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multimedia-on-web.ppt
multimedia-on-web.ppt
multimedia-on-web.ppt
multimedia-on-web.ppt
multimedia-on-web.ppt
multimedia-on-web.ppt
multimedia-on-web.ppt
multimedia-on-web.ppt
multimedia-on-web.ppt
multimedia-on-web.ppt
multimedia-on-web.ppt
multimedia-on-web.ppt
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multimedia-on-web.ppt

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  • A crawler (also called spider) is a program that automatically fetches Web pages. Most pages contain links to other pages. Therefore, a spider can start from almost any page and yet traverse a large number of diverse and distinct pages. Typically, used by search engines
  • Transcript

    • 1. Characteristics of Streaming Media Stored on the Web
      • M. Li, M. Claypool, R. Kinicki, and J. Nichols
      • To appear in ACM Transactions on Internet Technology , 2005.
    • 2. Introduction (1/3)
      • Several factors contribute to the growth of streaming media on the Web
        • Availability of broadband
        • Desktop processing capabilities
        • Compression technology
        • Commercial interest
      • E.g., RealNetworks estimated 350,000 hours of streaming media traffic (2001)
      • E.g., Significant fraction of Internet traffic (CAIDA, 2002)
    • 3. Introduction – Related Work (2/3)
      • Characterize streaming application performance (e.g., see references [10-16])
      • “ TCP-friendly” streaming protocols (e.g., [4],[5])
      • Queuing disciplines (e.g., [6-9])
      • Acharya & Smith [19] studied all video URLs available in Alta Vista in 1997
        • Internet can not support real-time streaming
    • 4. Introduction – Research Questions (3/3)
      • What are the most popular streaming media applications on the Web?
        • Real, Windows, QuickTime, MPEG
      • What is the ratio of streaming audio versus streaming video?
        • Audio requires lower bitrates?
      • Are media playback durations of stored media long-tailed?
      • What are typical streaming media bitrates?
        • Indications of bandwidth requirements
      • What fraction of streaming media codec's being used?
        • Compression efficiency
    • 5. Methodology
      • Develop a specialized Web crawler
      • Traverse 17 million URLs;
        • Selected 17 Web pages as starting points
        • Considered popularity, demography, connectivity
      • Identified ~ 30,000 media clips
        • Used protocol information in URLS
        • E.g., rtsp://, mms:// etc
      • Individually access media clips using custom built tools
        • Encoding format, target bitrate, frame size, codec
    • 6. Analysis - Outline
      • Aggregate analysis (Section III-A)
      • Commercial product analysis (Section III-B)
        • Video
        • Audio
      • Codec Analysis (Section III-C)
    • 7. Aggregate Analysis
      • Each spider collected 1 million URLs
        • Approximately 11 million distinct URLs
        • About 55,000 streaming media URLs
      • In 1997, 23,000 streaming media URLs in 25 million Web pages
        • A five-fold increase in streaming!
      • Fig 1: ~ 1% of the servers provide 100 or more media URLs per server
      • Fig 2: Real Media accounts for almost half of all the streaming media URLs
        • QuickTime, AVI, MPEG were very popular in 1997, not any more!
    • 8. Commercial Product Analysis
      • About 98% of the streaming media URLs are for pre-recorded media
      • Most audio/video clips are of short duration
        • Median for audio ~ 4 minutes (a typical song)
        • Median for video ~ 2 minutes (a typical trailer)
        • In 1997, 90% of clips lasted 45 seconds or less
        • Duration still shorter than typical TV programs
      5 1474 28 QuickTime 100 16545 12842 Total 32 6567 2591 Windows 63 8504 9863 Real Percentage Video Audio Media Type
    • 9. Video/Audio Clips
      • Median bitrate ~ 200Kbps
      • Approximately 70% of video targeted towards broadband connections; only 1% targets T1
        • In 1997, 20% videos were targeted at T1
      • Scalable streaming – multiple bitrates per stream
        • About 12% of Windows Media streams use scalable streaming
      • About 50% of the videos have less than 320x240 resolution – video resolutions are low
      • About 90% of the streaming audio is targeted for modem users
    • 10. Media Codecs
      • RealPlayer and Windows Media Player (latest version) buffer content at rates significantly higher than the playback rates
      • Raises “fairness” concern
    • 11. Sampling Issues
      • How are the results influenced if there are fewer crawler starting points?
      • How are the results influenced if there are fewer than 1 million URLs per starting point?
      • How does sampling affect distributions?
      • How does choice of starting points affect distributions?
    • 12. Conclusions
      • Streaming media on the Web increased 600% in the past 5 years
      • Real Media most popular, followed by Windows Media
      • Video and Audio are both equally popular
      • On-demand streaming dominates
      • Growth potential
        • Better resolutions
        • Higher bitrates?

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