Methods for Serving SMIL Presentations

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    Methods for Serving SMIL Presentations - Presentation Transcript

    1. 4 Serving SMIL Methods for Serving SMIL Presentations
    2. 4.1 Serving Up SMIL
      • SMIL files are text files they contain no binary data
        • No more than few 10’s of KB
        • Many are < 10KB in size
      • SMIL clients differ in the file formats that can be handled
      • Media clips used in the presentation that are the issue
        • Text files are small and lightweight
          • HTML for XHTML+TIME
          • RealText for RealONE
          • In-line text within SMIL or plain text file
        • Images will vary in size
          • Edit to reduce size
        • Audio files do not need to be large
          • 20 to 30 Kbps is OK for voice
          • 64Kbps is OK for music
          • 32Kbps is approx. 240KB per minute
        • Video files are the largest
          • Use an encode limit that produces acceptable results
          • Approx. 350Kbps for 256x192 or 320x240
          • Good quality from professional formats
      • Work with your AVS and media production professionals
        • DIY may not be the most practical solution
        • Do this regardless of how content is to be served
      • IT infrastructure and SMIL clients need to be available as standard
    3. 4.2 Delivery Options
      • Use fixed write once media such as CD-R/DVD
        • Low media costs but administration overheads
      • Serve from fileserver
        • Works OK but no streaming protocol support
        • May have to replicate content across servers
      • Serve from HTTP server
        • Add required MIME types to HTTP server
        • No support for time based media delivery in HTTP
          • Multiple encodes in single media file not supported
      • Serve using dedicated Media Server
        • Ensures reliable delivery of time based
        • Allows bandwidth management
    4. 4.3 Delivering a SMIL Presentation
      • Use a media server supporting both RTSP and HTTP
        • Helix Universal Server from RealNetworks
        • Expensive but very reliable and robust
        • Runs on Linux, Solaris and Windows 2K
        • Streams QuickTime and Windows Media
      • Use an HTTP server such as Apache or IIS
        • Apache runs on many OS including Win 2K
        • Add the necessary MIME types and serve
          • Use .htaccess file in Apache
          • MIME types in IIS
        • Authentication to manage access to content
      • Place content on a file server
        • Manage access
        • For example use Active Directory users and groups
    5. 4.4 Using a Hybrid Approach
      • Source media clips from the most appropriate location
      • Allows scalability for serving time-based media
      • Enables cross-institutional collaboration and assistance
        • JISC initiatives
      • Streaming server
        • Video, audio files
      • HTTP server
        • SMIL file, text, images and animations
      • Use file system and/or HTTP approach
        • Small audiences, short clips and short duration
        • Reliable high-bandwidth network and servers
      • Use Helix Server and RealONE client
        • Afford the capital and ongoing support costs
        • Want “state-of-the-art” SMIL 2.0 infrastructure
      • Trial accounts on a Helix Server for evaluation
        • Contact: [email_address]
    6. 4.5 Pre-fetching content
      • <prefetch> manages client/server transfers of media
        • Prevents buffering delays for streamed media
      • Defined in the SMIL 2.0 Content Control Module
      • Not yet supported in RealONE player and Helix Server
      • Use for presentation with video and audio content
        • Requires preceding low-bandwidth content
        • Don’t use for content served via HTTP or files system
      • Manages pre-fetching using three attributes
        • bandwidth – how much of client bandwidth to use
        • mediaSize – amount of the clips total data to pre-fetch
        • mediaTIme – amount of a clips total duration to pre-fetch
      <par> <!– Preceding low bandwidth seciton --> … <prefetch src=“rtso://boombox.ucs.ed.ac.uk/video1.rm” mediaTime=“15” bandwidth=“100000”/> <!--video plays later --> <video id=“video1” src=“rtsp://boombox.ucs.ed.ac.uk/video1.rm” …/> </par>
    7. 4.6 Review
      • SMIL and XHTML+TIME files are small
      • Media clips that are large 
      • Optimise video, image and audio
      • Select a delivery method that matches your budget and intended use
      • Use existing HTTP and File server systems
      • Using Helix Server and RealONE
        • Experiment with pre-fetching data

    + jsmithjsmith, 4 years ago

    custom

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