live555学习笔记【7】---客户端（二）

上文我们已经讲过了，客户端的DESCRIBE命令，接下来，我们继续讲一下剩下的RTSP命令。

发送SETUP命令，就是告诉服务器我们已经准备好了，可以建立连接进行数据传输了。之后，客户端通过之前设置好的RTP/RTCP端口去取流，进行数据的保存或播放，专业点叫做FileSink。

void createPeriodicOutputFiles() {
  // Create a filename suffix that notes the time interval that's being recorded:
  char periodicFileNameSuffix[100];
  snprintf(periodicFileNameSuffix, sizeof periodicFileNameSuffix, "-%05d-%05d",
	   fileOutputSecondsSoFar, fileOutputSecondsSoFar + fileOutputInterval);
  createOutputFiles(periodicFileNameSuffix);
  //按持续时间进行切片
  // Schedule an event for writing the next output file:
  periodicFileOutputTask
    = env->taskScheduler().scheduleDelayedTask(fileOutputInterval*1000000,
					       (TaskFunc*)periodicFileOutputTimerHandler,
					       (void*)NULL);
}

void createOutputFiles(char const* periodicFilenameSuffix) {
  char outFileName[1000];
  //这边表示创建文件
  if (outputQuickTimeFile || outputAVIFile) {
    if (periodicFilenameSuffix[0] == '\0') {
      // Normally (unless the '-P <interval-in-seconds>' option was given) we output to 'stdout':
      sprintf(outFileName, "stdout");
    } else {
      // Otherwise output to a type-specific file name, containing "periodicFilenameSuffix":
      char const* prefix = fileNamePrefix[0] == '\0' ? "output" : fileNamePrefix;
      snprintf(outFileName, sizeof outFileName, "%s%s.%s", prefix, periodicFilenameSuffix,
	       outputAVIFile ? "avi" : generateMP4Format ? "mp4" : "mov");
    }
    //封装为MP4文件
    if (outputQuickTimeFile) {
      qtOut = QuickTimeFileSink::createNew(*env, *session, outFileName,
					   fileSinkBufferSize,
					   movieWidth, movieHeight,
					   movieFPS,
					   packetLossCompensate,
					   syncStreams,
					   generateHintTracks,
					   generateMP4Format);
      if (qtOut == NULL) {
	*env << "Failed to create a \"QuickTimeFileSink\" for outputting to \""
	     << outFileName << "\": " << env->getResultMsg() << "\n";
	shutdown();
      } else {
	*env << "Outputting to the file: \"" << outFileName << "\"\n";
      }
      //开始数据传输，启动取流处理流程
      qtOut->startPlaying(sessionAfterPlaying, NULL);
    } else { // outputAVIFile
      aviOut = AVIFileSink::createNew(*env, *session, outFileName,
				      fileSinkBufferSize,
				      movieWidth, movieHeight,
				      movieFPS,
				      packetLossCompensate);
      if (aviOut == NULL) {
	*env << "Failed to create an \"AVIFileSink\" for outputting to \""
	     << outFileName << "\": " << env->getResultMsg() << "\n";
	shutdown();
      } else {
	*env << "Outputting to the file: \"" << outFileName << "\"\n";
      }
      
      aviOut->startPlaying(sessionAfterPlaying, NULL);
    }
  } 
}

FileSink已经创建好了，下面就是直接发送PLAY命令，通知服务器进行数据传输了。

//发送PLAY命令，一个是相对时间，一个是绝对时间
void startPlayingSession(MediaSession* session, double start, double end, float scale, RTSPClient::responseHandler* afterFunc) {
  ourRTSPClient->sendPlayCommand(*session, afterFunc, start, end, scale, ourAuthenticator);
}

void startPlayingSession(MediaSession* session, char const* absStartTime, char const* absEndTime, float scale, RTSPClient::responseHandler* afterFunc) {
  ourRTSPClient->sendPlayCommand(*session, afterFunc, absStartTime, absEndTime, scale, ourAuthenticator);
}

之后，客户端源源不断的接收服务器发送来的RTP数据包，并进行数据处理，最后收到服务器一个BYE的RTP包后，整个流程就结束了。