一般音週標記(pitch period marking 語音週期標記)需要先決定音高(音高追蹤 pitch tracking, pitch determination)，再計算音週標記。音週標記只是語音波形的局部最大值數列的子集合。本研究提出一個不經過音高追蹤的步驟，直接計算週期標記的方法，此方法是將音週標記當作 組合空間搜尋的 問題來處理，叫做擴展修剪演算法， 或ET演算法。 ET代表Extending 及Trimming，分別是探索組合空間的方法，以及可能性低路徑的刪減方法。所得到的音週標記，配合我們先前提出的(音節)雙拼合成方法，台語的單音節語音合成系統，可以較輕力實作。

Speech pitch period marking usually requires pitch determination first. In this study we regard the pitch period marking as a searching problem through the combinatorial space of local maxima of a speech waveform, and propose an ET algorithm for pitch period marking without going through pitch determination. ET stands for “extending” and “trimming”; extending prescribes a way to explore the combinatorial search space, and trimming specify a way to limit the search space. With resulting pitch period marks and previously proposed binary combination method, a syllable-based Taiwanese synthesis system can be implemented with relatively little effort.

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