臺灣博碩士論文加值系統

在主動式網路上常將多媒體服務應用其上，即時轉碼器就是其中的應用之一，其可根據用戶的需求提供不同等級和即時轉碼的服務，讓不同的用戶設備可存取同一個媒體伺服器。
即時轉碼器基本的功能，就是將來源媒體即時轉換為另一種格式、位元率，或不同解析度大小的媒體，以適應不同的用戶端設備，而其最在意的就是轉碼的速度和轉碼後的影像品質；本文主要探討在即時轉碼器中的大小調整機制，我們先比較了傳統的大小調整機制做法，進而提出運算速度更快，影像品質更好的直接映射演算法。
根據實驗模擬顯示，直接映射的方法比傳統的最近鄰模式提昇了25%的運算速度，使用直接映射的RGB交錯模式之PSNR也比最近鄰模式高1.6 dB，所以若使用直接映射的方法將可增進即時轉碼器的效率，則結果可讓更多的用戶同時存取媒體伺服器，並達到即時轉碼的保證。

Multimedia services are always implement on active networks. The real-time transcoder is one of their applications that can provide different services level agreement. The real-time transcoding depends on the customer devices and requirements. The basic function of a real-time transcoder is to transform the source medias to other formats. The speed and the transcoded imagine quality are the most concerned issues. We have discussed the conventional resizer, and propose a direct mapping method to improve the transocding speed and enhancing the image quality.
Simulation results show that the direct mapping method is 25% faster than the conventional nearest resizer, and the PSNR of interlaced RGB pick up of direct mapping is 1.6 dB higher than the nearest method. The method can be implemented into a real-time transcoder on active network that yield better performance of network.

第一章 緒論------ 1
1.1 簡介--------- 1
1.2 動機與目的--- 2
1.3 論文架構----- 2
第二章 背景知識-- 4
2.1 主動式網路--- 4
2.2 即時轉碼器----6
第三章 傳統的大小調整機制-----11
3.1 影像幾何轉換--------------11
3.1.1空間轉換-----11
3.1.2灰階插值-----13
3.1.3理想的內插函數----------14
3.2 最近鄰模式----15
3.3 雙線性模式----17
3.4 雙立方模式--- 19
3.5 平均模式----- 21
第四章 直接映射大小調整機制-------- 23
4.1 直接映射的慨念-------- 23
4.2 4取1模式-------------- 25
4.2.1四種基本模式---------25
4.2.2 4取1模式與最近鄰模式的關係---27
4.3 16取4交錯模式--------- 30
4.4 RGB交錯模式----------- 35
4.5 RGB+交錯模式---------- 38
第五章 模擬與比較 ---------40
5.1 執行速度的比較-------- 40
5.2 影像品質的比較-------- 43
第六章 結論與未來工作----- 53
6.1 結論------------------ 53
6.2 未來工作-------------- 54
參考文獻------------------ 55

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