數位電視量測比較與浮水印

Abstract

數位電視系統提供品質更好的影像與聲音，而且，他也能夠傳送各式各樣的數位資料。在21世紀，它將會成為新的數位資訊傳輸媒介。然而，它與傳統類比電視有很大的不同。在本論文裡，我們將會討論數位電視的傳輸特性以及提出如何安全地傳輸數位資訊。主要分為三個部份：(1) ATSC 數位電視標準在鄰頻干擾下的場測 (2) 其他國家ATSC 與 DVB-T 數位電視系統的比較 (3) 利用浮水印保護影像與視訊資料的所有權 在鄰頻干擾的情況下，接收能力是很重要的一個測試，特別是當數位電視訊以及類比電視訊號一起存在的時候。因為它可能會互相干擾。由測試的結果來看，不管有無鄰頻干擾，數位電視的接收率都一樣。雖然類比電視的接收訊號會因為鄰頻數位電視訊號的干擾，而導致C/N 值下降約 4~5 dB，但是觀察所得的接收品質卻沒有什麼不同。 還有一些其他國家或是研究單位關於 ATSC 與 DVB-T 的比較測試。由於一些設定參數的不同，測試結果也不完全一樣。但是大方向的結果是差不多的。在本論文中，我們將會把這些測試結果整理比較一下。 浮水印是一種將訊息嵌入數位資料的技術。它作為所有權的授權與認證。然而，不同的數位資料對於浮水印有不同的要求。我們將會討論一下數位電視對於浮水印的要求，並且提出一個可行的數位電視浮水印。

Digital TV (DTV) not only provides a better quality for video and audio services, it can also be used to carry other types of digital data. It will be one of the most important vehicles taking us to the information highway in the 21 century. However, it is different from the conventional TV in many aspects. In this thesis, we focus on the transmission characteristics of DTV and the content security issue. There are three parts in this thesis: (1) field test of ATSC DTV system for adjacent channel interference, (2) comparison of ATSC and DVB-T systems based on several sets of test data, and (3) digital watermarking for ownership protection of image/video data. The reception ability under adjacent channel interference is an important test item particularly during the analog and digital TV co-existing period, because they may interfere each other. Based on the field test results, the DTV signal reception is almost the same with or without the adjacent channel interference. In measuring DTV interference to NTSC, when the lower adjacent channel DTV signal is transmitted, the average of NTSC C/N value drops about 4~5 dB, but it does not change the visual quality much. There are several field tests around the world comparing two DTV systems, ATSC and DVB-T. due to different set-ups and parameters, these test results are not identical, but they show similar tendency. We did a comparison study and summarize our observations in this thesis. Watermarking is a technique that embeds invisible data into multimedia material. It can be used for ownership authentication and identification. There are specific requirements when this technique in this thesis to demonstrate its usefulness. We also discuss the requirements and system architecture for watermark embedding in DTV.