1. Multimedia objects
1.1. What is multimedia, multimedia data and multimedia programming
"Multimedia is when you have too many cables"
The term multimedia is used in several contexts emphasizing different
features:
- Multimedia presentations (encyclopedia)
- Multimedia workstations (technical view)
- Multimedia games - virtual reality (sense experience)
- Multimedia databases (repository of various media formats)
Common denominator - multimedia data.
Natural media - digital media
- Natural media - media data = Newspapers - books - film - photographs
- art - audiorecordings
- Each media type has its own media form and carrier.
- Natural media rely on physical elements - paper, stone, ink, paint,
musical instruments,
Digital media - media data
- text files - videofiles - GIF - JPEG - Sound files
- Each media type has its own format but the same carrier (file in a
computer storage)
- Digital media rely on the computer.
Artifact = object produced on a particular medium.
Media data = machine-readable representations of artifacts
Multimedia artifact = Composition of artifacts from various media.
- Spatial composition (multiple artifacts in the same space)
- Temporal composition (sequence of artifacts - syncronization in time)
Multimedia data = machine-readable representation of multimedia artifacts.
Multimedia programming = systematic manipulation of multimedia data
1.2. Multimedia Hardware
Digital media devices - media specific
- Capture : Keyboard, scanner, video grabber, audio grabber
- Presentation: Display driver, printer, synthetized, audio-converter
Analog media devices - media specific
- Sources: Microphone, camera, tape(video-audio) player,
- Sinks: Speaker, video display, tape recorder,
General purpose devices - non media-specific
Syncronizing devices sync generators timers - for audio - video sync.
Interaction devices mouse, joystick, keyboard
Multimedia platforms
PC - Mac - Workstation equipped with mm-devices (soundcard, videocard,
microphone, cd-player, speakers)
1.4. Multimedia applications
- Interactive videodisc
- Electronic games
- Hypermedia browsers
- Multimedia presentation systems
- MM authoring systems
- MM mail systyems
- Desktop video systems
- Desktop conferencing
- Multimedia services
2. Media types
In the previous section we identified common properties for different
digital media. The digital media artifact can be represented on digital
media as files or more generally as data in computer memory or storage.
Different media artifacts (text, video, image, sound) have also typical
properties of their own. Therefore we can characterize the different media
as media types.
In conventional programming we define variable types (integer, character,
floating-point number, records, files). The characterization of digital
media is on the machine level based in these types, but here we characterize
the media types on a higher abstraction level. We try to avoid references
to concrete types (such as GIF, AIFF, MPEG, ASCII), but try to characterize
the nature of the types.
Each type is described by two components
- Representation
- Operations
Representation:
How the artefact of that media type is represented on digital media,
standards, sizes, resolutions, number of bytes the data itself et c. are
part of the representation.
Operations:
How the artefact of this particular media can be manipulated. (created,
presented, changed, ..). Some operations can be common to several types
- some are specific to that particular type.
For example copying, moving, deleting can be considered as operation
system level operations (copy, move, delete file) and to be common to all
types.
This approach is compatible with the object oriented modelling which
we introduce later.
The media types can be described using the media type template
|
Media type <name>
Representation <aspects of representation>
Operations <aspects of operations>
|
Question1 :
Define the Audio CD Media type from the AudioCD-users point of view.
Question2 :
Define the TextTV Media type from the users point of view.
mj@uwasa.fi 24.2.1997