多媒体通信习题答案.ppt

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1、MMC 习题讲解Chapter 7Chapter 7Chapter 7Chapter 7Chapter 7Chapter 8Chapter 9Chapter 91XReductionReductionExpansion)(42XEX Expansion)(21XEX Only X4, D2, D1 need to encoder and transmit to the decoder side.1DChapter 9Chapter 9Chapter 10Chapter 10Chapter 10Chapter 11Chapter 11Chapter 11Chapter 11Chapter 12C

2、hapter 12Chapter 13&141000/)1000/(1041000/ )2 . 31000/(2 . 15 . 61000/)1000/)(8 . 0(64. 3)(33)2 . 31000/(6 . 08 . 12ffeffThresholddfdf0Hzf133041.3324Chapter 13&14Chapter 13&14 Draw a diagram of Channel Vocoder and explain the principle of it.Chapter 13&14 Explain the masking effect illustrated in Fi

3、g. 14.7Chapter 15&16 Describe how does TCP and UDP work, respectively. What are the main differences in the type of services that they can deliver? What is the difference in the transport delay involved?TCPUDP面向连接的传输面向无连接的传输高可靠性尽最大努力交付，不保证可靠交付有重传机制，时延与网络拥塞、差错控制等有关传送数据的速度仅仅是受应用程序生成数据的速度、计算机的能力和传输带宽的限

4、制UDP和TCP协议的主要区别是两者在如何实现信息的可靠传递方面不同。TCP协议中包含了专门的传递保证机制，当数据接收方收到发送方传来的信息时，会自动向发送方发出确认消息；发送方只有在接收到该确认消息之后才继续传送其它信息，否则将一直等待直到收到确认信息为止。 与TCP不同，UDP协议并不提供数据传送的保证机制。如果在从发送方到接收方的传递过程中出现数据报的丢失，协议本身并不能做出任何检测或提示。UDP协议也称为不可靠的传输协议Chapter 15&16 What is the primary function of the RTP protocol? What is the assumed

5、underlying transport protocol (TCP or UDP)? What does it enable the receiver to accomplish beyond the simple UDP protocol? How does RTP/UDP combination differ from TCP? Transmitting real-time data such as audio and video streams UDP Additional Parameters Payload Type, Timestamp, Sequence Number, Syn

6、chronization Source (SSRC) ID, Contributing Source (CSRC) ID RTP/UDP combination is better than RTP/TCP TCP is connection-oriented, more difficult to scale up in a multicast environment TCP needs to retransmit missing packets, to achieve it reliability, which is less important in multimedia data tra

7、nsmissions.Chapter 15&16 What is the primary function of the RTCP protocol? What is the primary function of the RTSP protocol? RTCP: Real Time Control Protocol Combined with RTP Monitoring QoS Helping synchronization of audio and video RTSP: Real Time Streaming Protocol For communication between cli

8、ents and media severs Requesting presentation description Session setup Requesting and receiving mediaSession closure Date transmitting using RTPChapter 15&16 What is network jitter? How can a streaming player smooth the jitter? Jitter: A measure of smoothness of the audio/video playback, related to

9、 the variance of frame/packet delays Smooth the jitter Large bufferHolding enough frames to allow the frame with the longest delay to arriveIncreasing the latency, not good in real-time application Rate control in source codingChapter 15&16 What is meaning of QoS? Collective effect of service performances that determine the degree of satisfaction of the user of that service. It has everything to do with how the user perceives it What are the major parameters of QoS?