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    Please use this identifier to cite or link to this item: http://asiair.asia.edu.tw/ir/handle/310904400/9615


    Title: 應用於壓縮視訊轉換編碼器之具有區塊大小混用之畫面解析度縮減方法
    Authors: 李育瑞
    Contributors: 資訊傳播學系
    資訊學院
    Keywords: 頻率域視訊處裡
    畫面解析度縮減
    視訊調適
    視訊轉換編碼
    視訊編碼
    視訊傳輸
    Compressed-domain processing
    spatial downscaling
    video adaptation,
    video transcoding
    video coding
    video transmission
    Date: 2008
    Issue Date: 2010-05-13 13:29:44 (UTC+8)
    Abstract: 網路多媒體傳輸之目標之一為達成泛用多媒體存取(UMA) 服務,亦即各個用戶可以在不同地點,使用不同之資訊接取設備,經由各種不同之網路平台 (例如:有線或無線網路、電話網路等) 獲取Content Server 所提供之多媒體資訊。但要達成UMA服務之目標,需要先克服各種網路環境 (頻寬、傳輸延遲、封包遺失率) 及接取設備(畫面解析度、編解碼標準、資料處理能力)之異質性。在異質性多媒體傳輸環境中,媒體閘路器(Media Gateway)用於解決此種異質性問題以達成UMA服務之目標。媒體閘路器中的調適引擎(Adaptation engine)之可行技術之一為視訊轉碼技術,其目的在處理由伺服器所傳送來的視訊串流資料,轉換成為能夠配合用戶端的環境需求與能夠解碼的格式。由於小型行動化的資訊裝置能夠存取網路資源且能夠播放視訊內容,然而小型行動裝置顯示螢幕解析度的限制,使得超出螢幕範圍的畫面需要進行縮小處理,造成計算資源消耗而使電池的電力消耗太快。因此,有必要在媒體閘路器利用視訊轉碼技術縮小畫面解析度,則小型行動裝置可以減少電力的消耗以及增長使用時間。

    本計畫將探討Three-tier 視訊串流系統中的媒體閘路器之調適功能,針對在頻率域進行視訊內容轉換時所需之轉換編碼技術,利用影片內容特性及人類視覺遮蔽效應發展高效能與低複雜度之視訊畫面解析度縮減演算法。並將研究可行的低複雜度頻率域視訊轉換編碼器演算法,在不致降低畫面的視覺品質的前提下大幅降低所需運算複雜度。另外,也將發展與解析度縮減相關的技術 (例如:重新計算motion vector 與重新決定macroblock 之編碼模式)。為了使轉換編碼架構符合MPEG-21標準之adaptation engine規範,我們將以三層式視訊串流系統為基礎,在MPEG-21 Testbed平台上發展演算法、測試與展示研究成果。
    Universal multimedia access (UMA) service is one goal of transmitting multimedia content through networks. With UMA services, clients can access various multimedia contents, which is provided by the content server, through heterogeneous networks (e.g., wired or wireless network) with various access devices (such as personal computer, cellular phone, mobile device or PDA) ubiquitously.

    In heterogeneous multimedia transmission, media gateway can be used to overcome the heterogeneity for achieving the goal of UMA services. An adaptation engine in the media gateway can employ transcoding techniques to convert the incoming video bitstreams into the formats which is suitable to be delivered over a particular network characteristic, and the receiving devices can decode and display the formats. Since many small mobile devices can access network resources and display videos, the limit of screen size makes these mobile devices must to downscale the video resolution when the frame size is larger than its screen size. The downscaling operation consumes electricity power, and shortens life-time of its battery. Therefore, the media gateway has a need to containing the spatial downscaling transcoding techniques for downscaling the spatial resolution of the transmitted videos, and reducing the power consumption of the mobile devices.

    In this project, the adaptation function of the media gateway in a three-tier video streaming system will be investigated. We focus on the DCT-domain video transcoding techniques performing video content conversion in DCT-domain. With considering the characteristics of video content and the masking features of the human visual system (HVS), we will develop efficient and low computational complexity algorithm for spatial downscaling in DCT-domain. We will also develop a low complexity algorithm for the cascaded DCT-domain video transcoder without sacrificing the video quality. In addition, the techniques related to the cascaded DCT-domain transcoding (for example, motion vector re-estimation, macroblock coding-mode re-decision) will be investigated in this project. We will setup a three-tier video streaming system based on the MPEG-21 testbed, and integrate the developed algorithms and techniques into the system. Then, we will conduct simulations on the system in order to evaluate the feasibility and performances of our proposed methods.
    Appears in Collections:[資訊傳播學系] 科技部研究計畫

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