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Transcript

  • 1. SFDV2001 – Web Development Lecture 8: Video
  • 2. History
    • Magic Lantern, Athanasius Kircher in 1671
    • Zoetrope, William George Horner 1834
    • Celluloid, invented in 1856
    • Zoopraxiscope, Muybridge 1878
    • Cinématographe, Lumière brothers 1894
    • Nickelodean 1905
      • Costs a nickel to watch a 15 minute movie
      • First actual movie theatre
    11/09/07 SFDV2001:21 - Video
  • 3. Moving Pictures
    • Flip book
    • Animation – GIF
    • Persistence of vision
    • Phi
    • Wagon wheel illusion
    • Movement detectors
    11/09/07 SFDV2001:21 - Video
  • 4. Video Basics
    • Length
      • seconds
    • Frame size
      • width and height
      • 160 x 120
      • 320 x 240
      • 640 x 480 NTSC
      • 768 x 576 PAL
    • Frame rate
      • frames per second
      • 10 -15 fps, web
      • 24 fps, Movies
    11/09/07 SFDV2001:21 - Video
  • 5. Video Basics
    • Quality
      • compression
      • noise
      • colour
    • Colour Depth
      • bits per pixel.
    • Data rate
      • kbps.
      • how fast you have to transfer data to let the movie play without interruption.
    • Audio.
      • Soundtrack.
    11/09/07 SFDV2001:21 - Video
  • 6. Video and the internet
    • Initially just treat like another file
    • Download the data and let the user sort it out.
    • Video players
      • Quicktime
      • MS break the law and steal Quicktime from Apple
    • Embed the player in a browser program
    • What about a plug-in rather than download
    • Now two types
      • Download
      • Streaming
    11/09/07 SFDV2001:21 - Video
  • 7. YouTube
    • Egalitarian access to video posting
    • Like blogs but with Video
    • OkGo – was a hit on YouTube first.
    • Lonelygirl15 – Viral marketing
    • Competition
      • Google Video
      • MS – SoapBox
    • Escape from the “mainstream media”
    11/09/07 SFDV2001:21 - Video
  • 8. Download
    • Just treat like any other file type.
    • A link to download
    • Using a plug-in
    • Advantages
      • No special plug-in for a normal link.
      • Download in the users own time.
      • Disadvantages
    • File copied to the users computer.
      • No fast forwarding.
      • No control over redistribution.
      • Whole file download.
    11/09/07 SFDV2001:21 - Video
  • 9. Streaming
    • Only send the next bit in the movie.
      • Throw away older stuff.
    • Advantages
      • Control of data.
      • Allows fast-forward and other control.
      • Constant communication allows flexible download.
      • Allows real-time web-casts.
    • Disadvantages
      • Must have special server and client software.
      • Users do not have a cached version and so have to access the site to view again.
      • Higher server load.
    11/09/07 SFDV2001:21 - Video
  • 10. Video File Formats
    • AVI: .avi MS 1992.
    • Quicktime: .mov files.
    • RealMedia: .rm files (.ram and .rpm for streaming versions).
    • Windows Media: .wmv files (.asx for streaming version).
    • MPEG 1,2 4: .mpg .mpeg.
    • Sorenson – low bandwidth.
    • H.264 – MPEG4 OSX high compression rate.
    11/09/07 SFDV2001:21 - Video
  • 11. MPEG
    • Moving Pictures Experts Group
    • First met in 1988
    • Digital storage finally getting big enough for video
    • Goal to develop encoding for digital video
    • Two levels suggested
      • MPEG-1 – Low quality
      • MPEG-2 – better quality
    11/09/07 SFDV2001:21 - Video
  • 12. MPEG-1
    • Multiple codecs - Co ding dec oding
    • Different Frames
      • I Key frame I
      • B Small changes with reference to I's and P's
      • P Reference frame
    • I's compressed like JPEG
    • B's and P's are differences
    • Lossy compression
    11/09/07 SFDV2001:21 - Video
  • 13. Quicktime
    • 1991 File format
      • *.mov
      • multimedia container file
      • Contains one or more tracks
        • audio
        • video
        • effects
        • text
      • Apple Video codec, Animation codec, Graphics codec
    • 1999 – added streaming support
    11/09/07 SFDV2001:21 - Video
  • 14. Video Compression
    • Spatial compression:
      • Compress each frame separately.
      • Done by MJPEG codec in digital video cameras.
    • Temporal compression:
      • Encode changes from frame to frame.
      • Uses keyframes to synchronise.
      • MPEG Sorenson use both.
      • Also utilise DCT:
        • convert to frequency.
        • quantise.
        • entropy-code.
    11/09/07 SFDV2001:21 - Video
  • 15. Flash
    • Adobe flash plug-in
      • Includes video content.
      • Allows full interaction with movie.
      • Open standard
      • Streaming format
      • Vector based movies very small compressed size.
      • Presentation completely under control..
    11/09/07 SFDV2001:21 - Video
  • 16. Examples Worth Looking At
    • BBC’s interview clips using RealMedia:
      • Notice the picture quality
      • obvious temporal compression.
      • Notice the use of buffering to allow for data rate issues.
    • Apple’s movie trailers site:
      • Notice use of different frame sizes.
      • Designed to show off Quicktime.
    • GDC TV
      • Intergration of video and presentation.
    • YouTube, Google Video
    11/09/07 SFDV2001:21 - Video
  • 17. Digital Format
    • Blu-ray vs HD-DVD
    • The digital format battle of the future
    • Blu-ray
      • The digital format battle of the future
      • Sony Playstation Blu-ray
      • 25 GB single layer, 50 GB double layer
      • Many companies
    • HD-DVD
      • Toshiba, NEC, Sanyo, and, most recently, Microsoft, HP
      • 15 GB single, 30 GB double
    • Both use MPEG2
    11/09/07 SFDV2001:21 - Video
  • 18. Summary
    • Video files are Huge
    • The future of the web includes video
    • Broadband required before video makes sense
    • Various Codec compress video
    • Steaming vs Download formats
      • When to use and the advantages/disadvantages
    • Temporal vs Spatial compression
      • How do they work
    11/09/07 SFDV2001:21 - Video