Digital Media Production means that computer information can be represented through audio, video, and animation in addition to traditional media (i.e., text, graphics/drawings, images).
Digital Media Production is the field concerned with the computer controlled integration of text, graphics, drawings, still and moving images (Video), animation, audio, and any other media where every type of information can be represented, stored, transmitted and processed digitally.
A Digital Media Production has four basic characteristics:
_ Digital media productions must be computer controlled.
_ Digital media productions are integrated.
_ The information they handle must be represented digitally.
_ The interface to the final presentation of media is usually
interactive.
Examples of Digital Media Applications include:
_ World Wide Web
_ Multimedia Authoring, e.g. Adobe/Macromedia Director
_ Hypermedia courseware
_ Video-on-demand
_ Interactive TV
_ Computer Games
_ Virtual reality
_ Digital video editing and production systems
_ Multimedia Database systems
Now let us consider the Components (Hardware and Software)required for a multimedia system:
Capture devices — Video Camera, Video Recorder, Audio
Microphone, Keyboards, mice, graphics tablets, 3D input
devices, tactile sensors, VR devices. Digitising Hardware
Storage Devices — Hard disks, CD-ROMs, DVD-ROM, etc
Communication Networks — Local Networks, Intranets,
Internet, Multimedia or other special high speed networks.
Computer Systems — Multimedia Desktop machines,
Workstations, MPEG/VIDEO/DSP Hardware
Display Devices — CD-quality speakers, HDTV,SVGA, Hi-Res
monitors, Colour printers etc.
Digital Media Data:Input and Format
Text and Static Data
_ Source: keyboard, speech input, optical character recognition,
data stored on disk.
_ Stored and input character by character:
– Storage of text is 1 byte per character (text or format character).
– For other forms of data (e.g. Spreadsheet files). May store
format as text (with formatting) others may use binary encoding.
_ Format: Raw text or formatted text e.g HTML, Rich Text Format
(RTF), Word or a program language source (C, Pascal, etc..
_ Not temporal — BUT may have natural implied sequence e.g.
HTML format sequence, Sequence of C program statements.
_ Size Not significant w.r.t. other Multimedia data.
Graphics
_ Format: constructed by the composition of primitive objects
such as lines, polygons, circles, curves and arcs.
_ Input: Graphics are usually generated by a graphics editor
program (e.g. Illustrator) or automatically by a program (e.g.
Postscript).
_ Graphics are usually editable or revisable (unlike Images).
_ Graphics input devices: keyboard (for text and cursor control),
mouse, trackball or graphics tablet.
_ graphics standards : OpenGL, PHIGS, GKS
_ Graphics files usually store the primitive assembly
_ Do not take up a very high storage overhead.
Images
_ Still pictures which (uncompressed) are represented as a
bitmap (a grid of pixels).
_ Input: digitally scanned photographs/pictures or direct from
a digital camera.
_ Input: May also be generated by programs “similar” to graphics
or animation programs.
_ Stored at 1 bit per pixel (Black and White), 8 Bits per pixel
(Grey Scale, Colour Map) or 24 Bits per pixel (True Colour)
_ Size: a 512x512 Grey scale image takes up 1/4 Mb, a 512x512
24 bit image takes 3/4 Mb with no compression.
_ This overhead soon increases with image size — modern
high digital camera 10+ Megapixels _ 29Mb uncompressed!
_ Compression is commonly applied.
Audio
_ Audio signals are continuous analog signals.
_ Input: microphones and then digitised and stored
_ CD Quality Audio requires 16-bit sampling at 44.1 KHz
Even higher audiophile rates (e.g. 24-bit, 96 KHz)
_ 1 Minute of Mono CD quality (uncompressed) audio requires
5 Mb.
_ 1 Minute of Stereo CD quality (uncompressed) audio requires
10 Mb.
_ Usually compressed (E.g. MP3, AAC, Flac, Ogg Vorbis).
Video
_ Input: Analog Video is usually captured by a video camera
and then digitised.
_ There are a variety of video (analog and digital) formats
_ Raw video can be regarded as being a series of single images.
There are typically 25, 30 or 50 frames per second.
_ E.g. A 512 _ 512 size monochrome video images take 25 _
0:25 = 6.25Mb for a minute to store uncompressed.
_ Typical PAL digital video (720 _ 576 pixels per colour frame)
_ 1:2 _ 25 = 30Mb for a minute to store uncompressed.
_ High Definition DVD (1440_1080 = 1.5 Megapixels per frame)
_ 4:5 _ 25 = 112.5Mb for a minute to store uncompressed.
(There are higher possible frame rates!)
_ Digital video clearly needs to be compressed for most times.
