Video

1
Video
2
History of Video

• Drama
• A multimedia experience. How?
• Film
• First technology to capture the multimedia
  experience of drama in a form that could be
  widely distributed.
• Television
• Offered a way to capture the combined media of
  voice, image, gesture, music, and motion (just as
  film did)
• Distributed via electronic signals rather than
  via film
• Today
• Television and Movies are broadcasted as well as
  saved and distributed.

3
Role of Video on Websites

• Telling a Story (example)
• Entertainment (examples)
• Explanation (example)
• Personalization of the web experienc

4
Check Out Video On Your Own

• Head on over to CNN, iFilm, Quicktime Movie
  Trailers. Check out the videos there.

5
Limitations of Video

• File Size can be HUGE
• Takes a while to download
• Requires plugins

6
How Video Works on the Web

• Video on the web works differently from film, tv,
  and video tape.
• Uses different technologies and different storage
  and transmission methods
• Video on the web is fully digital
• Goes through significant compression
• Can be downloaded as a file or streamed to the
  audience.
• Its file formats and codecs are complex
• Be sure to read pages 108-111 for this!
• There is a lot of info on how video works ?

7
Video Compression

• Repetition and Patterns
• Say we have a video of a horse running. The
  movement of the horses legs is the same step
  after step.
• The codec recognizes this repetition of a string
  of numbers over several frames that form a
  repeated pattern (the horses moving legs).
• The codec saves this data using a ditto, 319
  more times, or using a single number token to
  represent the repeated pattern.
• Relatively lossless

8
Video Compression

• Averaging
• Same method a JPEG uses
• Looks at a block of pixels and averages their
  color and brightness, saving one number rather
  than 4, 9, 16, etc. (see chapter 1 and 2 for
  more info on averaging)

9
Video Compression

• Range Reduction
• The range in brightness of an original video
  might be on a scale of 1 to 500, meaning that the
  lightest part of the sky is 500 times brighter
  than the darkest shadow under a forest.
• This brightness is recorded as a number for each
  pixel in each frame
• Wide range of brightness requires that a big
  number - 8 or 16 bits - be recorded for each
  pixel.
• The codec reduces the range to a scale of, say, 1
  to 100. The sky is still brighter, but only 100
  times or so brighter.
• Because the number is saved millions of times in
  the movie file, reducing its size can delete lots
  of data from the filemost people will not notice
  this range reduction.

10
Video Compression

• Frame-Difference
• For the first frame of a video, every pixel is
  recorded. For subsequent frames, only those
  pixels that have changed are recorded.

11
Downloads vs Streaming

• Downloading
• Simplest method. User downloads file, when file
  is finished downloading, user watches file.
• Fast-Start Downloading
• Video file downloads to the viewers computer but
  begins playing as soon as the first few hundred
  frames have been received.
• Works well for small and medium sized videos.

12
Downloading vs Streaming

• Streaming
• Displayed on the screen as soon as it arrives on
  the users computer.
• It is not downloaded to the hard disk.
• A streaming video server manages the connection
  with the user, monitoring the reception to ensure
  that the video is arriving fast enough to provide
  good viewing
• Makes use of data buffering. (temporarily storing
  portions of the data)

13
File Formats

• Downloadable Video
• QuickTime (.mov)
• Moving Picture Experts Group (.mpg)
• Audio-Video Interleaved (.avi)
• Windows Media (.wmv)

14
File Formats

• Streaming Video
• RealVideo (.ram)
• QuickTime (.mov)
• Windows Media (.asf)

15
Preparing Video for the Web

• Sources
• Camcorder and video tape (both require video
  capture software)
• DVD
• TV
• CD-ROM
• Web video
• Video from still images.
• We will use Windows Movie Maker.

16
Adding Video to your Webpage

• See pages 132-134
• Be kind to your users!