一個精細可調層次式到非可調層次式的位元流轉碼技術在串流視訊之應用

Abstract

近年來串流視訊的需求快速地成長。為了使串流視訊能在不同的網路環境傳送給多樣的設備，這篇論文即研究如何建構一個使用MPEG-4精細可調層次式位元流為儲存格式和MPEG-4精細可調層次式到單層之位元流轉碼器的串流視訊。將巨量的視訊資料先編碼成為精細可調層次式位元流，可以有效地節省媒體資料庫的儲存空間。除此之外，使用精細可調層次式位元流的伺服器，可以在不同的傳輸速率上動態調整傳輸的位元總量，以提供接收者適當的視訊品質。本論文所提出的精細可調層次式到單層之位元流轉碼器是根據兩項特性─餘弦轉換的線性特性和已壓縮位元流移動向量的重複使用。實驗結果顯示所提出的轉碼器，和串接方式的轉碼器相比，兩者在視訊品質上幾乎相同，且本論文之轉碼器在效能上卻有較低的複雜度。為了測試在網路環境下的位元率適性能力，也將具有位元率控制的轉碼器整合到MPEG-21多媒體測試平台上。這個串流視訊之原型系統可以提供三種不同的視訊格式給客端使用者，包括精細可調層次式、進階簡易規格、和簡易規格。

The demand of streaming video has grown rapidly in recently years. To enable video streaming over heterogeneous networks to various devices, this thesis proposes a video streaming approach using MPEG-4 Fine Granularity Scalability (FGS) archived content and an efficient FGS to Single Layer transcoding. The video content coded into FGS bitstreams can save the database volume. In addition, with the FGS archived bitstreams, the server can supply the video content with proper quality by matching transmission rates dynamically. The proposed FGS to MPEG-4 Simple Profile transcoder is based on the DCT linearity and the reuse of the motion vectors in the archived bitstream. Our results indicate that the transcoder has almost the same performance as that of the cascaded transcoding method, but with much lower complexity. The transcoder with the rate control is integrated into ISO/IEC 21000-12 Multimedia Test Bed to evaluate its rate adaptation ability under network environments. The resultant prototype can stream video to clients in three video formats including the FGS, Advanced Simple Profile, and Simple Profile.