Section
One: The Digital Video Process
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The simplest definition
of digital video is the representation or encoding of an analog video
signal in digital bits for storage, transmission and display. If you
have access to the World Wide Web, chances are you have viewed digital
video files. Examples include CNN news clips, movie trailers and,
of course, the popular dancing baby! Digital video files pervade the
analog television and 70 mm film world. Most special effects, such
as Godzilla trampling a building or a polar bear sipping a soft drink
in an advertisement, are created by editing digital video files. If
you have rented movies on demand in your hotel room, played a DVD,
a video game, or used a Direct TV satellite dish, you have experienced
digital video through your television set.
Digital video
is a growing presence in the academic arena, from digitized course
lectures to archival footage housed in the campus library. Video conferencing
— for collaboration, Internet-based communication and teaching —
is an important digital video service. Video conferencing is addressed
by ViDe in the Video
Conferencing Cookbook. Digital video-on-demand, another key service,
is defined for this white paper as the creation, storage, transmission
and display of archived digital video files in an IP network environment.
Digital video may be streamed to a computer, so that playback begins
before the entire video file is received, or non-streamed, requiring
that the entire file be downloaded be playing. Streaming videos may
be served as multicast or unicast streams. Video-on-Demand generally
refers to unicast, where a single video file is requested by a user
and streamed to the user's computer for playback. Multicast — the
transmission of a single digital video file to multiple users in a
scheduled environment — is included in this digital video-on-demand
white paper for convenience, since most vendors providing on-demand
video files to a single user (unicast) also provide products for multicast
of both stored files and live broadcasts.
There are three
basic components in the digital video process.
