P2P網路電視測試報告（原理篇）︱Mr./Ms.Days…


	P2P網路電視測試報告（原理篇）︱Mr./Ms.Days…
joeywo
10-11-2009 2:44 PM
58 views
tags:
pchome雜誌, p2p網路電視
joeywo says:
PCHOME165期10月號延伸閱讀，更多內容請上Mr./Ms.Days觀看
Add a Comment
Login to Comment. Not a member yet? Sign up
Today's Top Clips

visit the Top Clips page
View the Top Clips from October 11, 2009
Embed This Clip In Your Site...
<div style="margin: 12px 0px; font-family: arial; color: #333333; background: #ffffff; border: solid 4px #e5e5e5; width: 100%; clear: left;"><div class="CM_CTB_Content_Wrap" style="margin: 0px; padding: 0px;background-color: #ffffff;"><div style="border-bottom: solid 1px #dcdcdc; white-space: nowrap; margin-bottom: 8px; background-color: #eeeeee ;background-image: url(http://clipmarks.com/images/source-bg.gif); background-repeat: repeat-x; height: 24px; line-height: 24px; vertical-align: middle; padding-bottom: 4px; color: #666666; font-size: 10px;" ><a href="http://clipmarks.com/clip-to-blog/" title="see clips that are hot right now"><img src="http://content.clipmarks.com/blog_embed/72f02664-1b64-4d39-8684-c5c3e6b29951/5D5DE81C-E2FF-47F2-A755-5E075426ABD9/" alt="" width="19" height="19" border="0" style="vertical-align: middle; margin: 0px 4px; display: inline; border: none; float:none;" /></a>clipped from <a title="http://mmdays.wordpress.com/2007/04/19/p2p-tv/" href="http://mmdays.wordpress.com/2007/04/19/p2p-tv/" style="font-size: 11px;">mmdays.wordpress.com</a></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/"><DIV id="header">
<H1><A title="Mr./Ms. Days – 網路, 資訊, 觀察, 生活" href="http://mmdays.wordpress.com/" linkindex="4">Mr./Ms. Days – 網路, 資訊, 觀察, 生活</A></H1>
<H2>網路、產業、資訊、觀察、生活、電影、技術、新知、科技、媒體、趨勢、Web 2.0</H2>
</DIV></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/"><H2>P2P網路電視測試報告解讀(上) – 現行基本原理介紹</H2></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/"><div align="center"><img src="http://content7.clipmarks.com/blog_cache/mmdays.wordpress.com/img/46B209F3-C511-47E8-A385-66C5278A2121" alt="hierachy.jpg" /></div></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/"><div align="center"><img src="http://content8.clipmarks.com/blog_cache/mmdays.wordpress.com/img/6535635F-A524-47D8-951A-A516152E27E4" alt="random.jpg" /></div></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/">在此類的階層式架構中, 主要的研究議題是網路中該有幾個階層</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/">太多層會造成檔案從源頭傳到一般使用者的時間要很久</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/">太少層的話則每個分流者(源頭與超級使用者)的分擔會變重,因為要分流的對象變多了</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/">另外一種的分享方式則有別於固定的樹狀結構, 每個使用者並沒有固定的檔案來源, 也沒有一定的傳輸對象</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/">P2P網路電視在架構設計上需要比BT更有效率的訊息交流方式</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/"><P>在上述兩者中間還有一些不同的機制, 比如說把影片檔案切成好幾組, 每一組用不同的樹架構來進行傳送. 下圖是假設源頭把一個檔案切成三組, 用不同的方式傳送給 A, B, C三個人:</P></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/"><div align="center"><img src="http://content9.clipmarks.com/blog_cache/mmdays.wordpress.com/img/2A18F362-006F-484C-914C-006A63600C59" alt="splitstream.jpg" /></div></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/"><P>這個方法的好處在於每個人的上傳頻寬都會被用到, 而且假如A斷線了, 會受到影響的只有檔案片段1, 檔案片段2與3的傳輸仍然不受影響. 至於檔案片段1~3要怎麼切呢? 有兩種常見的切法:</P></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/">利用Layered Encoding來作切割</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/"> Layered Encoding的概念是, 把一個畫質很好的影片切成幾個畫質較差的小檔案, 待使用者收到後再組合為原來的影片</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/"> Layered Encoding的缺點是, 每一個檔案片段都是一個patch(補強檔), 會需要上一個檔案片段才能作用</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/">將第n秒的檔案歸類為檔案片段1, 第n+1秒的檔案歸類為片段2, 第n+3秒的為片段3. 這就是所謂 <STRONG><FONT color="#ff0000">MDC (Multiple Description Coding)</FONT></STRONG>的概念</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/">與1相較之下, 2的作法是比較理想的</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://mmdays.wordpress.com/2007/04/19/p2p-tv/">但詭異的來了, 現行的影片解碼器在開發的過程中幾乎都不支援MDC的功能</blockquote></div><div style="margin: 0px 6px 6px 4px;"><table style="font-size: 11px;border-spacing: 0px;padding: 0px;" cellpadding="0" cellspacing="0" width="100%"><tr><td style="background:transparent;border-width:0px;padding:0px;">&nbsp;</td><td align="right" style="background:transparent;border-width:0px;padding:0px;width:107px" width="107"><a href="http://clipmarks.com/share/5D5DE81C-E2FF-47F2-A755-5E075426ABD9/blog/" title="blog or email this clip"><img src="http://content6.clipmarks.com/images/c2b-foot.png" border="0" alt="blog it" width="107" height="17" style="border-width:0px;padding:0px;margin:0px;" /></a></td></tr></table></div></div>
New from the makers of Clipmarks: Amplify.com - Don't just share the news...Amplify it!
Clipmarks: Home; New Clips; Top Clips; Dashboard
Popular Topics: News; Life; Science; Technology; Entertainment
Get Started: Sign Up; Install Clipping Tool; How Clipping Works; Clip-to-Blog™; ClipSearch
Tools and Resources: FAQ; ClipWeek; Top Clippers; Top Tags; Site Map
About Clipmarks: About Us; Contact; Copyright; Privacy; EULA
Search Options

Today's Top Clips
