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題名 | 適用於H.261標準的連續顯像式視訊橋接器= |
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作者 | 王紋德; 朱榮華; 黃英華; 黃志雄; 甘果碩; 楊朝勳; |
期刊 | 電信研究 |
出版日期 | 19950600 |
卷期 | 25:3 1995.06[民84.06] |
頁次 | 頁415-423 |
分類號 | 448.88 |
語文 | chi |
關鍵詞 | 視訊橋接器; |
中文摘要 | 藉由視訊橋接器(Video Bridging)在網路上提供多點視訊會議服務是一種新生的網路 視訊應用。它除了能增加目前的網路使用率之外,並且亦可擴大點對點的視訊通訊普及率。 視訊橋接器按顯像方式來區分,有所謂的交換顯像式(Switched Presence)(即興會者至多只能 選擇看某一處的畫面),目前此種橋接器已有H.243標準規範。另蛉一種橋接器稱做連續顯像 式(Continuous Presence),它可供與會者同時選看多處的畫面。最近BELLOCRE[5]提出一種 高效率的Quarter-Common-Intermediate-Format(QCIF)視訊合成觀念,其可輕易地應用到連續 顯像式橋接器。不過由於它仍有許多技術問題難以克服,譬如非對稱性傳輸率,畫面同步以 及解碼端的緩衝器易於溢出等等。所以目前它的可行性仍在ITU-T-SG15的系統與視訊專家小 組內熱烈討論中。關於QCIF合成器的效能分析及模擬結果可參照文獻資料[4]。本文主要是 敘述如何利用個人電腦以及軟體的方式來建制QCIF合成器,此外我們也討論五山些解決系 統技術問題的辦法。本系統已成功地展現(i)使用QCIF合成器,所有的H.261語法及編碼堂 徵不所受到影響,(ii)多點視頻通訊的延遲效果及畫面品質是適合互動式交談通訊,(iii)軟體 就可即時地結合多重視頻訊號,(iv)利用低成本的BC/DOS環境就可建級連續顯像式的視訊橋 接器。 |
英文摘要 | Multi-point videoconferencing with video bridging by network servers represents a viable network service and extends the usability of two-point videoconferencing. A switched presence bridge, where the most active speaker is broadcast to every conferee, has been standardized in H. 243. A continuous presence bridge is still under research. Bellcore has proposed to ITU study group 15 an efficient Quarter-Common-Intermediate-Format (QCIF) combiner which is fully compatible with the H. 261 standard. However, because of certain technical difficulties, such as asymmetrical source channel frame synchronization and decoder buffer consistency, its practicality is still under debate in ITU-T-SG15's system and video s=expert groups. A through analysis and computer simulation of the proposed QCIF combiner has been given in [4]. This paper further describes implementation details of this experimental prototype combiner using a PC and software which can combine data generated by up to four video coders and transported through network and coding features can be preserved using the QCIF combiner, (ii) multipoint delay and picture quality performance are quite suitable for interactive communication, (iii) software can combine multiple video streams in real time, (iv) that a low cost implementation on PC/DOS is capable of doing the real time video combining. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。