本論文旨在探討壓縮音訊和編碼器相關特性的關係並據此發展以改良式離散餘弦轉換領域為主的位元層編碼新策略，位元層編碼被廣泛地利用於影像壓縮並且已納入JPEG2000的標準中，它成功地結合小波轉換的階層性結構與一組漸進式地掃描順序和編碼動作以達到在品質與傳輸可調性上的次佳化。在運用相同壓縮策略於發展可調式音訊壓縮法上時，研究人員面臨了兩種困難。其一，人類的聽覺感知與視覺感知截然不同，對於頻率係數的重要性判斷需要新的依據；多數音訊感知的實驗進行於傅立葉領域，而非小波領域，這使得編碼策略難以利用已知的感知現象。相反地，屬於一般傅立葉轉換的改良式離散餘弦轉換使用於音訊壓縮達十餘年並已成功地證明為一傑出的音訊轉換工具，然而它缺乏小波轉換之階層性自相似結構，很顯然地缺少此種自相似結構將無法使漸進式編碼策略達到其最佳的編碼效率，此為第二項困難。
透過理解內容式位元層編碼的zero-tree假設，作者嘗試著分析不同係數次序的編碼效率，以改善音訊在改良式離散餘弦轉換缺少自相似結構的問題；本論文的二項主要貢獻為：第一、依據幾項zero-tree位元層編碼器上的觀察，提出關於編碼次序與編碼效率的理論分析，有助於後續相關研究發展。第二、提出一個新的內容式位元層編碼演算法與相對應的頻帶拓展演算法，這個整合性的設計展示了一種由低階資料描述壓縮到高階參數化合成的漸進式方法論。

The purpose of this dissertation is to exploit the relationship between compressed audio and the coder-related characteristics to develop new algorithms when bit-plane coding strategy is applied on the Modified Discrete Cosine Transform (MDCT) domain. The bit-plane coding method has been extensively investigated in image compression domain and standardized in JPEG2000. It successfully combines the hierarchical content of the Wavelet transform with a set of progressive scanning and coding operations to achieve a sub-optimal performance in both quality and transmission scalabilities. There are two difficulties when researchers attempted to use the same compression strategy in developing scalable audio compression methods. The first difficulty is that human aural perception is quite different from human visional perception. New methods are needed to guide the order of the importance of transformed coefficients. Huge research literatures discussed the audio perceptual coding effects in the generic Fourier domain but less in the Wavelet domain. It is hard to determine coding strategies without appropriate audio perceptual criterions in the Wavelet domain. On the contrary, as one of generic Fourier transforms, the MDCT has been developed for audio coding for decades and is practically proven an outstanding tool. Different from the Wavelet transform applied to the image compression, the MDCT coefficients of an audio piece lack a hierarchical self-similarity structure. The second difficulty is revealed here that the coding efficiency of the progressive coding strategy may not be maximized without such kind of self-similarity context.
By understanding the zero-tree assumption of the context-based bit-plane coding, the author tried to analyze coding efficiencies of different ordering schemes to avoid the lack of self-similarity context in the MDCT representation；Two original contributions in this dissertation are presented. The first part is to provide a systemic analysis between the ordering scheme and the coding efficiency for zero-tree based bit-plane coding strategies. This analysis gives a strong groundwork for the follow-up researches. The second part consists of one novel bit-plane algorithm and one corresponding bandwidth extension algorithm. This integrated design demonstrated a progressive methodology from the low-level data representation/compression to the high-level parametric synthesis.

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