zoom ratio 中文意思是什麼
zoom ratio
解釋
變焦距倍率-
In fact, scaling technology is an essential component in many image / video processing such as to magnify / minify still image, to achieve special effect like picture - in - picture, to compress or transform digital video with spatial scalability etc. in this thesis we mainly employ this technology in video transcoding, which is a powerful but computationally intensive tools to convert one kind of video format into another, meeting different demand such as lower bitrates or various display terminals. in sum, there are two kinds of scaling schemes : one is in spatial domain and the other in transform domain. the scheme in transform domain can provide very good performance, that is, efficient computation and desirable image quality, whereas it has some disadvantage which is impossible or hardly to o vercome, especially some scenarios require arbitrary ratio zoom in horizontal and vertical, and excellent visual effect
兩種方法都各有其利弊：變換域的方法是利用現有常用的視頻壓縮方案都是基於dct這個特點，所以可以直接在變換域做處理，這樣可以節省大量的計算，但其缺點是由於dct是基於塊的變換，如8 8 ，所以很難找到一種方案可以進行任意比例的縮放，尤其是在縱橫縮放比例不一致的情形，但這對諸如hd縮放到sd和空域分級的壓縮方案來說尤為重要，基於空域濾波的方法卻沒有這樣的限制，同時可以保證縮放后的圖像的質量遠高於基於變換域的方法，為了達到高的縮放質量，就不可避免導致計算量過大。
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