H.264為現在壓縮效果及畫面品質都很好的視訊標準，而MPEG-2和H.263是目前使用率很高的視訊標準，目前很多的影像資料都是由此兩種標準所壓縮儲存，將它們轉換編碼成壓縮率較高的H.264視訊標準是非常重要的；在H.264轉換編碼的部份，為了因應不同網路環境下的傳輸頻寬能力不同，從高位元率的H.264串流到低位元率的H.264流，其轉換編碼也是有必要的。在做轉換編碼的時候和一般壓縮編碼最大的差別是有無原始資訊可參考利用；在一般壓縮編碼時，其資訊只能從視訊樣本中取出，所以其壓縮效益與壓縮時間都會受到比較大的限制，而在做轉換編碼時，我們可以從事先壓縮過的視訊串流中，將之解碼過後，得知之前標準壓縮過的資訊，於是我們就可以利用此原始資訊來協助H.264的重新編碼，不必進行完整的重新編碼流程。本篇論文即是探討在不同標準的轉換編碼下，如何有效率的使用原始資訊使之在畫面內模式與畫面間模式縮短他們的轉換編碼時間。 MPEG-2 and H.263 video coding standard are used in various applications so there are many video sources which are compressed by these video formats. Therefore, transcoding from MPEG-2 and H.263 to H.264 is an important topic recently. Applications of H.264/AVC become popular and important in multimedia content transfer between networks and devices from high definition television (HDTV) to mobile handsets so the technique of bit-rate reduction is also necessary. The most straightforward way to succeed transcoding and bit-rate reduction is to decode the video stream and re-encode the reconstructed video sequence. To whatever extent, the fully decoding and re-encoding process is quite involved and time consuming. Reusing information enclosing in the original incoming video stream can apparently reduce computational complexity. In this thesis, a powerful incorporated transcoder is studied and the computational complexity can be reduced.
