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    Lecture 8 Video Lecture 8 Video Presentation Transcript

    • SFDV2001 – Web Development Lecture 8: Video
    • 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
    • Moving Pictures
      • Flip book
      • Animation – GIF
      • Persistence of vision
      • Phi
      • Wagon wheel illusion
      • Movement detectors
      11/09/07 SFDV2001:21 - Video
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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