务器IP地址

• application-name: 应用名

• stream-name: 输入流的stream name. 不要用转码后的输出流的名字或StreamNameGroup的名字.

• format: 图片的格式:jpeg 或 png

• size: 截图的大小.如果没有设置，则会按一帧图像的完整大小返回

要使用这个HTTP服务,请用文本编辑器打开[install-dir]/conf/VHost.xml文件，将com.wowza.wms.transcoder.httpprovider.HTTPTranscoderThumbnail 中的 AuthenticationMethod 设置为: none。这样将关闭基于用户名和密码的认证。 

接下来, 对Wowza Server进行配置，以对一个输入流进行转码。

在下面的例子中, 假定我们要转码的流为myStream，应用名为live. 要获得这个实时流的当前截图，请在WEB浏览器上访问以下URL:

http://[wowza-ip-address]:8086/transcoderthumbnail?application=live&streamname=myStream&format=jpeg&size=320x240

注意: 这个URL是区分大小写的。

 

日志 
每一次请求截图时,你都会在[install-dir]/logs/wowzamediaserver_access.log中看到一个log消息：

commentserver       INFO         200  -        HTTPTranscoderThumbnail#GrabResult.onGrabFrame[live/_definst_/myStream]:Image result: format:jpeg size:320x240 timecode:107633

 

二、服务端 API
下面是一段代码例子，建立了莪一个名为grabFrame([stream-name])的方法，可供远程调用，获得实时流的当前截图: 

package com.wowza.wms.plugin.test.module;

 

import java.awt.image.*;

import javax.imageio.*;

import java.io.*;

import com.wowza.wms.amf.*;

import com.wowza.wms.client.*;

import com.wowza.wms.request.*;

import com.wowza.wms.module.*;

import com.wowza.wms.application.*;

import com.wowza.wms.stream.*;

import com.wowza.wms.transcoder.model.*;

import com.wowza.wms.transcoder.util.*;

 

public class ModuleTestTranscoderFrameGrabextends ModuleBase

{

         privateIApplicationInstance appInstance = null;

        

         classGrabResult implements ITranscoderFrameGrabResult

         {

                   publicvoid onGrabFrame(TranscoderNativeVideoFrame videoFrame)

                   {                          

                            BufferedImageimage = TranscoderStreamUtils.nativeImageToBufferedImage(videoFrame);

                            if(image != null)

                            {

                           

                                     getLogger().info("ModuleTestTranscoderFrameGrab#GrabResult.onGrabFrame:"+image.getWidth()+"x"+image.getHeight());

                                    

                                     StringstorageDir = appInstance.getStreamStoragePath();

                                    

                                     FilepngFile = new File(storageDir+"/thumbnail.png");

                                     FilejpgFile = new File(storageDir+"/thumbnail.jpg");

                                    

                                     try

                                     {

                                              if (pngFile.exists())

                                                        pngFile.delete();

                                               ImageIO.write(image,"png", pngFile);

                                               getLogger().info("ModuleTestTranscoderFrameGrab#GrabResult.onGrabFrame:Save image: "+pngFile);

                                     }

                                     catch(Exceptione)

                                     {

                                               getLogger().error("ModuleTestTranscoderFrameGrab.grabFrame:File write error: "+pngFile);

                                     }

                                    

                                     try

                                     {

                                               if(jpgFile.exists())

                                                        jpgFile.delete();

                                               ImageIO.write(image,"jpg", jpgFile);

                                               getLogger().info("ModuleTestTranscoderFrameGrab#GrabResult.onGrabFrame:Save image: "+jpgFile);

                                     }

                                     catch(Exceptione)

                                     {

                                               getLogger().error("ModuleTestTranscoderFrameGrab.grabFrame:File write error: "+jpgFile);

                                     }

                            }

                   }

         }

        

         publicvoid onAppStart(IApplicationInstance appInstance)

         {

                   getLogger().info("ModuleTestTranscoderFrameGrab.onAppStart["+appInstance.getContextStr()+"]");

                   this.appInstance= appInstance;

         }

        

         publicvoid grabFrame(IClient client, RequestFunction function, AMFDataList params)

         {

                   getLogger().info("ModuleTestTranscoderFrameGrab.grabFrame");

 

                   while(true)

                   {

                            StringstreamName = params.getString(PARAM1);

                            if(streamName == null)

                            {

                                     getLogger().warn("ModuleTestTranscoderFrameGrab.grabFrame:No streamName");

                                     break;

                            }

                           

                            IApplicationInstanceappInstance = client.getAppInstance();

                            if(appInstance == null)

                            {

                                     getLogger().warn("ModuleTestTranscoderFrameGrab.grabFrame:No appInstance");

                                     break;

                            }

                           

                            IMediaStreamstream = appInstance.getStreams().getStream(streamName);

                            if(stream == null)

                            {

                                     getLogger().warn("ModuleTestTranscoderFrameGrab.grabFrame:No stream");

                                     break;

                            }

                           

                            LiveStreamTranscoderliveStreamTranscoder =(LiveStreamTranscoder)stream.getLiveStreamTranscoder("transcoder");

                            if(liveStreamTranscoder == null)

                            {

                                     getLogger().warn("ModuleTestTranscoderFrameGrab.grabFrame:No liveStreamTranscoder");

                                     break;

                            }

                           

                            TranscoderStreamtranscodingStream = liveStreamTranscoder.getTranscodingStream();

                            if(transcodingStream == null)

                            {

                                     getLogger().warn("ModuleTestTranscoderFrameGrab.grabFrame:No transcodingStream");

                                     break;

                            }

                           

                            TranscoderStreamSourceVideosourceVideo = transcodingStream.getSource().getVideo();

                            if(sourceVideo == null)

                            {

                                     getLogger().warn("ModuleTestTranscoderFrameGrab.grabFrame:No sourceVideo");

                                     break;

                            }

                           

                            getLogger().info("ModuleTestTranscoderFrameGrab.grabFrame:Call grabFrame");

                            sourceVideo.grabFrame(newGrabResult(), 426, 240);

                            break;

                   }

         }

}

 

要在Flash应用中调用这个方法, 先用RTMP连接到Wowza Media Server，然后用下面的方式调用: 

nc.call(grabFrame, null,"[stream-name]");

其中 [stream-name] 就是你要获得截图的实时流的名字. 

 

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