Live555用做RTSPClient时，利用RTP时间戳进行音视频同步的解决方案(必须有RTCP支持才可行)
先看来自Live555官网的2个常见问题：
问题1：Why do most RTP sessions use separate streams for audio and video? How can a receiving client synchronize these streams?
回答：Sending audio and video in separate RTP streams provides a great deal of flexibility. For example, this makes it possible for a player to receive only the audio[......]