臺灣博碩士論文加值系統

當多媒體資料應用於許多領域時，例如：電腦、通訊、商業及娛樂，在資料儲存或傳送都需要龐大的儲存空間或佔用寬大的傳輸頻寬。因此，在無線通訊網路上運用一個適應有限頻寬與低功率需求的影像壓縮技術是非常重要的。
在多媒體無線通訊傳輸上，有兩個相當重要的瓶頸必須要克服的，一是傳輸頻寬，另一是計算能量與傳輸能量之損耗。當應用JPEG影像壓縮技術於多媒體無線傳輸時，為了要克服有限頻寬及低能量損耗的瓶頸，與保持影像品質在一定水準的目標，我們根據由 Taylor 和 Dey 所提的虛擬區塊大小之演算法，另提出鋸齒形掃描長度和混合形區塊大小兩種新的演算法來克服多媒體無線傳輸的兩大瓶頸。對於JPEG 演算法的每個8 8區塊經離散餘弦計算後，只選擇其中的一部分係數來量化編碼與傳送，例如：1 1(1個係數)，2 2(4個係數)，…，6 6(36個係數)，7 7(49個係數)，如此可減少傳輸頻寬、計算能量與傳輸能量的損耗。模擬結果在能量損耗方面這三種方式的損耗值都非常接近，但混合形區塊大小在影像品質方面的效能卻比其他兩種方式表現更好。

The multimedia data has been commonly used in many application fields such as computer, communication, business, and entertainment. When the multimedia data is stored in storage devices or transmitted in communication channel, it requires huge space of storage or occupies wide transmission bandwidth. Therefore, in the wireless communication network an adaptive image compression technology will be needed in order to reduce storage space, transmission bandwidth, and energy consumption requirements.
In the wireless multimedia transmission, two signification bottlenecks that need to be overcome are the bandwidth and energy consumption. We will use JPEG image compression technique to overcome these bottlenecks. On the other hand, we are not only to overcome bandwidth and energy issue but also to keep image quality received.
In the thesis, according to the adaptive JPEG image compression techniques by using the Virtual Block Size (VBS) proposed by Taylor and Dey in 2001, we propose two new energy-efficient algorithms, the Zig-Zag Scan Size (ZZS) and the Hybrid Block Size (HBS), which can overcome bandwidth and energy issue. We choose the parameter of the JPEG image compression algorithm to vary. This parameter affects the discrete cosine transform (DCT) portion of JPEG. The DCT still inputs the entire 8 8 block of pixels, but outputs a less amount of frequency information rather than an 8 8 block. After DCT, some frequency coefficients, such as 1 1 (1), 2 2 (4), …, 6 6 (36), 7 7 (49), are chosen to be quantized, encoded, and transmitted to reduce the transmission bandwidth, computation energy, and communication energy consumption. Simulation results show that the energy consumption (include computation and communication) are nearly for various block size of frequency coefficients chosen in the three methods, but the HBS method outperforms the others in the quality of image received.

Contents
Abstract (in Chinese)…………………………………………i
Abstract (in English)…………………………………………ii
Acknowledgment (in Chinese)…………………………………iv
Contents ……………………………………………………………v
List of Abbreviations…………………………………………viii
List of Figures …………………………………………………ix
List of Tables…………………………………………………xii
Chapter 1 Introduction…………………………………………1
1.1 Background of Research……………………………………1
1.2 Motivation of Research ……………………………………1
1.3 Organization of This Thesis ……………………………2
Chapter 2 JPEG Image Compression ……………………………4
2.1 Introduction ……………………………………………………4
2.2 JPEG Encoder and Decoder …………………………………5
2.2.1 JPEG Encoder …………………………………………………5
2.2.1.1 8x8 Discrete Cosine Transform (DCT)………………5
2.2.1.2 Quantization ………………………………………………7
2.2.1.3 DC Coding and Zig-Zag Scan …………………………9
2.2.1.4 Variable Length Coding (VLC) ………………………10
2.2.2 JPEG Decod………………………………………………………11
2.3 Energy Consumption……………………………………………14
2.3.1 Computation Energy …………………………………………14
2.3.2 Communication Energy………………………………………15
2.4 Performance Evaluation………………………………………15
2.4.1 Mean Square Error (MSE), Signal to Noise Ratio
(SNR), and Peak Signal to Noise Ratio (PSNR)
……………………………………………………………………15
2.4.2 Compression ratio ……………………………………………18
Chapter 3 Energy-Efficient JPEG Image Compression………19
3.1 Introduction ………………………………………………………19
3.2 Energy-Consumption for JEPG Compression ………………20
3.2.1 Fast Discrete Cosine Transform (FDCT) Computation…20
3.2.2 Bit Stream of Variable Length Coding (VLC)…………24
3.3 Energy-Efficient JEPG Image Encoder………………………25
3.3.1 Virtual Block Size (VBS) method …………………………25
3.3.2 Zig-Zag Scan Size (ZZS) method……………………………26
3.3.3 Hybrid Block Size (HBS) method …………………………29
Chapter 4 Simulation Results and Comparisons………………33
4.1 Introduction…………………………………………………………33
4.2 Simulation Results ………………………………………………33
4.3 Performance Comparisons…………………………………………59
4.4 Performance Analysis……………………………………………69
Chapter 5 Conclusions and Future Studies ……………………70
5.1 Conclusions……………………………………………………………70
5.2 Future Studies ………………………………………………………71
References …………………………………………………………………72
Vita …………………………………………………………………………74

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