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  • 學位論文

使用JPEG 2000完成使用接收端驅動之階層式Multicast影像傳輸系統

Receiver-Driven Layered Multicast Image Transmission System Based on JPEG 2000

指導教授 : 黃文吉
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摘要


摘要 由於網路蓬勃發展, 能提供不同碼率的多重碼率系統比以前重要. 多重碼率系統可分為兩大類: 正交與非正交系統. 本論文所提出兩種多重碼率系統: 階層式JPEG 2000 與多重描述系統, 這兩個系統又分別屬於正交累積與非正交非累積系統. 在階層式JPEG 2000的系統裡, 我們可獨立控制每一個階層的碼率與解析度, 為了要增加其編碼效能, 前幾層的編碼結果會被重覆利用. 在多重描述的系統裡 codeblock 會被分成兩群, 我們使用JPEG 2000獨立編碼這兩群的codeblock. 不管解碼端接收到那一群的資料, 都可用來還原一張圖. 當通道有雜訊時, 多重描述系統表現出較基本JPEG 2000 好的抗雜訊能力. 當通道無雜訊時, 多重描述系統的編碼效果幾乎跟基本的JPEG 2000一樣好. 為了增加影像編碼的彈性, 我們結和了階層式JPEG 2000 和ROI 編碼. 在這個系統裡, 傳送端先將低解析度的圖傳送給使用端, 讓使用端選擇他要的ROI區域與位移量, 使用端再將這些資訊傳回給傳送端. 傳送端再根據這些資訊, 再第二階段的傳送做ROI編碼的動作. 那麼使用端在還原這張圖時, 就會得到有ROI效果的影像. 關鍵詞: JPEG 2000, 階層式JPEG 2000, 多重描述系統, ROI 編碼

並列摘要


Abstract With the increase use of networks, multirate transmission becomes important since it can produce a data stream in multiple data rates. Multirate transmission system can be divided into two groups: the orthogonal scheme and the non-orthogonal scheme. This thesis presents two types of multirate image transmission system: the LJPEG 2000 and multiple description scheme which are categorized to orthogonal cumulative and non-orthogonal non-cumulative scheme, respectively. In the LJPEG 2000, the rate and resolution associated with each layer can be pre-specified. The algorithm encodes an image one layer at a time using the modified JPEG 2000 technique. The encoding results at the previous layers will be used in the current layer to accelerate the encoding process. In the multiple description scheme, the coefficients of each subband in the wavelet domain are divided into blocks, called codeblocks. These codeblocks are then partitioned into different groups, each group is a description of the original image, and is independently encoded using the JPEG 2000 technique. The decoders of the MD scheme can reconstruct the image by collecting the JPEG 2000 -encoded bitstreams from any group. MD attains comparable performance to basic JPEG 2000 for lossless channels. When the channels become lossy, it retains the rate-distortion performance for image reconstruction. To increase the flexibility of image coding, we combine the LJPEG 2000 and the ROI coding. In this scheme, the transmitter first transmits the lowest resolution to the receiver. After the image is reconstructed in the receiver, the ROI is then specified, and the shape information is delivered back to transmitter. Then the transmitter sends the full resolution with the ROI area shift up. At this step, the transmitter also used the encoding results of the previous step. The receiver then reconstructs the image after shifting back the ROI area. This receiver-driven scheme benefits both the transmitter and the receiver. Keywords: JPEG 2000, LJPEG 2000, multiple description scheme, ROI coding

參考文獻


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