| 1. | 2 ) on the basis of the analysis of the syntax of the ps and ts data stream , a motion compensation algorithm based on pseudo - phase - shift is proposed
( 2 )研究了mpeg - 2标准内容，特别是对节目流、传送流的语法定义进行了分析。 |
| 2. | To pc user s request , the system program can download the program data streams and send the program information data structure to the pc user
对于来自pc端用户请求，能够将用户相应地节目流数据和节目信息数据结构下载到pc用户。 |
| 3. | But since each stream is exclusive occupied by a single user , the cost per user is very high . therefore the price of the service may hinder the wide acceptance of the system
单播vod系统能提供独立的用户交互功能，但是每个用户独占一个节目流资源，比组播共享方式的成本高。 |
| 4. | For resource limited , the motion - video data stream with high bit - rate value used in mpeg - 2 standard can not forward exactly by media . or for the sake of resource more efficiently utilized , more multi - pass program streams can be forwarded in certain bandwidth
Mpeg - 2的视频数据流在带宽资源不够条件下，常常无法正常地传输，或者在一定的带宽资源条件下，如何传输更多的节目流，更有效地利用带宽资源？ |
| 5. | In order to address this problem , we carried out a deep study on vod server performance aiming at maximizing the total amount of concurrent data streams the system can bear as well as maximizing the user number the system can serve simultaneously
对如何提高vod服务器性能以提高并发节目流的个数和同时服务的用户个数，我们进行了深入的研究。从技术角度， vod系统可以分为两种基本类别：基于单播的vod系统和基于组播的vod系统。 |
| 6. | Hence the system can theoretically support unlimited number of users at one time . on the other hand , since each stream is shared by numerous users , it ' s difficult to provide sufficient interaction to make the users much satisfied . as a result , we can see that these two kinds of systems are complementary to each other
组播方式中，所有观看同一节目流的用户共享服务器资源，由智能的网络交换系统提供分发，用户只能象选择电视频道的方式更换节目，而没有象看录像机光盘节目所具有的快进搜索方面的功能。 |
| 7. | Because of the different context of program and channel , most of the bit - stream rates of programs video are different . when one tv station relays other ' s program , or when we convert program from hfc to vod , tcp / ip system , it is need to convert the bit - stream rate which could not meet the need of local channel
由于节目内容不同、信道不同，数字电视系统中节目流码率是千差万别的，当一个电视台转播其它电视台的节目之前，或者将节目转播到点播电视系统、网络电视系统中时，如果本地信道不能满足带宽要求，则必需进行码率转换。 |
| 8. | Cas scrambles service streams with control word at head - end and broadcast the encrypted control word together with services streams . it is cas ' s responsibility to make sure only entitled terminal can decrypt the control word and descramble service streams . this paper mainly focuses on the design and implement of conditional access systen
数字电视的条件接收总的思路是在前端对节目流进行数字加扰，同时把加扰控制字加密后广播出去，条件接收系统采用一定的策略使得只有授权用户可以解密控制字，然后用控制字解扰收看节目。 |
| 9. | The project bases on mpeg - 2 . after introducing the system , audio and video of mpeg - 2 standard , the article ulteriorly describes the coding rules of mpeg - 2 streams , builds the system model based on understanding the streams structure , and makes out a resolving blue print in the multiplexing and converting streams
在深度剖析了mpeg - 2标准的编码规则和理解mpeg - 2的码流结构的基础上,通过分析系统层、节目流和传输流音视频的不同层次,本文建立了码流合成与转换并输出播放的系统模型,并得出了码流合成与转换的实现方案。 |
