Introduction to Multimedia

Multimedia The word is composed of two parts Multi: from the latin word multus which means numerous. Medium: the plural of the latin word medium which means middle or center.

Media A means to distribute and represent information. Ex.: text, graphics, pictures, voice, music.

Multimedia Multimedia is media that utilizes a combination of different content forms. A collection of CDs is not multimedia. The term can be used as a noun (a medium with multiple content forms) or as an adjective describing a medium as having multiple content forms.

Multimedia

Multimedia Categories Multimedia may be broadly divided into linear and non-linear categories. Linear active content progresses without any navigation control for the viewer such as a cinema presentation. Non-linear content offers user interactivity to control progress as used with a computer game.

Multimedia Categories Multimedia presentations can be live or recorded. A recorded presentation may allow interactivity via a navigation system. A live multimedia presentation may allow interactivity via interaction with the presenter or performer.

Usages of Multimedia Commercial (advertising), Entertainment (special effects), Arts (media artists), Education (computer learning), Engineering (training, simulations), Industry (information broadcasting), Science and medicine (simulations),

Multimedia Features Multimedia presentations may be viewed in person on stage, projected, transmitted, or played locally with a media player. Broadcasts and recordings can be either analog or digital electronic media technology. Digital online multimedia may be downloaded or streamed. Streaming multimedia may be live or on-demand.

Perception Media Refers to the nature of information perceived by humans. Auditory media (music, sound and voice) are different from visual media (text, graphics, still and moving pictures).

Representation Media How is information represented internally to the computer. Ex.: ASCII text, GKS graphics, PCM sound, JPEG image, NTSC television signal.

Presentation Media Refers to the physical means used by systems to reproduce information for humans. The actual device presenting the media. For television: CRT + loudspeakers. Input (keyboards, cameras, mikes) and output (paper, monitors, speakers) presentation media.

Storage Media It is used in computing to refer to the various physical means to store data like tapes or disks. Paper is also storage media.

Transmission Media Refers to the physical means that allow transmission of multimedia information (cables, radio towers, satellites, Internet).

Information Exchange Media Include all data media used to transport information. In fact, all storage and transmission media. Ex.: removable disks, microfilms, paper, floppy disks, CD's, DVD's. Also direct exchanges via cables, optical fibres, radio waves.

Presentation Spaces Paper and computer monitors are examples of visual presentation spaces as is a slide-show projected from a computer. Stereophony and quadrophony are examples of acoustic presentation spaces.

Presentation Values Determine how information from various media is represented. Text is the medium presenting a sentence visually. Pressure waves can present a voice. We need a code to interpret the presentation values (ex. alphabet).

Presentation Values These symbols have meaning only if you know the context. These include cultural gestures.

Presentation Dimensions Each presentation space has one or more presentation dimension. A computer monitor has 2 dimensions. Time can be an additional dimension within each presentation space. There are two kinds of media with regard to time dimensions.

Discrete Media Text graphics and pictures are called discrete media as they are composed of time-independent information items. Discrete media are better processed as fast as possible since time is not a critical factor for its comprehension.

Continuous Media Sound and motion videos are called continuous media because they require a continuous play out to be understood. They are time-dependent Continuous media are better processed in the respect of the time dependency. The correctness of the media depends of the time condition.

Continuous Media A silent movie is not purely a continuous media but there is a time constraint nonetheless. Continuous vs. discrete has nothing to do with internal representation. It refers only to the viewer or auditor perception.

Multimedia Systems A multimedia system must be computer- controlled. It is integrated: It involves a minimal number of different devices. Must be able to handle both continuous and discrete media. Individual media must be independent. Must be synchronized. A text with graphics is not multimedia.

Data Streams Networked multimedia systems transmit both discrete and continuous media streams. Information is split in packets before it is transmitted. The packets are sent by one system (computer) (source) and received by another (sink).

Asynchronous Transmission Mode When a sender and receiver do not need to coordinate before data can be transmitted. Transmission may start at any instant. Ex.: Sending a text.

Synchronous Transmission Mode When a sender and receiver need to coordinate before data can be transmitted. Transmission may only take place at well- defined times. A clocking signal is necessary. Ex. : A live television show.

Isochronous Transmission Mode A periodic signal, pertaining to transmission in which the time interval separating any two corresponding transmissions is equal to the unit interval or a multiple of the unit interval. The Isochronous Transmission Format is also known as START-STOP mode or CHARACTER mode. Ex.: Transmission of a video over a network.

Continuous Media Data Streams The first property of data streams relates to the time intervals between completed transmissions of consecutive information units or packets. Strongly periodic data stream T Weakly periodic data stream T1 T2 T3 T T Aperiodic data stream T1 T2

Continuous Media Data Streams The second property of data streams concerns how the data quantity of consecutive information units or packets varies.

Continuous Media Data Streams Strongly regular data stream D1 D1 T Weakly regular data stream D2 t D3 D1 D2 D3 D1 Irregular data stream D2 t D3 Dn

Continuous Media Data Streams The third property of data streams concerns the continuity or the relationship between consecutive packets. Interrelated data stream: without gaps D1 D2 D3 D4 D Non-interrelated data stream: gaps between packets D1 D2 D3 D4 D IF NETWORK IS FASTER THAN MEDIA DELIVERY

Information Units Continuous media consist of a time- dependent sequence of individual information units called Logical Data Units (LDU). A symphony consists of independent movements. A movement consists of notes. Notes are sequences of sampled sounds.

Granularity A single image is not the only possible LDU in a motion video sequence. Each scene and each pixel are also logical data units. Film Clip Frame Blocks Pixels

END OF LESSON