Video and DVD

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Video and DVD
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What is DVD?

• DVD was the first distribution medium designed
  for digital video.
• Hence it originally stood for Digital Video Disc.
• Digital offers dramatic improvements in
  transmission efficiency compared to analogue
  video.

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Studio Quality Images

• DVD now stands for Digital Versatile Disc.
• It offers an optical (and audio) storage medium
  with enormous capacity and bandwidth compared to
  CD-ROM.
• Standard specifications include MPEG-2 video
  which gives studio quality 740X480 pixel images
  (VHS tape 320X240).

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Recordable DVD

• DVD-R Recordable once, read on DVD-ROM.
• DVD-RAM read and write to 2.6 GB DVD-RAM Disc and
  read and write once to 3.9 GB DVD-R Discs.
• DVD-Ram discs readable on DVD-R and DVD-ROM
  drives.

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High Capacity

• Full length films 133 minutes of MPEG-2.
• Single layer discs 4.7 Gbyte.
• Dual-layer discs 8.5 Gbyte.

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Double-sided DVDs

• Double-sided dual layer discs with back to back
  bonding.
• By combining with Dual layer a massive capacity
  of 17 Gbytes can be obtained.

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Data Storage on DVD

• Like CD-ROMs data is recorded in spiral of tiny
  pits.

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Capacity Gains over CD-ROM

• DVDs obtain significantly more capacity by
• Shorter wavelength laser
• Smaller pits (0.4 micrometers v 1.1 on CD-ROMS)
• Denser track pitch (0.74 micrometers v 1.6 on
  CD-ROMS)
• Increased efficiency in channel encoding.

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Construction of DVD
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Variable Bit Rate

• Average bit rate for DVD is 4.7 mbs.
• But the rate varies between gt3 to 10.07mbs.
• This enables high quality images to be generated
  from complex scenes.

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MPEGs (Moving Pictures Expert Group)

• Video standard for DVD, MPEG uses three types of
  video frame
• I-Frames contains all spatial info of video
  frame. These are used as the hooks, every scene
  change requires a new I-Frame.
• B-Frames (Highest compression).
• P-Frames.

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MPEG Advantages

• Universal compatibility MPEG files are system
  independent.
• Greater compression ratios than any other format
  (up to 2001).
• Highest quality compression does not lead to
  sacrifice in quality.
• MPEG delivers broadcast quality video.

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Advantages of DVD

• Added features over Video tape.
• Immediate scene access.
• There are more than 5,600 movie and music videos
  currently available.
• Same size as CD but can store an entire film.
• DVD offers superior picture and sound.

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Future of DVD?

• DVD or Sonys Phase-Change Rewritables (PCR) disc
  or NEC (Betamax v VHS).
• Hitachi propose a DVD-RAM disc with phase-change
  technology that will be retrospective to CD-ROM
  and DVD-ROM.
• Blue lasers developed in Japan mean a laser
  footprint even smaller than DVD can be obtained.

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History of Video on the Web

• Multimedia became commonplace back in 1992 with
  CD-ROMS.
• But the Web has low bandwidth and cannot cope
  easily with moving pictures.
• TV uses fat cable infrastructure, Web uses
  thin telephone infrastructure.
• Moving images on the Web like sucking a bowling
  ball through a garden hose.

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Video Compression

• Temporal compression frame by frame.
• Spatial compression deletes information common
  to entire file and defines areas rather than
  pixels.
• In addition, file size can be reduced by cutting
• Colours
• frame rate
• audio quality.

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Hardware v Software Codecs

• Hardware codecs are faster and require fewer CPU
  resources.
• Delivers high-quality results.
• But are more expensive.
• Software codecs are less expensive, e.g. freeware
  versions.
• Take long time to analyse and compress.

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DV Filmmaking

• Digital Video (DV) was introduced to U.S.
  consumers in 1994.
• Digital Video is a high resolution video format
  that stores, manipulates and relays data like any
  other computer data.

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Benefits of DV

• Excellent images, being digital the copy quality
  is identical to the original.
• Three separate signals for each colour offering
  good colour reproduction.
• Ability to use Firewires high speed connections
  in and out of computers.
• Portable and relatively inexpensive cameras.

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FireWire - Wired for Speed

• A high-speed serial bus cable designed by Apple
  to provide cheap digital interface.
• Based on the port found on Nintendo Gameboy.
• Provides a transfer rate of 50 megabytes/sec
  (Broadcast quality needs just 3.6)
• It can link up to 63 devices.
• Unlike SCSI no device IDs need to be set.

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Webmonkey Hints

• Use a tripod.
• Use tight close-ups.
• Use quality resources.
• Do not shoot very dark or light backgrounds.
• Capture rate no bigger than 320 x 240 pixels at
  10 frames per second.

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• The End