Promoting Digital Video Skills in Schools        Distribution Web
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Moving Images on the Web

The first, and most widely supported moving image is the Animated GIF

GIF and JPEG images are the two formats totally supported on the Web.

JPEG Joint Photographic Experts Group
Use this format to compress photographic images.
It supports 24-bit (16.7 million) colour and uses lossy compression.

GIF
The Graphic Interface Format was created by Compuserve.
Use this format to compress line art and images with areas of similar colours.
The GIF format supports 8-bit (256) colour.
Animation There are two versions of GIF: 89a, which can
save transparency and animation information, and 87a, which cannot.
Both are recognized by most browsers and use lossless compression.

When producing images for the Web, consider frame size, file size and colour depth.
   Frame Size is the size of the image measured in Pixels.
   Doubling the frame size will quadruple the file size
   File Size. As the size of an image file increases, it takes more time to download,
   so viewers have a longer wait.
   Use 30KB as the largest still image size, but aim for around 10KB or less.
   Colour Depth
   Some computers can only display up to 256 colours.
   Reduce the colour depth of the image to 8 bits (256 colours) before
   placing it in a Web page, for a more consistent appearance.
   Flash from Macromedia is a new vector based animation format.
   All browsers can view GIFs, but a "plug-in" is required to view Flash and video.
COMMON VIDEO FORMATS
The earliest video for the web were produced using the Real Systems RM format.

Quick Time
Is a collection of CODEC's on Apple computers, for tape CD and Web

AVI
Is a Microsoft container for CODECS [COmpression DE-CompreSsion]

Both MOV and AVI support the CINEPAK CODEC
Hence this a CODEC to use to reach the widest audience [on CD].

MPEG-1
Is a well supported video format, Primarily designed for for making VCDs
MPEG-1 has been around for many years now, and is acceptable for broadband

MPEG-2
DVDs use MPEG-2 compressed video, which produces excellent quality video, at the cost of very large file sizes, and is not suitable even for broadband users

MPEG-4
This is a relatively new kid on the the block, but is the video format of the future.
MPEG-4 forms the basis of video on the new generation of video phones Namely GP3
MPEG-4 has Scalable Quality from almost MPEG-2 quality to very small file sizes.
Combine MPEG-4 video with MP3 audio to achieve quality sound and vision with small file sizes.

To reach the widest audience the web video page needs offer choices to the visitor.

However web designers can interrogate the visitors web browser to see which
Plugins the visitor has, then automatically supply the video in the right format.
Video can be compressed
  •    lightly for broadband visitors eg MPEG-1
  •    For 56KB modems MPEG-4
  •    For 28KB modems use animated GIFs, Flash small asf / wmv
  •    For video mobile phones the new format is GP3

Commercial customers often want DVD quality with zero files size.
Video on the web is all about compromise,
and meeting the needs of the web page visitor.